//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 25828 SUBJECT: LIGO/Virgo S190924h: Upper limits from IceCube neutrino searches DATE: 19/09/24 03:01:57 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 S190924h in a time range of 1000 seconds [3] centered on the alert event time (2019-09-24 02:10:26.847 UTC to 2019-09-24 02:27:06.847 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 S190924h 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 S190924h ranges from 0.029 to 0.303 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: 25829 SUBJECT: LIGO/Virgo S190924h: Identification of a GW compact binary merger candidate DATE: 19/09/24 03:14:19 GMT FROM: Geoffrey Mo at LIGO The LIGO Scientific Collaboration and the Virgo Collaboration report: We identified the compact binary merger candidate S190924h during real-time processing of data from LIGO Hanford Observatory (H1), LIGO Livingston Observatory (L1), and Virgo Observatory (V1) at 2019-09-24 02:18:46.847 UTC (GPS time: 1253326744.847). The candidate was found by the GstLAL [1], PyCBC Live [2], MBTAOnline [3], and SPIIR [4] analysis pipelines. S190924h is an event of interest because its false alarm rate, as estimated by the online analysis, is 8.9e-19 Hz, or about one in 1e11 years. The event's properties can be found at this URL: https://gracedb.ligo.org/superevents/S190924h The classification of the GW signal, in order of descending probability, is MassGap (>99%), Terrestrial (<1%), BNS (<1%), BBH (<1%), or NSBH (<1%). Assuming the candidate is astrophysical in origin, there is indeterminate evidence for the lighter compact object having a mass < 3 solar masses (HasNS: 30%). 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,0, an updated localization generated by BAYESTAR [5], distributed via GCN notice about 6 minutes after the candidate For the bayestar.fits.gz,0 sky map, the 90% credible region is 515 deg2. Marginalized over the whole sky, the a posteriori luminosity distance estimate is 514 +/- 132 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] Nitz et al. PRD 98, 024050 (2018) [3] Adams et al. CQG 33, 175012 (2016) [4] Qi Chu, PhD Thesis, The University of Western Australia (2017) [5] Singer & Price PRD 93, 024013 (2016) //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 25831 SUBJECT: LIGO/Virgo S190924h: Global MASTER-Net observations report DATE: 19/09/24 03:29:16 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-SAAO robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in South Africa (South African Astronomical Observatory) started inspect of the LIGO/Virgo S190924h errorbox 1759 sec after notice time and 2222 sec after trigger time at 2019-09-24 02:55:48 UT, with upper limit up to 18.9 mag. The observations began at zenit distance = 73 deg. The sun altitude is -19.9 deg. MASTER-IAC robotic telescope located in Spain (IAC Teide Observatory) started inspect of the LIGO/Virgo S190924h errorbox 2641 sec after notice time and 3104 sec after trigger time at 2019-09-24 03:10:30 UT, with upper limit up to 15.2 mag. The observations began at zenit distance = 85 deg. The sun altitude is -47.3 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=10835 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 2312 | 2019-09-24 02:55:48 | MASTER-SAAO | (09h 19m 04.417s , -05d 52m 26.63s) | C | 180 | 17.3 | 2531 | 2019-09-24 02:59:27 | MASTER-SAAO | (09h 05m 19.012s , -07d 52m 15.64s) | C | 180 | 18.9 | 2914 | 2019-09-24 03:05:49 | MASTER-SAAO | (08h 33m 39.336s , +15d 54m 26.45s) | C | 180 | 16.7 | 3194 | 2019-09-24 03:10:30 | MASTER-IAC | (08h 27m 34.435s , +15d 53m 04.11s) | P| | 180 | 15.2 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 25835 SUBJECT: LIGO/Virgo S190924h: Coverage and upper limits from MAXI/GSC observations DATE: 19/09/24 04:42:46 GMT FROM: Satoshi Sugita at Aoyama Gakuin U. N. Kawai (Tokyo Tech), H. Negoro (Nihon U.), S. Sugita, M. Serino (AGU), 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.), Y. Kawakubo (LSU), M. Sugizaki (NAOC) report on behalf of the MAXI team: We examined MAXI/GSC