LIGO/Virgo S191216ap

A. Ridnaia, S. Golenetskii, R.Aptekar, D. Frederiks,
M. Ulanov, D. Svinkin, A. Tsvetkova, A. Lysenko, and T. Cline,
on behalf of the Konus-Wind team, report:

Konus-Wind (KW) was observing the whole sky at the time of the
LIGO/Virgo event S191216ap (2019-12-16 21:33:38.473 UTC, hereafter T0;
LIGO/Virgo Collaboration GCN Circ. 26454
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 ).

No triggered KW GRBs happened ~14 days before and ~1 day
after T0. The closest waiting-mode GRB was observed ~29 hours after T0.
Using waiting-mode data within the interval T0 +/- 100 s,
we found no significant (> 5 sigma) excess over the background
in both KW detectors on temporal scales from 2.944 s to 100 s.

We estimate an upper limit (90% conf.) on the 20 - 1500 keV fluence
to 8.1x10^-7 erg/cm^2 for a burst lasting less than 2.944 s and having a
typical KW short GRB spectrum (an exponentially cut off power law with
alpha =-0.5 and Ep=500 keV). For a typical long GRB spectrum (the Band
function with alpha=-1, beta=-2.5, and Ep=300 keV), the corresponding
limiting peak flux is 2.4x10^-7 erg/cm^2/s (20 - 1500 keV, 2.944 s scale).

All the quoted values are preliminary.

G. P. Smith (Birmingham), M. Nicholl (Birmingham), K. Sharon (Michigan), 
M. Bianconi (Birmingham), W. P. Varricatt (UKIRT), S. Benigni (UKIRT), 
and E. J. Ridley (Birmingham) report on behalf of the Gravitationally 
Lensed Gravitational Wave Hunters:

As part of our search for strongly-lensed gravitational waves and their 
electromagnetic counterparts, we observed a contiguous area of 0.75 
square degrees within the sky localization of the gravitational wave 
trigger S191216ap (GCN #26454
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 ) with the WFCAM instrument on UKIRT 
through the z-band.  The observations were centered on the position of 
the HAWC sub-threshold detection of gamma-ray flux reported by 
Martinez-Castellanos (GCN #26472
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 ), and encompassed the full extent of 
their 68% confidence region.  The observations comprise two epochs:

Epoch  Date(UT)    Start(UT)  End(UT)   Airmass  FWHM(arcsec)
1      2019-12-20  04:45:21   05:45:57  1.3-1.7  1.2-1.6
2      2019-12-21  04:31:26   05:43:34  1.3-1.8  1.6-1.8

We estimate that Epoch 1 reaches a 5 sigma point source sensitivity of 
AB~21.5.  Epoch 2 is less sensitive than Epoch 1, with noticeable 
variations in Epoch 2 between the four observations required to achieve 
contiguous coverage with WFCAM.

A preliminary comparison of Epoch 1 with templates derived from 
Pan-STARRS1 data (nominal sensitivity of AB=22.3) identified two 
candidate transient sources.  Neither source is known to the Transient 
Name Server, and Minor Planet Center.  The celestial coordinates and 
estimated z-band apparent AB magnitudes of these two candidates are:

Name      RA(J2000)    Dec(J2000)   AB(Epoch1)  AB(Epoch2)
GLGWc19a  21:32:45.50  +05:19:58.0  20.8+/-0.1  ~22
GLGWc19b  21:35:20.11  +04:55:19.8  20.6+/-0.1  >20(tentative)

Neither source is associated with an obvious candidate gravitational 
lens (i.e. massive galaxy, group or cluster) to the depth of the PS1 
data.  However, GLGWc19a is 7 arcsec West, 1 arcsec North of the center 
of an edge-on disk galaxy (possible host?) that is located at 
21:32:45.97 +5:19:57.0.

These sources are observable at Airmass<2 for ~30 minutes following the 
end of evening twilight in the Northern Hemisphere in the next few 
nights, before becoming unobservable through the winter months.  We 
therefore encourage urgent follow-up observations of GLGWc19a, GLGWc19b 
and the candidate host galaxy adjacent to GLGWc19a.

We thank the Director of UKIRT, Klaus Hodapp, for quickly approving our 
urgent DDT proposal.  We are also grateful to Mike Irwin for kindly 
expediting the processing of our data at Cambridge Astronomy Survey Unit 
(CASU).

This circular is citable.

The LIGO Scientific Collaboration and the Virgo Collaboration report:

We have conducted further analysis of the LIGO Hanford Observatory
(H1) and Virgo Observatory (V1) data around the time of the compact
binary merger (CBC) candidate S191216ap (GCN Circular 26454
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 ).

Assuming the candidate is astrophysical, the updated parameter
estimation based classification of the GW signal, in order of
descending probability, is BBH (>99%), MassGap (<1%),
Terrestrial (<1%), BNS (<1%), or NSBH (<1%).

For further information about analysis methodology and the contents of
this alert, refer to the LIGO/Virgo Public Alerts User Guide
<https://emfollow.docs.ligo.org/userguide/>.

 [1] Veitch et al. PRD 91, 042003 (2015)

Q. Luo, Y. G. Zheng, C. Cai, S. Xiao, Q. B. Yi, 
Y. Huang, C. K. Li, G. Li, X. B. Li, J. Y. Liao, S. L. Xiong,
C. Z. Liu, X. F. Li, Z. W. Li, Z. Chang, A. M. Zhang, 
Y. F. Zhang, X. F. Lu, C. L. Zou (IHEP), Y. J. Jin, 
Z. Zhang (THU), T. P. Li (IHEP/THU), F. J. Lu, L. M. Song, 
M. Wu, Y. P. Xu, S. N. Zhang (IHEP), 
report on behalf of the Insight-HXMT team:

Insight-HXMT was taking data normally around the reported LIGO/Virgo 
S191216ap GW event (GCN #26454
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 ). At the GW trigger time 
2019-12-16T21:33:38.473 UTC (denoted as T0), 0.96% of the GW localization 
region was covered by the Insight-HXMT without occultation by the Earth.

Within T0 +/- 100 s, no significant excess events (SNR > 3 sigma) are 
found in a search of the Insight-HXMT/HE raw light curves.

Assuming the GW counterpart GRB with three typical GRB Band spectral 
models, two typical duration timescales (1 s, 10 s) from the center 
of the GW location probability map (RA=288.6 deg, DEC=61.1 deg)
without occultation by the Earth, the 5-sigma upper-limits fluence 
(0.2 - 5 MeV, incident energy) are reported below:

Band model 1 (alpha=-1.9, beta=-3.7, Ep=70 keV):
1 s:   5.8e-08 erg cm^-2
10 s:  1.9e-07 erg cm^-2

Band model 2 (alpha=-1.0, beta=-2.3, Ep=230 keV):
1 s:   1.0e-07 erg cm^-2
10 s:  3.4e-07 erg cm^-2

Band model 3 (alpha=-0.0, beta=-1.5, Ep=1000 keV):
1 s:   2.7e-07 erg cm^-2
10 s:  1.1e-06 erg cm^-2

Futhermore, from T0-15 minutes to T0+21 minutes, both the IceCube counterpart 
neutrino candidate (GCN #26450
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 ) and the HAWC sub-threshold event (GCN #26472
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 ) 
were invisible to Insight-HXMT due to the Earth shielding. 

Assuming that the counterpart GRB comes from the HAWC location 
(RA=323.5 deg, DEC=5.2 deg), we estimated 5-sigma upper-limits 
(0.2 - 5 MeV, incident energy) of the extended emission of this GRB 
at 2019-12-16T21:55:00.000 UTC (T0+1281.527 s) as follows: 

Band model 1 (alpha=-1.9, beta=-3.7, Ep=70 keV):
1 s:   2.0e-08 erg cm^-2 
10 s:  1.0e-07 erg cm^-2

Band model 2 (alpha=-1.0, beta=-2.3, Ep=230 keV):
1 s:   3.5e-08 erg cm^-2
10 s:  1.7e-07 erg cm^-2

Band model 3 (alpha=-0.0, beta=-1.5, Ep=1000 keV):
1 s:   1.5e-07 erg cm^-2
10 s:  5.6e-07 erg cm^-2

All measurements above are made with the CsI detectors operating in the
regular mode with the energy range of about 80-800 keV (deposited energy).
Only gamma-rays with energy greater than about 200 keV can penetrate
the spacecraft and leave signals in the CsI detectors installed inside
of the spacecraft.

O. McBrien, S. J. Smartt, K. W. Smith, D. R. Young, J. Gillanders. S. Srivastav, P. Clark, D. O'Neill, M. Fulton (QUB), K.C. Chambers , M. E. Huber, A.S.B. Schultz, T. de Boer, J. Bulger, J. Fairlamb, C.C. Lin, T. Lowe, E. Magnier , R. J. Wainscoat, M. Willman (IfA, Univ. Hawaii), A. Rest (STScI), C. Stubbs (Harvard), T.-W. Chen (Stockholm) on behalf of the Pan-STARRS collaboration report:

We have surveyed the sky localisation region of the gravitational wave event S191216ap (The LIGO Scientific Collaboration and the Virgo Collaboration, GCN 26454
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 ) with Pan-STARRS1 (Chambers et al. 2016, arXiv:1612.05560
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 ), according to the most recently available skymap (LALInference.fits.gz, GCN 26505
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 ), and find 15 transient objects within the 90% probability contour. Our survey covers 58.8% of this contour���s area.

Our coverage began on MJD 58834.210 (UTC 2019-12-17 05:01:45), though poor weather limited observing time severely on this night. Observations continued over the following 3 subsequent nights, all comprised of 45 second tiling exposures in the PS1-r band.

Of the 15 objects found, 8 are known objects already registered on the Transient Name Server. For the remaining 7 objects, 6 appear to be supernova-like events, with relatively flat lightcurves and a host visible in the exposures, while 1 is an M-dwarf flare. We discuss these 7 new objects below:

PS19him (AT2019xfh
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 ) was discovered at coordinates RA=21:22:43.25, Dec=+08:47:04.9 and magnitude 19.10 +/- 0.09 on MJD 58836.233 in the PS1-r band. PS19him is associated with the galaxy SDSS J212243.21+084705.7 at a photometric redshift of 0.117 +/- 0.034. The object was detected on the subsequent night at a similar magnitude. The flatness of the lightcurve suggests this is a supernova.

PS19hir (AT2019xfj
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 ) was discovered at coordinates RA=21:24:08.71, Dec=+13:46:38.8 and magnitude 19.80 +/- 0.15 on MJD 58836.235 in the PS1-r band. PS19hir is associated with the galaxy 2MASS J21240870+1346392 with a photometric redshift of 0.170 �� 0.0245. The object was detected on the subsequent night at a similar magnitude. The flatness of the lightcurve suggests this is a supernova.

PS19hik (AT2019xej
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 ) was discovered at coordinates RA=21:28:18.25, Dec=+03:48:56.8
and magnitude 19.12 +/- 0.11 on MJD 58836.232 in the PS1-r band. PS19hik is associated with the galaxy 2MASS J21281825+0348568 at a photometric redshift of 0.2260 �� 0.0627. The object was detected on the subsequent night at a similar magnitude. The flatness of the lightcurve suggests this is a supernova.

PS19hix (AT2019xfr
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 ) was discovered at coordinates RA=21:14:34.24, Dec=+29:03:22.0 and magnitude 20.54 +/- 0.27 on MJD 58836.229 in the PS1-r band. PS19hix does not appear to be associated with any catalogued galaxy, but lies near a faint, extended source in the PS1 exposure which is likely a galaxy. Additionally, the object was detected on the subsequent night at a similar magnitude, leading us to believe this is a supernova.

