September 2021 - vsnet-grb-info - ooruri.kusastro.kyoto-u.ac.jp

[vsnet-grb-info 28780] GRB 210919A CAHA 2.2m Observations: Afterglow/Host Galaxy Candidate
by GCN Circulars 26 Sep '21

26 Sep '21

TITLE: GCN CIRCULAR NUMBER: 30883 SUBJECT: GRB 210919A CAHA 2.2m Observations: Afterglow/Host Galaxy Candidate DATE: 21/09/26 22:58:23 GMT FROM: Alexander Kann at IAA-CSIC <kann(a)iaa.es> D. A. Kann (HETH/IAA-CSIC), A. Rossi (INAF-OAS), A. de Ugarte Postigo (HETH/IAA-CSIC, DARK/NBI), C. Thoene, M. Blazek, J. F. Agui Fernandez (all HETH/IAA-CSIC), and P. Minguez (CAHA) report: We obtained observations of the enhance XRT position (Goad et al., GCN 30850) of the Swift short GRB 210919A (Tohuvavohu et al., GCN #30846) with CAFOS mounted on the 2.2m telescope at CAHA, Almeria, Spain. We obtained 30 x 90 s images in the i' band, starting at 03:38 UT on September 19, under good observing conditions. In the stacked image, we detect a faint source within the enhanced XRT error circle at: RA (J2000) = 05:21:01.098 Dec. (J2000) = +01:18:43.15 with an error of 0".5. Compared to three nearby comparison stars from the PanSTARRS catalog, we measure: i' = 24.14 +/- 0.30 mag (AB) @ 0.1525 days after the GRB. We suggest this source to be either the afterglow or the host galaxy of GRB 210919A. Other teams have reported upper limits so far: CR > 18.6 @ 0.007824 d (deepest, Lipunov et al., GCN #30847) CR > 17.5 @ 0.002975 d (Hu et al., GCN #30848) Rc > 20.5, Ic > 18.7 @ 0.05083 - 0.06958 d (Strausbaugh et al., GCN #30849) Rc > 22.1 @ 0.03194 d (Pankov et al., GCN #30851) r' > 23.4 @ 0.13125 d, i' > 23.9 @ 0.14458 d (Perley et al., GCN #30852) Rc > 20.5 @ 0.7208 d (Takamatsu et al., GCN #30855) Rc > 21.716 @ 0.426 d (AB); r' > 20.16 @ 0.6558 d; i' > 19.107 @ 0.6595 d (Kim et al., GCN #30856) white > 20.8 @ 0.001826 d (Siegel et al., GCN #30857) Kp > 21.5 @ 0.5542 d (AB) (Zhang et al., GCN #30858) r' > 23.6 @ 2.4635 d (Gottlieb et al., GCN #30860) i' > 24.1, z' > 23.6 @ 2.343 d (Pierel et al., GCN #30868) None of these limits are as deep as our image, with the NOT imaging (Perley et al., GCN #30852) slightly earlier and the late DeCam imaging (Pierel et al., GCN #30868) coming closest. This leaves it unclear as to whether the source is fading, we can therefore not discern whether it is an afterglow candidate or a host-galaxy candidate. Deeper imaging is needed, if the source is undetected to deeper limits, it is very likely the afterglow. If it is the host, it should be detected at higher significance.

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[vsnet-grb-info 28779] IceCube-210922A: JCMT/SCUBA2 observations
by GCN Circulars 26 Sep '21

26 Sep '21

TITLE: GCN CIRCULAR NUMBER: 30882 SUBJECT: IceCube-210922A: JCMT/SCUBA2 observations DATE: 21/09/26 12:09:36 GMT FROM: Kuiyun Huang at IANCU/NTNU <kuiyun(a)gmail.com> Y. Urata and K. Huang on behalf of a larger collaboration We observed the field of IceCube-210922A (GCN Circ. 30862) using Scuba-2 attached to JCMT. The observation was started at 2021/09/24 13:15 UTC and SCUBA-2 imaged the field centered at RA 04:02:55.200, Dec -04:10:48.00 with 50 arcmin diameter. There is one bright submm source with ~70 mJy/beam at 850um not listed in the Planck catalog of compact sources. The position is RA 04:02:05.362 Dec -04:24:28.80 Within the JCMT beam (14 arcsec), there are two catalog sources, WISEA J040205.29-042428.5 and NVSS J040205-042434. Based on the Pan-STARRS1 images, there are no optical sources. Additional monitoring observation with Scuba-2 is scheduled. Further detailed multi-wavelength investigation of the source is encouraged. We would like to thank Harriet Parsons and JCMT staff.

