//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 25752 SUBJECT: LIGO/Virgo S190915ak: Global MASTER-Net observations report DATE: 19/09/16 00:25:26 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs 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-Kislovodsk robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) started inspect of the LIGO/Virgo S190915ak errorbox 20 sec after notice time and 488 sec after trigger time at 2019-09-16 00:05:10 UT, with upper limit up to 18.0 mag. The observations began at zenit distance = 66 deg. The sun altitude is -28.9 deg. MASTER-Tavrida robotic telescope located in Russia (Lomonosov MSU, SAI Crimea astronomical station) started inspect of the LIGO/Virgo S190915ak errorbox 42 sec after notice time and 510 sec after trigger time at 2019-09-16 00:05:32 UT, with upper limit up to 17.9 mag. The observations began at zenit distance = 66 deg. The sun altitude is -32.6 deg. MASTER-IAC robotic telescope located in Spain (IAC Teide Observatory) started inspect of the LIGO/Virgo S190915ak errorbox 58 sec after notice time and 526 sec after trigger time at 2019-09-16 00:05:48 UT, with upper limit up to 15.4 mag. The observations began at zenit distance = 80 deg. The sun altitude is -56.6 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=10805 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 538 | 2019-09-16 00:05:10 | MASTER-Kislovodsk | (12h 28m 43.081s , +69d 10m 37.29s) | C | 100 | 17.9 | 538 | 2019-09-16 00:05:10 | MASTER-Kislovodsk | (12h 51m 21.032s , +68d 43m 30.04s) | C | 100 | 18.0 | 561 | 2019-09-16 00:05:32 | MASTER-Tavrida | (12h 37m 08.804s , +69d 06m 05.53s) | C | 100 | 16.9 | 561 | 2019-09-16 00:05:32 | MASTER-Tavrida | (12h 39m 58.560s , +69d 11m 14.24s) | C | 100 | 17.9 | 582 | 2019-09-16 00:05:48 | MASTER-IAC | (12h 38m 17.588s , +69d 16m 19.88s) | P| | 110 | 14.9 | 582 | 2019-09-16 00:05:48 | MASTER-IAC | (12h 40m 14.677s , +69d 12m 29.84s) | P- | 110 | 15.4 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 25753 SUBJECT: LIGO/Virgo S190915ak: Identification of a GW compact binary merger candidate DATE: 19/09/16 00:27:49 GMT FROM: Alan Weinstein at Caltech/LIGO The LIGO Scientific Collaboration and the Virgo Collaboration report: We identified the compact binary merger candidate S190915ak during real-time processing of data from LIGO Hanford Observatory (H1), LIGO Livingston Observatory (L1), and Virgo Observatory (V1) at 2019-09-15 23:57:02.691 UTC (GPS time: 1252627040.691). The candidate was found by the GstLAL [1], SPIIR [2], CWB [3], and MBTAOnline [4] analysis pipelines. S190915ak is an event of interest because its false alarm rate, as estimated by the online analysis, is 9.7e-10 Hz, or about one in 32 years. The event's properties can be found at this URL: https://gracedb.ligo.org/superevents/S190915ak The classification of the GW signal, in order of descending probability, is BBH (>99%), Terrestrial (<1%), BNS (<1%), MassGap (<1%), or NSBH (<1%). Assuming the candidate is astrophysical in origin, there is strong evidence against the lighter compact object having a mass < 3 solar masses (HasNS: <1%). Using the masses and spins inferred from the signal, there is strong evidence against matter outside the final compact object (HasRemnant: <1%). 