PS19his (AT2019xfk
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 ) was discovered at coordinates RA=21:17:50.87, Dec=+29:32:55.1 and magnitude 20.78 +/- 0.29 on MJD 58836.229 in the PS1-r band. PS19his does not appear to be associated with any catalogued galaxy, but lies near a faint, extended source in the PS1 exposure which is likely a galaxy. Additionally, the object was detected on the subsequent night at a similar magnitude, leading us to believe this is a supernova.

PS19hiy (AT2019xgz
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 ) was discovered at coordinates RA=21:18:49.41, Dec=+12:38:49.5 and magnitude 20.15 +/- 0.25 on MJD 58836.260 in the PS1-r band. PS19hiy is associated with the galaxy SDSS J211849.20+123849.5 at a photometric redshift of 0.284 �� 0.106. The object was detected on the subsequent night at a similar magnitude. The flatness of the lightcurve suggests this is a supernova.
PS19hiv (AT2019xfn
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 ) was discovered at coordinates RA=21:14:01.57, Dec=+22:36:54.9 and magnitude 18.41 +/- 0.05 on MJD 58837.270 in the PS1-r band. PS19hiv is a fast fading, faint, red source. As such, we believe this to be an M-dwarf flare.

Kunal Mooley (NRAO, Caltech; Jansky Fellow), Steve Myers, Dale Frail 
(NRAO), Alessandra Corsi, Arvind Balasubramanian, Deven Bhakta (TTU), 
Gregg Hallinan, Shri Kulkarni (Caltech), report on behalf of the JAGWAR team

We have initiated deep C band (4-8 GHz) multi-epoch observations of the 
1-sigma containment region (0.3 sq deg; HAWC Collaboration, GCN 25333
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 ) 
coincident with the GW event S191216ap with the Karl G. Jansky Very 
Large Array. A total of 37 pointings (7 arcmin FWHM primary beam at 6 
GHz; pointing coordinates given below), observed as part of the JAGWAR 
program, will achieve a uniform RMS noise of ~8 uJy over the survey 
region. We will report any radio transients found through the GCN system.

Ra, Dec of the VLA C band pointings:
21:33:11.42�� +05:08:26.36
21:33:00.22�� +05:14:02.38
21:33:11.42�� +05:19:38.36
21:33:33.82�� +04:57:14.34
21:33:22.62�� +05:02:50.35
21:33:33.82�� +05:08:26.34
21:33:22.62�� +05:14:02.35
21:33:33.82�� +05:19:38.34
21:33:22.62�� +05:25:14.35
21:33:33.83�� +05:30:50.34
21:33:56.22�� +04:57:14.31
21:33:45.02�� +05:02:50.33
21:33:56.22�� +05:08:26.31
21:33:45.02�� +05:14:02.32
21:33:56.22�� +05:19:38.31
21:33:45.02�� +05:25:14.32
21:33:56.23�� +05:30:50.31
21:34:18.62�� +04:57:14.29
21:34:07.42�� +05:02:50.30
21:34:18.62�� +05:08:26.29
21:34:07.42�� +05:14:02.30
21:34:18.62�� +05:19:38.29
21:34:07.43�� +05:25:14.30
21:34:18.63�� +05:30:50.29
21:34:41.02�� +04:57:14.26
21:34:29.82�� +05:02:50.27
21:34:41.02�� +05:08:26.26
21:34:29.82�� +05:14:02.27
21:34:41.03�� +05:19:38.26
21:34:29.83�� +05:25:14.27
21:34:41.03�� +05:30:50.26
21:34:52.22�� +05:02:50.25
21:35:03.42�� +05:08:26.23
21:34:52.22�� +05:14:02.25
21:35:03.43�� +05:19:38.23
21:34:52.23�� +05:25:14.25
21:35:14.63�� +05:14:02.22

We thank the NRAO staff for scheduling and executing these observations.

Kunal Mooley (NRAO, Caltech; Jansky Fellow), Steve Myers, Dale Frail 
(NRAO), Gregg Hallinan, Shri Kulkarni, Mansi Kasliwal (Caltech), 
Alessandra Corsi (TTU), Leo Singer (GSFC) report on behalf of the JAGWAR 
team

We observed the 9 GLADE galaxies (Singer et al. GCN 26479
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 ) consistent 
with the HAWC/gamma-ray (Martinez-Castellanos et al. GCN 26472
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 ) and 
S191216ap/BAYESTAR localization volume (Piotrzkowski et al. GCN 26454
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 ) 
with the VLA between 4-8 GHz on 2019 Dec 18-19. No point-like sources 
are detected within 50 kpc of any of the galaxies down to 20 uJy 
(3sigma), except many of the galaxies have radio sources coincident with 
their nuclei (see table below). Follow up VLA observations are planned.

| RAJ2000������ | DEJ2000���� | Dist�� | Flux_6GHz| Comments
| deg�������������� | deg������������ | Mpc���� | uJy���������� |
| ---------- | --------- | ----- | -------- | --------------------
| 323.482422 | +5.279632 | 274.4 | 820���������� | unresolved (12" beam)
| 323.056030 | +4.832057 | 219.1 | 370���������� | marginally resolved
| 322.921936 | +5.503483 | 232.2 | 80������������ | resolved
| 322.838806 | +5.255421 | 179.3 | 140���������� | unresolved
| 322.821228 | +5.553754 | 338.7 | 180���������� | unresolved **
| 322.749084 | +5.108610 | 330.8 | 155���������� | unresolved **
| 323.173767 | +4.467985 | 292.5 | <20 �������� |
| 322.906006 | +5.850705 | 323.1 | <15���������� |
| 323.034882 | +4.482058 | 340.7 | <20���������� | **

(**) We note that only these 3 galaxies (Ahumada et al. GCN 26507
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 ) lie 
within the 95% 3D credible volume in the latest LALInference map 
(Piotrzkowski et al. GCN 26505
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 ) for S191216ap.

We thank the NRAO staff for scheduling and executing these observations.

V. Lipunov,  E. Gorbovskoy, V.Kornilov, N.Tyurina, P.Balanutsa,A.Kuznetsov,F.Balakin, K.Zhirkov,
V.Vladimirov, D. Vlasenko, I.Gorbunov, D.Zimnukhov, V.Senik, T.Pogrosheva, A.Chasovnikov, 
D.Kuvshinov (Lomonosov Moscow State University, SAI, Physics Department),
O.A. Gres, N.M. Budnev, O.Ershova (Irkutsk State University, API),
R. Podesta, C.Lopez, F. Podesta, C.Francile(Observatorio Astronomico FelixAguilar OAFA),
H.Levato(Instituto de Ciencias Astronomicas, de la Tierra y del Espacio ICATE),
R. Rebolo, M. Serra(The Instituto de Astrofisica de Canarias),
D. Buckley(South African Astronomical Observatory),
V. Yurkov, A. Gabovich, Yu. Sergienko(Blagoveschensk Educational State University)
A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory),

MASTER covered 812 square degrees of S191216ap
( MassGap (>99%); 324+/-78Mpc LVC GCN 26454
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 , Lipunov et al. GCN 26457
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 , GCN 26474
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 ;
Barthelmy collection https://gcn.gsfc.nasa.gov/other/S191216ap.gcn3)
  that is equal to 92% of full error-box
https://master.sai.msu.ru/site/master2/ligo_1.php?id=11073

We report MASTER observation of the galaxies cross-matched with LVC and HAWC localization (Singer et al. GCN 26479
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 )
without OT detection with the following limits:

Galaxy_Coordinates   MASTER_first_image_UT    mlim (unfiltered) MASTER_observatory
323.482422 +5.279632 2019-12-17 09:53:01      17.0 MASTER-Amur
                      2019-12-17 10:54:13      18.6 MASTER-Tunka
                      2019-12-17 15:53:25      18.6 MASTER-Kislovodsk

323.056030 +4.832057 2019-12-17 09:41:42 17.3 MASTER-Amur
                      2019-12-17 12:09:47 18.6 MASTER-Tunka
                      2019-12-20 15:39:40 18.6 MASTER-Tavrida

322.921936 +5.503483 2019-12-17 09:53:01 17.0  MASTER-Amur
 		     2019-12-17 10:54:13 18.3  MASTER-Tunka
                      2019-12-20 15:39:40 18.6  MASTER-Tavrida
                      2019-12-18 16:40:44 18.5  MASTER-Kislovodsk

322.838806 +5.255421 2019-12-17 09:53:01 17.0 MASTER-Amur
                      2019-12-17 12:09:47 18.6 MASTER-Tunka
                      2019-12-17 15:53:25 18.6 MASTER-Kislovodsk
                      2019-12-20 15:39:40 18.6 MASTER-Kislovodsk

322.821228 +5.553754 2019-12-17 09:53:01 17.0 MASTER-Amur
                      2019-12-17 10:54:13 18.3 MASTER-Tunka
                      2019-12-20 15:39:40 18.6 MASTER-Tavrida

322.749084 +5.108610 2019-12-17 09:53:01 17.0 MASTER-Amur
                      2019-12-17 12:09:47 18.6 MASTER-Tunka
                      2019-12-17 15:32:09 19.6 MASTER-Tavrida
                      2019-12-18 15:54:04 20.0 MASTER-Tavrida

323.173767 +4.467985 2019-12-17 09:41:42 17.3 MASTER-Amur
                      2019-12-17 15:53:25 18.6 MASTER-Kislovodsk
                      2019-12-20 15:39:40 18.6 MASTER-Tavrida

322.906006 +5.850705 2019-12-17 09:53:01 17.0 MASTER-Amur
                      2019-12-17 10:54:13 18.3 MASTER-Tunka
                      2019-12-17 16:30:37 18.5 MASTER-Kislovodsk
                      2019-12-20 15:39:40 18.6 MASTER-Tavrida

323.034882 +4.482058 2019-12-17 09:41:42 17.3 MASTER-Amur
                      2019-12-17 15:53:25 18.6 MASTER-Tunka
                      2019-12-20 15:39:40 18.6 MASTER-Tavrida

The analysys will be continued.
The message may be cited.

P.A. Duverne (LAL), S. Agayeva (SHAO), M. Blazek (HETH/IAA-CSIC), M.
Masek (FZU), S. Karpov, M. Prouza (FZU), M. Boer (Artemis),
N. Christensen (Artemis), L. Eymar (Artemis), A. Klotz (IRAP),
K. Noysena (Artemis,IRAP), S. Antier (APC), A. Coleiro (APC),
D. Corre (LAL), M. Coughlin (Caltech), D. Coward (OzGrav-UWA),
J.G. Ducoin (LAL), B. Gendre (OzGrav-UWA), P. Hello (LAL),
D. A. Kann (HETH/IAA-CSIC), N. Kochiashvili (Iliauni),
C. Lachaud (APC), N. Leroy (LAL), C. Thoene (HETH/IAA-CSIC),
D. Turpin (AIM-CEA), X. Wang (THU)

report on behalf of the FRAM, TAROT and GRANDMA collaborations.

We performed tiled observations of LIGO/Virgo S191216ap event
(#GCN 26454) with the FRAM-Auger, FRAM-CTA-N, TAROT-Calern (TCA),
TAROT-Chili (TCH) telescopes.

FRAM-Auger is located at Pierre Auger Observatory. FRAM-CTA-N is
located at Observatorio del Roque de los Muchachos. TCA is located at
Calern site at the Cote d'Azur observatory. TCH is located at La Silla
  ESO observatory (LaS/ESO).

