LIGO/Virgo G277583

M. E. Huber, K. W. Smith, P. Clark, D. O'Neill (QUB), T. Lowe (IfA), K. C. Chambers (IfA), E. Kankare (QUB), J. Tonry, L. Denneau, A. Heinze, B. Stalder, H. Weiland (IfA), S. J. Smartt, D. E. Wright, D. R. Young (QUB), H. Flewelling, E. A. Magnier, A. S. B. Schultz, C. Waters, R. J. Wainscoat, M. Willman (IfA), C. W. Stubbs (Harvard), A. Rest (STScI), T.-W. Chen (MPE), M. Coughlin (Harvard), R. Kotak (QUB), K. Maguire (QUB)

Further to GCN 20881
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 , the following transients were discovered by ATLAS and Pan-STARRS1 during normal operations imaging through the skymap (Cho et al.  GCN 20860
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 ) of G277583, the possible coherent wave burst of 20170313 (MJD=57825.94).  Spectra were taken with the UH88/SNIFS on the dates noted below.  Four objects have discovery dates before the G277583 detection time, but are reported here for completeness. 

name       TNS name  ra          dec         disc mjd disc mag PC type    z    specdate Notes  
PS17bra    SN2017byn 10:38:15.58 +15:13:59.7 57816.41 19.15 c  90 Ia     0.1   20170418   1.
PS17buq    SN2017cgt 09:01:46.98 +33:12:03.5 57817.30 18.78 c  70 Ia     0.060 20170404   2.
ATLAS17czq SN2017cij 10:01:26.16 +18:01:47.0 57817.40 19.12 c  80 Ia     0.067 20170328   3.
ATLAS17czg SN2017cil 15:38:49.11 +24:35:39.8 57817.59 19.08 c  70 Ib     0.039 20170328   4.
PS17bvw    SN2017cms 11:57:51.71 -23:57:22.0 57828.42 18.65 i  90 Ia     0.054 20170420   5.
ATLAS17czi SN2017cik 07:54:13.07 +21:47:36.0 57829.34 18.64 o  60 IIn    0.015 20170408   6.
ATLAS17czf SN2017ciu 15:50:11.30 +32:22:53.6 57829.63 18.78 o  80 Ia     0.070 20170410   7.
ATLAS17cqi SN2017cgg 08:28:40.38 +38:57:24.3 57830.34 17.59 o  90 Ia     0.038 20170328   8.
PS17bxh    SN2017cls 16:08:45.04 +57:50:55.9 57830.59 18.39 o  90 Ia     0.080 20170328   9.
PS17byj    SN2017cnb 10:56:23.77 +09:45:18.6 57831.43 20.73 i  90 Ia     0.061 20170420  10.
ATLAS17czr SN2017cio 07:38:34.92 +37:38:25.0 57834.34 18.12 c  70 II     0.013 20170328  11.
ATLAS17dzk SN2017daj 16:11:48.11 +60:35:09.4 57834.60 18.80 c  90 II     0.014 20170421  12.
ATLAS17dhv SN2017col 10:53:35.97 +06:43:11.3 57836.45 18.98 c  90 Ia     0.055 20170419  13.
ATLAS17dks SN2017ctt 15:30:01.97 +14:57:22.1 57841.54 18.44 c  80 Ia     0.090 20170410  14.
ATLAS17dkf SN2017csc 15:24:12.30 +03:58:38.2 57844.57 18.17 c  90 Ic     0.023 20170421  15.
PS17ciu    SN2017ddl 16:23:20.79 -13:44:24.1 57847.56 17.19 w  70              20170421  16.
ATLAS17doh SN2017cwz 16:00:04.56 +35:43:06.8 57850.50 17.31 o  90 Ia-91T 0.050 20170410  17.
ATLAS17dul AT2017cyd
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  06:40:14.00 +04:08:08.7 57852.24 17.60 o  80              20170418  18.
   -       SN2017dgj 11:57:51.53 -23:57:24.2 57863.27 ~19.5 V  90 II     0.054 20170420  19.

PC = probability contour within which the object lies 

Notes

 1. Registered on TNS as PS17bra, but actually discovered a day earlier by ATLAS as ATLAS17dip, so ATLAS photometry is listed. +11 to +20 days.
 2. SNIa or SNIa-91T, +2 weeks.  Registered on TNS as PS17buq, but actually discovered 8 days earlier by ATLAS as ATLAS17cxv, so ATLAS photometry is listed.
 3. Around +2 weeks.
 4. SNIb-pec? +1 week.
 5. Redshift from SDSS. SNIFS spectrum inconclusive, but observed again on 20170422 at NTT.  NTT spectrum reported above. See ATel #10315.
 6. Narrow Halpha and He I. Nice 20 day rise, discovery 3.5 days after GW170313. No clear epoch based on SNID, based on light curve rising or near peak. At z=0.015 the most recent magnitude o = 17.2 corresponds to roughly -17 mag, therefore more likely a Type IIn than a SN impostor. See also classification by at NTT on 20170423 in ATel #10318.
 7. +11 to +20 days.
 8. Around peak.
 9. Around peak.  Registered on TNS as PS17bxh, but discovered 14 minutes earlier by ATLAS as ATLAS17deq, so ATLAS photometry is listed.
10. Redshift from SDSS. +8 to +10 days.
11. Redshift from SDSS.  Around peak.  Confirmed as SNII on 20170510 by LOSS.  See TNS report.
12. > +20 days.
13. Redshift from SDSS. +11 to +20 days.
14. +11 to +20 days.  Also observed by NTT on 20170423 with NTT.  See ATel #10318.
15. > +20 days. Also observed by FLOYDS on 20170504. See TNS report.
16. Noisy spectrum, no clear features, blue continuum. Confirmed as stellar by NTT observation on 20170429.  See ATel #10334.
17. ���7 to ���4 days. Forced photometry shows activity on MJD 57829.
18. Flat, featureless continuum. Classification unclear.
19. Redshift from SDSS. Discovered serendipitously when observing 2017cms. SNIFS spectrum inconclusive, but observed again on 20170422 at NTT. NTT spectrum reported above. See ATel #10315.

Sheng Yang (INAF-OAPd, UC Davis), Stefano Valenti(UC Davis), David Sand (TTU), Leonardo Tartaglia (TTU, UC Davis), Enrico Cappellaro(INAF-OAPd), Dan Reichart, Josh Haislip (UNC) report on behalf of the Gravitational Wave Follow-Up by DLT40.