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 [5], distributed via GCN notice about 6 minutes after the candidate trigger time. For the bayestar.fits.gz sky map, the 90% credible region is 528 deg2. Marginalized over the whole sky, the a posteriori luminosity distance estimate is 1557 +/- 381 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 . [1] Messick et al. PRD 95, 042001 (2017) [2] Qi Chu, PhD Thesis, The University of Western Australia (2017) [3] Klimenko et al. PRD 93, 042004 (2016) [4] Adams et al. CQG 33, 175012 (2016) [5] Singer & Price PRD 93, 024013 (2016) [GCN OPS NOTE(15sep19): Per author's request, "trigger time." was added to the end of the first sentence in the fifth paragraph.] //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 25754 SUBJECT: LIGO/Virgo S190915ak: Upper limits from IceCube neutrino searches DATE: 19/09/16 00:28:14 GMT FROM: Raamis Hussain at IceCube IceCube Collaboration (http://icecube.wisc.edu/) reports: Searches [1,2] for track-like muon neutrino events detected by IceCube consistent with the sky localization of gravitational-wave candidate S190915ak in a time range of 1000 seconds [3] centered on the alert event time (2019-09-15 23:48:42.691 UTC to 2019-09-16 00:05:22.691 UTC) have been performed. During this time period IceCube was collecting good quality data. No significant track-like events are found in spatial coincidence of S190915ak calculated from the map circulated in the 1-Preliminary notice. IceCube's sensitivity assuming an E^-2 spectrum (E^2 dN/dE) to neutrino point sources within the locations spanned by the 90% spatial containment of S190915ak ranges from 0.032 to 0.083 GeV cm^-2 in a 1000 second time window. 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] Bartos et al. arXiv:1810.11467 (2018) and Countryman et al.arXiv:1901.05486 (2019) [2] Braun et al., Astroparticle Physics 29, 299 (2008) [3] Baret et al., Astroparticle Physics 35, 1 (2011) //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 25755 SUBJECT: LIGO/Virgo S190915ak: No counterpart candidates in INTEGRAL SPI-ACS prompt observation DATE: 19/09/16 00:40:53 GMT FROM: Francesca Onori at INAF/IAPS Francesca Onori, Antonio Martin-Carrillo V. Savchenko, C. Ferrigno (ISDC/UniGE, Switzerland) J. Rodi (IAPS-Roma, Italy) A. Coleiro (APC, France) S. Mereghetti (INAF IASF-Milano, Italy) on behalf of the INTEGRAL multi-messenger collaboration: https://www.astro.unige.ch/cdci/integral-multimessenger-collaboration Using INTEGRAL/SPI-ACS realtime data (following [1]) we have performed a search for a prompt gamma-ray counterpart of S190915ak (GCN 25753). At the time of the event (2019-09-15 23:57:02 UTC, hereafter T0), INTEGRAL was operating in nominal mode. The peak of the event localization probability was at an angle of 94 deg with respect to the spacecraft pointing axis. This orientation implies strongly suppressed (8.3% of optimal) response of ISGRI, strongly suppressed (24% of optimal) response of IBIS/Veto, and near-optimal (8 8% of optimal) response of SPI-ACS. The background within +/-300 seconds around the event was very stable (excess variance 1.1). We have performed a search for any impulsive events in INTEGRAL SPI- ACS (as described in [2]) data. We do not detect any significant counterparts and estimate a 3-sigma upper limit on the 75-2000 keV fluence of 2e-07 erg/cm^2 (within the 50% probability containment region of the source localization) for a burst lasting less than 1 s with a characteristic short GRB spectrum (an exponentially cut off power law with alpha=-0.5 and Ep=600 keV) occurring at any time in the interval within 300 s around T0. For a typical long GRB spectrum (Band function with alpha=-1, beta=-2.5, and Ep=300 keV), the derived peak flux upper