September 2024 - vsnet-grb-info - ooruri.kusastro.kyoto-u.ac.jp

[vsnet-grb-info 35480] LIGO/Virgo/KAGRA S240920bz: Identification of a GW compact binary merger candidate
by GCN Circulars 20 Sep '24

20 Sep '24

TITLE: GCN CIRCULAR NUMBER: 37562 SUBJECT: LIGO/Virgo/KAGRA S240920bz: Identification of a GW compact binary merger candidate DATE: 24/09/20 08:05:49 GMT FROM: Elisa Bigongiari at University of Pisa <e.bigongiari1(a)studenti.unipi.it> The LIGO Scientific Collaboration, the Virgo Collaboration, and the KAGRA Collaboration report: We identified the compact binary merger candidate S240920bz during real-time processing of data from LIGO Hanford Observatory (H1), LIGO Livingston Observatory (L1), and Virgo Observatory (V1) at 2024-09-20 07:34:24.482 UTC (GPS time: 1410852882.482). The candidate was found by the cWB [1], cWB BBH [2], GstLAL [3], MBTA [4], PyCBC Live [5], and SPIIR [6] analysis pipelines. S240920bz is an event of interest because its false alarm rate, as estimated by the online analysis, is 3.2e-10 Hz, or about one in 1e2 years. The event's properties can be found at this URL: https://gracedb.ligo.org/superevents/S240920bz The classification of the GW signal, in order of descending probability, is BBH (>99%), Terrestrial (<1%), BNS (<1%), or NSBH (<1%). Assuming the candidate is astrophysical in origin, the probability that the lighter compact object is consistent with a neutron star mass (HasNS) is <1%. [7] Using the masses and spins inferred from the signal, the probability of matter outside the final compact object (HasRemnant) is <1%. [7] Both HasNS and HasRemnant consider the support of several neutron star equations of state for maximum neutron star mass. The probability that either of the binary components lies between 3 and 5 solar masses (HasMassGap) is <1%. Two sky maps are available at this time and can be retrieved from the GraceDB event page: * bayestar.multiorder.fits,0, an initial localization generated by BAYESTAR [8], distributed via GCN notice about 30 seconds after the candidate event time. * bayestar.multiorder.fits,1, an initial localization generated by BAYESTAR [8], distributed via GCN notice about 5 minutes after the candidate event time. The preferred sky map at this time is bayestar.multiorder.fits,1. For the bayestar.multiorder.fits,1 sky map, the 90% credible region is 545 deg2. Marginalized over the whole sky, the a posteriori luminosity distance estimate is 1660 +/- 401 Mpc (a posteriori mean +/- standard deviation). For further information about analysis methodology and the contents of this alert, refer to the LIGO/Virgo/KAGRA Public Alerts User Guide https://emfollow.docs.ligo.org/. [1] Klimenko et al. PRD 93, 042004 (2016) doi:10.1103/PhysRevD.93.042004 [2] T. Mishra et al. PRD 105, 083018 (2022) doi:10.1103/PhysRevD.105.083018 [3] Tsukada et al. PRD 108, 043004 (2023) doi:10.1103/PhysRevD.108.043004 and Ewing et al. (2023) arXiv:2305.05625 [4] Aubin et al. CQG 38, 095004 (2021) doi:10.1088/1361-6382/abe913 [5] Dal Canton et al. ApJ 923, 254 (2021) doi:10.3847/1538-4357/ac2f9a [6] Chu et al. PRD 105, 024023 (2022) doi:10.1103/PhysRevD.105.024023 [7] Chatterjee et al. ApJ 896, 54 (2020) doi:10.3847/1538-4357/ab8dbe [8] Singer & Price PRD 93, 024013 (2016) doi:10.1103/PhysRevD.93.024013 View this GCN Circular online at https://gcn.nasa.gov/circulars/37562. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 35479] EP240919a: EP-WXT detection of a fast X-ray transient
by GCN Circulars 20 Sep '24

