//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 25406 SUBJECT: Fermi GBM-190816: A subthreshold GRB candidate potentially associated with a subthreshold LIGO/Virgo compact binary merger candidate DATE: 19/08/20 05:23:25 GMT FROM: Adam Goldstein at Fermi-GBM, USRA The LIGO Scientific Collaboration, the Virgo Collaboration and the Fermi GBM team report: In routine Fermi GBM follow-up analysis of subthreshold GW triggers from LIGO/Virgo, a potential short gamma-ray burst counterpart GBM-190816 was identified. Offline analysis of data from LIGO Livingston Observatory (L1) and Virgo Observatory (V1) identified a possible compact binary merger candidate at 2019-08-16 21:22:13.027 UTC (GPS time: 1250025751.027). The LIGO Hanford Observatory was not collecting low-noise data at the time. The candidate was found by the PyCBC Live [1], MBTAOnline [2], and GstLAL [3] analysis pipelines. The GBM Targeted Search [4,5,6], a sensitive and coherent search for subthreshold GRB-like signals, was run from +/-30 s around the GW candidate and identified a candidate gamma-ray signal starting at 21:22:14.563 UTC, 1.5 s after the GW trigger time. GBM-190816 is approximately 0.1 s in duration and was identified with the hard spectral template [6]. The offset, duration, and spectral properties are consistent with a short GRB origin, while the observed properties are inconsistent with other astrophysical or terrestrial transients that GBM observes. The False Alarm Rate (FAR) for the GBM Targeted Search detection statistic is 1.2E-4 Hz. Neither the GW trigger nor the potential short GRB are significant enough to report on their own merit. However, these events are of interest because of their potential association. Investigation on the data quality of the gravitational-wave event is ongoing. At this time we cannot reliably estimate the FAR of the gravitational-wave event. Analysis is ongoing in establishing the FAR, data-quality and overall potential astrophysical nature of the event. The skymap available at this moment is obtained primarily by combining the localization from L1-V1 using BAYESTAR [7] with the Fermi-GBM localization; the 90% error area corresponds to 5855 sq. deg. while the 50% error area is 1257 sq. deg. This skymap is available through the OpenLVEM wiki page at https://wiki.gw-astronomy.org/OpenLVEM/FermiGBM-LVC From a preliminary inspection of the GW analysis, if the signal is astrophysical, the lighter compact object may have a mass < 3 solar masses. [1] Nitz et al. PRD 98, 024050 (2018) [2] Adams et al. CQG 33, 175012 (2016) [3] Messick et al. PRD 95, 042001 (2017) [4] Blackburn et al. 2015, ApJS 217, 8 [5] Goldstein et al. arXiv:1612.02395 [6] Goldstein et al. arXiv:1903.12597 [7] Singer & Price PRD 93, 024013 (2016) //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 25407 SUBJECT: Fermi GBM-190816: Location-dependent upper limits from INTEGRAL/SPI-ACS prompt observation DATE: 19/08/20 09:08:59 GMT FROM: Volodymyr Savchenko at ISDC,U of Geneve V. Savchenko, C. Ferrigno (ISDC/UniGE, Switzerland) S. Molkov (IKI, Russia), 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 GBM-190816 (GCN 25406). At the time of the event (2019-08-16 21:22:14.6 UTC, hereafter T0), INTEGRAL was operating in nominal mode. The peak of the event localization probability was at an angle of 98 deg with respect to the spacecraft pointing axis. This orientation implies strongly suppressed (7.7% of optimal) response of ISGRI, strongly suppressed (22% of optimal) response of IBIS/Veto, and near-optimal (87% 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 impulsive events in INTEGRAL SPI- ACS data, as described in [2]. We do not detect any significant counterparts and estimate a 3-sigma upper limit on the 75-2000 keV fluence of 1.8e-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 ~1.5e-07 (5.5e-08) erg/cm^2/s at 1 s (8 s) time scale in 75-2000 keV energy range. For the mean reported distance 362 Mpc this corresponds to the limit on the total isotropic equivalent energy in 1 s of 2.8e+48 erg for the short GRB spectrum and for