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[vsnet-grb-info 28778] GRB 210925A: GECAM detection
by GCN Circulars 26 Sep '21

26 Sep '21

TITLE: GCN CIRCULAR NUMBER: 30881 SUBJECT: GRB 210925A: GECAM detection DATE: 21/09/26 09:27:52 GMT FROM: Chao Zheng at IHEP <zhengchao97(a)ihep.ac.cn> C. Zheng, S. L. Xiong, S. Xiao, Y. Q. Zhang, W. C. Xue, X. Y. Song, X. Y. Zhao, Y. Huang, S. L. Xie, C. Cai, Y. Zhao, Z. W. Guo, X. L. Zhang, C. Y. Li, C. W. Wang, Q. B. Yi, B. X. Zhang, P. Zhang, W. X. Peng, R. Qiao, D. Y. Guo, X. B. Li, X. Ma, P. Wang, J. Wang, Z. Zhang, S. J. Zheng, W. Chen, J. J. He, G. Y. Zhao, Y. Q. Du, H. Wu, J. Liang, Q. Luo, J. C. Liu, L. M. Song, F. J. Lu, S. N. Zhang (IHEP), report on behalf of GECAM team: During the commissioning phase, GECAM-B was triggered in-flight by a long bright burst, GRB 210925A, at 2021-09-25T19:12:34.600 UTC (denoted as T0), which was also detected by Fermi/GBM (GCN #30880). Its alert data was promptly downlinked to the ground through the short message service of BeiDou Navigation Satellite System (BDS). The time latency of the first BeiDou message relative to the trigger time is about 1 minute. According to the BDS alert data, this burst mainly consists of multiple pulses with duration of about 10 s. The GECAM light curve could be found here: http://twiki.ihep.ac.cn/pub/GECAM/GRBList/utn210925_191234_GECAMb.png An automatic in-flight localization was calculated using the light curves and spectrum. Although the in-flight calibration of energy response and l ocalization has not been finalized yet, GECAM-B localized this burst to the following position (J2000): Ra: 357.83 deg Dec: -24.58 deg Err: 3.50 deg (1-sigma, statistical only) The current systematic error of location is estimated to be several degrees which could be minimized by the ongoing calibration. Please note that all GECAM results here are preliminary. The final analysis will be published in journal papers or GECAM online catalog. Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor (GECAM) mission consists of two small satellites (GECAM-A and GECAM-B) in Low Earth Orbit (600 km, 29 deg), launched on Dec 10, 2020 (Beijing Time), which was funded by the Chinese Academy of Sciences (CAS).

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[vsnet-grb-info 28777] GRB 210925A: Fermi GBM Final Real-time Localization
by GCN Circulars 25 Sep '21

25 Sep '21

TITLE: GCN CIRCULAR NUMBER: 30880 SUBJECT: GRB 210925A: Fermi GBM Final Real-time Localization DATE: 21/09/25 19:22:53 GMT FROM: Fermi GBM Team at MSFC/Fermi-GBM <do_not_reply(a)GIOC.nsstc.nasa.gov> The Fermi GBM team reports the detection of a likely LONG GRB At 19:12:27 UT on 25 Sep 2021, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 210925A (trigger 654289952.965146 / 210925800). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 347.4, Dec = -17.1 (J2000 degrees, equivalent to J2000 23h 09m, -17d 06'), with a statistical uncertainty of 3.3 degrees. The angle from the Fermi LAT boresight is 82.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210925800/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210925800/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210925800/…

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[vsnet-grb-info 28776] GRB 210919A: Chandra rapid ToO upper limit
by GCN Circulars 25 Sep '21

25 Sep '21

TITLE: GCN CIRCULAR NUMBER: 30879 SUBJECT: GRB 210919A: Chandra rapid ToO upper limit DATE: 21/09/25 01:27:01 GMT FROM: Takanori Sakamoto at AGU <tsakamoto(a)phys.aoyama.ac.jp> T. Sakamoto (AGU), E. Troja (NASA/GSFC/ORAU), J. Norris (BSU), S. D. Barthelmy (GSFC), J. L. Racusin (GSFC), N. Kawai (Tokyo Tech), A. Fruchter (STScI), M. Im (SNU), B. Cenko (GSFC) A Chandra ToO observation of a short GRB 200919A (Tohuvavohu et al., GCN Circ. 30846) started on February 21 02:54 UT (~2.1 days after the GRB trigger) for a total of 19.8 ksec. We do not detect an X-ray afterglow at the location of the enhanced XRT position (Goad et al., GCN Circ. 30850). The calculated 3-sigma upper limit is 3.4 x 10^-4 c/s in the 0.3-8 keV band using aprates of the CIAO software package. Assuming N_H of 1.5 x 10^21 cm^-2 and photon index of 2, we estimated an 3-sigma unabsorbed flux upper limit of 6.9 x 10^-15 erg/cm2/s in the 0.3-8 keV band. We would like to thank Patrick Slane, Harvey Tananbaum, Andrea Prestwich, and the Chandra operation team for rapidly approving and making this observation.