+-------------+---------+----------+-------------+------------+
| Telescope   | Delay   | Filter   | f.o.v.      | Limiting   |
|             | [min]   |          | [deg]       | Mag.       |
|-------------+---------+----------+-------------+------------|
| FRAM-Auger  | 228     | R        | 1.0 x 1.0   | 18.0 (60s) |
| FRAM-CTA-N  | 1296    | R        | 0.45 x 0.45 | 17.0 (90s) |
| TCA         | 1166    | Clear    | 1.9 x 1.9   | 18.0 (60s) |
| TCH         | 1658    | Clear    | 1.9 x 1.9   | 18.0 (60s) |
+-------------+---------+----------+-------------+------------+

We performed the following joint tiled observations [1] :

+-------------+------------+------------+---------+---------+---------+
| Telescope   | TStart     | TEnd       | RA      | DEC     | Proba   |
|             | [UTC]      | [UTC]      | [deg]   | [deg]   | [%]     |
|-------------+------------+------------+---------+---------+---------|
| FRAM-Auger  | 2019-12-17 | 2019-12-17 | 321.186 | -1.460  | 0.3     |
|             | 01:20:58   | 01:22:58   |         |         |         |
| FRAM-Auger  | 2019-12-17 | 2019-12-17 | 321.081 | -2.432  | 0.2     |
|             | 01:25:12   | 01:29:39   |         |         |         |
| FRAM-Auger  | 2019-12-17 | 2019-12-17 | 321.081 | -3.405  | 0.2     |
|             | 01:31:14   | 01:33:14   |         |         |         |
| FRAM-Auger  | 2019-12-17 | 2019-12-17 | 320.976 | -5.351  | 0.2     |
|             | 01:48:45   | 01:53:12   |         |         |         |
| FRAM-Auger  | 2019-12-17 | 2019-12-17 | 320.763 | -8.270  | 0.3     |
|             | 01:54:07   | 01:58:34   |         |         |         |
| FRAM-Auger  | 2019-12-17 | 2019-12-17 | 320.870 | -6.324  | 0.2     |
|             | 01:59:16   | 02:03:43   |         |         |         |
| FRAM-Auger  | 2019-12-17 | 2019-12-17 | 321.744 | -8.270  | 0.2     |
|             | 02:04:34   | 02:09:01   |         |         |         |
| FRAM-Auger  | 2019-12-17 | 2019-12-17 | 321.534 | -10.216 | 0.2     |
|             | 02:19:59   | 02:24:26   |         |         |         |
| -----       | -----      | -----      | -----   | -----   | -----   |
| FRAM-CTA-N  | 2019-12-17 | 2019-12-17 | 318.536 | 27.312  | 0.2     |
|             | 19:09:06   | 19:13:12   |         |         |         |
| FRAM-CTA-N  | 2019-12-17 | 2019-12-17 | 318.365 | 27.749  | 0.2     |
|             | 19:13:31   | 19:17:37   |         |         |         |
| FRAM-CTA-N  | 2019-12-17 | 2019-12-17 | 318.668 | 25.565  | 0.2     |
|             | 19:17:52   | 19:21:58   |         |         |         |
| FRAM-CTA-N  | 2019-12-17 | 2019-12-17 | 318.045 | 27.312  | 0.2     |
|             | 19:22:14   | 19:26:20   |         |         |         |
| FRAM-CTA-N  | 2019-12-17 | 2019-12-17 | 319.110 | 24.254  | 0.2     |
|             | 19:26:36   | 19:30:42   |         |         |         |
| FRAM-CTA-N  | 2019-12-17 | 2019-12-17 | 319.184 | 25.565  | 0.2     |
|             | 19:31:02   | 19:35:08   |         |         |         |
| FRAM-CTA-N  | 2019-12-17 | 2019-12-17 | 317.209 | 31.681  | 0.2     |
|             | 19:35:24   | 19:39:30   |         |         |         |
| FRAM-CTA-N  | 2019-12-17 | 2019-12-17 | 317.126 | 30.808  | 0.2     |
|             | 19:39:45   | 19:43:51   |         |         |         |
| FRAM-CTA-N  | 2019-12-17 | 2019-12-17 | 317.025 | 32.118  | 0.2     |
|             | 19:44:05   | 19:48:11   |         |         |         |
| FRAM-CTA-N  | 2019-12-17 | 2019-12-17 | 317.392 | 31.244  | 0.2     |
|             | 19:48:30   | 19:52:36   |         |         |         |
| FRAM-CTA-N  | 2019-12-17 | 2019-12-17 | 316.777 | 32.555  | 0.2     |
|             | 19:52:51   | 19:56:57   |         |         |         |
| FRAM-CTA-N  | 2019-12-17 | 2019-12-17 | 318.192 | 28.186  | 0.2     |
|             | 19:57:14   | 20:01:20   |         |         |         |
| FRAM-CTA-N  | 2019-12-17 | 2019-12-17 | 318.018 | 28.623  | 0.2     |
|             | 20:01:34   | 20:05:40   |         |         |         |
| FRAM-CTA-N  | 2019-12-17 | 2019-12-17 | 319.864 | 19.885  | 0.2     |
|             | 20:06:02   | 20:10:08   |         |         |         |
| FRAM-CTA-N  | 2019-12-17 | 2019-12-17 | 316.589 | 32.992  | 0.2     |
|             | 20:10:30   | 20:14:36   |         |         |         |
| FRAM-CTA-N  | 2019-12-17 | 2019-12-17 | 317.843 | 29.060  | 0.2     |
|             | 20:14:54   | 20:19:00   |         |         |         |
| FRAM-CTA-N  | 2019-12-17 | 2019-12-17 | 317.717 | 29.497  | 0.2     |
|             | 20:19:13   | 20:23:19   |         |         |         |
| FRAM-CTA-N  | 2019-12-17 | 2019-12-17 | 319.616 | 24.254  | 0.1     |
|             | 20:23:36   | 20:27:42   |         |         |         |
| FRAM-CTA-N  | 2019-12-17 | 2019-12-17 | 317.308 | 30.371  | 0.2     |
|             | 20:27:58   | 20:32:04   |         |         |         |
| FRAM-CTA-N  | 2019-12-17 | 2019-12-17 | 317.488 | 29.934  | 0.2     |
|             | 20:32:24   | 20:36:30   |         |         |         |
| -----       | -----      | -----      | -----   | -----   | -----   |
| TCA         | 2019-12-17 | 2019-12-18 | 316.229 | 35.280  | 2.9     |
|             | 16:59:02   | 20:11:43   |         |         |         |
| TCA         | 2019-12-17 | 2019-12-20 | 317.995 | 26.002  | 2.5     |
|             | 18:07:04   | 18:43:14   |         |         |         |
| TCA         | 2019-12-17 | 2019-12-20 | 313.891 | 38.991  | 3.1     |
|             | 18:13:50   | 18:49:58   |         |         |         |
| TCA         | 2019-12-18 | 2019-12-18 | 315.090 | 37.136  | 3.2     |
|             | 19:13:09   | 19:19:31   |         |         |         |
| TCA         | 2019-12-20 | 2019-12-20 | 317.502 | 27.857  | 2.7     |
|             | 18:17:44   | 18:24:03   |         |         |         |
| TCA         | 2019-12-20 | 2019-12-20 | 318.715 | 24.146  | 2.4     |
|             | 18:24:28   | 18:30:47   |         |         |         |
| TCA         | 2019-12-20 | 2019-12-20 | 317.048 | 33.424  | 2.6     |
|             | 18:51:09   | 18:57:29   |         |         |         |
| TCA         | 2019-12-20 | 2019-12-20 | 315.950 | 31.569  | 2.4     |
|             | 19:02:54   | 19:09:13   |         |         |         |
| TCA         | 2019-12-20 | 2019-12-20 | 312.628 | 40.847  | 2.7     |
|             | 19:09:35   | 19:11:35   |         |         |         |
| TCA         | 2019-12-20 | 2019-12-20 | 319.571 | 27.857  | 1.3     |
|             | 19:33:09   | 19:35:09   |         |         |         |
| TCA         | 2019-12-20 | 2019-12-20 | 314.852 | 33.424  | 1.9     |
|             | 19:39:53   | 19:41:53   |         |         |         |
| TCA         | 2019-12-20 | 2019-12-20 | 313.993 | 35.280  | 1.6     |
|             | 19:48:00   | 19:54:19   |         |         |         |
| TCA         | 2019-12-20 | 2019-12-20 | 309.886 | 44.558  | 2.1     |
|             | 19:54:45   | 20:01:04   |         |         |         |
| TCA         | 2019-12-20 | 2019-12-20 | 320.726 | 23.671  | 0.7     |
|             | 20:01:29   | 20:07:49   |         |         |         |
| -----       | -----      | -----      | -----   | -----   | -----   |
| TCH         | 2019-12-18 | 2019-12-18 | 319.592 | -9.050  | 0.2     |
|             | 01:11:08   | 01:17:27   |         |         |         |
| TCH         | 2019-12-18 | 2019-12-18 | 319.385 | -10.868 | 0.2     |
|             | 01:17:52   | 01:24:10   |         |         |         |
| TCH         | 2019-12-21 | 2019-12-21 | 319.797 | -7.232  | 0.3     |
|             | 01:34:12   | 01:38:21   |         |         |         |
+-------------+------------+------------+---------+---------+---------+

TStart and TEnd refers respectively to the time of the first and last
exposure for a given tile. Observations are not necessarily continuous
  in this interval.
The Probability refers to the 2D spatial probability of the GW skymap
enclosed in a given tile.

These observations cover about 35.4% of the cumulative probability of
the LALInference skymap created on 2019-12-19 17:30:31 (UTC).

The coverage map is available at:
https://grandma-owncloud.lal.in2p3.fr/index.php/s/XgtMhPRxcyL09gR/
download?path=%2F&files=GRANDMA_S191216ap_1576913351.png


No significant transient candidates were found during our low latency
analysis [2,3].

GRANDMA (Global Rapid Advanced Network Devoted to the Multi-messenger
Addicts) is a network of robotic telescopes connected all over the
world with both photometry and spectrometry capabilities for Time-
domain Astronomy [2](https://grandma.lal.in2p3.fr/).
Details on the different telescopes are available on the GRANDMA web
pages.

[1] M. W Coughlin et al., MNRAS 2019, https://doi.org/10.1093/mnras/stz2485
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[2] S. Antier et al., MNRAS 2019, https://doi.org/10.1093/mnras/stz3142
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[3] K. Noysena et al., ApJ 2019, arXiv:1910.02770
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V. Shenoy (IITB), Aarthy E. (PRL), V. Bhalerao (IITB), D. Bhattacharya (IUCAA), A. R. Rao (TIFR), S. Vadawale (PRL) report on behalf of the AstroSat CZTI collaboration:

We have carried a search for X-ray candidates in Astrosat CZTI data in a 100 sec window around the trigger time of the MassGap merger event S191216ap (UTC 2019-12-16 21:33:38, GraceDB event). CZTI is a coded aperture mask instrument that has considerable effective area for about 29% of the entire sky, but is also sensitive to brighter transients from the entire sky. At the time of merger, Astrosat's nominal pointing is RA,DEC = 08:19:21.4,70:39:40.4 (124.8392,70.6612), which is ~79 deg away from the maximum probability location, which severely reduces the effective area of CZTI. At the time of merger event, the Earth-satellite-transient angle corresponding to maximum probability location is ~ 151 deg and hence is not occulted by Earth in satellite's frame. In a time interval of 100 sec around the event, the region of the LALInference map (LVC GCN 26505
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 ) which is not occulted by Earth in the satellite's frame has a cumulative probability of 1.0 (100%).