limit is ~1.8e-07 (5.2e-08) erg/cm^2/s at 1 s (8 s) time scale in 75-2000 keV energy range. For the mean reported distance 1557.0 Mpc this corresponds to the limit on the total is otropic equivalent energy in 1 s of 5.9e+49 erg for the short GRB spectrum and for a long GRB spectrum isotropic equivalent luminosity in 1 s (8 s) of 4.5e+49 erg/s (1.5e+49 erg/s) We report for completeness and in order of FAP, all excesses identified in the search region. We find: 8 likely background excesses: scale | T | S/N | luminosity ( x 1e+50 erg/s) | FAP 0.05 | 0.193 | 3.1 | 3.61 +/- 1.38 +/- 2.12 | 0.0612 2.4 | 42.8 | 3.7 | 5.52 +/- 1.96 +/- 3.24 | 0.0912 2.1 | 79.6 | 3.4 | 5.8 +/- 2.09 +/- 3.41 | 0.319 0.4 | -44.5 | 4 | 16.4 +/- 4.83 +/- 9.64 | 0.368 0.2 | -6.88 | 3.1 | 18.3 +/- 6.84 +/- 10.7 | 0.585 0.8 | 152 | 4 | 11.5 +/- 3.41 +/- 6.76 | 0.609 3.75 | 144 | 3 | 3.75 +/- 1.57 +/- 2.2 | 0.911 0.05 | -4.46 | 3.2 | 3.77 +/- 1.38 +/- 2.21 | 0.971 Note that FAP estimates (especially at timescales above 2s) may be possibly further affected by enhanced non-stationary local background noise. This list excludes any excesses for which FAP is close to unity. All results quoted are preliminary. This circular is an official product of the INTEGRAL Multi-Messenger team. [1] Savchenko et al. 2017, A&A 603, A46 [2] Savchenko et al. 2012, A&A 541A, 122S GCN pipeline version: a76508f https://sandbox.zenodo.org/record/369583 -- Dr. Francesca Onori Postdoctoral Researcher IAPS, via Fosso del Cavaliere, 100, 00133 - Rome, Italy e-mail: francesca.onori@inaf.it Tel: +39 06 45488128 //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 25756 SUBJECT: LIGO/Virgo S190915ak: No counterpart candidate in AGILE-MCAL observations DATE: 19/09/16 03:37:32 GMT FROM: Fabrizio Lucarelli at SSDC/INAF-OAR F. Lucarelli, F. Verrecchia (SSDC, and INAF/OAR), M. Tavani (INAF/IAPS, and Univ. Roma Tor Vergata), C. Casentini, M. Cardillo, G. Piano, A. Ursi (INAF/IAPS), C. Pittori (SSDC, and INAF/OAR), A. Bulgarelli, V. Fioretti, N. Parmiggiani (INAF/OAS-Bologna), M. Pilia (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 S190915ak at T0 = 2019-09-15 23:57:02 (UT), a preliminary analysis of the AGILE minicalorimeter (MCAL) triggered data found no event candidates within a time interval covering -/+ 15 sec from the LIGO/Virgo T0. At the T0, the whole S190915ak 90 c.l. localization region was accessible to the AGILE MCAL. Three-sigma upper limits (ULs) are obtained for a 1 s integration time at different celestial positions within the accessible S190915ak localization region, from a minimum of 1.6E-06 erg cm^-2 to a maximum of 7.0E-06 erg cm^-2 (assuming as spectral model a single power law with photon index 1.5). The AGILE-MCAL detector is a CsI detector with a 4 pi FoV, sensitive in the energy range 0.4-100 MeV. Additional analysis of AGILE data is in progress. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 25757 SUBJECT: LIGO/Virgo S190915ak: Upper Limits from AGILE-GRID observations DATE: 19/09/16 05:16:04 GMT FROM: Francesco Verrecchia at ASDC F. Verrecchia, F. Lucarelli (SSDC, and INAF/OAR), M. Tavani (INAF/IAPS, and Univ.Roma Tor Vergata), C. Casentini, M. Cardillo, G. Piano, A. Ursi (INAF/IAPS), C. Pittori (SSDC, and INAF/OAR), A. Bulgarelli, V. Fioretti, N. Parmiggiani (INAF/OAS-Bologna), M. Pilia (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 S190915ak at T0 = 2019-09-15 23:57:02.691 UTC a preliminary analysis of the AGILE exposure at T0 shows that the Gamma-Ray Imaging Detector (GRID) exposure