We report the observation of 55 galaxies within the LVC error region for the GW trigger G277583 using the 'bayestar' GW localization map. We selected 112 galaxies from the GWGC catalogue within 80.0% of the trigger error region, within a distance of 40.0 Mpc, brighter that -17.5 mag and at a Declination < 20 degree. 55 of those galaxies have been observed using the Prompt 5 telescope and are part of the ongoing DLT40 search. They represent the 2.1% of all galaxies within 40.0 Mpc in the Glade catalogue within the LVC error region for the GW trigger and contains 4.5% of all B band luminosity of those galaxies. We started to observe this sample of galaxies on 2017-3-13 and monitored them for 2 weeks after the GW trigger. No interesting transients have been identified down to a limit magnitude of 19.5 mag.

Below follow the list of galaxies observed:
Name RA(J2000) DEC(J2000) Dist(Mpc) BMAG KMAG
ESO380-006 183.8926 -35.6298 38.93 -21.31 -24.7914
NGC2339 107.0856 18.7803 37.84 -21.21 -24.3848
NGC1954 83.2014 -14.0628 38.02 -20.93 -23.7991
IC2977 178.8111 -37.6963 39.01 -20.82 -23.8369
NGC6181 248.0877 19.8259 33.57 -20.73 -23.9578
NGC4373A 186.4071 -39.3195 37.33 -20.63 -24.0563
NGC4444 187.1515 -43.2618 36.98 -20.63 -23.4348
NGC5962 234.132 16.6078 30.2 -20.55 -23.867
NGC4112 181.7896 -40.208 34.67 -20.54 -23.4958
NGC4219 184.1136 -43.3244 20.99 -20.51 -23.5181
NGC1784 76.3629 -11.8714 30.48 -20.5 -23.9051
ESO320-031 178.5285 -39.8676 38.18 -20.45 -24.8702
IC3370 186.9046 -39.3379 26.79 -20.37 -24.2819
ESO380-019 185.5093 -35.7928 38.02 -20.37 -24.2441
ESO321-025 185.4292 -39.7694 29.38 -20.32 -22.5763
NGC1832 78.0136 -15.6878 25.12 -20.32 -23.6121
NGC6118 245.4526 -2.2833 20.99 -20.21 -22.9071
PGC016894 77.9203 -14.7895 27.42 -20.19 -22.0013
ESO321-016 183.8614 -38.144 38.02 -20.15 -21.9751
NGC5970 234.6249 12.1862 26.06 -20.13 -23.2639
ESO321-021 185.0676 -40.3908 39.65 -20.07 -22.6372
ESO322-027 188.6788 -40.3005 39.54 -20.03 -23.2642
UGC03691 107.0052 15.1783 28.84 -20.0 -21.988
UGC10288 243.6042 -0.2079 32.96 -19.99 -23.1989
NGC6010 238.5796 0.543 25.35 -19.91 -23.0859
NGC1924 82.0083 -5.3106 28.84 -19.83 -22.959
ESO321-018 183.9762 -38.0935 38.65 -19.78 -19.5997
IC2098 72.6844 -5.4185 32.36 -19.77 -22.352
ESO321-019 184.2678 -39.0508 37.64 -19.77 -22.8222
NGC6012 238.5579 14.6011 25.83 -19.76 -22.5206
ESO321-005 181.4475 -38.8539 36.46 -19.75 -22.1991
UGC03457 95.4604 0.3661 33.42 -19.66 -24.324
ESO321-010 182.9254 -38.5485 38.02 -19.66 -22.7921
NGC1666 72.1369 -6.5701 33.08 -19.63 -23.1598
NGC6106 244.6957 7.4094 24.66 -19.6 -22.341
UGC03258 77.6793 0.4085 35.13 -19.59 -22.3694
UGC09977 235.4983 0.7128 31.33 -19.48 -21.8758
ESO595-014 301.9053 -21.1252 29.92 -19.48 -22.3808
NGC6063 241.804 7.9789 37.5 -19.48 -22.3202
NGC3882 176.5266 -56.3909 23.12 -19.47 -23.7099
NGC6014 238.9891 5.9318 31.19 -19.42 -22.6711
ESO322-020 187.3036 -40.6922 39.58 -19.39 -20.4714
IC1151 239.6347 17.4415 24.21 -19.38 -21.508
ESO460-026 295.7482 -27.4192 18.11 -19.38 -21.9636
NGC5951 233.4294 15.0073 25.94 -19.37 -22.0178
NGC5956 233.7445 11.7501 26.28 -19.37 -22.2251
ESO267-016 181.5949 -44.4484 39.26 -19.36 -22.3008
PGC016917 78.0954 -14.3597 29.78 -19.36 -20.5076
ESO554-002 82.2814 -19.9339 36.21 -19.32 -20.3021
NGC1665 72.0711 -5.4276 33.1 -19.32 -23.3421
UGC10041 237.2556 5.1887 35.81 -19.27 -19.429
ESO320-035 179.1936 -38.1925 27.04 -19.22 -21.871
NGC1843 78.5256 -10.6268 29.92 -19.22 -22.6698
NGC1681 72.9586 -5.8033 32.36 -19.2 -22.149
PGC017323 82.0588 -16.1243 25.35 -19.19 -20.8399
_______________________________
Sheng Yang

D. Svinkin, S. Golenetskii, R.Aptekar, D. Frederiks, P. Oleynik,
M. Ulanov, A. Tsvetkova, A.Lysenko, A. Kozlova, 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
event G275697 (2017-03-13 22:40:09.593 UTC, hereafter T0; LIGO/VIRGO
Collaboration GCN Circ. 20860
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 ).

No triggered KW event happened from ~2 days before to ~3 days
after T0. Using waiting mode data within the interval T0 +/- 100 s,
we also 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 10 keV ��� 10 MeV fluence to
7.8x10^-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 3.0x10^-7 erg/cm^2/s (10 keV - 10 MeV, 2.944 s scale).

All the quoted values are preliminary.

Adam Goldstein (USRA) and Colleen Wilson-Hodge (NASA/MSFC) report on behalf
of the GBM-LIGO Group:
Lindy Blackburn (CfA), Michael S. Briggs (UAH), Jacob Broida (Carleton
College), Eric Burns (UAH), Jordan Camp (NASA/GSFC), Tito Dal Canton
(NASA/GSFC), Nelson Christensen (Carleton College), Valerie Connaughton
(USRA), Rachel Hamburg (UAH), C. Michelle Hui (NASA/MSFC), Pete Jenke
(UAH), Dan Kocevski (NASA/MSFC), Nicolas Leroy (LAL), Tyson Littenberg
(NASA/MSFC), Julie McEnery (NASA/GSFC), Rob Preece (UAH), Judith Racusin
(NASA/GSFC), Peter Shawhan (UMD), Karelle Siellez (GA Tech), Leo Singer
(NASA/GSFC), John Veitch (Birmingham), Peter Veres (UAH)

At the time of G277583, Fermi was passing through the South Atlantic
Anomaly, therefore the GBM detectors were disabled.