CZTI data were de-trended to remove orbit-wise background variation. We then searched data from the four independent, identical quadrants to look for coincident spikes in the count rates. Searches were undertaken by binning the data in 0.1s, 1s, and 10s respectively. Statistical fluctuations in background count rates were estimated by using data from 10 (+-5) neighbouring orbits. We selected confidence levels such that the probability of a false trigger in a 1000 sec window is 10^-4. We do not find any evidence for any hard X-ray transient in this window, in the CZTI energy range of 20-200 keV.

We use a detailed mass model of the satellite to calculate the direction-dependent instrument response for points in the visible sky. We then assume the source is modelled as a power law with photon index alpha = -1, and convert our count rate upper limits to direction-dependent flux limits. We obtain the following upper limits for source flux in the 20-200 keV band by taking a probability weighted mean over the visible sky:

0.1 s: flux limit= 3.69e-05 ergs/cm^2/s; fluence limit = 3.69e-06 ergs/cm^2
1.0 s: flux limit= 1.09e-05 ergs/cm^2/s; fluence limit = 1.09e-05 ergs/cm^2
10.0 s: flux limit= 1.61e-06 ergs/cm^2/s; fluence limit = 1.61e-05 ergs/cm^2

CZTI is built by a TIFR-led consortium of institutes across India, including VSSC, ISAC, IUCAA, SAC and PRL. The Indian Space Research Organisation funded, managed and facilitated the project.

T. Ohgami, N. Tominaga (Konan U.), R. Ohsawa, Y. Niino, T. Morokuma (U. Tokyo),  T. Terai, Y. Takagi, K. Yanagisawa, M. Yoshida (NAOJ), M. Sasada (Hiroshima U.), M. Tanaka (Tohoku U.), Y. Sekiguchi (Toho U.), Y. Utsumi (Stanford/SLAC) on behalf of J-GEM collaboration

Following detections of S191216ap by LIGO-Virgo (Piotrzkowski et al., GCN Circ. 26454
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 , 26505
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 ) and possible related events by IceCube (Hussain et al., CGN Circ. 26460) and by HAWC (Martinez-Castellano et al., GCN Circ. 26472
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 ), we selected a galaxy, GL213356+051647 (ra, dec = 323.4824, 5.2796 at 274.42 Mpc), from our candidate selection algorithm based on the GLADE v2.3 catalog (Dalya et al., 2018) and the localization maps. Our candidate galaxy is also ranked as the top candidate in Singer et al. (GCN Circ. 26479
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 ).

Using a 1.5 deg circular aperture of Subaru/Hyper Suprime-Cam which covers the HAWC's 68% credible region, we imaged a region around GL213356+051647 with an integration time of 2730 sec for z-band, starting from 2019-12-20 05:06 UT. An estimated limiting magnitude is 25.5. We found no apparent transient associated with GL213356+051647. More detailed analysis is ongoing, and further follow-up observations are planned.

We thank Subaru's staff for making this observation.

T. Ahumada (UMD), S. Anand (Caltech), and L.P. Singer (NASA-GSFC)�report on behalf of the GROWTH collaboration:

Based on the new LALInference map (GCN 26505
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 ), we re-ran our galaxy cross-match from GCN 26479
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  with the HAWC position (GCN 26472
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 )and the GLADE v2.3 catalog (Dalya et al., 2018), to identify sources within the 90% LIGO/Virgo credible volume and within a 3-sigma radius of the HAWC candidate. Our updated search yields only three matching galaxies, which were in our previously reported list of galaxies (GCN 26479
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 ). All of the galaxies in our previous list are within the 95% 3D credible level in the LALInference map; we report only those galaxies still within the 90% 3D credible level.

The distance parameters from the LALInference localization at the
position of the HAWC candidate are DISTMU= 272.35 Mpc and DISTSIGMA= 44.52 Mpc.

In the table below, we give the right ascensions and declinations in
degrees and luminosity distances in Mpc. The "GW C.L." column
provides the LIGO/Virgo 3D credible level within which the galaxy is
found (smaller values mean more consistent with the GW position). The
"HAWC sigma" column gives the separation from the HAWC position,
divided by the HAWC 1-sigma error radius.

| RAJ2000 � �| DEJ2000 � | Dist �| GW C.L. | HAWC sigma |
| ---------- | --------- | ----- |-------- | ---------- |
| 322.821228 | +5.553754 | 338.7 | 81 � � �| 2.59 � � � |
| 322.749084 | +5.108610 | 330.8 | 78 � � �| 2.62 � � � |
| 323.034882 | +4.482058 | 340.7 | 86 � � �| 2.99 � � � |

GROWTH is a worldwide collaboration comprising of Caltech, USA; IPAC,
USA; WIS, Israel; OKC, Sweden; JSI/UMD, USA; U Washington, USA; DESY,
Germany; MOST, Taiwan; UW Milwaukee, USA; LANL USA; Tokyo Tech,
Japan; IITB, India; IIA, India; LJMU, UK; TTU, USA; SDSU, USA and
USyd, Australia. ZTF acknowledges the generous support of the NSF
under AST MSIP Grant No 1440341. GROWTH acknowledges generous support
of the NSF under PIRE Grant No 1545949.

The LIGO Scientific Collaboration and the Virgo Collaboration report:

We have conducted further analysis of the LIGO Hanford Observatory
(H1) and Virgo Observatory (V1) data around the time of the compact
binary merger (CBC) candidate S191216ap (GCN Circular
26454
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 ). Parameter estimation has been performed using
LALInference [1] and a new sky map, LALInference.fits.gz,0,
distributed via GCN Notice, is available for retrieval from the
GraceDB event page:

https://gracedb.ligo.org/superevents/S191216ap

The preferred sky map at this time is LALInference.fits.gz,0. For the
LALInference.fits.gz,0 sky map, the 90% credible region is 253 deg2.
Marginalized over the whole sky, the a posteriori luminosity distance
estimate is 376 +/- 70 Mpc (a posteriori mean +/- standard deviation).

For further information about analysis methodology and the contents of
this alert, refer to the LIGO/Virgo Public Alerts User Guide
<https://emfollow.docs.ligo.org/userguide/>.

 [1] Veitch et al. PRD 91, 042003 (2015)

P.A. Evans (U. Leicester), J.A. Kennea (PSU), A. Tohuvavohu (U.
Toronto), S.D. Barthelmy (NASA/GSFC), A.P. Beardmore (U. Leicester),
M.G. Bernardini (INAF-OAB), A.A. Breeveld (UCL-MSSL), P. Brown (TAMU),
D.N. Burrows (PSU), S. Campana (INAF-OAB), S.B. Cenko (NASA/GSFC), G.
Cusumano (INAF-IASF PA), A. D'Ai (INAF-IASFPA), P. D'Avanzo (INAF-OAB),
V. D'Elia(ASDC), S.W.K. Emery (UCL-MSSL), P. Giommi (ASI), C. Gronwall
(PSU), D. Hartmann (U. Clemson), H.A. Krimm (CRESST/GSFC/USRA), N.J.
Klingler (PSU), N.P.M. Kuin (UCL-MSSL), A.Y. Lien (GSFC/UMBC), F.E.
Marshall (NASA/GSFC), A. Melandri (INAF-OAB), J.A. Nousek (PSU), S.R.
Oates (U. Birmingham), P.T. O'Brien (U. Leicester), J.P. Osborne (U.
Leicester), C. Pagani (U. Leicester), K.L. Page (U.Leicester), M.J.Page
(UCL-MSSL), D.M. Palmer (LANL), M. Perri (ASDC), J.L. Racusin
(NASA/GSFC), B. Sbarufatti (INAF-OAB/PSU), M.H. Siegel (PSU), G.
Tagliaferri (INAF-OAB), E. Troja (NASA/GSFC/UMCP) report on behalf of
the Swift team:

Swift has carried out further observations of S191216ap. We performed a
series of tiles to cover the HAWC error region (GCN Circ. 26472
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 ) for
500 s per tile, and then 3ks observations of each of the galaxies
listed by Singer et al (GCN Circ. 26479
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 ). All of the Swift pointings
and associated metadata have been reported to the Treasure Map (Wyatt
et al., GCN Circ. 26244
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 ;
http://treasuremap.space/alerts?graceids=S191216ap).

In these observations, we detected 17 X-ray sources, these are either
new detections, or have been given a higher 'rank' than in the last
circular. Each source is assigned a rank of 1-4 which describes how
likely it is to be related to the GW trigger, with 1 being the most
likely and 4 being the least likely. The ranks are described at
https://www.swift.ac.uk/ranks.php.

We have found:

  * 0 sources of rank 1
  * 0 sources of rank 2
  * 13 sources of rank 3
  * 4 sources of rank 4


RANK 3 sources
==============

These are uncatalogued X-ray sources, however they are not brighter
than previous upper limits, so do not stand out as likely counterparts
to the GW trigger.

| Source ID	 | RA		  | Dec 	   | Err90   |
|  S191216ap_X4  | 21h 33m 49.19s | +04d 57' 18.9" |	6.7" |
|  S191216ap_X5  | 21h 33m 18.81s | +05d 17' 04.9" |	6.9" |
|  S191216ap_X6  | 21h 34m 53.19s | +05d 19' 11.0" |	6.6" |
|  S191216ap_X7  | 21h 32m 44.20s | +04d 20' 06.0" |	5.8" |
|  S191216ap_X8  | 21h 32m 47.89s | +04d 27' 52.2" |	5.5" |
|  S191216ap_X9  | 21h 32m 26.75s | +04d 21' 31.6" |	5.3" |
| S191216ap_X10  |  21h 32m 6.50s | +04d 18' 38.2" |	6.9" |
| S191216ap_X12  | 21h 31m 46.59s | +05d 44' 44.4" |	7.0" |
| S191216ap_X13  | 21h 31m 56.80s | +05d 11' 22.4" |	8.0" |
| S191216ap_X17  | 21h 31m 43.77s | +05d 25' 15.7" |	6.0" |
| S191216ap_X19  | 21h 31m 57.63s | +04d 43' 38.4" |	7.4" |
| S191216ap_X20  | 21h 31m 31.98s | +04d 54' 03.0" |	5.0" |
| S191216ap_X21  | 21h 31m 44.49s | +05d 23' 12.0" |	7.4" |


RANK 4 sources
==============

These are catalogued X-ray sources, showing no signs of outburst
compared to previous observations, so they are not likely to be related
to the GW trigger.

| Source ID	 | RA		  | Dec 	   | Err90   |
| S191216ap_X11  | 21h 32m 41.01s | +04d 24' 18.6" |	6.2" |
| S191216ap_X14  | 21h 30m 32.91s | +05d 02' 18.4" |	7.6" |
| S191216ap_X15  | 21h 30m 26.31s | +05d 06' 07.0" |	7.2" |
| S191216ap_X16  | 21h 31m 22.64s | +05d 02' 37.5" |	5.4" |

For all flux conversions and comparisons with catalogues and upper
limits from other missions, we assumed a power-law spectrum with
NH=3x10^20 cm^-2, and photon index (Gamma)=1.7

The results of the XRT automated analysis, including details of the
sources listed above, are online at
https://www.swift.ac.uk/LVC/S191216ap

This circular is an official product of the Swift XRT team.