20 Sep '24

TITLE: GCN CIRCULAR NUMBER: 37561 SUBJECT: EP240919a: EP-WXT detection of a fast X-ray transient DATE: 24/09/20 07:39:06 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> Y. F. Liang (PMO, CAS), H. Q. Cheng, M. J. Liu, X. Pan, X. P. Xu, H. N. Yang(NAOC, CAS), Z. J. Zhang (HKU), C. Y. Dai (NJU), C. X. Zhang (HUST), C. C. Jin, H. W. Pan, Z. X. Ling, W. M. Yuan, Y. Liu, C. Zhang, W. Chen, , C. Z. Cui, D. W. Fan, H. B. Hu, J. W. Hu, M. H. Huang, D. Y. Li, H. Y. Liu, Z. Z. Lv, T. Y. Lian, X. Mao, H. Sun, W. X. Wang, Y. L. Wang, Y. F. Xu, M. Zhang, W. D. Zhang, W. J. Zhang, Z. Zhang, D. H. Zhao (NAOC, CAS), Y. Chen, S. M. Jia, W. W. Cui, D. W. Han, C. K. Li, L. M. Song, X. F. Zhao, J. Zhang, S. N. Zhang (IHEP, CAS), E. Kuulkers, A. Santovincenzo (ESA), P. O'Brien (Univ. of Leicester), K. Nandra, A. Rau (MPE), B. Cordier (CEA) on behalf of the Einstein Probe team We report on the detection of a fast X-ray transient designated EP240919a, which was detected by EP-WXT at 2024-09-19T14:47:40 (UTC), and triggered the on-board processing unit at 2024-09-19T14:53:43 (trigger ID: 01709054141). An autonomous observation was performed by the Follow-up X-ray Telescope (FXT) about five minutes later. Afterwards, the FXT on-board processing unit was also triggered, showing that an uncatalogued source was detected at R.A. = 334.2797, DEC = -9.7362 (J2000) with an uncertainty of about 20 arcsec (radius, 90% C.L. statistical and systematic). The light curve of the transient observed by the WXT lasts more than 400 seconds. The average 0.5-4 keV spectrum can be fitted with an absorbed power-law with a photon index of 1.3(+0.3/-0.3) (with the column density fixed at the Galactic value of 5.4x10^20 cm^-2). The absorbed average flux in 0.5-4 keV is 7.0(+1.8/-1.5) x 10^(-10) erg/s/cm^2. The quoted uncertainties are at the 90% confidence level for the above parameters. No previously known bright X-ray sources are found within the error circle around the source position. Further follow-up observations are encouraged to identify the nature of this X-ray transient. Launched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with onboard X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics). View this GCN Circular online at https://gcn.nasa.gov/circulars/37561. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 35478] GRB 240918A and GRB 240918B : INTEGRAL SPI ACS LIGHT CURVE
by GCN Circulars 19 Sep '24

19 Sep '24

TITLE: GCN CIRCULAR NUMBER: 37560 SUBJECT: GRB 240918A and GRB 240918B : INTEGRAL SPI ACS LIGHT CURVE DATE: 24/09/19 23:14:33 GMT FROM: Devraj Pawar at R. J. College, Mumbai - 86, India <devrajdp(a)gmail.com> Devraj Pawar (R. J. College, Mumbai-86, India) on behalf of a collaboration studying transients. GRB 240918A and GRB 240918B were reported by the Fermi GBM team in GCN 37549 and GCN 37558 respectively. We analyzed the INTEGRAL SPI ACS data around the T0 given in GCN 37549 and detected two peaks separated by ~108 seconds in the light curve. These events occur at the times reported in GCN 37549 and GCN 37558. SPI ACS is sensitive above 80 keV : the peak of the first burst is at ~3550 counts/s and peak count rate of the second burst is 3800 counts/s. The steady count rate preceding the events is around 3350 counts/s. The count rate is affected by the instruments orientation with respect to the direction of the sources and hence the relative intensity of the two bursts cannot be compared with the analysis done so far. GRB 240918A is not visually detected with the 0.05 s resolution of the INTEGRAL SPI ACS, hence we time averaged the light curve. The light curves at various time resolutions and the burst profiles are given in the link below and any further analysis will be shared on the same link : [GRB 240918A and GRB 240918B : INTEGRAL SPI ACS LIGHT CURVES](https://docs.google.com/document/d/15b887kxPSdQVyT9NLfZZzb8XMLhijew… This work is based on observations with INTEGRAL, an ESA project with instruments and a science data center funded by ESA member states (especially the PI countries: Denmark, France, Germany, Italy, Switzerland, Spain), and with the participation of Russia and the USA. The SPI-ACS detector system has been provided by MPE Garching/Germany. View this GCN Circular online at https://gcn.nasa.gov/circulars/37560. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 35477] LIGO/Virgo/KAGRA S240919bn: Updated Sky localization
by GCN Circulars 19 Sep '24