a long GRB spectrum isotropic equivalent luminosity in 1 s (8 s) of 2.4e+48 erg/s (8.6e+47 erg/s) Since the GW localization region includes regions with particularly large range of SPI-ACS sensitivities, the upper limit from SPI-ACS is very location-dependent. We find 10 excesses in the search region, reported below in order of FAP. The excesses are likely due to background noise. scale   | T     | S/N | luminosity ( x 1e+48 erg/s)    | FAP 0.45    | 1.73  | 3   |     13.6 +/- 6.57   +/- 13.8   | 0.0917 0.1     | 0.901 | 3.1 |     29.1 +/- 14.1   +/- 29.5   | 0.171 0.35    | 12.9  | 3.7 |     18.6 +/- 7.47   +/- 18.9   | 0.191 0.45    | 15.9  | 3.5 |     15.5 +/- 6.58   +/- 15.7   | 0.25   1.6     | -126  | 3.8 |     9.12 +/- 3.48   +/- 9.25   | 0.344 4.3     | 197   | 3.4 |     5.27 +/- 2.12   +/- 5.35   | 0.411 0.15    | -5.32 | 3.3 |     25.4 +/- 11.5   +/- 25.7   | 0.421 0.2     | -8.25 | 3.2 |     21.2 +/- 9.9    +/- 21.6   | 0.625 0.35    | 40.7  | 3.5 |     17.7 +/- 7.47   +/- 18     | 0.789 0.05    | 231   | 8.6 |     11.9 +/- 2.08   +/- 12.1   | 0.819 Where uncertainties are statistical and systematic. Systematic uncertainty includesdependency on the unknown location and assumed 20% systematics in the response. For any given fluence measured by Fermi/GBM, INTEGRAL observation can constrainthe event location. In particular, the GW localization lobe near RA=12h corresponds to considerably less constraining upper limit, corresponding to the directions through the bottomof the spacecraft. Hence INTEGRAL non-detection suggests that a source in the GW localization lobe near RA=12h of is more likely compatible with the possible GBM detection: https://doi.org/10.5281/zenodo.3372187 However we caution that this conclusion depends on unknown event spectrum and fluence. All results quoted are preliminary. This circular is an official product of the INTEGRAL Multi-Messenger team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 25408 SUBJECT: Fermi GBM-190816+LIGO/Virgo : no neutrino counterpart candidate in ANTARES search DATE: 19/08/20 13:03:18 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 Fermi GBM-190816+LIGO/Virgo subthreshold GW trigger event using the 90% contour of the joint probability map provided by Fermi-GBM + LSC-Virgo (GCN#25406 ). 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/2019-08-16_GBM-190816-w.png . Considering the location probability provided by the Fermi-GBM and LIGO/Virgo, there is a 37% 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 2019-08-16 21:22:13 and in the 90% contour of the GBM-190816+LIGO/Virgo event. The expected number of atmospheric background events in the region visible by ANTARES is 3.1e-03 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 2.2e-02 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: 25410 SUBJECT: Fermi GBM-190816: No counterpart candidates in HAWC observations DATE: 19/08/20 15:45:06 GMT FROM: Israel Martinez-Castellanos at UMD/HAWC The HAWC Collaboration (https://www.hawc-observatory.org) reports: The HAWC Collaboration performed a follow-up of the GRB-GW sub-threshold event Fermi GBM-190816 (GCN #25406). At the time of the trigger the HAWC local zenith was oriented towards (RA, Dec) = (188.0 deg, 19.1 deg). 45}% of the candidate sky location probability fell within our observable field of view (0-45 deg zenith angle). We performed a search for a short timescale emission using 6 sliding time windows (dt = 0.3s, 1s, 3s, 10s, 30s and 100s), shifted forward in time by 20% of their width. We searched the 95% probability containment area in a timescale-dependent time period, from t0-5dt to t0+10dt, where t0 is the time of the trigger. No significant gamma-ray detection above the background was observed. The sensitivity of this analysis is greatly dependent on zenith angle, ranging from 0 deg to 45 deg for the area searched in this analysis. The 5sigma detection sensitivity to a 1s (100s) burst in the 80-800GeV energy range goes from 1.2e-06 erg/cm^2 to 1.1e-04 erg/cm^2 (6.4e-06 erg/cm^2 to 5.0e-04 erg/cm^2), depending on the zenith angle. HAWC is a TeV gamma ray water Cherenkov array located in the state of Puebla, Mexico. It is sensitive to the energy range ~0.1-100TeV, and monitors 2/3 of the sky every day with an instantaneous field-of-view of ~2 sr. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 25414 SUBJECT: Fermi GBM-190816: Upper limits from IceCube neutrino searches DATE: 19/08/20 20:43:26 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 the joint gravitational-wave and GRB candidate Fermi GBM-190816 in a time range of 1000 seconds [3] centered on the GW event time (2019-08-16 21:13:53.027 UTC to 2019-08-16 21:30:33.027 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 Fermi GBM-190816 calculated from the map circulated in GCN 25406. 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 the combined map of Fermi GBM-190816 and the GW event candidate ranges from 0.029 to 1.15 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: 25418 SUBJECT: Fermi GBM-190816: One candidate counterpart from the Zwicky Transient Facility DATE: 19/08/20 22:12:39 GMT FROM: Robert Stein at DESY Robert Stein (DESY), Anna Franckowiak (DESY), Mansi M. Kasliwal (Caltech), Igor Andreoni (Caltech), Michael W. Coughlin (Caltech), Shreya Anand (Caltech), report on behalf of the Zwicky Transient Facility (ZTF) and Global Relay of Observatories Watching Transients Happen (GROWTH) collaborations: We serendipitously observed the localization region of the subthreshold joint Fermi GBM-LVC gravitational wave trigger Fermi GBM-190816 (GCN 25406) with the Palomar 48-inch telescope equipped with the 47 square degree ZTF camera (Bellm et al. 2019, Graham et al. 2019). Observations were conducted on multiple nights, as part of the public survey, with exposures of 30s and a typical depth of ~20.5 mag. In total, 31% of the localisation region was observed at least twice by ZTF. This coverage estimate does not account for chip gaps. The images were processed in real-time through the ZTF reduction and image subtraction pipelines at IPAC to search for potential counterparts (Masci et al. 2019). AMPEL (Nordin et al. 2019) was used to vet candidates based on their light curves. After rejecting stellar sources (Tachibana and Miller 2018) and moving objects and applying machine learning algorithms (Mahabal et al. 2019), and after removing candidates with history of variability prior to the merger time, one new transient candidates were identified by our pipeline in the 90% localization. ------------------------------------------------------- ZTF Name | RA (deg) | DEC (deg) ------------------------------------------------------- ZTF19abqanpy | 56.264326 | 41.998417 ------------------------------------------------------- This candidate was detected three times since merger, it is rising and offset from its putative host galaxy. The light curve is below: -------------------------------------------------------------------- Filter | Mag | Mag Err | Observation Time (JD) ------------------------------------------------------------------- r | 19.53 | 0.14 | 2458712.9510 g | 19.67 | 0.21 | 2458712.9893 r | 18.59 | 0.07 | 2458715.9438 -------------------------------------------------------------------- ZTF and GROWTH are worldwide collaborations comprising Caltech, USA; IPAC, USA, WIS, Israel; OKC, Sweden; JSI/UMd, USA; U Washington, USA; DESY, Germany; MOST, Taiwan; UW Milwaukee, USA; LANL USA; Tokyo Tech, Japan; IIT-B, India; IIA, India; LJMU, UK; TTU, USA; SDSU, USA and USyd, Australia. ZTF acknowledges the generous support of the NSF under AST MSIP Grant No 1440341. GROWTH acknowledges generous support of the NSF under PIRE Grant No 1545949. Alert distribution service provided by DIRAC@UW (Patterson et al. 2019). Alert filtering and follow-up co-ordination is being undertaken by the GROWTH marshal system (Kasliwal et al. 2019). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 25421 SUBJECT: Fermi GBM-190816: ZTF19abqanpy 10.4m GTC spectroscopy DATE: 19/08/21 04:38:12 GMT FROM: Alberto J. Castro-Tirado at IAA-CSIC A. F. Valeev (SAO-RAS), Y.