Yanagisawa, K.; Yoshida, M. (NAOJ); Onozato, H.; Takahashi, J. (U. Hyogo); Itoh, R. (Bisei Astronomical observatory); Takarada, T. (Saitama U.); Sasada, M. (Hiroshima U.); Utsumi, Y. (Stanford/SLAC); Toma, S.; Adachi, R.; Murata, K. L. (Tokyo Tech.) 
on behalf of J-GEM collaboration

Following detections of the LIGO-Virgo (S191216ap; Piotrzkowski, GCN Circ. 26454
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 ), IceCube (Hussain, CGN Circ. 26460) and HAWC (Martinez-Castellano, GCN Circ. 26472
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 ), we performed imaging observations of a galaxy, GL213356+051647, selected from our candidate selection algorithm based on the GLADE v2.3 catalog (Dalya et al., 2018) and those localizations. Our candidate galaxy is also ranked as the top candidate in Singer, GCN Circ. 26479
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 . We started our observations from 2019-12-18 08:11 UT (MJD=58835.34) and ended at 2019-12-18 10:27 UT (MJD=58835.44).

We found no apparent transient objects in these galaxies to 5 sigma limiting magnitudes in the AB system listed below.

    galid         ra     dec    dist   J    H    Ks   Ic   g$B!G(B   Rc                   obsid                  
--------------- -------- ------ ------ ---- ---- ---- ---- ---- ---- ----------------------------------------
GL213356+051647 323.4824 5.2796 274.42 17.8 18.3 18.1 18.5 16.5 17.0 OAOWFC,Nayuta-NIC,BAO101cm,MITSuME-Akeno

BAO101cm: 101 cm telescope at Bisei Astronomical Observatory and CCD optical camera (Ic)
MITSuME-Akeno: 50 cm MITSuME telescope at Akeno Observatory and a 3 color imager (g$B!G(B, Rc, Ic)
Nayuta-NIC: 200 cm Nayuta telescope at Nishi-Harima Astronomical Observatory and Nishiharima Infrared Camera, NIC (J, H, Ks)
OAOWFC: 91 cm Okayama Astrophysical Observatory NIR Wide Field Camera, OAOWFC (J) (Yanagisawa et al., 2019, PASJ, 71, 118)

D. Xu (NAOC) reports:

We note that the name of the GW event in the title of GCN 26488
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  should 
not be S191213g. It should be S191216ap instead. Sorry for any 
inconveniences.

Tianrui Sun, Chen Zhang, Yiding Ping, Xuefeng Wu.(PMO).

We observed the corrected list of galaxies coincident with LIGO/Virgo and HAWC positions by Leo Singer (GCN 26479
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 ).

The observation used the 80cm telescope with the FOV of 2x2 deg^2 of the CHanging Event Survey at the YaoAn observation station(101.1811E, 25.528N) in Yunnan Province, China. 
Our observations started at 12:04:04UT and ends at 12:55:05UT Dec 18, 2019, with 11 exposure 60 seconds in white filter.

Our results for these galaxies:
| RA               | DEC         |  Mag(White) | SDSS(r)    |
| 323.482422 | 5.279632 |  16.42      | 16.50    |
| 323.056030 | 4.832057 |  15.94      | 15.83    |
| 322.921936 | 5.503483 |  15.70      | 15.57    |
| 322.838806 | 5.255421 |  15.60      | 15.41    |
| 322.821228 | 5.553754 |  15.64      | 15.83    |
| 323.173767 | 4.467985 |  16.09      | 16.10    |
| 322.906006 | 5.850705 |  16.69      | 16.84    |
| 323.034882 | 4.482058 |  16.27      | 16.24    |

And the observations of CHES:
Date-obs             RA       DEC    MAG   FWHM
2019-12-18T12:04:04  323.1053 5.3952 18.07 3.67 
2019-12-18T12:07:48  323.6028 6.0834 17.92 4.18 
2019-12-18T12:19:03  323.1023 6.0505 18.08 3.61 
2019-12-18T12:20:11  323.1023 6.0507 18.05 3.71 
2019-12-18T12:21:26  323.2811 4.3005 17.98 3.83 
2019-12-18T12:23:49  323.1022 6.0512 18.02 3.68 
2019-12-18T12:24:57  323.1023 6.0515 18.03 3.68 
2019-12-18T12:51:43  323.4745 5.3269 17.94 3.87 
2019-12-18T12:53:58  323.4746 5.3273 17.91 3.96
2019-12-18T12:55:05  323.4746 5.3273 17.90 3.96 
2019-12-18T12:09:03  323.7238 5.8421 17.43 5.50 

We did not detect any candidate source related to these galaxies in 5 sigma limit at 18.86 (median combined) generated from G band in  Gaia DR2.

F. Verrecchia (SSDC, and INAF/OAR), M. Tavani (INAF/IAPS, and Univ. Roma
Tor Vergata), M. Cardillo, A. Ursi, C. Casentini, G. Piano (INAF/IAPS),
F. Lucarelli, C. Pittori (SSDC, and INAF/OAR), M. Pilia
(INAF/OA-Cagliari), A. Bulgarelli, V. Fioretti, N. Parmiggiani
(INAF/OAS-Bologna), F. Longo (Univ. Trieste, and INFN Trieste), report on
behalf of the AGILE Team:

In response to the LIGO-Virgo GW event S191216ap at T0 = 2019-12-16
21:33:38.473 UTC and the candidate IceCube neutrino (GCN Circ. 26463
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 ),
an analysis of the AGILE exposure at T0 shows that both the GW
localization region (LR) and neutrino error circle (EC) were occulted by
the Earth.

We performed an analysis of the GRID data over time intervals before and
after T0, when good exposures of the S191216ap LR and neutrino EC were
available.

No candidate gamma-ray transient was detected.

The following preliminary GRID values of 3-sigma upper limits (ULs) in
the 100 MeV - 10 GeV energy band are obtained over the neutrino position:

- 6.9e-11 erg cm^-2 s^-1, with exposure over the time interval
(T0 - 3 days; T0);
- 4.6e-11 erg cm^-2 s^-1, with exposure over the time interval
(T0 - 7 days; T0).

As the S191216ap LR became visible, we obtained the following preliminary
GRID values of 3-sigma ULs:

from 7.7e-08 to 3.9e-07 erg cm^-2 s^-1, with exposure of about 80% of the
LR over the time interval (T0 + 1.6ks ; T0 + 1.8ks);

These measurements were obtained with AGILE observing a large portion of
the sky in spinning mode. Additional analysis of AGILE data is in
progress.

A. Rossi, M. Dadina, E. Maiorano, R. Gualandi (INAF-OAS), P. D'Avanzo, A. Melandri (INAF-OABr), M.T. Botticella (INAF-OAC), and E. Brocato (INAF-Abruzzo) report on behalf of GRAWITA

We observed the inner part of the error box obtained by the HAWC collaboration (Martinez-Castellano GCN #26472
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 ) during the follow-up of the GW trigger S191216ap (GCN #26454
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 ) with the 152cm Cassini Telescope at Loiano Observatory. The pointing was performed using the R filter. Four 10min exposures have been obtained starting at 18:12:29 on 2019-12-17 (UT), covering a mosaic of ~20'x20'. The observation was affected by bad seeing (4"), low elevation, and passing clouds.

In preliminary analysis, assuming R=14.4 for the star at coordinates RA,DEC(J2000) 21:33:59, +05:16:21.5), for the galaxy #1 reported by Singer et al (GCN #26479
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 ) we measure R=16.6+-0.1. This is consistent with r=16.5 reported in SDSS catalog, within the photometric system and filter differences.

No other obvious candidate is visible down to R=18.5 mag and in comparison to DSS2 survey.

���Sent from BlueMail ���

T. Sakamoto, A. Yoshida, V. Pal'shin, S. Sugita (AGU), 
Y. Kawakubo (LSU), K. Yamaoka (Nagoya U), S. Nakahira (RIKEN),
Y. Asaoka, S. Torii (Waseda U), Y. Shimizu, 
T. Tamura (Kanagawa U), N. Cannady (GSFC/UMBC), 
M. L. Cherry (LSU), S. Ricciarini (U of Florence),
P. S. Marrocchesi (U of Siena),
and the CALET collaboration:

The CALET Gamma-ray Burst Monitor (CGBM) was operating at the trigger 
time of S191216ap T0 = 2019-12-16 21:33:38.473 UT (The LIGO Scientific 
Collaboration and Virgo Collaboration, GCN Circ. 26454
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 ).

No CGBM on-board trigger occurred around the event time.  Based on the
LVC high probability localization region, the summed LIGO probabilities
inside the CGBM HXM (7 - 3000 keV) and SGM (40 keV - 28 MeV) fields
of view are 0 % and 2 %, respectively (and 26 % credible region of the
initial localization map was above the horizon).  The HXM and SGM fields
of view were centered at RA = 178.2 deg, Dec = 19.5 deg and 
RA = 186.8 deg, Dec = 13.9 deg at T0, respectively.

Based on the analysis of the light curve data with 0.125 sec time 
resolution from T0-60 sec to T0+60 sec, we found no significant excess
(signal-to-noise ratio >= 7) around the trigger time in either the HXM or
the SGM data.

The CALET Calorimeter (CAL) was operating in the low energy trigger
mode at the trigger time of S191216ap. Using the CAL data, we have
searched for gamma-ray events in the 1-10 GeV band from -60 sec
to +60 sec from the GW trigger time and found no candidates. There 
is no significant overlap with the LVC high probability localization 
region at T0+-60 sec. The CAL FOV was centered at RA=186.8 deg,
Dec=13.9 deg at T0.

L. Singer (GSFC), T. Ahumada (UMD), S. Anand (Caltech), J. S. Bloom
(UCB), M. M. Kasliwal (Caltech), H. Kumar (IITB), A. Sagu��s Carracedo
(OKC, Stockholm University), I. Andreoni (Caltech), V. Bhalerao
(IITB) report on behalf of the GROWTH collaboration:

Reanalysing the data used in GCN 26476
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 , we provide a revised galaxy
list.

We cross-matched the LIGO/Virgo localization (GCN 26454
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 ) with the
HAWC position (GCN 26472
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 ) and the GLADE v2.3 catalog (Dalya et al.,
2018), to identify sources within the 90% LIGO/Virgo credible volume
and within a 3-sigma radius of the HAWC candidate. We find nine
matching galaxies, all of which are also in SDSS.

The distance parameters from the BAYESTAR localization at the
position of the HAWC candidate are DISTMU = 233.78 Mpc, DISTSIGMA =
63.57 Mpc. The mean and standard deviation of distance in this
direction are DISTMEAN = 265.97 Mpc, DISTSTD = 59.68 Mpc, and the
median distance in this direction is 265.40 Mpc.

In the table below, we give the right ascensions and declinations in
degrees and luminosity distances in Mpc. The "GW C.L." column
provides the LIGO/Virgo 3D credible level within which the galaxy is
found (smaller values mean more consistent with the GW position. The
"HAWC sigma" column gives the separation from the HAWC position,
divided by the HAWC 1-sigma error radius.

| RAJ2000    | DEJ2000   | Dist  | GW C.L. | HAWC sigma |
| ---------- | --------- | ----- |-------- | ---------- |
| 323.482422 | +5.279632 | 274.4 | 86      | 0.23       |
| 323.056030 | +4.832057 | 219.1 | 72      | 2.06       |
| 322.921936 | +5.503483 | 232.2 | 72      | 2.21       |
| 322.838806 | +5.255421 | 179.3 | 73      | 2.30       |
| 322.821228 | +5.553754 | 338.7 | 81      | 2.59       |
| 322.749084 | +5.108610 | 330.8 | 78      | 2.62       |
| 323.173767 | +4.467985 | 292.5 | 88      | 2.80       |
| 322.906006 | +5.850705 | 323.1 | 85      | 2.93       |
| 323.034882 | +4.482058 | 340.7 | 86      | 2.99       |

We highlight the first galaxy in this list since it is consistent
with both LIGO/Virgo 3D localization and the HAWC 1-sigma angular
separation. There is no evidence for significant variability of
within this galaxy in either PTF or ZTF.