19 Sep '24

TITLE: GCN CIRCULAR NUMBER: 37559 SUBJECT: LIGO/Virgo/KAGRA S240919bn: Updated Sky localization DATE: 24/09/19 16:32:43 GMT FROM: Colm Talbot at University of Chicago <talbotcolm(a)gmail.com> The LIGO Scientific Collaboration, the Virgo Collaboration, and the KAGRA Collaboration report: We have conducted further analysis of the LIGO Hanford Observatory (H1), LIGO Livingston Observatory (L1), and Virgo Observatory (V1) data around the time of the compact binary merger (CBC) candidate S240919bn (GCN Circular 37552). Parameter estimation has been performed using Bilby [1] and a new sky map, Bilby.multiorder.fits,0, distributed via GCN Notice, is available for retrieval from the GraceDB event page: https://gracedb.ligo.org/superevents/S240919bn For the Bilby.multiorder.fits,0 sky map, the 90% credible region is well fit by an ellipse with an area of 16 deg2 described by the following DS9 region (right ascension, declination, semi-major axis, semi-minor axis, position angle of the semi-minor axis): icrs; ellipse(03h35m, +36d30m, 2.83d, 1.79d, 75.95d) Marginalized over the whole sky, the a posteriori luminosity distance estimate is 1711 +/- 490 Mpc (a posteriori mean +/- standard deviation). For further information about analysis methodology and the contents of this alert, refer to the LIGO/Virgo/KAGRA Public Alerts User Guide https://emfollow.docs.ligo.org/. [1] Ashton et al. ApJS 241, 27 (2019) doi:10.3847/1538-4365/ab06fc and Morisaki et al. PRD 108, 123040 (2023) doi:10.1103/PhysRevD.108.123040 View this GCN Circular online at https://gcn.nasa.gov/circulars/37559. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 35476] GRB 240918B: Fermi GBM Detection
by GCN Circulars 19 Sep '24

19 Sep '24

TITLE: GCN CIRCULAR NUMBER: 37558 SUBJECT: GRB 240918B: Fermi GBM Detection DATE: 24/09/19 15:47:35 GMT FROM: rachel.hamburg(a)ijclab.in2p3.fr The Fermi GBM team reports the detection of a likely LONG GRB. At approximately 20:56:58 UT on 18 Sep 2024, the Fermi Gamma-ray Burst Monitor (GBM) detected GRB 240918B, which was observed about 107 s after GBM triggered on GRB 240918A (trigger 748385716/240918872) (Fermi GBM Team 2024; GCN 37549). Due to the GBM trigger buffer of 10 min, the GBM did not trigger on this GRB. The on-ground calculated location, using the Fermi GBM trigger data from 107.52 s to 115.71 s after trigger time, is RA = 142.54, Dec = -17.36 (J2000 degrees, equivalent to J2000 9h 30m, -17d 36'), with a statistical uncertainty of 2.03 degrees. The angle from the Fermi LAT boresight is 64 degrees. The GBM Targeted Search [1], the most sensitive, coherent search for GRB-like signals, was also used to identify GRB-like emission around the time of GRB 240918B. This search finds a multi-peaked emission episode on timescales up to 4.096 s and showing a localization consistent with the on-ground location. The brightest peak (at 20:57:01 UT) was found to be the most significant (FAR = 5.4e-06 Hz) on the 0.512 s timescale and best fit with a "normal" GRB spectrum as described in [1]." [1] Goldstein et al. 2019 arXiv:1903.12597 View this GCN Circular online at https://gcn.nasa.gov/circulars/37558. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 35475] LIGO/Virgo/KAGRA S240917cb: Updated Sky localization and EM Bright Classification
by GCN Circulars 19 Sep '24

