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

[vsnet-grb-info 34429] Konus-Wind detection of GRB 240529A
by GCN Circulars 31 May '24

31 May '24

TITLE: GCN CIRCULAR NUMBER: 36584 SUBJECT: Konus-Wind detection of GRB 240529A DATE: 24/05/31 22:37:34 GMT FROM: Dmitry Svinkin at Ioffe Institute <svinkin(a)mail.ioffe.ru> D. Svinkin, D. Frederiks, M. Ulanov, A. Tsvetkova, A. Lysenko, A. Ridnaia, and T. Cline on behalf of the Konus-Wind team, report: The long-duration GRB 240529A (Swift-BAT detection: Eyles-Ferris et al., GCN 36556; AstroSat-CZTI detection: Joshi et al., GCN 36560; Insight-HXMT/HE detection: Tan et al., GCN 36578; IPN triangulation: Kozyrev et al., GCN 36583) triggered Konus-Wind at T0=10304.829 s UT (02:51:44.829). The burst light curve shows two separated multipeaked emission episodes. The first episode starts at ~T0-14.1 s and has a total duration of ~150 s, the second (detected by Swift-BAT) starts at ~T0+344 s and lasts up to ~T0+520 s. The emission is seen up to ~3 MeV. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB240529_T10304/ As observed by Konus-Wind, the burst had a fluence of 1.3(-0.5,+0.4)x10^-4 erg/cm2, and a 64-ms peak flux, measured from T0+6.960 s, of 3.40(-0.93,+1.10)x10^-6 erg/cm2/s (both in the 20 keV - 10 MeV energy range). The time-averaged spectrum of the burst (measured from T0 to T0+491.264 s) is best fit in the 20 keV - 3 MeV range by the GRB (Band) model with the following parameters: the low-energy photon index alpha = -1.11(-0.36,+1.61), the high energy photon index beta = -2.02(-7.98,+0.22), the peak energy Ep = 161(-100,+203) keV (chi2 = 56/66 dof). The spectrum near the maximum count rate (measured from T0 to T0+7.936 s) is best fit in the 20 keV - 3 MeV range by the GRB (Band) model with the following parameters: the low-energy photon index alpha = -1.00(-0.10,+0.15), the high energy photon index beta = -2.85(-1.37,+0.50), the peak energy Ep = 210(-33,+26) keV (chi2 = 61/66 dof). Assuming the redshift z=2.695 (Ugarte Postigo et al., GCN 36574) and a standard cosmology model with H_0 = 67.3 km/s/Mpc, Omega_M = 0.315, and Omega_Lambda = 0.685 (Planck Collaboration, 2014), we estimate the following rest-frame parameters: the isotropic energy release E_iso is 2.2(-0.8,+0.7)x10^54 erg, the peak luminosity L_iso is 2.1(-0.6,+0.7)x10^53 erg/s, the rest-frame peak energy of the time-integrated spectrum Ep,i,z is 595(-370,+750) keV, and the rest-frame peak energy at the peak of the emission Ep,p,z is 776(-122,+96) keV. With the obtained estimates, GRB 240529A is inside 90% prediction band for the 'Amati' relation and inside 68% prediction band for the 'Yonetoku' relation derived for the sample of >300 long KW GRBs with known redshifts (Tsvetkova et al., 2017; Tsvetkova et al., 2021), see http://www.ioffe.ru/LEA/GRBs/GRB240529_T10304/GRB240529A_rest_frame.pdf All the quoted errors are at the 90% confidence level. All the quoted values are preliminary. View this GCN Circular online at https://gcn.nasa.gov/circulars/36584. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 34428] IPN triangulation of the initial episode of GRB 240529A
by GCN Circulars 31 May '24