Follow-up of these galaxies is encouraged. Further analysis is
ongoing.

GROWTH is a worldwide collaboration comprising of Caltech, USA; IPAC,
USA; WIS, Israel; OKC, Sweden; JSI/UMD, USA; U Washington, USA; DESY,
Germany; MOST, Taiwan; UW Milwaukee, USA; LANL USA; Tokyo Tech,
Japan; IITB, India; IIA, India; LJMU, UK; TTU, USA; SDSU, USA and
USyd, Australia. ZTF acknowledges the generous support of the NSF
under AST MSIP Grant No 1440341. GROWTH acknowledges generous support
of the NSF under PIRE Grant No 1545949.

D. Xu, Z.P. Zhu, H.J. Wang, L. Ge, T.M. Zhang, X. Zhou, C.Z. Cui, Y.F. 
Xu (NAOC), X. Zhang, J.Z. Liu (XAO), H.B. Zhao, B. Li (PMO), J.R. Mao 
(YNAO), X. Gao (Urumqi No.1 Senior High School) report on behalf of the 
GWFUNC collaboration:

We observed the localization regions of the LIGO/Virgo gravitational 
wave trigger S191216ap (GCN #26454
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 ), the IceCube neutrino counterpart 
candidate (GCN #26460
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 ), and the HAWC gamma-ray counterpart candidate 
(GCN #26472
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 ), using the Nanshan 1-meter telescope with the FOV of 
1.3x1.3 deg^2. Observations started at 11:57:05 UT and ended at 15:19:31 
UT on 2019-12-17.

Our survey area covers No.1 (ra: 323.124298, dec: 5.346313) and No.4 
(ra: 323.298126, dec: 4.682521) GLADE galaxies, reported in Kumar et al. 
(GCN #26476
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 ). No 1. galaxy has m(r) ~ 15.67 mag in our image, being 
consistent with m(r) = 15.60 mag in SDSS. No. 4 galaxy has m(r) ~ 17.02 
mag in our image, being consistent with m(r) = 16.99 mag in SDSS. Any 
significant optical transient within these two galaxies can be ruled out.

Full data analysis of the searching is ongoing.

H. Kumar (IITB), A. Sagu��s Carracedo (OKC, Stockholm University), T. Ahumada (UMD), I. Andreoni (Caltech), V. Bhalerao (IITB) report on behalf of the GROWTH collaboration:

We cross-matched the HAWC trigger position (HAWC Collaboration, GCN 26472
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 ) with the GLADE catalog (Dalya et al., 2018), to identify sources within 0.9 degrees (approximately 3-sigma) of the HAWC position RA, Dec = 323.53, 5.23. We further applied a distance constraint based on the 3D Bayestar localisation provided by the LVC (bayestar.fits.gz,1), using mean distance = 95.6 Mpc and distance sigma = 37.4 Mpc, appropriate for this direction. We find four objects in GLADE 1 (http://vizier.u-strasbg.fr/viz-bin/VizieR-3?-source=VII/275/glade1) that are consistent with the position and distance at 3-sigma:

ra         dec        sep   dist     sigma
323.124298 5.346313    0.42 85.3405  1.43
323.741486 5.792747   0.601 150.166  2.48
323.621368 6.034144   0.809 85.5611  2.71
323.298126 4.682521   0.594 173.891  2.88

(sep = separation in degrees).

If we use the newer Glade 2.3 catalog (https://vizier.u-strasbg.fr/viz-bin/VizieR?-source=VII/281), we find only the first two objects as consistent within 3-sigma.

Further observations of these galaxies are under way.

P.A. Evans (U. Leicester), A. Keivani (Colombia U.), J.A. Kennea (PSU), A.
Tohuvavohu (U. Toronto), S. Countryman (Colombia U.), I. Bartos (U. Florida), D.
Fox (PSU), S. Marka (Colombia U.), Zsuzsa Marka (Colombia U.) S.D. Barthelmy
(NASA/GSFC), A.P. Beardmore (U. Leicester), M.G. Bernardini (INAF-OAB), A.A.
Breeveld (UCL-MSSL), P. Brown (TAMU), D.N. Burrows (PSU), S. Campana (INAF-OAB),
S.B. Cenko (NASA/GSFC), G. Cusumano (INAF-IASF PA), A. D'Ai (INAF-IASFPA), P.
D'Avanzo (INAF-OAB), V. D'Elia(ASDC), S.W.K. Emery (UCL-MSSL), P. Giommi (ASI),
C. Gronwall (PSU), D. Hartmann (U. Clemson), H.A. Krimm (CRESST/GSFC/USRA), N.J.
Klingler (PSU), N.P.M. Kuin (UCL-MSSL), A.Y. Lien (GSFC/UMBC), F.E. Marshall
(NASA/GSFC), A. Melandri (INAF-OAB), J.A. Nousek (PSU), S.R. Oates (U. Birmingham),
P.T. O'Brien (U. Leicester), J.P. Osborne (U. Leicester), C. Pagani (U.
Leicester), K.L. Page (U.Leicester), M.J.Page (UCL-MSSL), D.M. Palmer (LANL), M.
Perri (ASDC), J.L. Racusin (NASA/GSFC), B. Sbarufatti (INAF-OAB/PSU), M.H.
Siegel (PSU), G. Tagliaferri (INAF-OAB), E. Troja (NASA/GSFC/UMCP) report on
behalf of the Swift team:

Swift has carried out 100 observations of the overlap between the LVC (GCN Circ.
26454
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 ) and IceCube (GCN Circ. 26463
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 ) error regions for the GW trigger S191216ap.
The observations span from 22 ks to 42 ks after the LVC trigger, and the XRT has
covered 10.2 deg^2 on the sky (corrected for overlaps). This covers 3.3% of the
probability in the bayestar skymap, and 5.8% after convolving with the 2MPZ
galaxy catalogue, as described by Evans et al. (2016, MNRAS, 462, 1591). It
covers 65% of the probability contained within the combined GW and neutrino
localisations. These pointings and associated metadata have been reported to the
Treasure Map (Wyatt et al., GCN Circ. 26244
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 ;
http://treasuremap.space/alerts?graceids=S191216ap).

We have detected 3 X-ray sources. Each source is assigned a rank of 1-4
which describes how likely it is to be related to the GW trigger, with
1 being the most likely and 4 being the least likely. The ranks are
described at https://www.swift.ac.uk/ranks.php.

We have found:

  * 0 sources of rank 1
  * 0 sources of rank 2
  * 1 source of rank 3
  * 2 sources of rank 4

For all flux conversions and comparisons with catalogues and upper
limits from other missions, we assumed a power-law spectrum with
NH=3x10^20 cm^-2, and photon index (Gamma)=1.7

The results of the XRT automated analysis are online at
https://www.swift.ac.uk/LVC/S191216ap

This circular is an official product of the Swift XRT team.

V. Lipunov,  E. Gorbovskoy, V.Kornilov, N.Tyurina, P.Balanutsa,
A.Kuznetsov,F.Balakin, V.Vladimirov, D. Vlasenko, I.Gorbunov, 
D.Zimnukhov, V.Senik, T.Pogrosheva,
D.Kuvshinov(Lomonosov Moscow State University, SAI, Physics Department),

O.A. Gres, N.M. Budnev, O.Ershova (Irkutsk State University, API),

A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo 
Observatory),

V. Yurkov, A. Gabovich, Yu. Sergienko(Blagoveschensk Educational State
University)

R. Podesta, C.Lopez, F. Podesta, C.Francile(Observatorio Astronomico Felix
Aguilar OAFA),

H.Levato(Instituto de Ciencias Astronomicas, de la Tierra y del Espacio ICATE),

R. Rebolo, M. Serra(The Instituto de Astrofisica de Canarias),

D. Buckley(South African Astronomical Observatory),


During a MASTER-net  inspect of LIGO/Virgo S191216ap (Lipunov et al., GCN 
26457
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 )   MASTER-Amur robotic telescope  (Global MASTER-Net: 
http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, 
vol. 2010, 30L)  located in Russia (Blagoveshchensk State Pedagogical 
University) started inspect of the LIGO/Virgo S191216ap  IceCube  neutrino 
counterpart  errorbox (GCN 26460
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 ,26463
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 )   41727 sec after trigger time at 
2019-12-17 09:17:25 UT, with upper limit up to  17.4 mag. Observations 
started at twilight.  The observations began at zenith distance = 50 deg. 
The sun  altitude  is -16.2 deg.

MASTER-Tunka robotic telescope  located in Russia (Applied Physics 
Institute, Irkutsk State University) started inspect of the LIGO/Virgo 
S191216ap  IceCube  neutrino counterpart   errorbox  44823 sec after 
trigger time at 2019-12-17 10:09:01 UT, with upper limit up to  19.0 mag. 
Observations started at twilight.  The observations began at zenith 
distance = 50 deg. The sun  altitude  is -10.0 deg.

MASTER OF J212806.11+023221.9s - Optical Flare known CV.

MASTER-Tunka auto-detection system ( Lipunov et al., "MASTER Global 
Robotic Net", Advances in Astronomy, 2010, 30L )
  discovered OF at  (RA, Dec) = 21h 28m 06.11s +02d 32m 21.9s on 
2019-12-17.43984 UT.

This flash falls off with the position of the famous CV CSS 151110: 212806 
+ 023221 (U Gem type).

The OT magnitude in 'C' filter is 17.0m
(mlim18.3=).

The OT is seen in 2 images. There is no minor planet at this place.

We have reference image on 2010-08-29.64730 UT with  unfiltered mlim= 
18.8m.

Spectral observations are required.


Real time updated cover map and OT discovered available here:
https://master.sai.msu.ru/site/master2/observ.php?id=1228593

The observation and reduction will continue. The message may be cited.

Michael J. Lundquist, David J. Sand (UA),  Wen-fai Fong, Jillian
Rastinejad, Kerry Paterson (Northwestern), Jennifer Andrews (UA), Sam Wyatt
(UA), Eric Christensen, Alex Gibbs, Frank Shelly, report on behalf of the
SAGUARO collaboration:

We initiated observations of 24 fields (each 5 deg^2, totalling 120 deg^2)
within the LVC localization region for the GW trigger S191216ap (LVC Circ
26454) starting on 2019-12-17 at 1:25 UT (3.9 hours after the GW trigger)
with the 1.5m Catalina Sky Survey (CSS) telescope on Mt. Lemmon, AZ.

Below are the field centers observed.

RA   Dec

321.5850 1.10417

321.3495 3.3125

321.3495 5.52081

321.1110 7.72917

321.1110 9.93747

320.8695 12.1458

323.1060 12.1458

320.3775 14.3541

322.6410 14.3541

320.1255 16.5625

322.4055 16.5625

321.9225 18.7708

319.6155 18.7708

321.4290 20.9792

319.0905 20.9792

320.9205 23.1875

318.5520 23.1875

320.1330 25.3958

317.7180 25.3958

319.3155 27.6042

316.8495 27.6042

318.4605 29.8125

317.5710 32.0208

316.6425 34.2291

Overall image quality was poor. We perform real-time processing and image
subtraction (described in Lundquist et al. 2019, ApJL, 881, 2). After
discarding known moving objects, stellar sources and known transients
(cross-correlating with the Transient Name Server and the ZTF alert
stream), we find no significant candidates with S/N>5, although a more
detailed analysis is ongoing.