19 Sep '24

TITLE: GCN CIRCULAR NUMBER: 37557 SUBJECT: LIGO/Virgo/KAGRA S240917cb: Updated Sky localization and EM Bright Classification DATE: 24/09/19 12:42:50 GMT FROM: Colm Talbot at University of Chicago <talbotcolm(a)gmail.com> The LIGO Scientific Collaboration, the Virgo Collaboration, and the KAGRA Collaboration report: We have conducted further analysis of the LIGO Hanford Observatory (H1) and LIGO Livingston Observatory (L1) data around the time of the compact binary merger (CBC) candidate S240917cb (GCN Circular 37534). Parameter estimation has been performed using Bilby [1] and a new sky map, Bilby.offline0.multiorder.fits,0, distributed via GCN Notice, is available for retrieval from the GraceDB event page: https://gracedb.ligo.org/superevents/S240917cb Based on posterior support from parameter estimation [1], under the assumption that the candidate S240917cb is astrophysical in origin, the probability that the lighter compact object is consistent with a neutron star mass (HasNS) is <1%. [2] Using the masses and spins inferred from the signal, the probability of matter outside the final compact object (HasRemnant) is <1%. [2] Both HasNS and HasRemnant consider the support of several neutron star equations of state. The probability that either of the binary components lies between 3 and 5 solar masses (HasMassGap) is <1%. For the Bilby.offline0.multiorder.fits,0 sky map, the 90% credible region is 8644 deg2. Marginalized over the whole sky, the a posteriori luminosity distance estimate is 6657 +/- 3466 Mpc (a posteriori mean +/- standard deviation). For further information about analysis methodology and the contents of this alert, refer to the LIGO/Virgo/KAGRA Public Alerts User Guide https://emfollow.docs.ligo.org/. [1] Ashton et al. ApJS 241, 27 (2019) doi:10.3847/1538-4365/ab06fc and Morisaki et al. PRD 108, 123040 (2023) doi:10.1103/PhysRevD.108.123040 [2] Chatterjee et al. ApJ 896, 54 (2020) doi:10.3847/1538-4357/ab8dbe View this GCN Circular online at https://gcn.nasa.gov/circulars/37557. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 35474] LIGO/Virgo/KAGRA S240916ar: Updated Sky localization and EM Bright Classification
by GCN Circulars 19 Sep '24

19 Sep '24

TITLE: GCN CIRCULAR NUMBER: 37556 SUBJECT: LIGO/Virgo/KAGRA S240916ar: Updated Sky localization and EM Bright Classification DATE: 24/09/19 12:28:50 GMT FROM: Colm Talbot at University of Chicago <talbotcolm(a)gmail.com> The LIGO Scientific Collaboration, the Virgo Collaboration, and the KAGRA Collaboration report: We have conducted further analysis of the LIGO Hanford Observatory (H1), LIGO Livingston Observatory (L1), and Virgo Observatory (V1) data around the time of the compact binary merger (CBC) candidate S240916ar (GCN Circular 37530). Parameter estimation has been performed using Bilby [1] and a new sky map, Bilby.multiorder.fits,0, distributed via GCN Notice, is available for retrieval from the GraceDB event page: https://gracedb.ligo.org/superevents/S240916ar Based on posterior support from parameter estimation [1], under the assumption that the candidate S240916ar is astrophysical in origin, the probability that the lighter compact object is consistent with a neutron star mass (HasNS) is <1%. [2] Using the masses and spins inferred from the signal, the probability of matter outside the final compact object (HasRemnant) is <1%. [2] Both HasNS and HasRemnant consider the support of several neutron star equations of state. The probability that either of the binary components lies between 3 and 5 solar masses (HasMassGap) is 2%. For the Bilby.multiorder.fits,0 sky map, the 90% credible region is 570 deg2. Marginalized over the whole sky, the a posteriori luminosity distance estimate is 1273 +/- 380 Mpc (a posteriori mean +/- standard deviation). For further information about analysis methodology and the contents of this alert, refer to the LIGO/Virgo/KAGRA Public Alerts User Guide https://emfollow.docs.ligo.org/. [1] Ashton et al. ApJS 241, 27 (2019) doi:10.3847/1538-4365/ab06fc and Morisaki et al. PRD 108, 123040 (2023) doi:10.1103/PhysRevD.108.123040 [2] Chatterjee et al. ApJ 896, 54 (2020) doi:10.3847/1538-4357/ab8dbe View this GCN Circular online at https://gcn.nasa.gov/circulars/37556. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 35473] EP240918b and EP240918c: EP-WXT detection of two fast X-ray transients
by GCN Circulars 19 Sep '24