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[vsnet-grb-info 28775] GRB 210924A: Fermi GBM Final Real-time Localization
by GCN Circulars 24 Sep '21

24 Sep '21

TITLE: GCN CIRCULAR NUMBER: 30878 SUBJECT: GRB 210924A: Fermi GBM Final Real-time Localization DATE: 21/09/24 23:13:09 GMT FROM: Fermi GBM Team at MSFC/Fermi-GBM <do_not_reply(a)GIOC.nsstc.nasa.gov> The Fermi GBM team reports the detection of a likely SHORT GRB At 23:02:52 UT on 24 Sep 2021, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 210924A (trigger 654217377.138008 / 210924960). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 107.1, Dec = 45.3 (J2000 degrees, equivalent to J2000 07h 08m, 45d 17'), with a statistical uncertainty of 10.5 degrees. The angle from the Fermi LAT boresight is 22.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210924960/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210924960/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210924960/…

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[vsnet-grb-info 28774] IceCube-210922A: No Candidate Counterparts from Swift/XRT follow up observations
by GCN Circulars 24 Sep '21

24 Sep '21

TITLE: GCN CIRCULAR NUMBER: 30877 SUBJECT: IceCube-210922A: No Candidate Counterparts from Swift/XRT follow up observations DATE: 21/09/24 20:52:44 GMT FROM: Hugo Ayala at Pennsylvania State University <hgayala(a)psu.edu> Felicia Krauss, Timothée Gregoire, Derek Fox, Doug Cowen, Hugo Ayala (PSU) and Alexis Coleiro (APC) report for AMON (https://amon.psu.edu/) The Neil Gehrels Swift Observatory X-ray Telescope (XRT) observed the uncertainty region of the IceCube neutrino event IceCube-210922A (GCN Circ. 30862) on 2021-09-23, between 02:00 and 21:52 UTC . A 6-point tiling observation centered on the neutrino position was taken for a total of 3.5 ksec. Of the 90% confidence 1.23 sq. degrees uncertainty region, the XRT observations cover roughly 75% of the central area. No X-ray candidate counterparts were detected above a level of 3 sigma. The 3 sigma upper limit for the flux is 1.2x10^(-13) ergs/s/cm^2.

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[vsnet-grb-info 28773] IceCube-210922A: No significant detection in HAWC
by GCN Circulars 24 Sep '21

24 Sep '21

TITLE: GCN CIRCULAR NUMBER: 30876 SUBJECT: IceCube-210922A: No significant detection in HAWC DATE: 21/09/24 17:51:30 GMT FROM: Hugo Ayala at Pennsylvania State University <hgayala(a)psu.edu> Hugo Ayala (Penn State) reports on behalf of the HAWC collaboration (http://www.hawc-observatory.org/collaboration) On 2021/09/22 18:17:20 UTC, the IceCube collaboration reported a track-like very-high-energy event that has a high probability of being an astrophysical neutrino, IceCube-210922A. Location is at RA: 60.73 (+0.96/-0.66 deg 90% PSF containment) J2000 Dec: -4.18 (+0.42/-0.55 deg 90% PSF containment) J2000 (GCN circular 30862). We performed two types of analyses for the follow-up. The first is for a steady source in archival data and the second is a search for a transient source. We assume a power-law spectrum with an index of -2.3 for both analyses. Search for a steady source in archival data: The archival data spans from November 2014 to June 2019. We searched inside the reported IceCube error region. The most significant location, with p-value 3.72e-2 (0.26 post-trials), is at RA 60.03 deg, Dec -3.84 deg (±0.30 deg 68% containment) J2000. We set a time-integrated 95% CL upper limit on gamma rays at the maximum position of: E^2 dN/dE = 3.42e-13 (E/TeV)^-0.3 TeV.cm^-2.s^-1 Search for a transient source. Since the event was not in our field of view at the time reported, we report the combined result for the transits before and after the IceCube event. Data acquisition started on 2021/09/21 12:58:23 UTC and ended 2021/09/23 13:05:05 UTC. The most significant location, with p-value 0.12 (0.64 post-trials), is at RA 60.12 deg, Dec -4.74 deg (±0.30 deg 68% containment) J2000. We set a time-integrated 95% CL upper limit at the position of maximum significance of: E^2 dN/dE = 8.8e-12 (E/TeV)^-0.3 TeV.cm^-2.s^-1 HAWC is a very-high-energy gamma-ray observatory operating in Central Mexico at latitude 19 deg. north. Operating day and night with over 95% duty cycle, HAWC has an instantaneous field of view of 2 sr and surveys 2/3 of the sky every day. It is sensitive to gamma rays from 300 GeV to 100 TeV.

