LIGO/Virgo S190808ae

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-IAC robotic telescope  (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L)  located in Spain (IAC Teide Observatory) started inspect of the LIGO/Virgo S190808ae errorbox  0 sec after notice time and 471 sec after trigger time at 2019-08-08 22:29:12 UT, with upper limit up to  17.3 mag. The observations began at zenit distance = 59 deg. The sun  altitude  is -31.4 deg. 

The galactic latitude b = -60 deg., longitude l = 98 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/ligo_1.php?id=10669

We obtain a following upper limits.  

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

     517 | 2019-08-08 22:29:12 |          MASTER-IAC | ( 14h 11m 14.84s , +22d 53m 56.62s) |  P| |    90 | 17.3 |        
     517 | 2019-08-08 22:29:12 |          MASTER-IAC | ( 14h 10m 27.24s , +22d 58m 10.79s) |  P- |    90 | 15.7 |        


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

The LIGO Scientific Collaboration and the Virgo Collaboration report:


We identified the compact binary merger candidate S190808ae during
real-time processing of data from LIGO Hanford Observatory (H1), LIGO
Livingston Observatory (L1), and Virgo Observatory (V1) at 2019-08-08
22:21:21.496 UTC (GPS time: 1249338099.496). The candidate was found
by the GstLAL [1] analysis pipeline.

S190808ae is an event of interest because its false alarm rate, as
estimated by the online analysis, is 3.4e-08 Hz, or about one in 11
months. The event's properties can be found at this URL:

https://gracedb.ligo.org/superevents/S190808ae

The classification of the GW signal, in order of descending
probability, is Terrestrial (57%), BNS (43%), BBH (<1%), MassGap
(<1%), or NSBH (<1%).

Assuming the candidate is astrophysical in origin, there is strong
evidence for the lighter compact object having a mass < 3 solar masses
(HasNS: >99%). Using the masses and spins inferred from the signal,
there is strong evidence for matter outside the final compact object
(HasRemnant: >99%).

One sky map is available at this time and can be retrieved from the
GraceDB event page:
 ��* bayestar.fits.gz, an updated localization generated by BAYESTAR
[2], distributed via GCN notice about 6 minutes after the candidate

For the bayestar.fits.gz sky map, the 90% credible region is 5365
deg2. Marginalized over the whole sky, the a posteriori luminosity
distance estimate is 208 +/- 77 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] Singer & Price PRD 93, 024013 (2016)

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 S190808ae in a
time range of 1000 seconds [1] centered on the alert event time
(2019-08-08 22:13:01.496 UTC to 2019-08-08 22:29:41.496 UTC) have been
performed.
During this time period IceCube was collecting good quality data. 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].

One track-like event is found in spatial and temporal coincidence with the
gravitational-wave candidate S190808ae calculated from the map circulated in
the 2-Initial notice. This represents an overall p-value of 0.0448 (1.70
sigma) from the generic transient search and an overall p-value of 0.068
(1.49 sigma) for the Bayesian search. These p-values measure the
consistency of the observed track-like events with the known atmospheric
backgrounds.

The reported p-values can differ due to the estimated distance of the GW
candidate. The distance is used as a prior in the 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(bayesian)
-----+--------+---------+------------------------+------------------+--------------------------
 -37 | 216.29 |-15.35     | 0.43                     |0.045
      |0.070

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.
p-value = the p-value for this specific track event from each search.
RA & Dec = Right ascension and declination in degrees quoted in J2000 epoch

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] 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)```

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

The HAWC Collaboration performed a follow-up of the gravitational wave
trigger S190808ae (GCN #25296
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 ). At the time of the trigger the HAWC
local zenith was oriented towards (RA, Dec) = (194.9 deg, 19.1 deg).
64% 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
(6.4e-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.

David O. Cook (Caltech/IPAC), Angela Van Sistine (UW Milwaukee), Leo Singer (NASA/GSFC), Igor Andreoni (Caltech), Michael Coughlin (Caltech), Bob Aloisi (UW Milwaukee), Patrick R. Brady (UW Milwaukee), Rick Ebert (Caltech/IPAC), George Helou (Caltech/IPAC), David Kaplan (UW Milwaukee), Mansi M. Kasliwal (Caltech), Joseph M. Mazzarella (Caltech/IPAC), and Marion Schmitz (Caltech/IPAC)

On behalf of the Global Relay of Observatories Watching Transients Happen (GROWTH) collaboration and the NASA/IPAC Extragalactic Database (NED) Team.

We spatially cross-matched the LIGO/Virgo S190808ae trigger sky localization (50% containment volume) with the Census of the Local Universe (CLU; Cook et al. 2017; arxiv:1710.05016) galaxy catalog and found 11018 galaxies within the volume. The CLU catalog is a compilation of galaxies with existing redshifts from many sources (e.g., NED, SDSS, etc) and new galaxies from a 3PI narrow-band survey to look for redshifted Halpha emission out to 200 Mpc with the Palomar Oschin 48-inch telescope (Cook et al. 2017; arxiv:1710.05016). We list here the top 20 galaxies sorted by stellar mass (Mstar) for galaxies whose location on the sky and distance falls in the 50% volume reported by the BAYESTAR probability sky map (Singer et al. 2016). We also list the dust-corrected star formation rates (SFRs) for galaxies with GALEX FUV detections and a 'nan' for those with no detection.