covered the 22% of the 90% c.l. localization region (LR) (33% of 90% c.l. localization region (LR) is occulted by Earth) at an off-axis angle of about 70 degrees. We performed an analysis of the GRID data in the energy range 50 MeV - 10 GeV on T0, where good exposure of the S190915ak 90% c.l. LR was available. No candidate gamma-ray transient was detected. The following preliminary GRID values of 3-sigma upper limit (UL) are obtained: from 4.0e-06 to 1.0e-05 erg cm^-2 s^-1, with exposure of about 22% of the LR over the time interval ( T0 -2s ; T0 + 2s ) at an off-axis angle of about 70 degrees; from 1.6e-06 to 1.0e-05 erg cm^-2 s^-1, with exposure of about 37% of the LR over the time interval ( T0s ; T0 + 10s ) at an off-axis angle of about 70 degrees; from 3.9e-08 to 4.0e-07 erg cm^-2 s^-1, with exposure of about 75% of the LR over the time interval ( T0s+ 100s ; T0 + 200s ) at an off-axis angle between 30 and 70 degrees; A map in Galactic coordinates showing the AGILE FoV at T0 is available at the site: https://tools.ssdc.asi.it/ImgView/Agile/AGILE_FOV_LIGOS190915ak_190915011120 These measurements were obtained with AGILE observing a large portion of the sky in spinning mode. Additional analysis of AGILE data is in progress. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 25758 SUBJECT: LIGO/Virgo S190915ak : no neutrino counterpart candidate in ANTARES search DATE: 19/09/16 06:23:35 GMT FROM: Damien Dornic at CPPM,France 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 S190915ak event using the 90% contour of the Initial bayestar probability map provided by the GW interferometers (GCN#25753). 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/S190915ak_Initial.png . Considering the location probability provided by the LIGO/Virgo collaborations, there is a 45.6% 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 2019-09-15 23:57:02 and in the 90% contour of the S190915ak event. The expected number of atmospheric background events in the region visible by ANTARES is 2.31e-04 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 is 1.66e-03 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. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 25761 SUBJECT: LIGO/Virgo S190915ak: Coverage and upper limits from MAXI/GSC observations DATE: 19/09/16 12:54:11 GMT FROM: Motoko Serino at RIKEN/MAXI M. Serino, S. Sugita (AGU), H. Negoro (Nihon U.), N. Kawai (Tokyo Tech), 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. Sugizaki, 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.), Y. Kawakubo (LSU) report on behalf of the MAXI team: We examined MAXI/GSC all-sky X-ray images (2-20 keV) after the LVC trigger S190915ak at 2019-09-15 23:57:02.690 UTC (GCN 25753). At the trigger time of S190915ak, 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 35% of the 90% credible region of the bayestar skymap from 00:26:35 to 00:50:01 UTC (T0+1773 to T0+3179 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. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 25763 SUBJECT: LIGO/Virgo S190915ak: No counterpart candidates in Fermi-LAT observations DATE: 19/09/16 14:29:21 GMT FROM: Sara Cutini at INFN M. Axelsson (KTH and Stockholm Univ.), S. Cutini (INFN Perugia), M. Arimoto (Kanazawa Univ.), N. Omodei (Stanford Univ.), D. Kocevski (NASA/MSFC), F. Piron (CNRS/IN2P3/LUPM), F. Longo (Univ. and INFN Trieste) and E. Bissaldi (Politecnico and INFN Bari) report on behalf of the Fermi-LAT Collaboration: We have searched data collected by the Fermi Large