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[vsnet-grb-info 28772] IceCube-210922A: No neutrino counterpart candidates in ANTARES search
by GCN Circulars 24 Sep '21

24 Sep '21

TITLE: GCN CIRCULAR NUMBER: 30875 SUBJECT: IceCube-210922A: No neutrino counterpart candidates in ANTARES search DATE: 21/09/24 12:32:06 GMT FROM: Antoine Kouchner at ANTARES Collaboration <kouchner(a)apc.in2p3.fr> Alexis Coleiro (APC/Universite de Paris) and Damien Dornic (CPPM/CNRS) on behalf of the ANTARES Collaboration. Using data from the ANTARES detector, we have performed a follow-up analysis of the recently reported single track-like event IceCube-210922A (GCN #30862). The reconstructed origin was -37 degrees below the horizon for ANTARES. No up-going muon neutrino candidate events were recorded within 90% error box of the IceCube event during a +/- 1h time-window centered on the IceCube event time, and over which the potential source remained visible all time. This leads to a preliminary 90% confidence level upper limit on the muon-neutrino fluence from a point source of 16 GeV.cm^-2 over the energy range 3 TeV – 3.3 PeV (the range corresponding to 5-95% of the detectable flux) for an E^-2 power-law spectrum, and 30 GeV.cm^-2 (580 GeV - 300 TeV) for an E^-2.5 spectrum. A search over an extended time window of +/- 1 day has also yielded no detection (52% visibility). ANTARES <http://antares.in2p3.fr/ <http://antares.in2p3.fr/>> is the largest undersea neutrino detector (Mediterranean Sea) and it is primarily sensitive to astrophysical 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.

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[vsnet-grb-info 28771] GRB 210923B: GECAM detection
by GCN Circulars 24 Sep '21

24 Sep '21

TITLE: GCN CIRCULAR NUMBER: 30874 SUBJECT: GRB 210923B: GECAM detection DATE: 21/09/24 06:05:39 GMT FROM: Xiaolu Zhang at IHEP <xlzhang(a)ihep.ac.cn> GRB 210923B: GECAM detection X. L. Zhang, S. L. Xiong, X. Y. Zhao, Y. Huang, X. Y. Song, C. Cai, S. Xiao, S. L. Xie, Y. Q. Zhang, Y. Zhao, Z. W. Guo, C. Zheng, W. C. Xue, C. Y. Li, C. W. Wang, Q. B. Yi, B. X. Zhang, P. Zhang, W. X. Peng, R. Qiao, D. Y. Guo, X. B. Li, X. Ma, P. Wang, J. Wang, Z. Zhang, S. J. Zheng, W. Chen, J. J. He, G. Y. Zhao, Y. Q. Du, H. Wu, J. Liang, Q. Luo, J. C. Liu, L. M. Song, F. J. Lu, S. N. Zhang (IHEP), report on behalf of GECAM team: During the commissioning phase, GECAM-B was triggered ground by a short bright burst, GRB 210923B, at 2021-09-23 02:11:29.000 UTC (denoted as T0), which was also detected by Konus-Wind. According to the GECAM-B light curves in about 15-3500 keV, this burst mainly consists of a broad pulse with a duration of about 0.679 s. The GECAM light curve could be found here: http://twiki.ihep.ac.cn/pub/GECAM/GRBList/utn210923_021129_GECAMb_lc.png GECAM-B localized this burst to the following position (J2000): Ra: 287.25 deg Dec: -12.03 deg Err: 6.29 deg (1-sigma, statistical only) The current systematic error of location is estimated to be several degrees which could be minimized by the ongoing calibration. Please note that all GECAM results here are preliminary. The final analysis will be published in journal papers or GECAM online catalog. Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor (GECAM) mission consists of two small satellites (GECAM-A and GECAM-B) in Low Earth Orbit (600 km, 29 deg), launched on Dec 10, 2020 (Beijing Time), which was funded by the Chinese Academy of Sciences (CAS).

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