31 May '24

TITLE: GCN CIRCULAR NUMBER: 36583 SUBJECT: IPN triangulation of the initial episode of GRB 240529A DATE: 24/05/31 22:31:27 GMT FROM: Dmitry Svinkin at Ioffe Institute <svinkin(a)mail.ioffe.ru> A.S. Kozyrev, D.V. Golovin, M.L. Litvak, I.G. Mitrofanov, and A.B. Sanin on behalf of the HEND/Mars Odyssey team, D. Svinkin, D. Frederiks, A. Ridnaia, A. Lysenko, and T. Cline on behalf of the Konus-Wind team, E. Burns, on behalf of the IPN, S. Barthelmy, J. Cummings, H. Krimm, D. Palmer, and A. Tohuvavohu on behalf of the Swift-BAT team, and W. Boynton, C. Fellows, K. Harshman, H. Enos, R. Starr, and A.S. Gardner on on behalf of the GRS-Odyssey GRB team, report: The long-duration GRB 240529A (Swift-BAT detection: Eyles-Ferris et al., GCN 36556; AstroSat-CZTI detection: Joshi et al., GCN 36560; Insight-HXMT/HE detection: Tan et al., GCN 36578) was detected by Swift (BAT), Konus-Wind, AstroSat (CZTI), Insight-HXMT (HE), and Mars-Odyssey (HEND). The burst triggered Swift-BAT at T0(BAT) = 10710.788 s UT (02:58:30.788). The Konus-Wind lightcurve shows two emission episodes at ~T0(BAT)-400 s and ~T0(BAT)-300 s. These episodes was also detected by Swift (BAT), probably outside the coded FoV, and Mars-Odyssey (HEND). We have triangulated the most intense episode (at ~T0(BAT)-400 s) to a preliminary, 3 sigma error box whose coordinates are: --------------------------------------------- RA(2000), deg Dec(2000), deg --------------------------------------------- Center: 336.181 (22h 24m 43s) +52.215 (+52d 12' 55") Corners: 341.510 (22h 46m 02s) +56.219 (+56d 13' 07") 331.787 (22h 07m 09s) +47.993 (+47d 59' 34") 332.038 (22h 08m 09s) +47.767 (+47d 46' 02") 341.743 (22h 46m 58s) +55.982 (+55d 58' 54") --------------------------------------------- The error box area is 2.61 sq. deg, and its maximum dimension is 10.2 deg (the minimum one is 15 arcmin). The Sun distance was 73 deg. Triangulation of the less intense episode (at ~T0(BAT)-400 s) is consistent with this IPN localization. This localization is consistent with the Swift localization of GRB 240529A, implying the episodes belong to GRB 240529A and extending the burst duration up to ~600 s. A triangulation map and HEALPix FITS file are posted at http://www.ioffe.ru/LEA/GRBs/GRB240529_T10304/IPN The HEALPix triangulation map is the multi-order HEALPix in units of probability density. The Konus-Wind time history and spectrum will be given in a forthcoming GCN Circular. View this GCN Circular online at https://gcn.nasa.gov/circulars/36583. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 34427] GRB 240529A: SAO RAS optical observations
by GCN Circulars 31 May '24

31 May '24

TITLE: GCN CIRCULAR NUMBER: 36582 SUBJECT: GRB 240529A: SAO RAS optical observations DATE: 24/05/31 19:24:45 GMT FROM: Moskvitin Alexander at SAO RAS <mosk(a)sao.ru> A. S. Moskvitin, O. I. Spiridonova and V. V. Vlasyuk (SAO RAS), report on behalf of the GRB follow-up team. We observed the field of the GRB 240529A (Eyles-Ferris et al. GCN 36556; Osborne et al. GCN 36557; Joshi et al. GCN 36560; Dichiara et al. GCN 36564; Markwardt et al. GCN 36566; Tan et al. GCN 36578) with the SAO RAS 1m telescope Zeiss-1000 equipped with CCD-photometer. We obtained 4 x 300 sec frames in Rc band on May 30, 23:35:04--23:56:50 UT (t_mid - T0 = 1.8663 days). The OT (Kumar et al. GCN 36559; Fu et al. GCN 36561; Shilling et al. GCN 36562; Perez-Garcia et al. GCN 36563; Dutton et al. GCN 36568; Mo et al. GCN 36569; Odeh et al. GCN 36573; de Ugarte Postigo et al. GCN 36574; Adami et al. GCN 36575; Mohan et al. GCN 36576; Vinko et al., GCN 36577; Lim et al. GCN 36579) is clearly detected in the stacked frame with the brightness of R = 20.02 +/- 0.10. The magnitudes were calibrated using R2 magnitudes of nearby USNO-B1.0 stars. View this GCN Circular online at https://gcn.nasa.gov/circulars/36582. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 34426] LIGO/Virgo/KAGRA S240531bp: Updated Sky localization
by GCN Circulars 31 May '24