-D. Hu (IAA-CSIC), A. J. Castro-Tirado and E. Fernandez-Garcia (IAA-CSIC), V. V. Sokolov (SAO-RAS), I. Carrasco and A. Castellon (UMA) and J. Font Serra (GRANTECAN, IAC, ULL), on behalf of a larger collaboration, report: Following the detection of ZTF19abqanpy (Stein et al., GCN 25418 ) in the error box for the subthreshold joint Fermi GBM-LVC gravitational wave trigger Fermi GBM-190816 (GCN 25406), we obtained imaging and optical spectra covering the range 3700-10000 A with the 10.4m GTC telescope equipped with OSIRIS in La Palma (Spain) starting on Aug 21, 03:00 UT. ZTF19abqanpy magnitude on Aug 21, 03:45 UT was measured to be i = 18.65 +/- 0.05. The ZTF19abqanpy spectrum displays broad lines and is consistent with a SN Ia at one week before maximum located at the nearby (13 arcsec to the East) host galaxy (at redshift z = 0.043 +/- 0.001, based on the narrow emission lines from the host galaxy). The projected distance from ZTF19abqanpy to the center of the galaxy is 10.9 kpc. Therefore we conclude that ZTF19abqanpy is unrelated to the above-mentioned Fermi-GW event. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 25424 SUBJECT: Fermi GBM-190816: AGILE in SAA at T0 DATE: 19/08/21 10:03:37 GMT FROM: Francesco Longo at U of Trieste,INFN Trieste F. Longo (Univ. Trieste, and INFN Trieste), C.Pittori, F. Verrecchia, F.Lucarelli (SSDC, and INAF/OAR), M. Tavani (INAF/IAPS, and Univ. Roma Tor Vergata), M. Cardillo, C. Casentini, G. Piano, A. Ursi (INAF/IAPS), A. Bulgarelli, V. Fioretti, N. Parmiggiani (INAF/OAS-Bologna), M. Pilia (INAF/OA-Cagliari) report on behalf of the AGILE Team: In response to Fermi GBM-190816 sub threshold event, corresponding to a possible compact binary merger candidate at LVC GW trigger time T0 = 2019-08-16 21:22:13.027 UT (GCN 25406), analysis of AGILE data shows that the satellite at T0 was in the South Atlantic Anomaly (SAA). Additional analysis of AGILE data is in progress. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 25426 SUBJECT: Fermi GBM-190816: No counterpart candidates in Fermi-LAT observations DATE: 19/08/21 15:25:01 GMT FROM: Magnus Axelsson at Stockholm U. M. Axelsson (KTH and Stockholm Univ.), F. Longo (Univ. and INFN Trieste), D. Kocevski (NASA/MSFC) and A. Berretta (University and INFN, Perugia) report on behalf of the Fermi-LAT Collaboration: We have searched data collected by the Fermi Large Area Telescope (LAT) on Aug 16, 2019, for possible high-energy (E > 100 MeV) gamma-ray emission in spatial/temporal coincidence with the sub threshold event LIGO/Virgo and Fermi GBM-190816 (GCN 25406). 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 a time, and "cumulative coverage" as the integral of the instantaneous coverage over time. Fermi-LAT had instantaneous coverage of 75% of the joint GBM and LIGO/Virgo probability region at the time of the trigger (T0 = 2019-08-16 21:22:13.021 UTC) and reached ~100% coverage around T0+6 ks. We performed a search for a transient counterpart within the observed region of the 90% contour of the LIGO/Virgo 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 1.3e-10 and 1.4e-9 [erg/cm^2/s]. The Fermi-LAT point of contact for this event is Alessandra Berretta (alessandra.berretta@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: 25430 SUBJECT: Fermi GBM-190816: Four additional candidates from the Zwicky Transient Facility DATE: 19/08/21 18:04:13 GMT FROM: Robert Stein at DESY Robert Stein (DESY), Anna Franckowiak (DESY), Mansi M. Kasliwal (Caltech), Igor Andreoni (Caltech), Michael W. Coughlin (Caltech), Shreya Anand (Caltech), report on behalf of the Zwicky Transient Facility (ZTF) and Global Relay of Observatories Watching Transients Happen (GROWTH) collaborations: We have continued serendipitous observations of the localization region of the subthreshold joint Fermi GBM-LVC gravitational wave trigger Fermi GBM-190816 (GCN 25406) using the Palomar 48-inch telescope equipped with the 47 square degree ZTF camera (Bellm et al. 2019, Graham et al. 2019). Additional observations were conducted as part of the public survey, with exposures of 30s and