//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 27247 SUBJECT: GRB 200228A: Fermi GBM Final Real-time Localization DATE: 20/02/28 07:08:54 GMT FROM: Fermi GBM Team at MSFC/Fermi-GBM The Fermi GBM team reports the detection of a likely LONG GRB At 06:58:33 UT on 28 Feb 2020, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 200228A (trigger 604565918.806272 / 200228291). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 328.0, Dec = -46.5 (J2000 degrees, equivalent to J2000 21h 52m, -46d 30'), with a statistical uncertainty of 1.5 degrees. The angle from the Fermi LAT boresight is 33.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2020/bn200228291/quicklook/glg_skymap_all_bn200228291.png The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2020/bn200228291/quicklook/glg_healpix_all_bn200228291.fit The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2020/bn200228291/quicklook/glg_lc_medres34_bn200228291.gif //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 27248 SUBJECT: GRB 200228A: BALROG localization (Fermi Trigger 604565918 / GRB 200228291) DATE: 20/02/28 07:24:28 GMT FROM: Jochen Greiner at MPE,Garching F. Kunzweiler, B. Biltzinger, F. Berlato, J. Burgess & J. Greiner (all MPE Garching) report: The public trigdat data of the Fermi Gamma-ray Burst Monitor (GBM) trigger 604565918 at 06:58:33 on 28 Feb. 2020 were automatically fitted for spectrum and sky location with BALROG (Burgess et al. 2018, MNRAS 476, 1427; Berlato et al. 2019, ApJ 873, 60). The best-fit position (1 sigma statistical errors) is: RA(2000.0) = 332.9+/-0.9 deg Decl.(2000.0) = -39.9+/-1.0 deg We estimate an additional systematic error of 1 deg. Further details are available at: https://grb.mpe.mpg.de/grb/GRB200228291/ The Healpix map can be downloaded from: https://grb.mpe.mpg.de/grb/GRB200228291/healpix The location parameters are available as JSON at: https://grb.mpe.mpg.de/grb/GRB200228291/json //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 27253 SUBJECT: GRB 200228B: Fermi GBM Final Real-time Localization DATE: 20/02/28 11:25:00 GMT FROM: Fermi GBM Team at MSFC/Fermi-GBM The Fermi GBM team reports the detection of a likely LONG GRB At 11:14:43 UT on 28 Feb 2020, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 200228B (trigger 604581288.894278 / 200228469). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 258.4, Dec = 9.6 (J2000 degrees, equivalent to J2000 17h 13m, 9d 35'), with a statistical uncertainty of 16.7 degrees. The angle from the Fermi LAT boresight is 62.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2020/bn200228469/quicklook/glg_skymap_all_bn200228469.png The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2020/bn200228469/quicklook/glg_healpix_all_bn200228469.fit The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2020/bn200228469/quicklook/glg_lc_medres34_bn200228469.gif //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 27254 SUBJECT: GRB 200228B: Swift detection of a burst DATE: 20/02/28 11:27:30 GMT FROM: Scott Barthelmy at NASA/GSFC S. Laha (GSFC/UMBC/CRESST), S. D. Barthelmy (GSFC), P. A. Evans (U Leicester), C. Gronwall (PSU), J.D. Gropp (PSU) and K. L. Page (U Leicester) report on behalf of the Neil Gehrels Swift Observatory Team: At 11:14:41 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 200228B (trigger=958733). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 252.026, +16.960, which is RA(J2000) = 16h 48m 06s Dec(J2000) = +16d 57' 37" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve shows a single peak with a duration of about 25 sec. The peak count rate was ~2000 counts/sec (15-350 keV), at ~5 sec after the trigger. The XRT began observing the field at 11:16:56.8 UT, 135.7 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source located at RA, Dec 252.04730, 16.98505 which is equivalent to: RA(J2000) = 16h 48m 11.35s Dec(J2000) = +16d 59' 06.2" with an uncertainty of 5.7 arcseconds (radius, 90% containment). This location is 116 arcseconds from the BAT onboard position, within the BAT error circle. This position may be improved as more data are received; the latest position is available at https://www.swift.ac.uk/sper. No spectrum from the promptly downlinked event data is yet available to determine the column density. UVOT data are unavailable at this time. Burst Advocate for this burst is S. Laha (sib.laha AT gmail.com). Please contact the BA by email if you require additional information regarding Swift followup of this burst. In extremely urgent cases, after trying the Burst Advocate, you can contact the Swift PI by phone (see Swift TOO web site for information: http://www.swift.psu.edu/) //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 27256 SUBJECT: GRB 200228B: Enhanced Swift-XRT position DATE: 20/02/28 14:16:49 GMT FROM: Phil Evans at U of Leicester P.A. Evans, M.R. Goad, J.P. Osborne and A.P. Beardmore (U. Leicester) report on behalf of the Swift-XRT team. Using 87 s of XRT Photon Counting mode data and 1 UVOT images for GRB 200228B, we find an astrometrically corrected X-ray position (using the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue): RA, Dec = 252.04640, +16.98523 which is equivalent to: RA (J2000): 16h 48m 11.14s Dec (J2000): +16d 59' 06.8" with an uncertainty of 3.5 arcsec (radius, 90% confidence). This position may be improved as more data are received. The latest position can be viewed at http://www.swift.ac.uk/xrt_positions. Position enhancement is described by Goad et al. (2007, A&A, 476, 1401) and Evans et al. (2009, MNRAS, 397, 1177). This circular was automatically generated, and is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 27259 SUBJECT: GRB 200228A: Swift/BAT detection and arcminute localization from GUANO DATE: 20/02/28 14:53:21 GMT FROM: Aaron Tohuvavohu at U Toronto Aaron Tohuvavohu (U Toronto), James DeLaunay (PSU), and Jamie Kennea (PSU) report: Swift/BAT did not trigger on GRB 200228A, likely due to a slew. The Fermi/GBM Flight-Position notice, distributed at T0+23 seconds, from the Fermi/GBM detected GRB 200228A (GCN. 27247) triggered the Swift Mission Operations Center operated Gamma-ray Urgent Archiver for Novel Opportunities (GUANO; Tohuvavohu et al. 2020, in prep). The GUANO is a fully autonomous, extremely low latency, spacecraft commanding pipeline designed for targeted recovery of BAT event mode data around the times of compelling astrophysical events to enable more sensitive GRB searches. Upon trigger by the Fermi notice, GUANO sent a command to the Swift Burst Alert Telescope (BAT) to save 200 seconds of BAT event-mode data from [-50,+150] seconds around the time of GRB 200228A. All the requested event mode data was delivered to the ground. In a ground analysis of the data, using the normal BAT imaging technique, we detect GRB 200228A with a SNR of 40. The BAT ground-calculated position is RA, Dec = 333.8928, -42.9443 deg which is RA(J2000) = 333d 53’ 34.08” Dec(J2000) = -42d 56' 39.48" with an uncertainty of 3 arcmin, (radius, sys+stat, 90% containment). The partial coding was 34%. This arcminute location is consistent with the localization region distributed by the Fermi/GBM team (GCN. 27247). No XRT or UVOT follow-up will take place due to the source’s proximity to the sun (0.5 hours). We encourage follow-up from instruments capable of observing near the sun. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 27260 SUBJECT: GRB 200228A: Fermi GBM observation DATE: 20/02/28 17:03:56 GMT FROM: Elisabetta Bissaldi at INFN,Bari E. Bissaldi (Politecnico and INFN Bari) reports on behalf of the Fermi GBM Team: "At 06:58:33.81 UT on 28 February 2020, the Fermi Gamma-Ray Burst Monitor (GBM) triggered and located GRB 200228A (trigger 604565918 / 200228291), as reported by the Fermi GBM Final Real-time Localization (GCN 27247). The GBM localization is consistent with the Swift GUANO localization (Tohuvavohu et al. 2020, GCN 27259). The angle from the Fermi LAT boresight at the GBM trigger time is 33 degrees. The GBM light curve consists of a single bright peak with a duration (T90) of about 4 s (50-300 keV). The time-averaged spectrum from T0 to T0+4 s is adequately fit by a power law function with an exponential high-energy cutoff. The power law index is -0.61 +/- 0.04 and the cutoff energy, parameterized as Epeak, is 165 +/- 5 keV. The event fluence (10-1000 keV) in this time interval is (6.44 +/- 0.13)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0+1.0 s in the 10-1000 keV band is 20.4 +/- 0.4 ph/s/cm^2. A Band function fits the spectrum equally well with Epeak= 153 +/- 7 keV, alpha = -0.54 +/- 0.05 and beta = -2.85 +/- 0.23. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog: https://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html For Fermi GBM data and info, please visit the official Fermi GBM Support Page: https://fermi.gsfc.nasa.gov/ssc/data/access/gbm/" //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 27261 SUBJECT: GRB 200228C: Insight-HXMT/HE detection DATE: 20/02/28 17:24:58 GMT FROM: Qi Luo at IHEP Q. Luo, Y. G. Zheng, C. Cai, S. Xiao, Q. B. Yi, Y. F. DU, W. C. Xue, Y. Huang, C. K. Li, G. Li, X. B. Li, J. Y. Liao, S. L. Xiong, C. Z. Liu, X. F. Li, Z. W. Li, Z. Chang, A. M. Zhang, Y. F. Zhang, X. F. Lu, C. L. Zou (IHEP), Y. J. Jin, Z. Zhang (THU), T. P. Li (IHEP/THU), F. J. Lu, L. M. Song, M. Wu, Y. P. Xu, S. N. Zhang (IHEP), report on behalf of the Insight-HXMT team: At 2020-02-28T06:00:57.700 (T0), Insight-HXMT/HE detected GRB 200228C (trigger ID: HEB200228250) in a routine search of the data. The Insight-HXMT/HE light curve mainly consists of multiple pulses with a duration (T90) of 3.375 s measured from T0-1.210 s. The 1-ms peak rate, measured from T0+0.091 s, is 2991 cnts/sec. The total counts from this burst is 5127 counts. URL_LC: http://www.hxmt.org/images/GRB/HEB200228250_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 of 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://www.hxmt.org. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 27263 SUBJECT: GRB 200228B: KAIT Optical Upper Limit DATE: 20/02/28 19:09:52 GMT FROM: Weikang Zheng at UC Berkeley WeiKang Zheng and Alexei V. Filippenko (UC Berkeley) report on behalf of the KAIT GRB team: The 0.76-m Katzman Automatic Imaging Telescope (KAIT), located at Lick Observatory, responded to Swift GRB 200228B (Laha et al., GCN 27254) starting at 11:21:06 UT, 395 s after the burst. Observations were performed with an automatic sequence in the clear (roughly R), V, and I filters, and the exposure time was 20 s per image. We do not detect any optical afterglow candidate within the enhanced XRT position error circle (Evans et al., GCN 27256), neither in single image, nor in the co-add images. The typical limiting magnitude of our single clear image is about 18.0 mag calibrated to the Pan-STARRS1 catalog. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 27266 SUBJECT: GRB 200228B: Fermi GBM observation DATE: 20/02/28 20:54:53 GMT FROM: Joshua Wood at MSFC/Fermi-GBM E. Bissaldi (Politecnico and INFN Bari), C. Meegan (UAH), and J. Wood (NASA/MSFC) report on behalf of the Fermi GBM Team: "At 11:14:43.89 UT on 28 February 2020, the Fermi Gamma-Ray Burst Monitor (GBM) triggered and located GRB 200228B (trigger 604581288 / 200228469), which was also detected by the Swift/BAT (Laha et al. 2020, GCN 27254). The GBM on-ground location is consistent with the Swift position. The angle from the Fermi LAT boresight at the GBM trigger time is 59 degrees. The GBM light curve shows a single emission episode with a duration (T90) of about 14 s (50-300 keV). The time-averaged spectrum from T0-4 s to T0+11 s is adequately fit by a power law function with an exponential high-energy cutoff. The power law index is -1.17 +/- 0.33 and the cutoff energy, parameterized as Epeak, is 76 +/- 16 keV. The event fluence (10-1000 keV) in this time interval is (1.30 +/- 0.18)E-07 erg/cm^2. The 1-sec peak photon flux measured starting from T0-0.3 s in the 10-1000 keV band is 1.4 +/- 0.2 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog: https://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html For Fermi GBM data and info, please visit the official Fermi GBM Support Page: https://fermi.gsfc.nasa.gov/ssc/data/access/gbm/" //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 27267 SUBJECT: GRB 200228B: RATIR Optical Observations DATE: 20/02/28 21:07:26 GMT FROM: Emma Margarita Pereyra Talamantes at IA-UNAM Ensenada Margarita Pereyra (UNAM), Nat Butler (ASU), Alan M. Watson (UNAM), Alexander Kutyrev (GSFC), William H. Lee (UNAM), Michael G. Richer (UNAM), Ori Fox (STScI), J. Xavier Prochaska (UCSC), Josh Bloom (UCB), Antonino Cucchiara (UVI), Eleonora Troja (GSFC), Owen Littlejohns (ASU), Enrico Ramirez-Ruiz (UCSC), Jesús González (UNAM), Carlos Román-Zúñiga (UNAM), Harvey Moseley (GSFC), John Capone (UMD), V. Zach Golkhou (U. Wash.), and Vicki Toy (UMD) report: We observed the field of GRB 200228B (Laha et al., GCN Circ. 27254) with the Reionization and Transients Infrared Camera (RATIR; www.ratir.org) on the 1.5m Harold Johnson Telescope at the Observatorio Astronómico Nacional on Sierra San Pedro Mártir from 2020/02 28.48 to 2020/02 28.53 UTC (0.27 to 1.52 hours after the BAT trigger), obtaining a total of 0.62 hours exposure in the r and i bands. For a source within the Swift-XRT enhanced error circle (Evans et al., GCN Circ. 27256), in comparison with the SDSS DR9 and 2MASS catalogs, we obtain the following upper limits (3-sigma): r > 21.48 i > 21.40 These magnitudes are in the AB system and are not corrected for Galactic extinction in the direction of the GRB. We thank the staff of the Observatorio Astronómico Nacional in San Pedro Mártir. -- *Dr. Margarita Pereyra * *FFTF, Schlumberger Foundation Alumnae* ---------------------------------------------------------------------------------------------------------------- *Catedrático Conacyt* *Instituto de Astronomía de la UNAM,* *Km. 107 Carretera Tijua**na-Ensenada, * *Ensenada Baja California, México. C.P. 22860* Oficina: 405 Skype: margarita-pereyra //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 27268 SUBJECT: GRB 200228B: Swift/UVOT Upper Limits DATE: 20/02/28 22:23:32 GMT FROM: Paul Kuin at MSSL N. P. M. Kuin (UCL-MSSL) and S. L. Laha (GSFC/UMBC/CRESST) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 200228B 137 s after the BAT trigger (Laha et al., GCN Circ. 27254). No optical afterglow consistent with the XRT position (Evans et al., GCN Circ. #27256 is detected in the initial UVOT exposures. Preliminary 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first finding chart (FC) exposure and subsequent exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag u_FC 137 387 246 >20.1 v 4992 10685 676 >20.1 b 4580 6012 393 >20.6 u 137 5807 442 >20.4 w1 5402 5602 197 >19.5 m2 5197 5396 197 >19.8 w2 4786 6218 393 >19.4 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.092 in the direction of the burst (Schlegel et al. 1998). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 27269 SUBJECT: Swift GRB 200228B: Global MASTER-Net observations report DATE: 20/02/29 00:12:08 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs V. Lipunov, E. Gorbovskoy, V.Kornilov, N.Tyurina, P.Balanutsa, A.Kuznetsov, F.Balakin, V.Vladimirov, D. Vlasenko, I.Gorbunov, D.Zimnukhov, V.Senik, T.Pogrosheva, D.Kuvshinov, D. Cheryasov (Lomonosov Moscow State University, SAI, Physics Department), R. Podesta, C.Lopez, F. Podesta, C.Francile (Observatorio Astronomico Felix Aguilar OAFA), H.Levato (Instituto de Ciencias Astronomicas, de la Tierra y del Espacio ICATE), R. Rebolo, M. Serra (The Instituto de Astrofisica de Canarias), D. Buckley (South African Astronomical Observatory), O.A. Gres, N.M. Budnev, O.Ershova (Irkutsk State University, API), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), V. Yurkov, A. Gabovich, Yu. Sergienko (Blagoveschensk Educational State University) MASTER-Kislovodsk robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) was pointed to the Swift GRB 200228B ( S. Laha et al., GCN 27254) errorbox 45652 sec after trigger time at 2020-02-28 23:55:33 UT, with upper limit up to 18.6 mag. The observations began at zenith distance = 51 deg. The sun altitude is -41.7 deg. The galactic latitude b = 34 deg., longitude l = 36 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=1300236 We obtain a following upper limits. Tmid-T0 | Site |Filt.| Expt. | Limit| Comment _________|_____________________|_____|_______|______|________ 45742 | MASTER-Kislovodsk | C | 180 | 18.4 | 45742 | MASTER-Kislovodsk | C | 180 | 18.6 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 27270 SUBJECT: GRB 200228B: Swift-XRT refined Analysis DATE: 20/02/29 05:26:50 GMT FROM: Kim Page at U.of Leicester K.L. Page (U. Leicester) and S. Laha (GSFC/UMBC/CRESST) report on behalf of the Swift-XRT team: We have analysed 4.6 ks of XRT data for GRB 200228B (Laha et al. GCN Circ. 27254), from 143 s to 18.2 ks after the BAT trigger. The data are entirely in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Evans et al. (GCN Circ. 27256). The light curve can be modelled with a power-law decay with a decay index of alpha=0.65 (+0.10, -0.12). A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 3.0 (+0.8, -0.7). The best-fitting absorption column is 1.6 (+0.8, -0.6) x 10^22 cm^-2, in excess of the Galactic value of 6.4 x 10^20 cm^-2 (Willingale et al. 2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.5 x 10^-11 (2.3 x 10^-10) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 1.6 (+0.8, -0.6) x 10^22 cm^-2 Galactic foreground: 6.4 x 10^20 