Using the Earth Occultation technique (Wilson-Hodge et al. 2012, ApJS, 201,
33) to estimate the amount of persistent emission during a 48-hour period
centered on the LIGO trigger time, we place the following range of 3-sigma
day-averaged flux upper limits based on observed sources over the entire
LIGO sky map:

Energy       min  max  median
--------------------------------
 12- 27 keV: 0.07 0.56 0.10 Crab
 27- 50 keV: 0.13 0.84 0.17 Crab
 50-100 keV: 0.18 1.16 0.25 Crab
100-300 keV: 0.34 1.98 0.46 Crab
300-500 keV: 2.20 13.2 3.15 Crab

These limits are based on the minimum requirement that each source in the
Earth Occultation catalog was Earth-occulted at least 6 times in each of
the 24 hour periods preceding and following the LIGO trigger and that the
occultations were well separated from nearby bright sources.

R. Sunyaev (IKI, Russia) on behalf of the INTEGRAL group:
R. Krivonos (IKI, Russia),
V. Savchenko (ISDC, University of Geneva, CH),
A. Lutovinov, S. Grebenev (IKI, Russia),
S. Mereghetti (IASF-Milano, Italy),
C. Ferrigno (ISDC, University of Geneva, CH),
E. Kuulkers (ESTEC/ESA, The Netherlands),
A. Bazzano (IAPS-Roma, Italy),
E. Bozzo, T. J.-L. Courvoisier (ISDC, University of Geneva, CH),
J. Chenevez, S. Brandt (DTU - Denmark),
R. Diehl (MPE-Garching, Germany) ,
L. Hanlon (UCD, Ireland), P. Laurent (APC, Saclay/CEA, France),
  J.P. Roques (CESR, France), P. Ubertini (IAPS-Roma, Italy)

We report on serendipitous follow-up INTEGRAL observations of the part
of the LIGO localization area carried out several hours after the
trigger for the LIGO/Virgo burst candidate G277583.  During these
observations (from 2017-03-14 11:21:32 to 2017-03-16 09:26:32 with the
total net exposure of 120 ks) the satellite monitored the Galactic
Center region. The total LIGO localization probability in the region
observed by ISGRI/IBIS is 19.5% for cWB localization and 11.5% for the
recommended combined cWB_plus_LIB map.

No new sources were found in the IBIS field of view (FOV) during these
observations with 3-sigma upper limits of 5.1 mCrab (6.3?-11
erg/s/cm2) in the fully coded FOV of IBIS and 4.2 mCrab (5.1?-11
erg/s/cm2) at the peak sensitivity of ISGRI in the 20-60 keV energy
band.  A 3-sigma upper limit of 50 mCrab in the 3-10 keV energy band
for any new sources was derived from the JEM-X instrument as well,
which covered <3% of the LIGO probability area.

During these observations INTEGRAL/SPI-ACS and IBIS/Veto performed
nearly continuous monitoring of the whole LIGO localization region
with an approximate 1-s peak flux sensitivity of 9e-7 erg/cm2
(assuming a typical short GRB spectrum described by a cutoff powerlaw
model with alpha=-0.5 and E_peak=500 keV). No GRB-like events have
been detected.

Finally, we also inspected earlier INTEGRAL observations of the same
region, which finished about 15 minutes before the LIGO trigger (from
2017-03-11 19:34:35 to 2017-03-13 22:25:18 with the total net exposure
of 113 ks). Also in this time frame did we not find any new sources or
unusual events, with approximately the same upper limits.

K. Yamaoka (Nagoya U), A. Yoshida, T. Sakamoto, Y. Kawakubo,
M. Moriyama, Y. Yamada (AGU), S. Nakahira (JAXA), I. Takahashi (IPMU),
Y. Asaoka, S. Ozawa, S. Torii (Waseda U), Y. Shimizu, T. Tamura (Kanagawa U),
W. Ishizaki (ICRR), M. L. Cherry (LSU), S. Ricciarini (U of Florence),
A. V. Penacchioni, P. S. Marrocchesi (U of Siena)
and the CALET collaboration:

The CALET Gamma-ray Burst Monitor (CGBM) was operating at the trigger time
of G277583 (GCN Circ. 20860
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 ).  No CGBM on-board trigger occurred at the time
of the event.  Based on the LIGO localization sky map (cWB_plus_LIB.fits),
the part of the southern arc of the high probability area was in the field-of-view of
CGBM.  The summed LIGO probabilities inside the HXM and the SGM field of view
are 19% and 41%.

Based on the analysis of the light curve data with 0.125 sec time resolution
from -60 sec to 60 sec from the trigger time, we found no significant excess
around the trigger time in either the HXM (7-3000 keV) or the SGM (40 keV -28 MeV)
data.

The CALET Calorimeter (CAL) was operating in high energy trigger mode at the
trigger time of G277583.  However, no LIGO high probability region was included
in the CAL's field of view at the time of the trigger.

L. Tomasella, E. Cappellaro, S. Benetti (INAF OAPd), D. Malesani 
(DARK/NBI, Denmark), G. Greco (Urbino University/INFN Firenze), A. 
Rossi, E. Palazzi (INAF-IASF Bo), M. Branchesi (Urbino University/INFN 
Firenze), L. Amati (INAF-IASF Bo), L. A. Antonelli, S. Ascenzi 
(INAF-OAR), M.T. Botticella (INAF-OAC), S. Campana, S. Covino, P. 
D'Avanzo (INAF-OAB), V. D'Elia (INAF-ASDC), F. Getman, A. Grado, L. 
Limatola (INAF-OAC), M. Lisi (INAF-OAR), A. Melandri (INAF-OAB), L. 
Nicastro (INAF-IASF Bo), E. Pian (SNS-Pisa), S. Piranomonte, L. Pulone 
(INAF-OAR), G. Stratta (Urbino University/INFN Firenze), G. Tagliaferri 
(INAF-OAB), V. Testa (INAF-OAR), S. Yang (INAF-OAPD), E. Brocato 
(INAF-OAR) on behalf of GRAvitational Wave Inaf TeAm (GRAWITA) report:

We report spectroscopic observations of the ATLAS transients ATLAS17byo 
and ATLAS17cgg (Smartt et al., LVC Circ. 20881), discovered in the 
skymap (cWB_plus_LIB.fits) of G277583 (LVC Circ. 20860), with event time 
2017-03-13 22:40:09.593 UT (MJD 57825.945).

The observations were performed with the Asiago 1.82 m Copernico 
Telescope equipped with AFOSC (range 340-820 nm; resolution 1.4 nm).

Name        RA           DEC        z      Host Galaxy
ATLAS17byo  16:33:19.87 +23:43:52.4 0.033  SDSS J163319.94+234356.4
ATLAS17cgg  08:03:55.23 +26:31:12.3 0.0217 IC 0491

1) ATLAS17byo was observed at MJD=57830.05 under bad sky conditions. 
However, the noisy spectrum shows that this transient is a normal type 
Ia SN, around maximum light.