31 May '24

TITLE: GCN CIRCULAR NUMBER: 36581 SUBJECT: LIGO/Virgo/KAGRA S240531bp: Updated Sky localization DATE: 24/05/31 15:23:15 GMT FROM: Charlie Hoy at University of Portsmouth <charlie.hoy(a)port.ac.uk> 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 S240531bp (GCN Circular 36580). 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/S240531bp For the Bilby.multiorder.fits,0 sky map, the 90% credible region is 1323 deg2. Marginalized over the whole sky, the a posteriori luminosity distance estimate is 3766 +/- 1491 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. (2023) arXiv:2307.13380 View this GCN Circular online at https://gcn.nasa.gov/circulars/36581. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 34425] LIGO/Virgo/KAGRA S240531bp: Identification of a GW compact binary merger candidate
by GCN Circulars 31 May '24

31 May '24

TITLE: GCN CIRCULAR NUMBER: 36580 SUBJECT: LIGO/Virgo/KAGRA S240531bp: Identification of a GW compact binary merger candidate DATE: 24/05/31 08:23:28 GMT FROM: Monica Seglar-Arroyo at Institut de Física d'Altes Energies (IFAE) <mseglar(a)ifae.es> The LIGO Scientific Collaboration, the Virgo Collaboration, and the KAGRA Collaboration report: We identified the compact binary merger candidate S240531bp during real-time processing of data from LIGO Hanford Observatory (H1), LIGO Livingston Observatory (L1), and Virgo Observatory (V1) at 2024-05-31 07:52:48.463 UTC (GPS time: 1401177186.463). The candidate was found by the CWB [1], GstLAL [2], and MBTA [3] analysis pipelines. S240531bp is an event of interest because its false alarm rate, as estimated by the online analysis, is 3.7e-12 Hz, or about one in 1e4 years. The event's properties can be found at this URL: https://gracedb.ligo.org/superevents/S240531bp After parameter estimation by RapidPE-RIFT [4], the classification of the GW signal, in order of descending probability, is BBH (>99%), Terrestrial (<1%), NSBH (<1%), or BNS (<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%. [5] Using the masses and spins inferred from the signal, the probability of matter outside the final compact object (HasRemnant) is <1%. [5] 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%. 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 [6], distributed via GCN notice about 26 seconds after the candidate event time. * bayestar.multiorder.fits,1, an initial localization generated by BAYESTAR [6], 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 1648 deg2. Marginalized over the whole sky, the a posteriori luminosity distance estimate is 4357 +/- 1294 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] Tsukada et al. PRD 108, 043004 (2023) doi:10.1103/PhysRevD.108.043004 and Ewing et al. (2023) arXiv:2305.05625 [3] Aubin et al. CQG 38, 095004 (2021) doi:10.1088/1361-6382/abe913 [4] Rose et al. (2022) arXiv:2201.05263 and Pankow et al. PRD 92, 023002 (2015) doi:10.1103/PhysRevD.92.023002 [5] Chatterjee et al. ApJ 896, 54 (2020) doi:10.3847/1538-4357/ab8dbe [6] Singer & Price PRD 93, 024013 (2016) doi:10.1103/PhysRevD.93.024013 View this GCN Circular online at https://gcn.nasa.gov/circulars/36580. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 34424] GRB 240529A: MAAO 0.7m telescope optical afterglow detection
by GCN Circulars 31 May '24