Area Telescope (LAT) on Sep 15, 2019, for possible high-energy (E > 100 MeV) gamma-ray emission in spatial/temporal coincidence with the LIGO/Virgo trigger S190915ak (GCN 25753). We define "instantaneous coverage" as the integral over the region of the LIGO probability map that is within the LAT field of view at a given time, and "cumulative coverage" as the integral of the instantaneous coverage over time. Fermi-LAT had null instantaneous coverage of the LIGO probability region at the time of the trigger (T0 = 2019-09-15 23:57:02.691 UTC). Coverage of the region started around T0 + 2.5 ks, and reached 100% cumulative coverage at approximately T0 + 3.2 ks. We performed a search for a transient counterpart within the observed region of the 90% contour of the LIGO map in a fixed time window from T0 to T0 + 10 ks. No significant sources were found. We also performed a search which adapted the time interval of the analysis to the exposure of each region of the sky, and no additional excesses were found. Energy flux upper bounds for the fixed time interval between 100 MeV and 1 GeV for this search vary between 1.1E-10 and 5.3E-10 [erg/cm^2/s]. The Fermi-LAT point of contact for this event is Sara Cutini (sara.cutini@pg.infn.it). The Fermi-LAT is a pair conversion telescope designed to cover the energy band from 20 MeV to greater than 300 GeV. It is the product of an international collaboration between NASA and DOE in the U.S. and many scientific institutions across France, Italy, Japan and Sweden. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 25764 SUBJECT: LIGO/Virgo S190915ak: Upper limits from Fermi-GBM Observations DATE: 19/09/16 18:36:03 GMT FROM: Colleen A. Wilson at NASA/MSFC/NSSTC E. Burns (NASA/GSFC) and C.A. Wilson-Hodge (NASA/MSFC) reports on behalf of the Fermi-GBM Team and the GBM-LIGO/Virgo group For S190915ak and using the initial bayestar skymap, Fermi-GBM was observing 98.0% 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 S190915ak (GCN 25753). 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. Part of the LVC localization region is behind the Earth for Fermi, located at RA=129.5, Dec=-19.0 with a radius of 67.5 degrees. We therefore set upper limits on impulsive gamma-ray emission for the LVC localization region visible to Fermi at merger time. Using the representative soft, normal, and hard GRB-like templates described in arXiv:1612.02395, 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 norm hard -------------------------------------- 0.128 s: 11 13 23 1.024 s: 2.5 3.2 6.9 8.192 s: 1.1 1.3 1.6 Assuming the median luminosity distance of 1557 Mpc from the GW detection, we estimate the following intrinsic luminosity upper limits over the 1 keV-10 MeV energy range (in units of 10^50 erg/s): Timescale Soft Normal Hard ------------------------------------ 0.128 s: 4.7 5.0 15 1.024 s: 1.1 1.2 4.4 8.192 s: 0.47 0.50 1.0 //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 25765 SUBJECT: LIGO/Virgo S190915ak: no counterpart candidates in the Swift/BAT observations DATE: 19/09/16 22:54:38 GMT FROM: Amy Lien at GSFC A. Y. Lien (GSFC/UMBC), S. D. Barthelmy (NASA/GSFC), D. M. Palmer (LANL), 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-SSDC), 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 (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 S190915ak (LIGO/VIRGO Collaboration GCN Circ. 25753), where T0 is the LVC trigger time (2019-09-15T23:57:02.690 UTC). The center of the BAT field of view (FOV) at T0 is RA = 144.711 