2) ATLAS17cgg was observed starting from MJD=57829.88. We took 3 spectra 
showing that this transient is a young type IIn SN. The spectra display 
a blue continuum with over-imposed Balmer emission lines with composite 
profiles (FWHM ~ 1300-1700 km/s). The best match is found with SN 1998S 
(Fassia et al. 2000 MNRAS 318) before maximum. Multiband photometry was 
also collected and a preliminary analysis shows that: u = 17.66[0.014], 
g = 17.12[0.016] AB mag; B = 17.20[0.014], V = 17.13[0.018] Vega mag

Our spectral classifications are consistent with those provided by 
Blagorodnova et al. (LVC Circ. 20897).

S. Sugita, N. Kawai (Tokyo Tech), M. Serino (RIKEN), H. Negoro (Nihon U.),
S. Ueno, H. Tomida, S. Nakahira, M. Ishikawa, Y. Sugawara (JAXA),
Y. E. Nakagawa (JAMSTEC),
T. Mihara, M. Sugizaki, W. Iwakiri, M. Shidatsu, J. Sugimoto, T.
Takagi, M. Matsuoka (RIKEN),
N. Isobe, T. Yoshii, Y. Tachibana, Y. Ono, T. Fujiwara, S. Harita, Y.
Muraki (Tokyo Tech),
A. Yoshida, T. Sakamoto, Y. Kawakubo, Y. Kitaoka (AGU),
H. Tsunemi, R. Shomura (Osaka U.),
M. Nakajima, K. Tanaka, T. Masumitsu, T. Kawase (Nihon U.),
Y. Ueda, T. Kawamuro, T. Hori, A. Tanimoto, S. Oda (Kyoto U.),
Y. Tsuboi, Y. Nakamura, R. Sasaki (Chuo U.),
M. Yamauchi, K. Furuya (Miyazaki U.),
K. Yamaoka (Nagoya U.)
report on behalf of the MAXI team:

We examined the MAXI/GSC all-sky X-ray images (2-20 keV) obtained
in the orbit and the day after the LVC trigger
G277583 at 2017-03-13 22:40:09.593 UTC (GCN 20860
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 ).

At the trigger time of G277583,
the high-voltage of MAXI/GSC was off,
and on from T0+682 sec.
GSC scanned more than 74%
of the whole sky in the 92-min orbit, which includes 78.3% of the
90% regions in the skyprobcc_cWB skymap.
One day image covers 97.5% of the 90% regions
in the skyprobcc_cWB skymap.
No significant new source was found in these images.
The upper limits for the X-ray flux are different depending
on the part of the sky.
For instance, typical 2-20 keV 1-sigma (3-sigma) upper limits obtained
from the one-orbit and one-day images are
13(39) mCrab and  3(9) mCrab, respectively,

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

N. Blagorodnova, K. Burdge, S. M. Adams and M. M. Kasliwal (Caltech)

report on behalf of the GROWTH (Global Relay of Observatories Watching
Transients Happen) collaboration

On UT 2017-03-16, we spectroscopically classified the following ATLAS
optical transient candidates (LVC GCN#20881
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 ) using the Double Beam
Spectrograph (Oke & Gunn 1982) on the Palomar 200-inch Hale Telescope. All
spectra were reduced using the pyraf-dbsp pipeline (Bellm & Sesar 2016) and
spectral matching done using SNID and Superfit.

Name, Redshift, Classification, Notes
ATLAS17byq, z=0.045, SN Ia, best match is SN 1994D at -3 days
ATLAS17byo, z=0.03, SN Ia, best match is SN 2000dn at peak
ATLAS17cgg, z=0.02, SN IIn, best match is SN 1998S at -12 days

Sujay Mate (IIT Bombay), Varun Bhalerao (IIT Bombay), Dipankar Bhattacharya (IUCAA), Sukanta Bose (IUCAA), Gulab Chand Dewangan (IUCAA), Ranjeev Misra (IUCAA), Sanjit Mitra (IUCAA), A R Rao (TIFR), Tarun Souradeep (IUCAA), Santosh Vadawale (PRL), on behalf of the Astrosat CZTI team report:

We carried out offline analysis of data from AstroSat CZTI in a 100 second window centred on the G277583 trigger time, UT 2017-03-13 22:40:09.593, to look for any hard X-ray flash. CZTI is a coded aperture mask instrument that has considerable effective area for about 29% of the entire sky. Based on the pointing direction of AstroSat at the time of the GW event and the baystar skymap provided by LVC (skyprobcc_cWB.fits), the sky visible to CZTI has 28.2% probability of containing the EM counterpart.

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 count rates were estimated by using data from 8 neighbouring orbits. We selected confidence levels such that the probability of a false trigger in this 100s window is 10^-4. We do not find any evidence for any hard X-ray transient in this window. We model the source with a band function using standard parameters, with alpha = -1, beta = -2.5 and E_peak = 300 keV. The sensitivity of CZTI varies with direction. We weight the sensitivity by the baystar probability density map to calculate upper limits on any coincident emission from the source. In the 30-200 keV, the upper limits for source fluence are 1.92e-07 ergs/cm^2, 4.39e-07 ergs/cm^2 and 1.09e-06 ergs/cm^2 for search timescales of 0.1, 1, and 10 seconds respectively. The corresponding flux upper limits for the three timescales are 1.92e-06, 4.39e-07, and 1.09e-07 ergs/cm^2/sec respectively. 

Plots showing CZTI sensitivity as a function of direction for this event can be found at https://gracedb.ligo.org/apiweb/events/G277583/files/G277583_CZTI_limits.pdf,0

A. Y. Lien (GSFC/UMBC), S.D. Barthelmy (NASA/GSFC), D.M. Palmer (LANL),
T. Sakamoto (AGU), A. A. Breeveld (MSSL-UCL), A.P. Beardmore (U. Leicester),
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), P.A. Evans (U. Leicester), P. Giommi (ASI), C. Gronwall (PSU),
J. A. Kennea (PSU), H.A. Krimm (CRESST/GSFC/USRA), N.P.M. Kuin (UCL-MSSL),
F.E. Marshall (NASA/GSFC), A. Melandri (INAF-OAB), B. Mingo (U. Leicester),
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. 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:

We report the search results in the BAT data within T0 $B!^(B 100 s of the
LIGO event G277583 (LIGO/VIRGO Collaboration GCN Circ. 20860
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 ),
where T0 is the LIGO trigger time (2017-03-13T22:40:09.593 UTC).

The BAT pointing position at T0 is
RA = 44.214 deg,
DEC = -47.634 deg,
ROLL = 306.125 deg.
The BAT Field of View (>10% partial coding) covers 19.22% of the integrated
LIGO localization probability.