31 May '24

TITLE: GCN CIRCULAR NUMBER: 36579 SUBJECT: GRB 240529A: MAAO 0.7m telescope optical afterglow detection DATE: 24/05/31 06:20:31 GMT FROM: Gu Lim at Pusan National University <lim9gu(a)gmail.com> Lim, Gu (PNU), Kim, Dohyeong (PNU), Im, Myungshin (SNU), Park, Keun-Hong (MAAO), and Choi, Changmin (MAAO) report on behalf of the GECKO team We searched for the optical afterglow of GRB 240529A (Eyles-Ferris et al., GCN 36556) with a 0.7m telescope at Miryang Arirang Astronomical Observatory (MAAO; Lim et al. 2024), one of the facilities of the GW EM-Counterpart Korean Observatory (GECKO). We started the observation at 2024-05-29T17:18:13 UT and obtained 10 images of each 120s with I-band 14.3 hours after the Swift detection (GCN 36556). The photometry is performed using 2xFWHM diameter aperture. The flux is calibrated using the APASS DR9 catalog (Henden et al. 2016) by converting the Vega system to the AB system using the Lupton (2005) transformation equation. After the image subtraction using HOTPANTS (Becker et al. 2015), we detected the optical afterglow at: R.A (J2000): 22:21:25.92 Dec. (J2000): +51:33:43.46 This coordinate is within the uncertainty radius of the enhanced Swift-XRT report (Evans et al., GCN 36557). We determine a magnitude of I=17.46+/-0.19 AB mag without galactic extinction correction. Our detection is agreed with the results of (Odeh et al., GCN 36573). T0 = 2024-05-29T02:58:31 UT (Eyles-Ferris et al., GCN 36556) Tmid(UT) Exptime(s) Tmid-T0(hr) FWHM(") Mag+/-Magerr Depth_3sigma Filter --------------------------------------------------------------------------------------- 2024-05-29T17:32:38 180sx10 +14.3 5.6 17.46+/-0.19 18.40 I Gravitational-wave EM Counterpart Korean Observatory (GECKO; Im et al. 2023, Proceedings of IAU Symp. Vol. 363, pp. 207.; Paek et al. 2024, The Astrophysical Journal, Vol. 960, Number 2, 113.) is a network of 0.5m to 1m class telescopes worldwide. View this GCN Circular online at https://gcn.nasa.gov/circulars/36579. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 34423] GRB 240529A: Insight-HXMT/HE detection
by GCN Circulars 31 May '24

31 May '24

TITLE: GCN CIRCULAR NUMBER: 36578 SUBJECT: GRB 240529A: Insight-HXMT/HE detection DATE: 24/05/31 02:38:28 GMT FROM: tanwj(a)ihep.ac.cn Wenjun Tan, Shaolin Xiong , Xiaobo Li and Chengkui Li report on behalf of the Insight-HXMT team: At 2024-05-29T02:58:31.000 (T0), Insight-HXMT/HE detected GRB 240529A(trigger ID: HEB240529123) in a routine search of the data, which was also observed by Swift (Eyles-Ferris et al. GCN 36556; C. B. Markwardt et al. GCN 36566). The Insight-HXMT/HE light curve consists of multiple pulses with a duration (T90) of 66.23s measured from T0-37.26 s. The 1s peak rate, measured from T0-0.159 s, is 3138 cnts/sec. The total counts from this burst is 53027 counts. URL_LC: https://twikinew.ihep.ac.cn/pubhxmt/HXMT/GRBList/HEB240529123_lc.jpg All measurements above are made with the CsI detectors operating in the regular mode with the energy range of about 80-800 keV (deposited energy). Only gamma-rays with energy greater than about 200 keV can penetrate the spacecraft and leave signals in the CsI detectors installed inside the telescope. Insight-HXMT is the first Chinese space X-ray telescope, which was funded jointly by the China National Space Administration (CNSA) and the Chinese Academy of Sciences (CAS). More information about it could be found at: http://hxmtweb.ihep.ac.cn/ View this GCN Circular online at https://gcn.nasa.gov/circulars/36578. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 34422] GCN Announcement: Einstein Probe Notices, Astro Flavored Markdown Circulars, and Notices Schema v4.0.0
by GCN Announcements 30 May '24