all-sky X-ray images (2-20 keV) after the LVC trigger S190924h at 2019-09-24 02:18:46.846 UTC (GCN 25829). At the trigger time of S190924h, the high-voltage of MAXI/GSC was off, and it was turned on at T0+1113 sec (+18.6 min). The first one-orbit (92 min) scan observation with GSC after the event covered 34% of the 90% credible region of the bayestar skymap from 02:50:13 to 02:59:43 UTC (T0+1887 to T0+2457 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: 25836 SUBJECT: LIGO/Virgo S190924h : no neutrino counterpart candidate in ANTARES search DATE: 19/09/24 06:26:02 GMT FROM: Thierry Pradier at ANTARES/IPHC/U of Strasbourg 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 S190924h event using the 90% contour of the Initial bayestar probability map provided by the GW interferometers (GCN#25829 ). 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/S190924h_Initial.png . Considering the location probability provided by the LIGO/Virgo collaborations, there is a 39.6% 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 2019-09-24 02:18:46 and in the 90% contour of the S190924h event. The expected number of atmospheric background events in the region visible by ANTARES is 1.90e-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 1.37e-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: 25837 SUBJECT: LIGO/Virgo S190924h: No counterpart candidates in INTEGRAL SPI-ACS and IBIS prompt observation DATE: 19/09/24 07:12:08 GMT FROM: Antonio Martin-Carrillo at UCD,Space Science Group Antonio Martin-Carrillo (UCD), Francesca Onori, 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 combination of INTEGRAL all-sky detectors (following [1]): SPI/ACS, IBIS/Veto, and IBIS we have performed a search for a prompt gamma-ray counterpart of S190924h (GCN 25829). At the time of the event (2019-09-24 02:18:46 UTC, hereafter T0), INTEGRAL was operating in nominal mode. The peak of the event localization probability was at an angle of 124 deg with respect to the spacecraft pointing axis. This orientation implies strongly suppressed (4.3% of optimal) response of ISGRI, somewhat suppressed (57% of optimal) response of IBIS/Veto, and strongly suppressed (31% of optimal) response of SPI-ACS. The background within +/-300 seconds around the event was rather stable (excess variance 1.2). We have performed a search for any impulsive events in INTEGRAL SPI- ACS (as described in [2]), IBIS, and IBIS/Veto data. We do not detect any significant counterparts and estimate a 3-sigma upper limit on the 75-2000 keV fluence of 4.2e-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 ~3.8e-07 (7.5e-08) erg/cm^2/s at 1 s (8 s) time scale in 75-2000 keV energy range. For the mean reported distance 514.0 Mpc this corresponds to the limit on the total isotropic equivalent energy in 1 s of 1.3e+49 erg for the short GRB spectrum and for a long GRB spectrum isotropic equivalent luminosity in 1 s (8 s) of 6.5e+48 erg/s (2.4e+48 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+49 erg/s) | FAP 0.05 | -0.312 | 3 | 5.68 +/- 2.41 +/- 3.89 | 0.115 0.35 | -13.1 | 3.9 | 27.8 +/- 8.99 +/- 19 | 0.133 0.1 | -2.39 | 3.4 | 4.49 +/- 1.69 +/- 3.08 | 0.209 1 | -42.4 | 3.6 | 15.1 +/- 5.29 +/- 10.3 | 0.253 0.7 | 90.3 | 4 | 19.9 +/- 6.33 +/- 13.7 | 0.402 0.15 | -4.71 | 3.1 | 3.35 +/- 1.38 +/- 2.29 | 0.514 1 | 292 | 4.4 | 18.2 +/- 5.3 +/- 12.5 | 0.64 0.55 | -95.5 | 3.6 | 20.1 +/- 7.15 +/- 13.7 | 0.939 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 //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 25839 SUBJECT: LIGO/Virgo S190924h: No counterpart candidates in AGILE-MCAL observations DATE: 19/09/24 08:44:34 GMT FROM: Martina Cardillo at INAF-IAPS M. Cardillo, G. Piano (INAF/IAPS), M. Tavani (INAF/IAPS, and Univ. Roma Tor Vergata), C. Casentini, A. Ursi (INAF/IAPS), F. Lucarelli, C. Pittori, F. Verrecchia (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 S190924h at T0 = 2019-09-24 02:18:46 (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, about 10% of the S190924h 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 S190924h