19 Sep '24

TITLE: GCN CIRCULAR NUMBER: 37555 SUBJECT: EP240918b and EP240918c: EP-WXT detection of two fast X-ray transients DATE: 24/09/19 10:05:21 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> Y. F. Liang (PMO, CAS), Z. J. Zhang (HKU), M. J. Liu, X. P. Xu, C. C. Jin, Z. X. Ling, W. M. Yuan, Y. Liu, C. Zhang, W. Chen, H. Q. Cheng, C. Z. Cui, D. W. Fan, H. B. Hu, J. W. Hu, M. H. Huang, D. Y. Li, H. Y. Liu, Z. Z. Lv, T. Y. Lian, X. Mao, H. W. Pan, X. Pan, H. Sun, W. X. Wang, Y. L. Wang, Y. F. Xu, H. N. Yang, M. Zhang, W. D. Zhang, W. J. Zhang, Z. Zhang, D. H. Zhao (NAOC, CAS), Y. Chen, S. M. Jia, W. W. Cui, D. W. Han, C. K. Li, L. M. Song, X. F. Zhao, J. Zhang, S. N. Zhang (IHEP, CAS), E. Kuulkers, A. Santovincenzo (ESA), P. O'Brien (Univ. of Leicester), K. Nandra, A. Rau (MPE), B. Cordier (CEA) on behalf of the Einstein Probe team We report on the detection of two fast X-ray transients designated EP240918b and EP240918c, respectively, by the Einstein Probe (EP) mission. EP240918b was detected by EP-WXT at 2024-09-18T15:40:00 (UTC). The WXT position is R.A. = 258.66 deg, DEC = 66.739 deg (J2000) with an uncertainty of about 2.9 arcmin (radius, 90% C.L. statistical and systematic). The light curve of the transient observed by the WXT lasts around 200 seconds. The absorbed average flux in 0.5-4 keV is 2.6(+4.1/-1.2) x 10^(-10) erg/s/cm^2 with a freely fitted column density value of 3.2(+6.2/-3.2) x 10^21 cm^-2 and the photon index of 1.5(+1.8/-1.3). We note that a star, TYC 4210-373-1, is located within 3 arcmin around the source position. EP240918c was detected by EP-WXT at 2024-09-18T18:06:47 (UTC). The WXT position is R.A.=281.338 deg, DEC=-13.167 deg (J2000) with an uncertainty of about 2.3 arcmin (radius, 90% C.L. statistical and systematic), corresponding to Galactic l, b = 20.503, -4.638. The WXT light curve lasts around 100 seconds with a peak flux of ~ 5.8 x 10^(-9) erg/s/cm^2 in the 0.5-4 keV band. The average 0.5-4 keV spectrum can be fitted with an absorbed power law with a photon index of 1.6(+0.8/-0.8) (with column density fixed at the Galactic value 3.7 x 10^21 cm^-2). The derived average unabsorbed 0.5-4 keV flux is 1.5(+0.6/-0.2) x 10^(-9) erg/s/cm^2. The quoted uncertainties are at the 90% confidence level for the above parameters. No previously known bright X-ray sources are found within the error circle around the source position. Following the WXT detections, we performed two follow-up observations with the Follow-up X-ray Telescope (FXT) on board EP. Further follow-up observations are encouraged to identify the nature of this X-ray transient. Launched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with onboard X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics). View this GCN Circular online at https://gcn.nasa.gov/circulars/37555. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 35472] EP240918a: EP observation update
by GCN Circulars 19 Sep '24