No significant detections (signal-to-noise ratio > 4 sigma) are found
in the BAT raw light curves with time bins of 64 ms, 1 s, and 1.6 s, respectively.
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 4-sigma upper limit in the 1-s binned light
curve corresponds to a flux upper limit (15-350 keV) of ~ 6.7 x 10^-8 erg/s/cm^2.
Moreover, no event data are found within T0 +/- 100 s.

BAT retains decreased, but significant, sensitivity to rate increases for
gamma-ray events outside of its FOV. About 59.52% of the integrated LIGO
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 of those within the FOV.

All the BAT analyses use the LIGO sky map cWB_plus_LIB.fits.gz
(LIGO/VIRGO Collaboration GCN Circ. 20860
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 ).

S. B. Cenko (NASA GSFC), P. Gatkine (UMCP), and E. Troja (GSFC/UMCP) report on behalf of the GROWTH collaboration:

We imaged the reported location of ATLAS17cck (Tonry et al., LVC GCN 20877
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 ) with the Large Monolithic Imager on the 4.3m Discovery Channel Telescope in Happy Jack, AZ.  Observations were obtained in the r��� filter for a total of 900 s, beginning at 2:48 UT on 16 March. We do not detect any emission at this location, to a limiting magnitude of r��� > 25.2 (calculated with respect to nearby SDSS point sources in the image).  As reported by Chen et al. (LVC GCN 20878
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 ) and Littlefield et al. (LVC GCN 20879
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 ), we do detect nearby the minor planet (1056) Azalea approximately 45��� east of this location at this time.

S. J. Smartt, K. W. Smith, J. Tonry, L. Denneau, A. Heinze,
B. Stalder, H. Weiland (IfA), C. W. Stubbs (Harvard), A. Rest (STScI),
K. C. Chambers (IfA), T.-W. Chen (MPE), M. Coughlin (Harvard),
M. E. Huber (IfA), D. E. Wright, D. R. Young, E. Kankare (QUB),
H. Flewelling, T. Lowe, E. A. Magnier, A. S. B. Schultz, C. Waters,
R. J. Wainscoat, M. Willman (IfA),


Further to GCN20877
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 , we report ATLAS observations of the skymap
(cWB_plus_LIB.fits) of G277583 (GCN 20860
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 ), with event time
2017-03-13 22:40:09.593 == 57825.94498372

We started observing at MJD=57826.54, 14hrs after the LIGO alert and
covered approximately 3600 sq degrees during the first 2 days. This
corresponds to a probability coverage of approximately 60% of the
cWB_plus_LIB.fits skymap (final number currently being refined, map
plot will be available on GraceDB). The limiting magnitude in the 30 sec
exposures in the orange filters is o ~ 18.7

We find the following four transients which are within the 90% contour
for which we have no previous detections. We also list, for reference 
old objects which are within the skymap but discovered before G277583

We apologise for the earlier release of ATLAS17cck in GCN 20877
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 , which
is indeed minor planet Azalea (GCN 20879
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 , Littlefield &
Garnavich). The object passed through our automated positional scatter
and ephemeris filters for removing known and unknown moving objects
and therefore did not trigger automatic rejection. This was due to an
artificial magnitude split introduced into our local version (at QUB)
of the minor planet database, with objects brighter than a threshold
maximum magnitude not being checked. The magnitude calculation was an 
oversimplification, and has been removed. Additional checks have also 
been introduced to prevent leakage of minor planets into the stationary list.


Name        RA            DEC          MJD Discovery Mag   f    PC    Host/Comment                      
ATLAS17cdb  05:14:50.41  -32:09:46.9  57827.25431835 18.55 o    90   orphan                            
ATLAS17byq  17:07:47.34  +09:49:20.8  57826.61285455 17.61 o    90   2MASX J17074707+0949172           
ATLAS17byo  16:33:19.87  +23:43:52.4  57826.58056845 17.43 o    80   z=0.033, SDSS J163319.94+234356.4 
ATLAS17cgg  08:03:55.23  +26:31:12.3  57826.42460955 18.02 o    50   z=0.0217, IC 0491                

f = filter
PC = probability contour within which the object lies 


Old objects from before G277583
Name        RA            DEC          MJD Discovery Mag   f    PC    Host/Comment                      
ATLAS17bza  17:19:36.88  -25:01:04.2  57826.57606615 16.49 o    70     AT2017aby
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  (Gaia17agz), b=7, likely Galactic                         
ATLAS17bkc  15:27:56.20  +11:42:17.0  57816.61101455 18.40 c    80                                                 
ATLAS17bhd  06:26:20.16  -01:22:47.5  57808.37305585 16.55 c    90     b=-6.2, probable CV, faint source in PS1                                            
ATLAS17bib  09:44:23.18  +34:16:03.1  57805.44415665 18.87 c    90     AT 2017blg
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ATLAS17bkt  15:19:18.86  +28:13:44.4  57817.57088835 16.54 c    90     AT2017cak
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 , ATel 10152                   
ATLAS17cgp  16:32:23.53  -02:36:07.2  57816.65313705 18.30 c    40     AT2017ly
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ATLAS17bkb  15:20:07.83  +11:52:37.5  57816.61101455 18.25 c    90     AT2017byj
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 , ATel 10148                   
ATLAS17btj  12:14:16.03  -38:05:48.1  57807.56503375 18.66 c    80     AT2017bzg
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   ATel 10152                   
ATLAS17bhq  08:38:57.62  +28:24:40.0  57805.40020845 19.07 c    60     AT2017bhe
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C. Littlefield and P. Garnavich (Notre Dame) report:

We obtained images of the field around
the optical transient ATLAS17cck (GCN 20877
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 ) which
is within the localization region of LIGO/Virgo G277583.
Unfiltered CCD images were taken using the 0.8-m
Krizmanich telescope under poor conditions.

We detect a bright (r=16.5 mag) source at
07:44:53.33 +24:45:52.9 (J2000) which is
not visible in the SDSS DR12 images. This source
is 41 arcsec east of the position reported
for ATLAS17cck. Using MPChecker to
search for minor planets we find that
(1056) Azalea (V=16.3) was within 6 arcsec of
the position of ATLAS17cck at 2017 March 15.43 UT,
the time of the first ATLAS detection.

It is likely that minor planet Azalea is ATLAS17cck and
we suggest that fixed position photometry of this
moving source could mimic a fading transient.

T.-W. Chen and P. Wiseman (both MPE Garching) report:

We observed the field of ATLAS17cck (Tonry et al., GCN #20877
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 ) simultaneously in
g'r'i'z'JHK with GROND (Greiner et al. 2008, PASP 120, 405) mounted at the 2.2 m
MPG telescope at ESO La Silla Observatory (Chile).