a typical depth of ~20.5 mag. In total, 39% of the localisation region has now been observed at least twice by ZTF. This coverage estimate does not account for chip gaps. The images were processed in real-time through the ZTF reduction and image subtraction pipelines at IPAC to search for potential counterparts (Masci et al. 2019). AMPEL (Nordin et al. 2019) was used to vet candidates based on their light curves. After rejecting stellar sources (Tachibana and Miller 2018) and moving objects and applying machine learning algorithms (Mahabal et al. 2019), and after removing candidates with history of variability prior to the merger time, four new transient candidates were identified by our pipeline in the 90% localization. The detections from the most recent night of observations, August 21st, are summarised below. -------------------------------------------------------------------- ZTF Name | RA (deg) | DEC (deg) | Filter | Mag | Mag Err -------------------------------------------------------------------- ZTF19abqykei | 69.0926074 | 10.3722396 | r | 18.77 | 0.11 -- | -- | -- | g | 19.52 | 0.21 ZTF19abqrrto | 55.8037407 | 40.165587 | r | 19.16 | 0.13 ZTF19abqrqgm | 53.6462259 | 50.2638424 | r | 19.68 | 0.17 ZTF19abqgyxp | 104.4287931 | 56.0874661 | r | 19.14 | 0.13 -------------------------------------------------------------------- ZTF19abqykei, additionally reported as AT2019obh, was detected last night in both g and r. It has risen by 0.5 mag in r in the last three days, and is very red. ZTF19abqrrto has been detected twice in r, is rising, and is offset from its host galaxy. ZTF19abqrqgm has been detected three times in r, and is fading. ZTF19abqgyxp has been detected once in both g and r, and is offset from its host. ZTF and GROWTH are worldwide collaborations comprising Caltech, USA; IPAC, USA, WIS, Israel; OKC, Sweden; JSI/UMd, USA; U Washington, USA; DESY, Germany; MOST, Taiwan; UW Milwaukee, USA; LANL USA; Tokyo Tech, Japan; IIT-B, India; IIA, India; LJMU, UK; TTU, USA; SDSU, USA and USyd, Australia. ZTF acknowledges the generous support of the NSF under AST MSIP Grant No 1440341. GROWTH acknowledges generous support of the NSF under PIRE Grant No 1545949. Alert distribution service provided by DIRAC@UW (Patterson et al. 2019). Alert filtering and follow-up co-ordination is being undertaken by the GROWTH marshal system (Kasliwal et al. 2019). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 25432 SUBJECT: Fermi GBM-190816: Correction from the Zwicky Transient Facility DATE: 19/08/21 18:31:46 GMT FROM: Robert Stein at DESY In GCN # 25430, four transient were reported. For one of these, ZTF19abqykei, also known as AT2019obh, the position given was incorrect. A negative sign was missing from the declination. The correct position should be: --------------------------------------- ZTF Name | RA (deg) | DEC (deg) ---------------------------------------- ZTF19abqykei | 69.0926074 | -10.3722396 We apologise for any inconvenience caused. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 25434 SUBJECT: Fermi GBM-190816: Upper Limits from Swift/BAT Observations DATE: 19/08/21 19:22:00 GMT FROM: Aaron Tohuvavohu at PSU/Swift James DeLaunay (PSU) and Aaron Tohuvavohu (PSU) report: We report the upper limits from additional deeper searches of the BAT data for a counterpart to LVC-Fermi event GBM-190816 (GCN Circ. 25406). As reported in GCN Circ. 25415, Swift was in the middle of a slew at the time of the event. The BAT FOV with >10% partial coding, contained ~22.5% of the joint LVC-Fermi probability at LVC trigger time (2019-08-16T21:22:13.027 UTC). Event data was captured during the slew and is available from T0-65.5s to T0+150.36. Using a likelihood based approach (DeLaunay et al., in prep), a search was performed on the BAT event data for any short transient on the scale of 0.128s within +/-15s of the GBM-190816 event time. The search is performed by maximizing the likelihood of a power-law signal plus background model over the signal parameters (sky position, power-law index, and spectral normalization) in each