localization region, from a minimum of 1.60E-06 erg cm^-2 to a maximum of 7.42E-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: 25840 SUBJECT: LIGO/Virgo S190924h: no counterpart candidates in AGILE-GRID observations DATE: 19/09/24 09:14:06 GMT FROM: Giovanni Piano at INAF-IAPS G. Piano, M. Cardillo (INAF/IAPS), F. Verrecchia (SSDC, and INAF/OAR), M. Tavani (INAF/IAPS, and Univ. Roma Tor Vergata), C. Casentini, A. Ursi (INAF/IAPS), F. Lucarelli, 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 S190924h at T0 = 2019-09-24 02:18:46.847 UTC, a preliminary analysis of the AGILE data at T0 shows that the Gamma-Ray Imaging Detector (GRID) has no exposure of the 90% c.l. localization region (LR). The closest exposure in time occurred at T0 - 400 s, covering about 40% of the LR. We performed an analysis of the GRID data in the energy range 50 MeV - 10 GeV. The following preliminary GRID 3-sigma upper limit (UL) value is obtained over the exposed region of the LR: from 7.7e-08 to 3.0e-07 erg cm^-2 s^-1, over the time interval (T0 - 400 s; T0 - 300 s). This measurement was 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: 25841 SUBJECT: LIGO/Virgo S190924h: Upper limits from Fermi-GBM Observations DATE: 19/09/24 12:05:42 GMT FROM: Eric Burns at GSFC E. Burns (NASA/GSFC) reports on behalf of the Fermi-GBM Team and the GBM-LIGO/Virgo group For S190924h and using the initial bayestar skymap, Fermi-GBM was observing 100% 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 S190924h (GCN 25829). An automated, blind search for short gamma-ray bursts below the onboard triggering threshold in Fermi-GBM also identified no counterpart candidates. The GBM targeted search, the most sensitive, coherent search for GRB-like signals, was run from +/-30 s around merger time, and also identified no counterpart candidates. We set upper limits on impulsive gamma-ray emission for the LVC localization region. 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 Normal Hard ------------------------------------ 0.128 s: 5.9 8.9 15. 1.024 s: 1.6 3.0 5.4 8.192 s: 0.3 0.6 1.1 Assuming the median luminosity distance of 514 Mpc from the GW detection, we estimate the following intrinsic luminosity upper limits over the 1 keV-10 MeV energy range (in units of 10^49 erg/s): Timescale Soft Normal Hard ------------------------------------ 0.128 s: 2.7 3.8 11. 1.024 s: 0.7 1.3 3.8 8.192 s: 0.1 0.3 1.1 //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 25843 SUBJECT: LIGO/Virgo S190924h: no counterpart candidates in the Swift/BAT observations DATE: 19/09/25 01:21:33 GMT FROM: Amy Lien at GSFC D. M. Palmer (LANL), S. D. Barthelmy (NASA/GSFC), A. Y. Lien (GSFC/UMBC), T. Sakamoto (AGU), A. P. Beardmore (U. Leicester), M. G. Bernardini (INAF-OAB), A. A. Breeveld (MSSL-UCL), D. N. Burrows (PSU), S. Campana (INAF-OAB), S. B. Cenko (NASA/GSFC), G. Cusumano (INAF-IASF PA), A. D'Ai (INAF-IASFPA), P. D'Avanzo (INAF-OAB), V. D'Elia (ASI-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 S190924h (LIGO/VIRGO Collaboration GCN Circ. 25829), where T0 is the LVC trigger time (2019-09-24T02:18:46.846 UTC). The center of the BAT field of view (FOV) at T0 is RA = 159.491 deg, DEC = 44.352 deg, and the roll angle is 157.702 deg. The BAT FOV (>10% partial coding) covers 70.30% of the integrated LVC localization probability, and 71.67% of the galaxy convolved probability (Evans et al. 2016). Note that Swift was slewing from ~T0-10 s to ~T0+160 s. Also, 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 ~ 2.57 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 ~ 44.79 Mpc. No event data are available at this time. BAT retains decreased, but significant, sensitivity to rate increases for gamma-ray events outside of its FOV. About 29.70% 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/S190924h/web/source_public.html //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 25844 SUBJECT: LIGO/Virgo S190924h: Not observable by CALET DATE: 19/09/25 04:15:11 GMT FROM: Yuta Kawakubo at Louisiana State U./CALET T. Sakamoto, A. Yoshida, V. Pal'shin, S. Sugita (AGU), Y. Kawakubo (LSU), K. Yamaoka (Nagoya U), S. Nakahira (RIKEN), Y. Asaoka, S. Torii (Waseda U), Y. Shimizu, T. Tamura (Kanagawa U), N. Cannady (GSFC/UMBC), M. L. Cherry (LSU), S. Ricciarini (U of Florence), P. S. Marrocchesi (U of Siena), and the CALET collaboration: At the trigger time of the compact binary merger candidate S190924h, T0 = 2019-09-24 02:18:46.847 UT (The LIGO Scientific Collaboration and Virgo Collaboration, GCN Circ. 25829), the CALET Gamma-ray Burst Monitor (CGBM) high voltages were off (from T0-1 min to T0+16 min). The CALET Calorimeter (CAL) was operating in the high energy trigger mode at the trigger time of S190924h. 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 high probability localization region. The CAL FOV was centered at RA=273.4 deg, Dec=40.2 deg at T0. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 25845 SUBJECT: LIGO/Virgo S190924h: No counterpart candidates in Fermi-LAT observations DATE: 19/09/25 04:54:53 GMT FROM: Magnus Axelsson at Stockholm U. M. Axelsson (KTH and Stockholm Univ.), M. Moss (George Washington Univ.), N. Omodei (Stanford Univ.), D. Kocevski (NASA/MSFC), E. Bissaldi (Politecnico and INFN Bari), M. Arimoto (Kanazawa Univ.) and E. Moretti (IFAE, Barcelona) report on behalf of the Fermi-LAT Collaboration: We have searched data collected by the Fermi Large Area Telescope (LAT) on Sep 24, 2019, for possible high-energy (E > 100 MeV) gamma-ray emission in spatial/temporal coincidence with the LIGO/Virgo trigger S190924h (GCN 25829). 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 an instantaneous coverage of ~65% of the LIGO probability region at the time of the trigger (T0 = 2019-09-24 02:18:46.847 UTC) and reached 100% cumulative coverage at approximately T0 + 5.2 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 between 100 MeV and 1 GeV for the fixed time interval of this search vary between 2.3e-10 and 3.2e-9 [erg/cm^2/s]. The Fermi-LAT point of contact for this event is Elena Moretti (emoretti@ifae.es). 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: 25905 SUBJECT: LIGO/Virgo S190828h: Updated Sky Localization DATE: 19/10/01 18:48:58 GMT FROM: Geoffrey Mo at 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 S190924h (GCN Circular 25829). 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/S190924h The preferred sky map at this time is LALInference.fits.gz. The 90% credible region is 303 deg2. Marginalized over the whole sky, the a posteriori luminosity distance estimate is 548 +/- 112 Mpc (a posteriori mean +/- standard deviation). For further information about analysis methodology and the contents of this alert, refer to the LIGO/Virgo Public Alerts User Guide < https://emfollow.docs.ligo.org/userguide/>. [1] Veitch et al. PRD 91, 042003 (2015) [GCN OPS NOTE(02oct19): Please note, see Circ 25909 for a reissue of this Circ with the correction made. And after that reissue, GCN OPS has changed this archive copy of 25905's Subject-line from "S190828j" to "S190828h".] //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 25909 SUBJECT: LIGO/Virgo S190924h: Correction to GCN 25905, updated sky localization for S190924h DATE: 19/10/01 19:32:24 GMT FROM: Geoffrey Mo at LIGO What follows is the exact content of GCN 25905, which is being re-sent with a corrected subject. The original subject stated that this was an updated sky localization for S190828j, which was in error. Instead, this is the updated sky localization for S190924h. 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 S190924h (GCN Circular 25829). 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/S190924h The preferred sky map at this time is LALInference.fits.gz. The 90% credible region is 303 deg2. Marginalized over the whole sky, the a posteriori luminosity distance estimate is 548 +/- 112 Mpc (a posteriori mean +/- standard deviation). For further information about analysis methodology and the contents of this alert, refer to the LIGO/Virgo Public Alerts User Guide < https://emfollow.docs.ligo.org/userguide/>. [1] Veitch et al. PRD 91, 042003 (2015)