We have posted our pointings to the Treasure Map, and encourage others to
do the same:

http://treasuremap.space/alerts?graceids=S191216ap

SAGUARO is supported by the National Science Foundation under Award Nos.
AST-1909358 and AST-1908972.

The HAWC Collaboration (https://www.hawc-observatory.org) reports:

The HAWC Collaboration performed a follow-up of the gravitational wave
trigger S191216ap, reported in GCN Circular 26455
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 . We did not report
a significant detection after considering the trials incurred by
looking at the whole gravitational wave localization contour.

We however found that the most significant sub-threshold event is
coincident with the (corrected) localization of a neutrino event
reported by IceCube in GCN Circular 26463
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  (RA: 323.19 deg,
Dec: 4.53 deg, 90% cont.: 4.07 deg). The HAWC event coordinates are:

RA (J2000):   323.53 deg
Dec (J2000):  5.23 deg
68% cont.:    0.30 deg
Significance: 4.6 sigma (pre-trials)

This event was found in the 10 s search, starting at 1260567316.47 GPSs
(80.0 s after the time of coalescence).

We encourage follow-up observations of this location.

D. M. Palmer (LANL), S. D. Barthelmy (NASA/GSFC),
A. Y. Lien (GSFC/UMBC), T. Sakamoto (AGU),
A. P. Beardmore (U. Leicester), M. G. Bernardini (INAF-OAB),
A. A. Breeveld (MSSL-UCL), D. N. Burrows (PSU),
S. Campana (INAF-OAB), S. B. Cenko (NASA/GSFC),
G. Cusumano (INAF-IASF PA), A. D'Ai (INAF-IASFPA),
P. D'Avanzo (INAF-OAB), V. D'Elia (ASI-ASDC), S. Emery (UCL-MSSL),
P. A. Evans (U. Leicester), P. Giommi (ASI), C. Gronwall (PSU),
D. Hartmann (Clemson U.), J. A. Kennea (PSU),
N. Klingler (PSU), H. A. Krimm (NSF),
N. P. M. Kuin (UCL-MSSL), F. E. Marshall (NASA/GSFC),
A. Melandri (INAF-OAB), J. A. Nousek (PSU),
S. R. Oates (Uni. of Warwick), P. T. O'Brien (U. Leicester),
J. P. Osborne (U. Leicester), C. Pagani (U. Leicester),
K. L. Page (U.Leicester), M. J. Page (UCL-MSSL), M. Perri (ASDC),
J. L. Racusin (NASA/GSFC), B. Sbarufatti (INAF-OAB/PSU),
M. H. Siegel (PSU), G. Tagliaferri (INAF-OAB), A. Tohuvavohu (U. Toronto),
E. Troja (NASA/GSFC/UMCP) report on behalf of the Swift team:

We report the search results in the BAT data within T0 +/- 100 s of the
LVC event S191216ap (LIGO/VIRGO Collaboration GCN Circ. 26454
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 ),
where T0 is the LVC trigger time (2019-12-16T21:33:38.472 UTC).

The center of the BAT field of view (FOV) at T0 is
RA = 223.083 deg,
DEC = 20.198 deg,
and the roll angle is 133.749 deg.
The BAT FOV (>10% partial coding) covers 0.20% of the integrated
LVC localization probability, and 0.24% of the galaxy convolved
probability (Evans et al. 2016). Note that the sensitivity in the BAT FOV
changes with the partial coding fraction. Please see the BAT FOV figure
in the summary page (link below) for the specific location of the LVC
region relative to the BAT FOV.

Within T0 +/- 100 s, no significant detections (signal-to-noise ratio
>~ 5 sigma) are found in the BAT raw light curves with time bins of 64 ms,
1 s, and 1.6 s. Assuming an on-axis (100% coded) short GRB with a typical
spectrum in the BAT energy range (i.e., a simple power-law model with a
power-law index of -1.32, Lien & Sakamoto et al. 2016), the 5-sigma upper
limit in the 1-s binned light curve corresponds to a flux upper
limit (15-350 keV) of ~ 5.13 x 10^-8 erg/s/cm^2.
Assuming a luminosity of ~ 2 x 10^47 erg/s (similar to GW170817)
and an average Epeak of ~ 400 keV for short GRBs (Bhat et al. 2016),
this flux upper limit corresponds to a distance of ~ 100.31 Mpc.

Event data are available from T0-44.64 s to T0+45.42 s, and
T0+78.36 to T0+88.42 s. No significant detections (above our typical
image threshold of ~ 6.5 to 7 sigma) are found in the 15-350 keV images
created using intervals of T0-0.1 to T0+0.1 s, T0-2 s to T0+8 s, and the
whole event data range.

BAT retains decreased, but significant, sensitivity to rate increases for
gamma-ray events outside of its FOV. About 99.72% of the integrated LVC
localization probability was outside of the BAT FOV but above the
Earth's limb from Swift's location, and the corresponding flux upper limits
for this region are within roughly an order of magnitude higher than those
within the FOV.

The results of the BAT analysis are available at
https://swift.gsfc.nasa.gov/results/BATbursts/team_web/S191216ap/web/source_public.html

Shreya Anand (Caltech), Tomas Ahumada (UMD), Eric Bellm (UW), S. Bradley Cenko (NASA/GSFC), Michael Coughlin (Caltech), Dougal Dobie (USyd/CSIRO), Daniel Goldstein (Caltech), Albert Kong (NTHU), Harsh Kumar (IIT-B) Leo Singer (NASA/GSFC), Igor Andreoni (Caltech), David Kaplan (UWM), and Mansi M. Kasliwal (Caltech) report on behalf of the Zwicky Transient Facility (ZTF) and Global Relay of Observatories Watching Transients Happen (GROWTH) collaborations:

We observed the localization region of the gravitational wave trigger S191216ap (LVC, GCN #26454
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 ) with the Palomar 48-inch telescope equipped with the 47 square degree Zwicky Transient Facility camera (ZTF, Bellm et al. 2019, Graham et al. 2019).

The tiling was optimally determined and triggered using the GROWTH Target of Opportunity marshal (Coughlin et al. 2019a, Kasliwal et al. 2019b). We started obtaining target-of-opportunity observations in the g-band and r-band beginning at 2019-12-17 01:47 UT, covering 86% of the integrated probability based on the BAYESTAR skymap (LVC, GCN #26454
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 ). Each exposure was 300s, reaching a g-band median depth of 19.8 mag and r-band median depth of 18.5 mag. Due to the severe weather constraints at Palomar we were unable to acquire deeper images.

The images were processed in real-time through the ZTF reduction and image subtraction pipelines at IPAC to search for potential counterparts (Masci et al. 2019). Alert filtering and follow-up coordination was undertaken by the GROWTH Marshal system (Kasliwal et al. 2019). The ZTF alert stream was also queried using the Kowalski infrastructure (Duev et al., 2019). We required at least 2 detections with RB scores greater than 0.15 (Duev et al. 2019) separated by at least 30 minutes to reject artifacts and moving objects. Thus far, no candidate counterparts were identified by our pipeline in the observed area. Further analysis is in progress.


ZTF and GROWTH are worldwide collaborations comprising of Caltech, USA; IPAC, USA; WIS, Israel; OKC, Sweden; JSI/UMD, USA; U Washington, USA; DESY, Germany; MOST, Taiwan; UW Milwaukee, USA; LANL USA; Tokyo Tech, Japan; IITB, India; IIA, India; LJMU, UK; TTU, USA; SDSU, USA and USyd, Australia. ZTF acknowledges the generous support of the NSF under AST MSIP Grant No 1440341. GROWTH acknowledges generous support of the NSF under PIRE Grant No 1545949. Alert distribution service provided by DIRAC@UW (Patterson et al. 2019). Alert filtering and follow-up coordination is being undertaken by the GROWTH marshal system (Kasliwal et al. 2019). Alert database searches are done with using the Kowalski infrastructure (Duev et al., 2019).

The coordinates of the candidate neutrino event coincident with LIGO/Virgo
S191216ap circulated in the original GCN circular 26460
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  (
https://gcn.gsfc.nasa.gov/gcn3/26460.gcn3
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 ) contained an error. The correct
right ascension value is given in the table below:


  dt      ra(deg)   dec(deg)   90% Angular Uncertainty(deg)
p-value(generic transient) p-value(binary merger)

--------------------------------------------------------------------------------------------------------------------

 -43s   323.19     4.53       4.07                       0.219 0.0059


We sincerely apologize for the inconvenience this may have caused to
follow-up observers.

The IceCube realtime alert point of contact can be reached at
roc@icecube.wisc.edu

H. Negoro (Nihon U.), N. Kawai (Tokyo Tech), 
S. Sugita, M. Serino (AGU),
M. Nakajima, W. Maruyama, M. Aoki, K. Kobayashi, R. Takagi (Nihon U.),
T. Mihara, C. Guo, Y. Zhou, T. Tamagawa, M. Matsuoka (RIKEN),
T. Sakamoto, H. Nishida, A. Yoshida (AGU),
Y. Tsuboi, W. Iwakiri, R. Sasaki, H. Kawai, T. Sato (Chuo U.),
M. Shidatsu (Ehime U.), M. Oeda, K. Shiraishi (Tokyo Tech),
S. Nakahira, Y. Sugawara, S. Ueno, H. Tomida, M. Ishikawa, R. Shimomukai, M. Tominaga (JAXA),
Y. Ueda, A. Tanimoto, S. Yamada, S. Ogawa, K. Setoguchi, T. Yoshitake (Kyoto U.),
H. Tsunemi, T. Yoneyama, K. Asakura, S. Ide (Osaka U.),
M. Yamauchi, S. Iwahori, Y. Kurihara, K. Kurogi, K. Miike (Miyazaki U.),
T. Kawamuro (NAOJ), K. Yamaoka (Nagoya U.), Y. Kawakubo (LSU), M. Sugizaki (NAOC)
report on behalf of the MAXI team:

We examined MAXI/GSC all-sky X-ray images (2-20 keV) 
after the LVC trigger S191216ap at 2019-12-16 21:33:38.473 UTC (GCN 26454
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 ).

At the trigger time of S191216ap, the high-voltage of MAXI/GSC was on,
but the FOV was out of the 90% credible region of the bayestar skymap.
The first one-orbit (92 min) scan observation with GSC after the event covered 97% 
of the 90% credible region of the bayestar skymap from 21:34:38 to 22:13:47 UTC (T0+60 to T0+2409 sec).

No significant new source was found in the region in the one-orbit scan observation.
A typical 1-sigma averaged upper limit obtained in one scan observation
is 20 mCrab at 2-20 keV.

If you require information about X-ray flux by MAXI/GSC at specific coordinates,
please contact the submitter of this circular by email.

J. Wood (NASA/MSFC) reports on behalf of the Fermi-GBM Team and the GBM-LIGO/Virgo group

For S191216ap and using the initial bayestar.fits.gz skymap, Fermi-GBM was observing 99.8% of the localization probability at event time.