time bin being tested. Longer time scales would need to take into account the slewing effect and are not yet implemented in this search. No significant counterparts were found using this method. Upper limits can be set by finding what flux needs to be injected on top of the background to be detected above a certain threshold (signal-to-noise >~ 5 sigma) 90% of the time. For the upper limits we assume the same spectral shape as the hard template used by the GBM team for te claimed detection (GCN Circ. 25406). The sensitivity varies across the BAT field-of-view, so we report here the average upper limit over the joint LVC-Fermi localization that lands within the >10% coded BAT field-of-view. Average upper limit for Hard Spectral Template for 0.128s time scale: 3.1e-7 erg/cm2/s (14-195 keV) We also perform a search in events sensitive to all gamma-ray transients, even those originating from outside of the coded field-of-view. At T0, ~86% of the Fermi/LVC localization was above the Earth limb with respect to the spacecraft, and thus capable of depositing flux onto the detector array. We find no evidence for a gamma-ray transient within T0 +/- 10. We set the following average sensitivity limit for a 1-s long sGRB occurring in the part of the Fermi-LVC joint localization covered by the BAT field-of-view. Average upper limit for Hard Spectral Template for 1.024s time scale: 7.1 E-8 erg/cm2/s (14-195 keV) However, we cannot currently calculate an upper limit for the 63% of the localization outside of the coded field-of-view due to the varying and unknown detector response function at wide off-boresight angles. Upper limits are typically an order of magnitude higher for events outside of the field-of-view. Work is ongoing to better characterize this response. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 25446 SUBJECT: Fermi GBM-190816: MASTER-Net optical observation report DATE: 19/08/22 11:27:39 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs V. Lipunov, F.Balakin, E. Gorbovskoy, V. Kornilov, N.Tyurina, P.Balanutsa,A.Kuznetsov, F.Balakin, V. Vladimirov, D. Vlasenko, I. Gorbunov,D.Zimnukhov, V.Senik, A.Chasovnikov, A.Pozdnyakov, A.Chasovnikov, V.Topolev, D.Kuvshinov(Lomonosov Moscow State University, SAI, Physics Department), R. Rebolo, M. Serra (The Instituto de Astrofisica de Canarias IAC), 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), D. Buckley (South African Astronomical Observatory SAAO), O. Gress, 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 Global Robotic Net ( http://observ.pereplet.ru, Lipunov et al.,2010,Advances in Astronomy, vol. 2010, 30L) started Fermi GBM-190816 (LIGO/Fermi-GBM GCN 25406) inspect 73 sec after trigger time at 2019-08-16 21:23:26 UT . MASTER-IAC robotic telescope, located in Spain (IAC Teide Observatory) started inspect of Fermi GBM-190816 errorbox 73 sec after trigger time at 2019-08-16 21:23:26 UT,with upper limit up to 19.7 mag. The observations began at zenit distance = 49 deg. The sun altitude is -21.7 deg. MASTER-OAFA robotic telescope located in Argentina (OAFA observatory of San Juan National University) started inspect of Fermi GBM-190816 errorbox 5470 sec after trigger time at 2019-08-16 22:53:23 UT, with upper limit up to 18.4 mag. Observations started at twilight. The observations began at zenit distance = 49 deg. The sun altitude is -10.0 deg. MASTER-SAAO robotic telescope located in South Africa (South African Astronomical Observatory) started inspect of Fermi GBM-190816 errorbox 9193 sec after trigger time at 2019-08-16 23:55:26 UT,with upper limit up to 19.4 mag. The observations began at zenit distance = 60 deg. The sun altitude is -65.3 deg. MASTER-Kislovodsk robotic telescope located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) started inspect of Fermi GBM-190816 errorbox 11053 sec after trigger time at 2019-08-17 00:26:26 UT, with upper limit up to 19.0 mag. The observations began at zenit distance = 60 deg. The sun altitude is -18.4 deg. MASTER-Tunka robotic telescope located in Russia (Applied Physics Institute, Irkutsk State