30 May '24

The GCN Team is pleased to announce several new features and updates. Einstein Probe Notices ====================== GCN Notices for Einstein Probe (EP) are now available in JSON format over Kafka (https://gcn.nasa.gov/quickstart) EP notices are not available via GCN Classic or email. - Summary: EP is a mission of the Chinese Academy of Sciences (CAS) (https://ep.bao.ac.cn/ep/) in collaboration with the European Space Agency (ESA) (https://www.cosmos.esa.int/web/einstein-probe/mission) and the Max Planck Institute for Extraterrestrial Physics (MPE) (https://www.mpe.mpg.de/7867826/EinsteinProbe) It is dedicated to time-domain high-energy astrophysics. Its primary goals are to discover high-energy transients and monitor variable objects. - Rate: Approximately 100 notices per year. - Time Delay: EP sends alerts via GCN within ~60 seconds of detection. - Notice Type: The new WXT notice type gcn.notices.einstein_probe.wxt.alert (https://gcn.nasa.gov/missions/einstein-probe) provides trigger information including localization. - Notice Schema and Examples: The JSON schema defining the notice format and examples can be viewed in the Schema Browser (https://gcn.nasa.gov/docs/schema/stable/gcn/notices/einstein_probe/wxt/aler…) or the GCN schema repository (https://github.com/nasa-gcn/gcn-schema/tree/main/gcn/notices/einstein_probe…) Astro Flavored Markdown Circulars ================================= You can now add rich text formatting, data tables, and references to journals and common astronomical databases to GCN Circulars using Astro Flavored Markdown, a dialect of the popular Markdown lightweight markup language. See documentation on Astro Flavored Markdown (https://gcn.nasa.gov/docs/circulars/markdown) Notices Schema v4.0.0 ===================== Explore GCN Schema via the Schema Browser (https://gcn.nasa.gov/docs/schema/v4.0.0/gcn/notices) Changes to the GCN Schema include: - Addition of Einstein Probe WXT Notice topic - Addition of BurstCube Notice topic (not yet producing notices) - Change to localization core schema that simplifies localization uncertainty parameterization (now `ra_dec_error`) to allow either a single radius or three values that describe the localization region as an ellipse. This change is not backwards compatible. - Note that the `$schema` field in each GCN Notice identifies the version of the schema it is utilizing. gcn.notices.icecube.lvk_nu_track_search(https://gcn.nasa.gov/docs/schema/st… will update on the morning of June 18, 2024, and gcn.notices.swift.bat.guano (https://gcn.nasa.gov/docs/schema/stable/gcn/notices/swift/bat/Guano.schema.…) will be updated at a later date. For more details on this new feature and an archive of GCN news and announcements, see https://gcn.nasa.gov/news. For questions, issues, or bug reports, please contact us via: - Contact form: https://gcn.nasa.gov/contact - GitHub issue tracker: https://github.com/nasa-gcn/gcn.nasa.gov/issues --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 34421] GRB 240529A: optical photometry from Konkoly
by GCN Circulars 30 May '24