Observations started at 01:17 UT on 2017-03-16, 15 hours after the earliest
detection reported in Tonry et al. (GCN #20877
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 ). They were performed at an
average seeing of 1.4" and at an average airmass of 1.7.

Based on the 24.5 minutes (griz) and 21.3 minutes (JHK) of exposures, we do not
detect a source within the ATLAS17cck error circle of 2��� radius down to the
following 3 sigma limiting AB magnitudes:

g' > 23.9 mag,
r' > 23.9 mag,
i' > 23.3 mag,
z' > 23.1 mag,
J > 21.1 mag,
H > 20.6 mag, and
K > 18.8 mag

However, we note the detection of a bright, uncatalogued source located at RA,
Dec = 07:44:50.33, +24:45:54.8, equivalent to 116.22165, +24.76602, with an
r���-band magnitude of 16.2 mag. We believe this to be the same object as
ATLAS17cck, and that it corresponds to the asteroid (1056) Azalea, which is
expected at this location according to the IAU's Minor Planet Checker,
'http://www.minorplanetcenter.net/'.

The given limits are derived based on images calibrated against Pan-STARRS/2MASS
field stars, and are not corrected for the Galactic foreground extinction
corresponding to a reddening of E_(B-V)= 0.04 in the direction of the reported object
(Schlafly & Finkbeiner 2011).

We acknowledge the excellent support provided by the observer, Paula Sarkis, at
the telescope, and the support astronomer, Sam Kim, in obtaining these data. And
Ying-Tung Chen for checking the asteroid position.

J. Tonry, L. Denneau, A. Heinze, B. Stalder, H. Weiland (IfA),
C. W. Stubbs (Harvard), K. W. Smith, S. J. Smartt, D. R. Young
E. Kankare, (QUB), A. Rest (STScI), K. C. Chambers (IfA), M. Coughlin
(Harvard), M. E. Huber (IfA), D. E. Wright (QUB), H. Flewelling,
E. A. Magnier, A. S. B. Schultz, C. Waters, R. J. Wainscoat (IfA),
T. W Chen (MPE)


We observed the skymap of G277583 on MJD=57826 and 57827 with ATLAS
(see Tonry et al. GCN 20382
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 ) in the orange filter (a composite
r+i). 

Full details will follow soon, but we immediately draw attention to
the following fast declining transient. We plan further photometry
with Pan-STARRS1, but a spectrum as a soon as possible would 
be desirable.

The decline rate is 0.54 mag/hr

ATLAS17cck  07:44:50.33 +24:45:54.8  (116.20972 +24.76524)

Lightcurve : 
   Mag  err   MJD
 >18.97          57826.4410705
  15.78 0.03   57827.4286248
  15.81 0.03   57827.4315352
  15.87 0.03   57827.434911
  15.99 0.03   57827.4353887
  15.96 0.04   57827.4428893
  16.19 0.04   57827.4599793

We find no previous catalogued source at this position, neither
galaxy or star.

M. Boer, R. Laugier, K. Noysena (ARTEMIS - UCA/CNRS/OCA), A. Klotz (IRAP
- OMP/UPS/CNRS) report on behalf of the TZAC collaboration:

ERRATUM: The table of fields in LV GCN 20871
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  has been incorrectly formated. We apologize for the difficulties to read it, and provide below the table of observed fields in a simpler format.


0     05:49:43.36'    +20:35:54.6
1     05:54:55.60'    +18:38:09.5
2     05:49:51.76'    +22:17:42.1
3     05:53:25.62'    +24:25:48.8
4     05:57:51.55'    +20:34:17.6
5     05:58:01.71'    +22:27:34.7
6     06:05:57.39'    +21:55:44.4
7     06:04:43.28'    +24:04:45.5
8     06:14:10.43'    +21:51:14.3
9     06:13:06.44'    +24:08:47.3
10    06:20:05.27'    +26:04:06.9
11    06:30:25.58'    +23:24:28.6
12    06:24:06.40'    +27:57:13.6
13    06:29:33.19'    +25:26:56.6
14    06:39:59.35'    +24:27:36.7
15    06:35:43.67'    +29:13:31.2
16    06:38:15.47'    +27:12:43.7
17    06:53:38.60'    +22:33:21.6
18    06:50:05.18'    +28:32:13.6
19    06:52:10.23'    +30:33:05.3
20    07:04:09.58'    +23:51:32.4
21    06:59:41.61'    +28:24:19.1
22    07:04:48.51'    +25:51:21.9
23    07:13:16.96'    +23:23:27.8
24    07:13:36.84'    +25:22:33.4
25    07:09:21.06'    +31:30:15.8
26    07:08:59.26'    +29:36:45.6
27    07:12:59.10'    +27:47:40.1
28    07:20:11.66'    +29:39:59.8
29    07:25:09.46'    +25:13:34.1
30    07:22:33.86'    +27:25:27.6
31    07:33:59.92'    +25:28:39.7
32    07:28:56.40'    +29:34:52.1
33    07:34:35.36'    +27:36:11.8
34    06:50:15.75'    +24:37:59.6
35    06:47:35.50'    +26:33:37.1

M. Boer, R. Laugier, K. Noysena (ARTEMIS - UCA/CNRS/OCA), A. Klotz (IRAP 
- OMP/UPS/CNRS) report on behalf of the TZAC collaboration:

We have observed about 135 sq. deg. of the error box of G277583 in 36 
fields during the night of 14-15 March, starting at 18h10 UT at TCA 
(TAROT Calern Observatory). Each exposure lasted 120s, with no filter. 
Sky conditions were good, and the images are being examinated.

The list of the field centers follows:

Index Ra        Dec

0 05:49:43.36' +20:35:54.6

1 05:54:55.60' +18:38:09.5

2 05:49:51.76' +22:17:42.1

3 05:53:25.62' +24:25:48.8

4 05:57:51.55' +20:34:17.6

5 05:58:01.71' +22:27:34.7

6 06:05:57.39' +21:55:44.4

7 06:04:43.28' +24:04:45.5

8 06:14:10.43' +21:51:14.3

9 06:13:06.44' +24:08:47.3

10 06:20:05.27' +26:04:06.9

11 06:30:25.58' +23:24:28.6

12 06:24:06.40' +27:57:13.6

13 06:29:33.19' +25:26:56.6

14 06:39:59.35' +24:27:36.7

15 06:35:43.67' +29:13:31.2

16 06:38:15.47' +27:12:43.7

17 06:53:38.60' +22:33:21.6

18 06:50:05.18' +28:32:13.6

19 06:52:10.23' +30:33:05.3

20 07:04:09.58' +23:51:32.4

21 06:59:41.61' +28:24:19.1

22 07:04:48.51' +25:51:21.9

23 07:13:16.96' +23:23:27.8

24 07:13:36.84' +25:22:33.4

25 07:09:21.06' +31:30:15.8

26 07:08:59.26' +29:36:45.6

27 07:12:59.10' +27:47:40.1

28 07:20:11.66' +29:39:59.8

29 07:25:09.46' +25:13:34.1

30 07:22:33.86' +27:25:27.6

31 07:33:59.92' +25:28:39.7

32 07:28:56.40' +29:34:52.1

33 07:34:35.36' +27:36:11.8

34 06:50:15.75' +24:37:59.6

35 06:47:35.50' +26:33:37.1

LIGO/Virgo G277583: SVOM/Mini-GWAC observations of the initial skymap

J.Y. Wei (NAOC), X.H. Han (NAOC), C. WU (NAOC), N. Leroy (LAL),
S. Antier (LAL), L.P. Xin (NAOC), X.M. Meng (NAOC), L. Huang (NAOC),
Y. Xu (NAOC), H.B. Cai (NAOC), J. Wang (NAOC), X.M. Lu (NAOC),
Y.L. Qiu (NAOC), J.S. Deng (NAOC), L. Cao (NAOC), S. Wang (NAOC),
L. Jia (NAOC), S.C. Zou (NAOC), S.F. Liu (NAOC), Q.C. Feng (NAOC),
H.L. Li (NAOC), D.W. Xu (NAOC), Y.J. Xiao (NAOC), W.L. Dong (NAOC),
Y.T. Zheng (NAOC), E.W.Liang (GXU), X.G.Wang (GXU), Y.G. Yang (HBNU),
B. Cordier (CEA), S.N. Zhang (NAOC), D. Dornic (CPPM), B.B. Wu (IHEP),
J.L. Atteia (IRAP), D. Götz (CEA), C.Lachaud (APC),
on behalf of the SVOM Gravitational Astronomy group report:

We observed about 4800 square degree (12 sky regions) of the skymap
of the advanced LIGO trigger G277583, with SVOM/Mini-GWAC, at Xinglong
Observatory of NAOC equipped with U9000 camera (FOV~400 square
degree/camera).
SVOM/Mini-GWAC comprises 8 wide field angle cameras (aperture=7cm),
working with unfiltered band. The observations are operated in time-series
mode, taking one exposure in 15 seconds (10s exposure + 5s readout).
The limit magnitude is ~12 mag in R band. We estimate a 46.9% prior
probability that these 12 regions contain the true location of the
source.

The coordinates of the 12 regions and observation time are list following:

start-obs(UTC) end-obs(UTC) Ra Dec Camera_ID
2017-03-14 11:10:29 2017-03-14 17:59:02 09:10:29.8 +29:50:17 C1
2017-03-14 11:10:55 2017-03-14 17:59:54 09:13:10.6 +10:17:08 C2
2017-03-14 11:10:45 2017-03-14 16:40:29 07:46:15.6 +29:57:47 C3
2017-03-14 16:50:46 2017-03-14 21:30:00 16:14:18.2 +30:03:36 C3
2017-03-14 11:10:45 2017-03-14 16:40:01 07:50:25.4 +09:54:53 C4
2017-03-14 16:50:38 2017-03-14 21:30:00 16:18:18.2 +09:59:04 C4
2017-03-14 11:10:30 2017-03-14 13:33:01 04:55:10.8 +29:25:59 C5
2017-03-14 13:34:31 2017-03-14 21:30:00 14:36:21.1 +69:30:06 C5
2017-03-14 11:10:11 2017-03-14 13:33:39 04:58:00.5 +10:28:12 C6
2017-03-14 13:34:09 2017-03-14 21:30:00 14:40:07.7 +50:29:58 C6
2017-03-14 12:45:41 2017-03-14 14:56:37 06:18:37.7 +29:46:06 C7
2017-03-14 12:45:01 2017-03-14 15:56:16 06:20:02.3 +10:21:24 C8


The first image was taken ~12 hours 30 minutes after the event trigger.
Note that the observations have been done under poor conditions (partly
cloudy and full moon). The limit magnitude is ~10 mag in R band.
No any significant transient is found in our online pipeline. The
image analysis is ongoing in detailed processing with our offline
pipeline.

V. Savchenko (ISDC, University of Geneva, CH)
on behalf of the INTEGRAL group:
S. Mereghetti (IASF-Milano, Italy),
C. Ferrigno ((ISDC, University of Geneva, CH),
E. Kuulkers (ESTEC/ESA, The Netherlands),
A. Bazzano (IAPS-Roma, Italy), E. Bozzo,
T. J.-L. Courvoisier (ISDC, University of Geneva, CH)
S. Brandt (DTU - Denmark) R. Diehl (MPE-Garching, Germany)
L. Hanlon (UCD, Ireland) P. Laurent (APC, Saclay/CEA, France)
A. Lutovinov (IKI, Russia) J.P. Roques (CESR, France)
R. Sunyaev (IKI, Russia) P. Ubertini (IAPS-Roma, Italy)

The INTEGRAL spacecraft has a highly elliptical orbit and the
instruments are switched off around the perigee passage, every 2.6
days, to prevent radiation-induced damages. Unfortunately, at the time
of the LIGO/Virgo trigger G211117 (2017-03-13 22:40:09.59 UTC) the
spacecraft was preparing to the perigee passage between the orbits
number 1792 and 1793, and no scientific instrument data are available
after 2017-03-13T22:25:25.

M. Ageron (CPPM/CNRS), B. Baret (APC/CNRS), A. Coleiro (IFIC & APC/CNRS), D. Dornic (CPPM/CNRS), A. Kouchner (APC/Universite Paris Diderot), 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 G277583 event using the initial LIGO cWB probability map at event time (LVC GCN Circ. 20860
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 ). The ANTARES visibility at the time of the alert together with the 90% contour of the probability map are shown in: https://www.cppm.in2p3.fr/~dornic/events/G277583.png (gwantares/ANT@GW). Considering the location probability provided by the LIGO collaboration, there is a 48.5% chance that the GW emitter was in the ANTARES field of view.

No up-going muon neutrino candidate events were recorded within the 90% contour during a +/- 500s time-window centered on the G277583 event time. The expected number of atmospheric background events in the region visible by ANTARES is ~6.5e-3 in the +/- 500s time window. An extended search during +/- 1 hour gives no up-going neutrino coincidence.

An estimate of the upper limit on the associated neutrino fluence will be sent in a subsequent circular.

ANTARES, being installed in the Mediterranean Deep Sea, is the largest neutrino detector in the Northern Hemisphere.  It is primarily sensitive to astrophysical neutrinos in the TeV-PeV energy range.  At 10 TeV, the median angular resolution for muon neutrinos is below 0.5 degrees.  In the range 1-100 TeV, ANTARES has the best sensitivity to a large fraction of the Southern sky.