University) started inspect of the Fermi GBM-190816 errorbox 58429 sec after trigger time at 2019-08-17 13:36:02 UT, with upper limit up to 18.7 mag. Observations started at twilight. The observations began at zenit distance = 53 deg. The sun altitude is -10.4 deg. MASTER-Amur robotic telescope located in Russia (BSPU) started inspect of Fermi GBM-190816 errorbox 1 days 57077 sec after trigger time at 2019-08-18 13:13:30 UT, with upper limit up to 18.3 mag. The observations began at zenit distance = 53 deg. The sun altitude is -19.6 deg. MASTER auto-detection system didn't find OT, that could be connected with GRB/GW events (AGN flares, known cataclismic variables found during inspect are excluded from candidates to the counterpart) Reduction and analysis will be continued. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/ligo_1.php?id=10721 We obtain the following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 103 | 2019-08-16 21:23:26 | MASTER-IAC | ( 14h 5m 10.35s , +46d 7m 39.34s) | C | 60 | 17.8 | 104 | 2019-08-16 21:23:26 | MASTER-IAC | ( 14h 17m 00.51s , +46d 3m 24.59s) | C | 60 | 17.7 | 237 | 2019-08-16 21:25:39 | MASTER-IAC | ( 14h 5m 08.91s , +46d 7m 38.46s) | C | 60 | 17.7 | 237 | 2019-08-16 21:25:39 | MASTER-IAC | ( 14h 16m 59.07s , +46d 3m 23.79s) | C | 60 | 17.5 | 374 | 2019-08-16 21:27:57 | MASTER-IAC | ( 13h 36m 03.92s , +44d 7m 27.38s) | C | 60 | 16.8 | 434 | 2019-08-16 21:27:57 | MASTER-IAC | ( 13h 36m 03.92s , +44d 7m 27.37s) | C | 180 | 17.4 | Coadd 379 | 2019-08-16 21:28:01 | MASTER-IAC | ( 13h 47m 29.17s , +44d 3m 16.24s) | C | 60 | 16.9 | 439 | 2019-08-16 21:28:01 | MASTER-IAC | ( 13h 47m 29.17s , +44d 3m 16.18s) | C | 180 | 17.9 | Coadd 505 | 2019-08-16 21:30:08 | MASTER-IAC | ( 13h 36m 05.04s , +44d 7m 25.49s) | C | 60 | 16.6 | 505 | 2019-08-16 21:30:08 | MASTER-IAC | ( 13h 47m 30.28s , +44d 3m 14.84s) | C | 60 | 17.3 | 641 | 2019-08-16 21:32:24 | MASTER-IAC | ( 13h 36m 05.02s , +44d 7m 43.84s) | C | 60 | 16.8 | 642 | 2019-08-16 21:32:24 | MASTER-IAC | ( 13h 47m 30.34s , +44d 3m 33.27s) | C | 60 | 17.5 | 779 | 2019-08-16 21:34:42 | MASTER-IAC | ( 13h 43m 06.20s , +10d 7m 56.62s) | C | 60 | 16.6 | 839 | 2019-08-16 21:34:42 | MASTER-IAC | ( 13h 43m 06.20s , +10d 7m 56.62s) | C | 180 | 17.2 | Coadd 779 | 2019-08-16 21:34:42 | MASTER-IAC | ( 13h 51m 24.48s , +10d 3m 50.81s) | C | 60 | 16.6 | 839 | 2019-08-16 21:34:42 | MASTER-IAC | ( 13h 51m 24.48s , +10d 3m 50.77s) | C | 180 | 17.5 | Coadd 911 | 2019-08-16 21:36:53 | MASTER-IAC | ( 13h 51m 24.47s , +10d 3m 26.97s) | C | 60 | 16.9 | 911 | 2019-08-16 21:36:53 | MASTER-IAC | ( 13h 43m 06.16s , +10d 7m 33.08s) | C | 60 | 16.6 | 1050 | 2019-08-16 21:39:13 | MASTER-IAC | ( 13h 51m 25.89s , +10d 3m 24.47s) | C | 60 | 16.9 | 1050 | 2019-08-16 21:39:13 | MASTER-IAC | ( 13h 43m 07.61s , +10d 7m 30.25s) | C | 60 | 16.4 | 1194 | 2019-08-16 21:41:37 | MASTER-IAC | ( 13h 48m 44.63s , +12d 7m 45.96s) | C | 60 | 16.8 | 1254 | 2019-08-16 21:41:37 | MASTER-IAC | ( 13h 48m 44.62s , +12d 7m 45.93s) | C | 180 | 17.2 | Coadd 1308 | 2019-08-16 21:43:30 | MASTER-IAC | ( 13h 48m 43.18s , +12d 7m 44.31s) | C | 60 | 16.5 | 1308 | 2019-08-16 21:43:30 | MASTER-IAC | ( 13h 57m 04.90s , +12d 3m 37.82s) | C | 60 | 16.7 | 1446 | 2019-08-16 21:45:49 | MASTER-IAC | ( 13h 48m 43.18s , +12d 7m 22.49s) | C | 60 | 16.5 | 1449 | 2019-08-16 21:45:51 | MASTER-IAC | ( 13h 57m 04.95s , +12d 3m 16.28s) | C | 60 | 16.8 | 1583 | 2019-08-16 21:48:06 | MASTER-IAC | ( 14h 3m 53.91s , +14d 3m 11.38s) | C | 60 | 17.0 | 1643 | 2019-08-16 21:48:06 | MASTER-IAC | ( 14h 3m 53.91s , +14d 3m 11.44s) | C | 180 | 17.3 | Coadd 1583 | 2019-08-16 21:48:06 | MASTER-IAC | ( 13h 55m 27.96s , +14d 7m 18.21s) | C | 60 | 16.8 | 1643 | 2019-08-16 21:48:06 | MASTER-IAC | ( 13h 55m 27.96s , +14d 7m 18.13s) | C | 180 | 17.3 | Coadd 1715 | 2019-08-16 21:50:18 | MASTER-IAC | ( 14h 3m 53.89s , +14d 3m 30.30s) | C | 60 | 16.4 | 1715 | 2019-08-16 21:50:18 | MASTER-IAC | ( 13h 55m 27.96s , +14d 7m 37.20s) | C | 60 | 16.5 | 1852 | 2019-08-16 21:52:34 | MASTER-IAC | ( 13h 55m 26.50s , +14d 7m 35.65s) | C | 60 | 16.7 | 1852 | 2019-08-16 21:52:34 | MASTER-IAC | ( 14h 3m 52.46s , +14d 3m 29.14s) | C | 60 | 16.7 | 1989 | 2019-08-16 21:54:52 | MASTER-IAC | ( 13h 42m 05.48s , +46d 6m 59.38s) | C | 60 | 16.3 | 2049 | 2019-08-16 21:54:52 | MASTER-IAC | ( 13h 42m 05.48s , +46d 6m 59.42s) | C | 180 | 17.3 | Coadd 1989 | 2019-08-16 21:54:52 | MASTER-IAC | ( 13h 53m 55.01s , +46d 2m 49.01s) | C | 60 | 16.7 | 2049 | 2019-08-16 21:54:52 | MASTER-IAC | ( 13h 53m 55.02s , +46d 2m 48.95s) | C | 180 | 17.8 | Coadd 2122 | 2019-08-16 21:57:04 | MASTER-IAC | ( 13h 42m 06.87s , +46d 7m 00.29s) | C | 60 | 17.0 | 2122 | 2019-08-16 21:57:05 | MASTER-IAC | ( 13h 53m 56.53s , +46d 2m 50.30s) | C | 60 | 17.3 | 2255 | 2019-08-16 21:59:17 | MASTER-IAC | ( 13h 42m 06.86s , +46d 7m 20.30s) | C | 60 | 17.0 | 2255 | 2019-08-16 21:59:18 | MASTER-IAC | ( 13h 53m 56.63s , +46d 3m 10.34s) | C | 60 | 17.5 | ... the full list of optical limits is https://master.sai.msu.ru/site/master2/ligo_1.php?id=10721 //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 25452 SUBJECT: Fermi GBM-190816: Coverage and upper limits from MAXI/GSC observations DATE: 19/08/23 01:54:12 GMT FROM: Motoko Serino at RIKEN/MAXI N. Kawai, M. Sugizaki (Tokyo Tech), H. Negoro (Nihon U.), S. Sugita, M. Serino (AGU), Y. Kawakubo (LSU), M. Nakajima, W. Maruyama, M. Aoki, K. Kobayashi (Nihon U.), T. Mihara, T. Tamagawa, M. Matsuoka (RIKEN), T. Sakamoto, H. Nishida, A. Yoshida (AGU), Y. Tsuboi, W. Iwakiri, R. Sasaki, H. Kawai, T. Sato (Chuo U.), M. Shidatsu (Ehime U.), M. Oeda, K. Shiraishi (Tokyo Tech), S. Nakahira, Y. Sugawara, S. Ueno, H. Tomida, M. Ishikawa, N. Isobe, R. Shimomukai, M. Tominaga (JAXA), Y. Ueda, A. Tanimoto, S. Yamada, S. Ogawa, K. Setoguchi, T. Yoshitake (Kyoto U.), H. Tsunemi, T. Yoneyama, K. Asakura, S. Ide (Osaka U.), M. Yamauchi, S. Iwahori, Y. Kurihara, K. Kurogi, K. Miike (Miyazaki U.), T. Kawamuro (NAOJ), K. Yamaoka (Nagoya U.) report on behalf of the MAXI team: We examined MAXI/GSC all-sky X-ray images (2-20 keV) after Fermi GBM-190816 at 2019-08-16 21:22:14.563 UTC (GCN 25406). At the trigger time of Fermi GBM-190816, the high-voltage of MAXI/GSC was on, but the FOV was out of the 90% credible region of GBM-190816-with-LV-v1 skymap. The first one-orbit (92 min) scan observation with GSC after the event covered 86% of the 90% credible region of the skymap from 21:27:25 to 22:54:10 UTC (T0+312 to T0+5517 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: 25465 SUBJECT: Fermi GBM-190816: Updated localization of subthreshold GRB-GW candidate DATE: 19/08/24 16:42:36 GMT FROM: Peter Shawhan at U of Maryland/LSC The LIGO Scientific Collaboration, the Virgo Collaboration, and the Fermi GBM team report: LSC and Virgo members have conducted further analysis of the LIGO and Virgo data around the time of the possible compact binary coalescence (CBC) candidate described in GCN Circular 25406. Parameter estimation has been performed using LALInference [1] to produce a new sky map. Fermi GBM data has also been re-analyzed utilizing the GBM targeted search [2,3] on finer timescales to optimize the source window for a refined localization. The current preferred GBM localization is broadly consistent with the original localization, but the highest probability region has shifted. A new joint sky map has been produced. The joint localization is concentrated in similar areas of the sky but the high-probability regions have shifted significantly. The 90% error region area is 3219 sq. deg. while the 50% error region area is 744 sq. deg. This sky map is available with the file name GBM-190816-with-LV-v2.fits on the OpenLVEM wiki page at https://wiki.gw-astronomy.org/OpenLVEM/FermiGBM-LVC There is no change at this time in our assessment of the significance of either the potential short GRB or the GW trigger. Both remain sub-threshold individually; the estimated joint false alarm rate is on the order of the usual LIGO-Virgo public alert threshold of 1 per 2 months. [1] Veitch, et al. PRD 91, 042003 (2015) [2] Blackburn et al. 2015, ApJS 217, 8 [3] Goldstein et al. arXiv:1903.12597