cm^-2 Excess significance: 4.3 sigma Photon index: 3.0 (+0.8, -0.7) If the light curve continues to decay with a power-law decay index of 0.65, the count rate at T+24 hours will be 4.9 x 10^-3 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.7 x 10^-13 (1.1 x 10^-12) erg cm^-2 s^-1. The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00958733. This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 27271 SUBJECT: GRB 200228B: Liverpool Telescope imaging DATE: 20/02/29 13:57:42 GMT FROM: Daniel Perley at Liverpool JMU D. A. Perley and A. M. Cockeram (LJMU) report: On 2020-02-29 UT we obtained imaging of the position of GRB 200228B (Fermi GBM team, GCN 27253; Laha et al., GCN 27254) using the 2m robotic Liverpool Telescope. We collected 3x120s of exposure time in each of the the i-band and z-band filters, beginning at 05:53:44 and ending at 06:07:33 (UTC). No unambiguous source is detected in either stacked image, although a possible marginal (~3-sigma) source is present close to the center of the latest enhanced XRT error circle in the z-band image. Photometry of this potential source (calibrating relative to PS1 catalog stars in the field) gives an approximate magnitude of z = 21.7 +/- 0.3. 3-sigma limits are: dt(days) filter mag 0.7794 i >22.6 0.7844 z >21.7 We additionally note that Pan-STARRS1 imaging of the field shows several faint, probably-resolved sources close to the survey detection limit inside or closely outside the XRT error circle, which could represent a possible host galaxy or host group. Imaging of the field is available at: http://www.astro.ljmu.ac.uk/~aridperl/grb/200228b/GRB200228B_LT_PS1.png (The enhanced XRT error circle is shown in cyan with the marginal "detection" highlighted in red.) DisclaimerNone //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 27272 SUBJECT: GRB 200228B: RATIR Optical Observations DATE: 20/02/29 15:51:14 GMT FROM: Rosa Leticia Becerra Godinez at Inst. de Astronoma,UNAM Rosa L. Becerra (UNAM), Alan M. Watson (UNAM), Nat Butler (ASU), Alexander Kutyrev (GSFC), William H. Lee (UNAM), Michael G. Richer (UNAM), Ori Fox (STScI), J. Xavier Prochaska (UCSC), Josh Bloom (UCB), Antonino Cucchiara (UVI), Eleonora Troja (GSFC), Owen Littlejohns (ASU), Enrico Ramirez-Ruiz (UCSC), Jesús González (UNAM), Carlos Román-Zúñiga (UNAM), Harvey Moseley (GSFC), John Capone (UMD), V. Zach Golkhou (U. Wash.), and Vicki Toy (UMD) report: We observed the field of GRB 200228B (Fermi GBM team, GCN 27253, Laha, et. al. GCN 27254) with the Reionization and Transients Infrared Camera (RATIR; www.ratir.org) on the 1.5m Harold Johnson Telescope at the Observatorio Astronómico Nacional on Sierra San Pedro Mártir from 2020/02 29.36 to 2020/02 29.53 UTC (21.40 to 25.38 hours after the BAT trigger), obtaining a total of 2.27 hours exposure in the r and i bands. For a source within the Swift-XRT enhanced error circle (Evans et al., GCN Circ. 27256), in comparison with the SDSS DR9 and 2MASS catalogs, we obtain the following upper limits (3-sigma): r > 23.19 i > 23.11 These magnitudes are in the AB system and are not corrected for Galactic extinction in the direction of the GRB. We thank the staff of the Observatorio Astronómico Nacional in San Pedro Mártir. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 27273 SUBJECT: GRB 200228B: Swift-BAT refined analysis DATE: 20/02/29 23:49:33 GMT FROM: Amy Lien at GSFC C. B. Markwardt (GSFC), S. D. Barthelmy (GSFC), J. R. Cummings (CPI), H. A. Krimm (NSF), S. Laha (GSFC/UMBC), A. Y. Lien (GSFC/UMBC), D. M. Palmer (LANL), T. Sakamoto (AGU), M. Stamatikos (OSU), T. N. Ukwatta (LANL) (i.e. the Swift-BAT team): Using the data set from T-240 to T+297 sec from the recent telemetry downlink, we report further analysis of BAT GRB 200228B (trigger #958733) (Laha et al., GCN Circ. 27254). The BAT ground-calculated position is RA, Dec = 252.007, 16.964 deg which is RA(J2000) = 16h 48m 01.8s Dec(J2000) = +16d 57' 50.3" with an uncertainty of 2.5 arcmin, (radius, sys+stat, 90% containment). The partial coding was 31%. The mask-weighted light curve shows a weak pulse that starts at ~T-1 s, peaks at ~T+2 s, and ends at ~T+7 s. T90 (15-350 keV) is 7.37 +- 1.58 sec (estimated error including systematics). The time-averaged spectrum from T-0.84 to T+6.97 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 2.27 +- 0.36. The fluence in the 15-150 keV band is 3.0 +- 0.6 x 10^-7 erg/cm2. The 1-sec peak photon flux measured from T+1.32 sec in the 15-150 keV band is 1.0 +- 0.4 ph/cm2/sec. All the quoted errors are at the 90% confidence level. The results of the batgrbproduct analysis are available at http://gcn.gsfc.nasa.gov/notices_s/958733/BA/ //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 27274 SUBJECT: GRB 200228B: LCO Optical Upper Limit DATE: 20/03/01 11:29:15 GMT FROM: Robert Strausbaugh at U. of the Virgin Islands R. Strausbaugh (U. of the Virgin Islands), A. Cucchiara (U. of the Virgin Islands/College of Marin) report on behalf of a larger collaboration: We observed Swift GRB 200228B (Laha et al., GCN 27254) with the LCO 1-m Sinistro instrument at the McDonald Observatory, Texas, USA site, on February 29, from 10:52 to 11:42 UT (corresponding to 23.4 to 24.5 hours after the GRB trigger time) with the Bessel I and R filters. We performed a series of 10x120s exposures in I and R. We do not detect any uncatalouged sources in the individual frames (nor in stacked images) in the Swift error region. Using the USNO-B.1 catalog as reference, we obtain the following 3-sigma upper limits in stacked images: R > 22.08 I > 20.77 R.S. is funded by NSF AST grant #1831682 //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 27276 SUBJECT: GRB 200228B: Mondy, TSHAO, AbAO and CrAO optical observations, afterglow candidate DATE: 20/03/01 15:21:19 GMT FROM: Alexei Pozanenko at IKI, Moscow A. Pozanenko (IKI), S. Belkin (IKI), E. Klunko (ISTP), A. Kusakin (FAPHI), I. Reva (FAPHI), V. Rumyantsev (CrAO), R. Ya. Inasaridze (AbAO), E. Mazaeva (IKI), A. Volnova (IKI) report on behalf of IKI-GRB-FuN: We observed the field of GRB 200228B (Laha et al., GCN 27254; Fermi GBM Team, GCN 27253) with AZT-33IK 1.5-m telescope of Sayan observatory (Mondy) starting on Feb. 28 (UT) 19:24:43. We detected an optical object near the enhanced XRT position of the XRT afterglow (Evans et al., GCN 27256). The object is absent in the Pan-STARRS DR1 catalog. The coordinates of the object are (J2000) 16:48:10.88 +16:59:04.5 with uncertainty of 0.5 arcsec in both coordinates. Next we observed the filed with Zeiss-1000 1-m telescope of Tien Shan Astronomical Observatory starting on Feb. 28 (UT) 23:08:56, Abastumani starting on Feb. 29 (UT) 01:38:45, Tien Shan Astronomical Observatory starting on Feb. 29 (UT) 23:08:56, and CrAO starting on Mar. 01 (UT) 00:58:28. Preliminary photometry of the object and the field is following. Date UT start t-T0 Filter Exp. OT Err UL(3sigma) telescope (mid, days) (s) 2020-02-28 19:24:43 0.351 R 15*120 21.8 0.3 21.7 AZT-33IK 2020-02-28 23:08:56 0.516 R 3480 n/d n/d 22.3 Z-1000 