For an extended list of galaxies in the 90% volume go to the NED Gravitational Wave Followup service at https://ned.ipac.caltech.edu/uri/NED::GWF/. This service provides downloadable galaxy lists and visualizations for candidate host galaxies. For each GW alert, these products are automatically generated and made available within minutes to expedite efficient electromagnetic followup observations. The NED top 20 list is sorted by 2MASS absolute K-band magnitude, but users can sort the entire list on a variety of other criteria (probability density, UV magnitudes, etc) after download.


          name              ra      dec   distmpc logsfr_fuv logmstar  dP_dV  
------------------------ -------- ------- ------- ---------- -------- --------
                NGC 6196 249.4747 36.0731  141.00        nan    11.33 6.38e-07
                NGC 6240 253.2453  2.4009  101.93        nan    11.27 1.63e-06
            CGCG 169-020 254.5317 29.9106  160.64       0.58    11.19 1.69e-07
            CGCG 081-001 250.8074  9.9044  196.84       0.79    11.17 2.00e-07
                NGC 6113 244.7939 14.1336  124.09       0.49    11.16 3.61e-07
                NGC 6185 248.3243 35.3423  143.07      -0.11    11.16 7.34e-07
                 IC 4395 214.3378 26.8574  152.04       1.18    11.13 1.83e-07
            CGCG 074-028 209.9276 12.7368  188.00      -0.33    11.13 2.21e-07
                NGC 6097 243.6091 35.1092  153.00        nan    11.11 4.26e-07
                NGC 6078 243.0227 14.2088  130.25      -0.83    11.11 2.31e-07
            CGCG 049-183 232.4576  3.5109  160.00      -0.16    11.10 1.62e-07
SDSS J161948.55+374633.4 244.9523 37.7759  129.68        nan    11.09 3.39e-07
                 IC 1121 231.9336  6.8039  181.16        nan    11.09 1.52e-07
 2MASS J12545245+0353033 193.7186  3.8842  198.99        nan    11.08 1.58e-07
                NGC 6120 244.9504 37.7745  127.56       1.25    11.07 3.38e-07
 2MASX J16164545+1320492 244.1893 13.3469  138.64      -0.22    11.07 3.53e-07
          NGC 6230 NED01 252.6781  4.6050  133.49       0.50    11.07 1.24e-06
 2MASS J16224730+3733145 245.6972 37.5540  124.54      -0.77    11.06 3.92e-07
               UGC 10412 247.4005 15.6584  142.06      -0.29    11.05 4.64e-07
                NGC 6086 243.1481 29.4848  141.00      -0.77    11.05 2.05e-07

                                  
Table: Top 20 galaxies in CLU that fall in the 50% probability volume for S190808ae sorted by stellar mass. Column descriptions are as follows. name: galaxy name. ra: RA (J2000, decimal degrees). dec: Dec (J2000, decimal degrees). distmpc: galaxy distance (Mpc). logsfr_fuv: log10 of the star formation rate (SFR, Msun per year), derived from GALEX All Sky Kron FUV magnitudes via the prescription of Murphy et al. (2011), corrected for internal dust extinction using a combination of GALEX FUV and 22um ALLWISE fluxes (Hao et al. 2011). logmstar: log10 of the galaxy stellar mass (Msun), estimated from 3.4um ALLWISE fluxes and a mass-to-light ratio of 0.5 (McGaugh & Schombert et al. 2015).

M. Serino, S. Sugita (AGU), H. Negoro (Nihon U.),
N. Kawai, M. Sugizaki (Tokyo Tech), 
Y. Kawakubo (LSU),
M. Nakajima, W. Maruyama, M. Aoki, K. Kobayashi (Nihon U.),
T. Mihara, 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, N. Isobe, 
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.)
report on behalf of the MAXI team:

We examined MAXI/GSC all-sky X-ray images (2-20 keV)
after the LVC trigger S190808ae at 2019-08-08 22:21:21.496 UTC (GCN #25296
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 ).

At the trigger time of S190808ae, the high-voltage of MAXI/GSC was on.
The instantaneous field of view of GSC at the GW trigger time covered 
0.4% of the 90% credible region of the bayestar sky map, in which we 
found no significant new X-ray source.

The first one-orbit (92 min) scan observation with GSC after the event 
covered 98% of the 90% credible region of the bayestar skymap from 22:21:21 
to 23:53:18 UTC (T0+0 to T0+5517 sec).
The position of IceCube neutrino event (GCN #25297
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 ) was not observed during
the orbit.

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.

The LIGO Scientific Collaboration and the Virgo Collaboration report:

The trigger S190808ae (GCN Circular 25296
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 ) is no longer considered to
be a gravitational wave signal.

Further analysis after removing instrumental artifacts resulted in
the candidate no longer passing our threshold for a public alert.