deg, DEC = 51.949 deg, and the roll angle is 135.601 deg. The BAT FOV (>10% partial coding) covers 85.57% of the integrated LVC localization probability, and 84.76% 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 ~ 1.05 x 10^-7 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 ~ 70.25 Mpc. Event data is available from T0-101.315 to T0+98.701. No significant detections are found in the 15-350 keV images created using intervals of T0 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 13.67% 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/S190915ak/web/source_public.html //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 25770 SUBJECT: LIGO/Virgo S190915ak: No transient candidates in CALET observations DATE: 19/09/17 04:41:17 GMT FROM: Yuta Kawakubo at Louisiana State U./CALET P. S. Marrocchesi (U of Siena), A. Yoshida, T. Sakamoto, V. Pal'shin, S. Sugita (AGU), Y. Kawakubo (LSU), K. Yamaoka (Nagoya U), S. Nakahira (RIKEN), Y. Asaoka, S. Ozawa, S. Torii (Waseda U), Y. Shimizu, T. Tamura (Kanagawa U), N. Cannady (GSFC/UMBC), M. L. Cherry (LSU), S. Ricciarini (U of Florence), and the CALET collaboration: The CALET Gamma-ray Burst Monitor (CGBM) was operating at the trigger time of S190915ak T0 = 2019-09-15 23:57:02.691 UT (The LIGO Scientific Collaboration and Virgo Collaboration, GCN Circ. 25753). No CGBM on-board trigger occurred around the event time. Based on the LIGO-Virgo 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 1 % and 2 %, respectively (and 100 % credible region of the initial localization map was above the horizon). The HXM and SGM fields of view were centered at RA = 107.0 deg, Dec = -4.2 deg and RA = 99.7 deg, Dec = -11.1 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 high energy trigger mode at the trigger time of S190915ak. Using the CAL data, we have searched for gamma-ray events in the 10-100 GeV band from -60 sec to +60 sec from the GW trigger time and found no candidates. There is no significant overlap with the LIGO-Virgo high probability localization region. The CAL FOV was centered at RA=99.7 deg, Dec=-11.1 deg at T0. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 25773 SUBJECT: LIGO/Virgo S190915ak: Updated Sky Localization DATE: 19/09/17 19:29:00 GMT FROM: Alan Weinstein at Caltech/LIGO The LIGO Scientific Collaboration and the Virgo Collaboration report: We have conducted further analysis of the data from LIGO Hanford Observatory (H1), LIGO Livingston Observatory (L1) and Virgo Observatory (V1) around the time of the compact binary merger (CBC) candidate S190915ak (GCN Circular 25753). Parameter estimation has been performed using LALInference [1] and a new sky map, LALInference.fits.gz, distributed via GCN Notice, is available for retrieval from the GraceDB event page: https://gracedb.ligo.org/superevents/S190915ak The preferred sky map at this time is LALInference.fits.gz. The 90% credible region is 318 deg2. Marginalized over the whole sky, the a posteriori luminosity distance estimate is 1584 +/- 381 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 . [1] Veitch et al. PRD 91, 042003 (2015) //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 25781 SUBJECT: LIGO/Virgo S190915ak: No significant candidates in TAROT-GRANDMA observations DATE: 19/09/19 14:22:52 GMT FROM: Alexander Kann at IAA-CSIC D. A. Kann (HETH/IAA-CSIC), A. Simon (ASPD TSNUK), Z. Vidadi (Shao), S. Antier (APC), M. Boer (Artemis), N. Christensen (Artemis), L. Eymar (Artemis), A. Klotz (IRAP), S. Alishov (SHAO), K. Barynova (Kyiv Univ), D. Coward (OzGrav-UWA), K. Noysena (Artemis, IRAP), S. Basa (LAM), D. Corre (LAL), M. Coughlin (Caltech), J.G. Ducoin (LAL), B. Gendre (OzGrav-UWA), P. Hello (LAL), C. Lachaud (APC), N. Leroy (LAL), D. Turpin (NAOC) and X. Wang (THU) report on behalf of the TAROT network and GRANDMA collaborations: We performed tiled observations of LIGO/Virgo S190915ak event (GCN #25753) with the TAROT-Calern (TCA) telescope operating in the visible located at Calern site at the Cote d'Azur observatory. The observation started on 09/16/19 00:12:27 UTC which corresponds approximately to 16 minutes after the GW trigger time. We performed the following tiled observations : +------------+------------+---------+---------+---------+ | TStart | TEnd | RA | DEC | Proba | | [UTC] | [UTC] | [deg] | [deg] | [%] | |------------+------------+---------+---------+---------| | 2019-09-16 | 2019-09-16 | 195.545 | 68.682 | 1.0 | | 00:12:27 | 23:06:42 | | | | | 2019-09-16 | 2019-09-16 | 187.785 | 66.826 | 0.7 | | 00:19:13 | 23:13:29 | | | | | 2019-09-16 | 2019-09-18 | 190.68 | 68.682 | 1.1 | | 00:54:58 | 01:52:26 | | | | | 2019-09-16 | 2019-09-17 | 185.815 | 68.682 | 0.5 | | 01:20:35 | 01:17:26 | | | | | 2019-09-16 | 2019-09-18 | 192.342 | 66.826 | 1.6 | | 01:27:23 | 03:10:13 | | | | | 2019-09-16 | 2019-09-16 | 186.244 | 70.538 | 0.4 | | 01:34:07 | 22:57:41 | | | | | 2019-09-16 | 2019-09-17 | 191.538 | 70.538 | 0.8 | | 02:51:43 | 01:10:45 | | | | | 2019-09-16 | 2019-09-17 | 168.392 | 77.96 | 0.2 | | 23:58:22 | 00:04:42 | | | | | 2019-09-17 | 2019-09-18 | 195.774 | 64.971 | 1.9 | | 00:05:13 | 02:57:21 | | | | | 2019-09-17 | 2019-09-17 | 161.664 | 74.249 | 0.1 | | 00:17:49 | 02:54:26 | | | | | 2019-09-17 | 2019-09-17 | 196.899 | 66.826 | 1.3 | | 00:24:37 | 21:01:18 | | | | | 2019-09-17 | 2019-09-17 | 191.538 | 64.971 | 1.5 | | 02:15:22 | 20:54:35 | | | | | 2019-09-17 | 2019-09-17 | 180.95 | 68.682 | 0.4 | | 02:41:18 | 02:47:37 | | | | | 2019-09-17 | 2019-09-17 | 196.541 | 50.125 | 5.3 | | 19:19:28 | 21:40:15 | | | | | 2019-09-17 | 2019-09-17 | 195.704 | 51.981 | 4.9 | | 19:30:30 | 19:34:40 | | | | | 2019-09-17 | 2019-09-17 | 193.706 | 50.125 | 2.1 | | 20:16:20 | 20:22:40 | | | | | 2019-09-17 | 2019-09-17 | 196.832 | 46.414 | 1.7 | | 20:28:50 | 20:35:09 | | | | | 2019-09-17 | 2019-09-17 | 194.796 | 63.115 | 1.5 | | 20:41:28 | 20:47:47 | | | | | 2019-09-17 | 2019-09-17 | 197.021 | 55.692 | 1.3 | | 21:01:43 | 21:08:03 | | | | | 2019-09-17 | 2019-09-17 | 192.753 | 51.981 | 1.1 | | 21:13:51 | 21:20:10 | | | | | 2019-09-17 | 2019-09-17 | 200.95 | 53.837 | 1.1 | | 21:20:24 | 21:26:44 | | | | | 2019-09-17 | 2019-09-17 | 198.655 | 51.981 | 4.2 | | 21:46:35 | 21:52:54 | | | | | 2019-09-17 | 2019-09-17 | 197.873 | 53.837 | 3.3 | | 21:53:19 | 21:59:38 | | | | +------------+------------+---------+---------+---------+ 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. Each tile is 1.9x1.9 degrees. These observations cover about 36% the cumulative probability of the LALInference skymap available on Sep 17, 2019 14:16:39 UTC. The typical limiting magnitude is 18.0 for a 60.0 s exposure. The coverage map is available at: https://grandma-owncloud.lal.in2p3.fr/index.php/s/55vKDfmLJzbHyBn No significant transient candidates were found during our low latency analysis. 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 spectroscopy capabilities for Time-domain Astronomy (https://grandma.lal.in2p3.fr/). Details on the TCA telescope are available on the GRANDMA web pages or on http://tarot.obs-hp.fr/.