30 May '24

TITLE: GCN CIRCULAR NUMBER: 36577 SUBJECT: GRB 240529A: optical photometry from Konkoly DATE: 24/05/30 20:41:31 GMT FROM: Jozsef Vinko at Konkoly Observator <vinko(a)konkoly.hu> GRB 240529A: optical photometry from Konkoly J. Vinko, A. Sodor, R. Konyves-Toth, L. Kriskovics, A. Pal, R. Szakats (Konkoly Observatory, Hungary) We report detection and photometry of the optical afterglow of GRB 240529A (Eyles-Ferris et al. GCN 36556; Osborne et al. GCN 36557; Dichiara et al. GCN 36564; Markwardt et al. GCN 36566) taken with the RC80 robotic telescope at Piszkesteto Station of Konkoly Observatory, Hungary. The observations started on 2024-05-29 22:40:46.49 UT. 5 sets of 300 sec frames were collected through Sloan g', r'- and i' bands. The optical afterglow (Kumar et al. GCN 36559; Joshi et al. GCN 36560; Fu et al. GCN 36561; Shilling et al. GCN 36562; Perez-Garcia et al. GCN 36563; Dutton et al. GCN 36568; Mo et al. GCN 36569; Odeh et al. GCN 36573; de Ugarte Postigo et al. GCN 36574; Adami et al. GCN 36575; Mohan et al. GCN 36576) was detected on the stacked frames with the following magnitudes, calibrated via nearby PS1 stars: Date UT-middle t-T0(days) Exp(s) g'(AB) r'(AB) i'(AB) 2024-05-29 23:11:35.78 0.842 5x300 20.28 (0.21) 19.08 (0.09) 18.62 (0.09) The magnitudes above are not corrected for galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/36577. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 34420] GRB 240529A: GROWTH-India optical follow-up
by GCN Circulars 30 May '24

30 May '24

TITLE: GCN CIRCULAR NUMBER: 36576 SUBJECT: GRB 240529A: GROWTH-India optical follow-up DATE: 24/05/30 17:30:52 GMT FROM: vishwajeet.s(a)iitb.ac.in T. Mohan, V. Swain, A. Salgundi, R. Kumar, V. Bhalerao (IITB), G.C. Anupama, S. Barway (IIA) and K. Angail (IAO) report on behalf of the GIT team: We observed the field of GRB 240529A detected by Swift (Eyles-Ferris et al., GCN 36556) with 0.7m GROWTH-India Telescope (GIT). We started the observation at 2024-05-29 19:54:44 UT, i.e., 16.93 hours after the Swift trigger. We obtained multiple exposures of 400 seconds in the r', g' and i' filters. In our stacked images, we clearly detected the afterglow at the coordinates reported by Swift/UVOT Detection (Shilling et al., GCN 36562). The photometry results follow as: --------------------------------------------------------------------------------- | JD (mid) | t-t0 (days) | Filter | Total Exposure (s) | Magnitude (AB) | | ----------------- | ----------- |------- | ------------------ | -------------- | | 2460460.425332341 | 0.801 | g' | 7x400 | 20.43 +/- 0.09 | | 2460460.349607928 | 0.725 | r' | 8x400 | 19.14 +/- 0.05 | | 2460460.386415344 | 0.762 | i' | 7x400 | 18.46 +/- 0.08 | --------------------------------------------------------------------------------- The measurement is calibrated against PanSTARRS DR1 (Chambers et al., 2016) and not corrected for Galactic extinction. Based on the publicly avialable photometry (Fu et al., GCN Circ. 36561; Postigo et al., GCN Circ. 36574; Adami et al., GCN Circ. 36575) and our measurements, we find that the source in r'-filter is fading as a power-law with flux proportional to (t−t0)^−alpha where t0 is Swift/BAT triggered time and calculated alpha = 1.12 +/- 0.01. The GROWTH India Telescope (GIT; Kumar et al. 2022) is a 70-cm telescope with a 0.7-degree field of view, set up by the Indian Institute of Astrophysics (IIA) and the Indian Institute of Technology Bombay (IITB) with funding from DST-SERB and IUSSTF. It is located at the Indian Astronomical Observatory (Hanle), operated by IIA. We acknowledge funding by the IITB alumni batch of 1994, which partially supports the operations of the telescope. Telescope technical details are available at https://sites.google.com/view/growthindia/. View this GCN Circular online at https://gcn.nasa.gov/circulars/36576. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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