G. Minervini (INAF/IAPS), F. Verrecchia (ASDC and INAF/OAR), M. Cardillo
(INAF/IAPS), G. Piano (INAF/IAPS), C. Pittori (ASDC), M. Tavani (INAF/IAPS,
and Univ. Roma Tor Vergata), A. Bulgarelli, V. Fioretti, A. Zoli, N.  
Parmiggiani
(INAF/IASF-Bo),  F. Lucarelli (ASDC and INAF/OAR), P. Munar-Adrover  
(INAF/IAPS),
A. Argan, Y. Evangelista (INAF/IAPS), I. Donnarumma (ASI), F. Fuschino, M.
Marisaldi (INAF/IASF-Bo and Bergen University),  A. Giuliani (INAF/IASF-Mi),
M. Pilia, A. Trois (INAF/OA-Cagliari), F. Longo (Univ. Trieste and  
INFN Trieste)
report on behalf of the AGILE Team:

In response to the LIGO/Virgo event G277583 we performed an analysis of the
AGILE Gamma-Ray Imaging Detector (GRID) data on different timescales.

On LIGO trigger time (T0 = 2017-03-13 22:40:09.593 UT), the GRID exposure
covered about 35% of the LIGO localization region that was observed with
off-axis angles between 35 and 70 deg, approximately.

An analysis of the data in the energy range 50 MeV - 10 GeV was performed
on timescales from 2 to 100 sec centered at T0. Preliminary typical values of
3-sigma upper limits obtained within the accessible G277583  
localization region
are reported below:
4.0e-06 erg cm^-2 s^-1 for integration time of 2s,
2.7e-07 erg cm^-2 s^-1 for integration time of 20s,
7.0e-08 erg cm^-2 s^-1 for integration time of 100s.

These ULs apply to a large fraction of the GRID-exposed LIGO  
localization region.

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

M.Cardillo (INAF/IAPS), F. Verrecchia (ASDC and INAF/OAR), G. Minervini
(INAF/IAPS), G. Piano (INAF/IAPS), A. Bulgarelli (INAF/IASF-Bo), M. Tavani
(INAF/IAPS, and Univ. Roma Tor Vergata), C. Pittori (ASDC),  V. Fioretti,
A. Zoli, N. Parmiggiani (INAF/IASF-Bo),  F. Lucarelli (ASDC and INAF/OAR),
P. Munar-Adrover (INAF/IAPS), A. Argan, Y. Evangelista (INAF/IAPS), I.
Donnarumma (ASI), F. Fuschino, M. Marisaldi (INAF/IASF-Bo and Bergen
University), A. Giuliani (INAF/IASF-Mi), M. Pilia, A. Trois
(INAF/OA-Cagliari), F. Longo (Univ. Trieste and INFN Trieste) report on
behalf of the AGILE Team:

In response to the LIGO/Virgo GW event G277583 at T0 = 2017-03-13
22:40:09.593 UTC, a preliminary analysis of the AGILE-GW fast data
processing procedure found no AGILE MiniCALorimeter (MCAL) event candidates
within a time interval covering -/+ 50 sec from the LIGO T0.

Two data acquisitions were collected about 55 sec before and 30 sec after
the LIGO T0; they show no significant transient candidate event. About 40%
of the LIGO error box was observable by the AGILE MCAL. A 3-sigma UL was
computed for a 1 s integration time, on different celestial positions within
the G277583 error box and varies from a minimum of 5.5e-7 erg cm^-2 to a
maximum of 10 e-7 erg cm^-2, assuming as a spectral model a simple power
law with photon index 1.4. The AGILE-MCAL instrument is a CsI detector with
a 4-pi FoV, working in the range 0.4 - 100 MeV. Additional analysis of AGILE
data is in progress.

I. Bartos, S. Countryman (Columbia), C. Finley (U Stockholm), E. Blaufuss (U Maryland), R. Corley, Z. Marka, S. Marka (Columbia) on behalf of the IceCube Collaboration

We searched IceCube online track-like neutrino candidates (GFU) detected in a [-500,500] second interval about the LIGO-Virgo trigger G277583.  We compared the candidate source directions of 2 temporally-coincident neutrinos to the SKYPROBCC_CWB skymap, with the following parameters:

#            dt[s]     RA[deg]    Dec[deg]      E[TeV]  Sigma[deg]
------------------------------------------------------------------
1.         -333.80       161.5        27.6        1.33         1.3
2.          156.93       207.9        32.0        0.75         0.4


(dt--time from GW in [seconds]; RA/Dec--sky location in [degrees]; E--reconstructed secondary muon energy in [TeV]; Sigma--uncertainty of direction reconstruction in [degrees])

The analysis found NO COINCIDENT ONLINE TRACK-LIKE NEUTRINO CANDIDATES detected by IceCube within the 500 second window surrounding G277583 within the SKYPROBCC_CWB skymap.

In addition, we are performing coincident searches with other IceCube data streams, including the high-energy starting events (HESE) and Supernova triggers.  HESE events have typical energies > 60 TeV and start inside the detector volume, leading to a relatively pure event sample with a high fraction of astrophysical neutrinos.  The SN trigger system is sensitive to sudden increases in photomultiplier counts across the detector, which could indicate a burst of MeV neutrinos.  We will submit separate GCN circulars if coincident HESE or SN triggers are found.

The IceCube Neutrino Observatory is a cubic-kilometer neutrino detector operating at the geographic South Pole, Antarctica.  For a description of the IceCube realtime alert system, please refer to<http://adsabs.harvard.edu/cgi-bin/bib_query?arXiv:1610.01814
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 >; for more information on joint neutrino and gravitational wave searches, please refer to<http://adsabs.harvard.edu/cgi-bin/bib_query?arXiv:1602.05411
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 >.

The LIGO Scientific Collaboration and Virgo report:

The CWB Burst analysis identified candidate G277583 during real-time
processing of data from LIGO Hanford Observatory (H1) and LIGO
Livingston Observatory (L1) at 2017-03-13 22:40:09.593 UTC (GPS time:
1173480027.593).

G277583 is an event of interest because its false alarm rate, as
determined by the online analysis, is 8.4e-08 Hz or about one in 4
months. The event's properties can be found at this URL:

https://gracedb.ligo.org/events/G277583

Two sky maps are available at this time and can be retrieved from
the GraceDB event page:
  *skyprobcc_cWB.fits, an initial localization generated by cWB,
   included in the original GCN notice.
  *cWB_plus_LIB.fits.gz, a pixel-by-pixel arithmetic mean of the
   cWB and LIB sky maps. Since neither cWB nor LIB is favored
   over the other, this mean sky map is the preferred sky map at
   this time. The 50% confidence interval covers 2130 squares
   degrees and the 90% confidence interval covers 12140 square
   degrees.

Updates on our analysis of this event will be sent as they become
available.