There was no Fermi-GBM onboard trigger around the event time of the LIGO/Virgo detection of GW trigger S191216ap (GCN 26454
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 ). An automated, blind search for short gamma-ray bursts below the onboard triggering threshold in Fermi-GBM also identified no counterpart candidates. The GBM targeted search, the most sensitive, coherent search for GRB-like signals, was run from +/-30 s around merger time, and also identified no counterpart candidates.

We therefore set upper limits on impulsive gamma-ray emission. Using the representative soft, normal, and hard GRB-like templates described in arXiv:1612.02395
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 , we set the following 3 sigma flux upper limits over 10-1000 keV, weighted by GW localization probability (in units of 10^-7 erg/s/cm^2):

Timescale  Soft     Normal   Hard
------------------------------------
0.128 s:   5.7      8.5      16.
1.024 s:   2.1      3.6      5.7
8.192 s:   0.7      1.0      2.0

Assuming the median luminosity distance of 324 Mpc from the GW detection, we estimate the following intrinsic luminosity upper limits over the 1 keV-10 MeV energy range (in units of 10^48 erg/s):

Timescale  Soft     Normal   Hard
------------------------------------
0.128s:    11.      15.      47.
1.024s:    4.0      6.4      17.
8.192s:    1.4      1.8      5.9

IceCube Collaboration (http://icecube.wisc.edu/) reports:

Searches for track-like muon neutrino events detected by IceCube consistent
with the sky

localization of gravitational-wave candidate S191216ap in a time range of
1000 seconds [1]

centered on the alert event time (21:25:18.473 UTC to  21:41:58.473 UTC)
have been performed.

Up until 21:33:21 UTC IceCube was collecting good quality data, at which
point power issues at the experimental site caused issues with data
quality.  Only neutrino candidates collected before this time are
considered. Two hypothesis tests were conducted. The first search is a
maximum likelihood analysis which searches for a generic point-like
neutrino source coincident with the given GW skymap [2]. The second uses a
Bayesian approach to quantify the joint GW + neutrino event significance,
which assumes a binary merger scenario and accounts for known astrophysical
priors in the significance estimate, such as GW source distance [3].

1 track-like event is found in spatial and temporal coincidence with the
gravitational-wave

Candidate S191216ap calculated from the map circulated in the 2-Initial
notice. This

represents an overall p-value of 0.104 (1.26 sigma) from the generic
transient search

and an overall p-value of 0.0059 (2.52 sigma) for the Bayesian search.
These p-values

measure the consistency of the observed track-like events with the known
atmospheric backgrounds.  Both analyses assume 100% livetime during the
search window; the statistical significances are therefore lower limits.

The reported p-values can differ due to the estimated distance of the GW
candidate. The distance is used as a prior in Bayesian binary merger
search, while it is not taken into account in the generic transient
point-like source search.

Properties of the coincident event are shown below.

  dt      ra(deg)   dec(deg)   Angular Uncertainty(deg)  p-value(generic
transient) p-value(binary merger)

--------------------------------------------------------------------------------------------------------------------

 -43s   329.19     4.53       4.07                       0.219 0.0059


where:

dt = Time offset (sec) of track event with respect to GW trigger.

Angular uncertainty = Angular uncertainty of track event: the radius of a
circle

     representing 90% CL containment by area.

Pvalue = the pvalue for this specific track event from each search.


The IceCube Neutrino Observatory is a cubic-kilometer neutrino detector
operating at the

geographic South Pole, Antarctica. The IceCube realtime alert point of
contact can be

reached at roc@icecube.wisc.edu

[1] Baret et al., Astroparticle Physics 35, 1 (2011)

[2] PoS(ICRC2019)918, Braun et al., Astroparticle Physics 29, 299 (2008)

[3] Bartos et al. arXiv:1810.11467
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  (2018) and Countryman et
al.arXiv:1901.05486
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  (2019)

M. Ageron (CPPM/CNRS), B. Baret (APC/CNRS), A. Coleiro (APC/Universite de Paris), M. Colomer (APC/Universite de Paris), D. Dornic (CPPM/CNRS), A. Kouchner (APC/Universite de Paris), T. Pradier (IPHC/Universite de Strasbourg) report on behalf of the ANTARES Collaboration:


Using on-line data from the ANTARES detector, we have performed a follow-up analysis of the
recently reported LIGO/Virgo S191216ap event using the 90% contour of the Initial bayestar probability
map provided by the GW interferometers (GCN#26454
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  <https://gcn.gsfc.nasa.gov/gcn3/26454.gcn3
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 >). The ANTARES visibility at the time of the
alert, together with the 50% and 90% contours of the probability map are shown at http://antares.in2p3.fr/GW/S191216ap_Initial.png <http://antares.in2p3.fr/GW/S191216ap_Initial.png>.
Considering the location probability provided by the LIGO/Virgo collaborations, there is a
15.9% chance that the GW emitter was in the ANTARES **upgoing** field of view at the time of
the alert.

No up-going muon neutrino candidate events were recorded in the ANTARES sky during a
+/-500s time-window centered on the time 2019-12-16 21:33:38 and in the 90% contour of the S191216ap
event. The expected number of atmospheric background events in the region visible by ANTARES is
6.52e-05 in the +/- 500s time window. An extended search during +/- 1 hour gives no
up-going muon neutrino coincidence. The expected number of atmospheric background events in the
region visible by ANTARES overlapping with the 90% contour is 4.70e-04 in this larger time window.

ANTARES is the largest undersea neutrino detector, installed in the Mediterranean Sea, and it is
primarily sensitive to neutrinos in the TeV-PeV  energy range. At 10 TeV, the median angular
resolution for muon neutrinos is about 0.5 degrees. In the range 1-100 TeV ANTARES has a
competitive sensitivity to this position in the sky.

V. Lipunov, E. Gorbovskoy, V.Kornilov, N.Tyurina, P.Balanutsa, A.Kuznetsov, F.Balakin, 
V.Vladimirov, D. Vlasenko, I.Gorbunov, D.Zimnukhov, V.Senik, T.Pogrosheva, D.Kuvshinov 
(Lomonosov Moscow State University, SAI, Physics Department),

R. Podesta, C.Lopez, F. Podesta, C.Francile 
(Observatorio Astronomico Felix Aguilar OAFA),

H.Levato 
(Instituto de Ciencias Astronomicas, de la Tierra y del Espacio ICATE),

R. Rebolo, M. Serra 
(The Instituto de Astrofisica de Canarias),

D. Buckley 
(South African Astronomical Observatory),

O.A. Gres, N.M. Budnev, O.Ershova 
(Irkutsk State University, API),

A. Tlatov, D. Dormidontov 
(Kislovodsk Solar Station of the Pulkovo Observatory),

V. Yurkov, A. Gabovich, Yu. Sergienko 
(Blagoveschensk Educational State University)




MASTER-Tunka robotic telescope  (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L)  located in Russia (Applied Physics Institute, Irkutsk State University) started inspect of the LIGO/Virgo S191216ap errorbox  1752 sec after notice time and 2831 sec after trigger time at 2019-12-16 22:20:49 UT, with upper limit up to  17.1 mag. The observations began at zenith distance = 61 deg. The sun  altitude  is -24.3 deg. 

The galactic latitude b = -12 deg., longitude l = 77 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/ligo_1.php?id=11063

We obtain a following upper limits.  

Tmid-T0  |      Date Time      |          Site       |             Coord (J2000)          |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________

    2862 | 2019-12-16 22:20:49 |        MASTER-Tunka | (19h 00m 03.48s , +57d 38m 43.8s) |   C |    60 | 17.1 |        
Filter C is a clear (unfiltred) band. 


The observation and reduction will continue. 
The message may be cited.

D. Gotz (AIM/DAp CEA Saclay, France), A. Lutovinov (IKI, Russia)
V. Savchenko, C. Ferrigno (ISDC/UniGE, Switzerland)
S. Mereghetti (INAF IASF-Milano, Italy)
A. Coleiro (APC, France)
on behalf of the INTEGRAL multi-messenger collaboration report:
https://www.astro.unige.ch/cdci/integral-multimessenger-collaboration

At the time of LIGO/Virgo S191216ap event (GCN 26454
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 ) INTEGRAL was at its perigee,
and its instruments were turned off. No INTEGRAL coverage is thus available for
LIGO/Virgo S191216ap.

The HAWC Collaboration (https://www.hawc-observatory.org) reports:

The HAWC Collaboration performed a follow-up of the gravitational wave
trigger S191216ap (GCN #26454
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 ). At the time of the trigger the HAWC
local zenith was oriented towards (RA, Dec) = (311.1deg, 18.9deg).
99% of the GW candidate sky location probability fell within our
observable field of view (0-45 deg zenith angle).

We performed a search for a short timescale emission using 6 sliding
time windows (dt = 0.3s, 1s, 3s, 10s, 30s and  100s), shifted forward
in time by 20% of their width. We searched the 95% probability
containment area in a timescale-dependent time period, from t0-5dt to
t0+10dt, where t0 is the time of the GW trigger.

No significant gamma-ray detection above the background was observed.

The sensitivity of this analysis is greatly dependent on zenith angle,
ranging from 0 deg to 45 deg for the area searched in this
analysis. The 5sigma detection sensitivity to a 1s (100s) burst in the
80-800GeV energy range goes from 1.2e-6 erg/cm^2 to 1.1e-4 erg/cm^2
(6.8e-6 erg/cm^2 to 5.0e-4 erg/cm^2), depending on the zenith
angle.

HAWC is a TeV gamma ray water Cherenkov array located in the state of
Puebla, Mexico. It is sensitive to the energy range ~0.1-100TeV, and
monitors 2/3 of the sky every day with an instantaneous field-of-view
of ~2 sr.

The LIGO Scientific Collaboration and the Virgo Collaboration report:

We identified the compact binary merger candidate S191216ap during
real-time processing of data from LIGO Hanford Observatory (H1) and
Virgo Observatory (V1) at 2019-12-16 21:33:38.473 UTC (GPS time:
1260567236.473). The candidate was found by the GstLAL [1], MBTAOnline
[2], and PyCBC Live [3] analysis pipelines.

S191216ap is an event of interest because its false alarm rate, as
estimated by the online analysis, is 1.1e-23 Hz, or about one in 1e15
years. The event's properties can be found at this URL:
https://gracedb.ligo.org/superevents/S191216ap

The classification of the GW signal, in order of descending
probability, is MassGap (>99%), Terrestrial (<1%), BNS (<1%), BBH
(<1%), or NSBH (<1%).

Assuming the candidate is astrophysical in origin, the probability
that the lighter compact object has a mass < 3 solar masses (HasNS) is
19%. Using the masses and spins inferred from the signal, the
probability of matter outside the final compact object (HasRemnant) is
<1%.

One sky map is available at this time and can be retrieved from the
GraceDB event page:
 * bayestar.fits.gz,0, an initial localization generated by BAYESTAR
[4], distributed via GCN notice about 16 minutes after the candidate
event time.

For the bayestar.fits.gz,0 sky map, the 90% credible region is 300
deg2. Marginalized over the whole sky, the a posteriori luminosity
distance estimate is 324 +/- 78 Mpc (a posteriori mean +/- standard
deviation).

For further information about analysis methodology and the contents of
this alert, refer to the LIGO/Virgo Public Alerts User Guide
<https://emfollow.docs.ligo.org/userguide/>.

 [1] Messick et al. PRD 95, 042001 (2017)
 [2] Adams et al. CQG 33, 175012 (2016)
 [3] Nitz et al. PRD 98, 024050 (2018)
 [4] Singer & Price PRD 93, 024013 (2016)