19 Sep '24

TITLE: GCN CIRCULAR NUMBER: 37554 SUBJECT: EP240918a: EP observation update DATE: 24/09/19 08:42:10 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> Z. J. Zhang (HKU), Y. F. Liang (PMO, CAS), H. Y. Liu, W. Chen, T. Zhao , Z. X. Ling, J. W. Hu, W. M. Yuan, C. C. Jin, Y. Liu, C. Zhang, H. Q. Cheng, C. Z. Cui, D. W. Fan, H. B. Hu, M. H. Huang, D. Y. Li, M. J. Liu, Z. Z. Lv, T. Y. Lian, X. Mao, H. W. Pan, X. Pan, H. Sun, W. X. Wang, Y. L. Wang, X. P. Xu, Y. F. Xu, H. N. Yang, M. Zhang, W. D. Zhang, W. J. Zhang, Z. Zhang, D. H. Zhao (NAOC, CAS), X. F. Zhao, Y. Chen, S. M. Jia, W. W. Cui, D. W. Han, C. K. Li, L. M. Song, J. Zhang, S. N. Zhang (IHEP, CAS), E. Kuulkers, A. Santovincenzo (ESA), P. O'Brien (Univ. of Leicester), K. Nandra, A. Rau (MPE), B. Cordier (CEA) on behalf of the Einstein Probe team We have reported the detection of the fast X-ray transient EP240918a by the Einstein Probe (EP) mission (Zhang et al. GCN 37541). Based on the newly received EP telemetry data of this source, the transient event started at 2024-09-18T11:21:52 (UTC). The lightcurve of the transient obtained by the WXT lasts around 170 seconds and has a peak flux of around 3.2 x 10^(-9) erg/s/cm^2 in the 0.5-4 keV band. The average 0.5-4 keV spectrum can be fitted with an absorbed power law with a photon index of 1.7 (-0.6, +0.7) (with the column density fixed at the Galactic one of 9.9 x 10^20 cm^-2). The derived average unabsorbed 0.5-4 keV flux is 7.2 (-1.9, +2.8) x 10^(-10) erg/s/cm^2. The uncertainties are at the 90% confidence level for the above parameters. The EP-FXT autonomous follow-up observation started at 2024-09-18T11:25:55 (UTC). The observation clearly shows an uncatalogued X-ray source located at R.A. = 289.3933 deg, DEC = 46.1278 deg (J2000) with an uncertainty of 10 arcsec in radius (90% C.L. statistical and systematic). The EP-FXT light curve shows a fast decline and the flux decreased to around 1.0 x 10^(-13) erg/s/cm^2 within about 1000 s. Further follow-up observations are encouraged to identify the nature of this X-ray transient. Launched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics). View this GCN Circular online at https://gcn.nasa.gov/circulars/37554. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 35471] GRB 240910A: further Swift observations and confirmation of afterglow
by GCN Circulars 19 Sep '24

19 Sep '24

TITLE: GCN CIRCULAR NUMBER: 37553 SUBJECT: GRB 240910A: further Swift observations and confirmation of afterglow DATE: 24/09/19 07:02:34 GMT FROM: K.L. Page at U Leicester <klp5(a)leicester.ac.uk> P.A. Evans (U. Leicester), M.H. Siegel (PSU) and K.L. Page (U. Leicester) report on behalf of the Swift-XRT and UVOT teams: Swift has re-observed the putative afterglow of GRB 240910A, first reported by Julakanti et al. (GCN Circ. 37459) at two additional epochs. 2.8 ks of data were taken between T0+282 ks and T0+329 ks, and a further 4.2 ks between T0+679 ks and T0+708 ks. The X-ray counterpart (D'Ai et al., GCN Circ. 37461) clearly fades between epochs. The light curve can be modelled with a power-law decay with a decay index of alpha=1.1 (+0.4, -0.3). UVOT observed the field in the u, v and white filters. A faint source was detected in the first epoch at the XRT position with a u magnitude of 20.65 +/- 0.28 with a significance of 3.8 sigma. The second epoch detected no counterpart to a 3 sigma upper limit of 21.51. We therefore confirm that GOTO24fvl/AT2024vfp is the afterglow of GRB 240910A. This circular is an official product of the Swift-XRT and UVOT teams. View this GCN Circular online at https://gcn.nasa.gov/circulars/37553. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

2025

2024

2023

2022

2021

vsnet-grb-info September 2024