2020-02-29 01:38:45 0.616 R 46*60 n/d n/d 21.8 AS-32 2020-02-29 22:22:37 n/a R 5040 n/a n/a n/a Z-1000 2020-03-01 00:58:28 1.594 R 31*120 22.05 0.09 23.8 ZTSh Photometry is based on the USNO-B2.0 nearby stars. USNO-B1.0 R2 1069-0297786 18.42 1069-0297719 18.25 1069-0297797 14.78 The finding chart is available at http://193.232.11.154/GRB200228B/GRB200228B_AZT33IK_Z1000_ZTSh_FC.png (or http://grb.iki.rssi.ru/GRB200228B/GRB200228B_AZT33IK_Z1000_ZTSh_FC.png ). We suggest this object is a candidate in the afterglow of GRB 200228B after at least two epoch detections (see above), possible variability and absence of the bright object (R ~ 22) in the Pan-STARRS DR1. We did not detect any object at the position of NIR- candidate (Perley and Cockeram, GCN 27271). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 27302 SUBJECT: GRB 200228A: AstroSat CZTI detection DATE: 20/03/03 09:45:56 GMT FROM: Soumya Gupta at IUCAA/ASTROSAT S. Gupta, V. Sharma and D. Bhattacharya (IUCAA), V. Bhalerao (IIT-B), A. R. Rao (TIFR) and S. Vadawale (PRL) report on behalf of the AstroSat CZTI collaboration: Analysis of AstroSat CZTI data showed the detection of the long GRB 200228A, which was also detected by Fermi GBM Final Real-time Localization (GCN #27247), BALROG (Kunzweiler F. et al., GCN #27248) and Swift/BAT (Tohuvavohu A. et al., GRB #27259). The source was clearly detected in the 40-200 keV energy range. The light curve showed a single peak of emission peaking at 2020-02-28 06:58:33.01 UT. The measured peak count rate associated with the burst is 537 +/- 33.1 cts/s above the background in the combined data of four quadrants, with a total of 1496 +/- 9.8 cts. The local mean background count rate was 551 +/- 1.4 cts/s. Using cumulative rates, we measure a T90 of 4.8 +/- 0.02 s. It was also clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. CZTI GRB detections are reported regularly on the payload site at http://astrosat.iucaa.in/czti/?q=grb. CZTI is built by a TIFR-led consortium of institutes across India, including VSSC, ISAC, IUCAA, SAC and PRL. The Indian Space Research Organisation funded, managed and facilitated the project. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 27318 SUBJECT: GRB 200228B: continued optical observations DATE: 20/03/05 18:07:39 GMT FROM: Alexei Pozanenko at IKI, Moscow A. Pozanenko (IKI), S. Belkin (IKI), R. Ya. Inasaridze (AbAO), E. Klunko (ISTP), A. Kusakin (FAPHI), I. Reva (FAPHI), V. Rumyantsev (CrAO), E. Mazaeva (IKI), A. Volnova (IKI) report on behalf of IKI-GRB-FuN: We continue observations of the OT (Pozanenko et al., GCN 27276) associated with GRB 200228B (Laha et al., GCN 27254; Fermi GBM Team, GCN 27253) with AZT-33IK 1.5-m telescope of Sayan observatory (Mondy) and AS-32 telescope of Abastumani Astrophysical observatory. The OT is well observable (see photometry below in the table) and current XRT position ( https://www.swift.ac.uk/xrt_positions/00958733/ ) coincides with position of the OT. Preliminary photometry of the object following. Date UT start t-T0 Filter Exp. OT Err UL(3sigma) telescope (mid, days) (s) 2020-03-03 01:36:36 3.6186 R 58*60 21.65 0.13 22.6 AS-32 2020-03-03 21:03:33 4.4228 R 20*120 22.2 0.4 22.0 AZT-33IK 2020-03-04 23:44:59 5.5488 R 80*60 21.93 0.17 22.6 AS-32 Photometry is based on the USNO-B2.0 nearby stars used in previous observations (GCN 27276). The light curve in R-filter is available at http://grb.rssi.ru/GRB200228B/GRB200228B_lc_2.png We urge on spectroscopic and multicolor photometry to classify the OT.