//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 29699 SUBJECT: GRB 210323A: Swift detection of a short burst DATE: 21/03/23 22:20:56 GMT FROM: David Palmer at LANL J.D. Gropp (PSU), F. E. Marshall (NASA/GSFC), M. J. Moss (GWU), D. M. Palmer (LANL) and B. Sbarufatti (PSU) report on behalf of the Neil Gehrels Swift Observatory Team: At 22:02:18 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 210323A (trigger=1038247). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 317.952, +25.378 which is RA(J2000) = 21h 11m 49s Dec(J2000) = +25d 22' 40" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a single spike structure with a duration of about 1 sec. The peak count rate was ~10,000 counts/sec (15-350 keV), at ~0 sec after the trigger. The XRT began observing the field at 22:03:43.6 UT, 85.2 seconds after the BAT trigger. Using promptly downlinked data we find a fading, uncatalogued X-ray source located at RA, Dec 317.94609, 25.36990 which is equivalent to: RA(J2000) = 21h 11m 47.06s Dec(J2000) = +25d 22' 11.6" with an uncertainty of 3.5 arcseconds (radius, 90% containment). This location is 34 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. A power-law fit to a spectrum formed from promptly downlinked event data gives a column density in excess of the Galactic value (1.17 x 10^21 cm^-2, Willingale et al. 2013), with an excess column of 5.9 (+3.84/-3.14) x 10^21 cm^-2 (90% confidence). UVOT took a finding chart exposure of 150 seconds with the White filter starting 88 seconds after the BAT trigger. No credible afterglow candidate has been found in the initial data products. The 2.7'x2.7' sub-image covers 100% of the XRT error circle. The typical 3-sigma upper limit has been about 19.6 mag. The 8'x8' region for the list of sources generated on-board covers 100% of the XRT error circle. The list of sources is typically complete to about 18 mag. No correction has been made for the expected extinction corresponding to E(B-V) of 0.132. Burst Advocate for this burst is J.D. Gropp (jdg44 AT psu.edu). 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: 29700 SUBJECT: GRB 210323A: Nanshan/NEXT optical upper limit DATE: 21/03/23 23:09:33 GMT FROM: Dong Xu at NAOC/CAS S.Y. Fu (NAOC), Z.P. Zhu (NAOC, HUST), X. Liu, D. Xu (NAOC), X. Gao (Urumqi No.1 Senior High School), J.Z. Liu (XAO) report: We observed the field of GRB 210323A (Gropp et al., GCN 29699) using the NEXT-0.6m telescope located at Nanshan, Xinjiang, China. Observations automatically started at 22:03:49 UT on 2021-03-23 (i.e., 91 s after the BAT trigger), and 3x40 s, 4x60 s and 12x90 s frames were obtained in the Sloan r-filter. No optical source is detected in our stacked image at the XRT position (Gropp et al., GCN 29699), down to a limiting magnitude of r~20.4, calibrated with nearby PanSTARRS stars. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 29702 SUBJECT: Swift GRB 210323A: Global MASTER-Net observations report DATE: 21/03/24 05:09:24 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), 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-IAC robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Spain (IAC Teide Observatory) was pointed to the Swift GRB 210323A ( J.D. Gropp et al., GCN 29699) errorbox 20222 sec after notice time and 20288 sec after trigger time at 2021-03-24 03:40:27 UT, with upper limit up to 16.5 mag. The observations began at zenith distance = 84 deg. The sun altitude is -43.3 deg. The galactic latitude b = -16 deg., longitude l = 73 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=1575256 We obtain a following upper limits. Tmid-T0 | Site |Filt.| Expt. | Limit| Comment _________|_____________________|_____|_______|______|________ 20379 | MASTER-IAC | C | 180 | 16.5 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 29703 SUBJECT: GRB 210323A: NOT optical afterglow candidate DATE: 21/03/24 06:43:12 GMT FROM: Daniele B Malesani at DTU Space D. B. Malesani (DTU Space), A. de Ugarte Postigo (HETH/IAA-CSIC and DARK/NBI), Z. Zhu, D. Xu (NAO/CAS), D. A. Kann (HETH/IAA-CSIC), J. Martikainen (NOT and Univ. Helsinki) report on behalf of a larger collaboration: We observed the field of the short GRB 210323A (Gropp et al., GCN 29699) using the Nordic Optical Telescope (NOT) equipped with the ALFOSC camera. Three observations of 10 min each were secured in the SDSS r filter, starting on 2021 Mar 24.229 UT (7.45 hr after the GRB). The field was observed at an airmass of ~2 and the seeing was 1.6". No sources are detected within the currently available XRT error circle (3.5"; Gropp et al., GCN 29699). We note however the presence of an object about 2" S-E of the XRT circle, with coordinates (J2000): RA = 21:11:47.33 DEC = +25:22:09.2 Its magnitude is r = 22.91 +- 0.09 AB, calibrated against nearby stars from Pan-STARRS. This object is not readily visible in the Pan-STARRS images, though its magnitude is close to the survey limit. We consider this object as a viable afterglow candidate to GRB 210323A, but a confirmation is necessary to assess variability. Further observations are planned. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 29704 SUBJECT: GRB 210323A: Enhanced Swift-XRT position DATE: 21/03/24 09:55:18 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 1396 s of XRT Photon Counting mode data and 2 UVOT images for GRB 210323A, 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 = 317.94665, +25.36930 which is equivalent to: RA (J2000): 21h 11m 47.20s Dec (J2000): +25d 22' 09.5" with an uncertainty of 1.6 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: 29705 SUBJECT: GRB 210323A: Swift-XRT refined Analysis DATE: 21/03/24 10:23:44 GMT FROM: Phil Evans at U of Leicester A.P. Beardmore (U. Leicester), P.A. Evans (U. Leicester), E. Ambrosi (INAF-IASFPA) , M. Capalbi (INAF-IASFPA), M. Perri (SSDC & INAF-OAR), J. D. Gropp (PSU), J.A. Kennea (PSU), A. Tohuvavohu (U. Toronto), J.P. Osborne (U. Leicester) and J.D. Gropp report on behalf of the Swift-XRT team: We have analysed 6.8 ks of XRT data for GRB 210323A (Gropp et al. GCN Circ. 29699), from 88 s to 34.2 ks after the BAT trigger. The data comprise 25 s in Windowed Timing (WT) mode with the remainder in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Evans et al. (GCN Circ. 29704). The light curve can be modelled with a series of power-law decays. The initial decay index is alpha=1.69 (+0.17, -0.12). At T+719 s the decay flattens to an alpha of 0.46 (+0.09, -0.25) before breaking again at T+12.2 ks to a final decay with index alpha=2.9 (+5.1, -0.6). A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 1.70 (+0.20, -0.19). The best-fitting absorption column is 2.7 (+1.0, -0.8) x 10^21 cm^-2, in excess of the Galactic value of 1.2 x 10^21 cm^-2 (Willingale et al. 2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 4.4 x 10^-11 (5.6 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 2.7 (+1.0, -0.8) x 10^21 cm^-2 Galactic foreground: 1.2 x 10^21 cm^-2 Excess significance: 3.0 sigma Photon index: 1.70 (+0.20, -0.19) If the light curve continues to decay with a power-law decay index of 2.9, the count rate at T+24 hours will be 2.0 x 10^-4 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 8.9 x 10^-15 (1.1 x 10^-14) erg cm^-2 s^-1. The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/01038247. This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 29708 SUBJECT: GRB 210323A: Mondy optical observations, counterpart detection DATE: 21/03/24 12:20:09 GMT FROM: Alexei Pozanenko at IKI, Moscow A. Pozanenko (IKI), N. Pankov (HSE), E. Klunko (ISTP), S. Belkin (IKI) report on behalf of GRB IKI FuN: We observed the field of short GRB 210323A (Gropp et al., GCN 29699) with AZT-33IK telescope of Sayan observatory (Mondy) starting on 2021-03-23 (UT) 22:05:05, i.e. 167 s after GRB trigger. We obtained 10 images in R-filter. In the first image we detect an object (S/N = 4.2) in coordinates of (J2000) 21:11:47.35, 25:22:09.4 with uncertainty of 0.6" in each coordinate. The coordinates are in agreement with reported by NOT an afterglow candidate (Malesani et al., GCN 29703) and enhanced XRT position (Evans et al., GCN 29704). In the next two stacked images the object is barely detected (S/N =1.8), while in rest stacked images we do not detect the object. Preliminary photometry of the object and the field in stacked images is following Date UT start t-T0 Filter Exp. OT Err. UL(3sigma) (mid, days) (s) 2021-03-23 22:05:05 0.00229 R 1*60 18.4 0.25 18.9 2021-03-23 22:06:07 0.00333 R 2*60 19.2 S/N =1.8 19.0 2021-03-23 22:08:06 0.00403 R 5*60 n/d n/d 18.9 The photometry is based on the nearby USNO-B1.0 star USNO-B1.0_id R2 1153-0524625 14.44 The non-detection of the object in Nanshan/NEXT observations up to deeper limiting magnitude of r~20.4 (Fu et al., GCN 29700) might be due to searching of the afterglow in a stacked image but non in early single images. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 29709 SUBJECT: GRB 210323A: Fermi GBM detection DATE: 21/03/24 13:30:47 GMT FROM: Rachel Hamburg at UAH R. Hamburg (UAH) and C. Meegan (UAH) report on behalf of the Fermi GBM Team: "At 22:02:18.40 UT on 23 March 2021, the Fermi Gamma-Ray Burst Monitor (GBM) triggered and located GRB 210323A (trigger 638229743 / 210323918), which was also detected by the Swift/BAT and Swift/XRT (Gropp et al. 2021, GCN 29699). The GBM on-ground location is consistent with the Swift position. The angle from the Fermi LAT boresight at the GBM trigger time is 92 degrees. The GBM light curve shows a single-peaked structure with a duration (T90) of about 1 s (50-300 keV). The time-averaged spectrum from T0-0.064 s to T0+0.192 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -0.97 +/- 0.05 and the cutoff energy, parameterized as Epeak, is 2.1 +/- 0.4 MeV. A Band function also fits the spectrum with Epeak = 2.1 +/- 0.5 MeV, alpha = -0.97 +/- 0.05 and beta = -3.02 +/- 1.02. The event fluence (10-1000 keV) in this time interval is (1.2 +/- 0.1)E-06 erg/cm^2. The 64-ms peak photon flux measured starting from T0+0.064 s in the 10-1000 keV band is 21.3 +/- 1.5 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: 29710 SUBJECT: GRB 210323A: Kitab optical upper limit DATE: 21/03/24 15:05:43 GMT FROM: Alexei Pozanenko at IKI, Moscow N. Pankov (HSE), A. Pozanenko (IKI), A. Novichonok (Petrozavodsk State University, KIAM), A. Zhornichenko (KIAM), S. Belkin (IKI), Sh. Ehgamberdiev (UBAI) report on behalf of GRB IKI FuN: We observed the field of short GRB 210323A (Swift detection: Gropp et al., GCN 29699; GBM/Fermi detection: Hamburg et al., GCN 29709) with Kitab-ISON RC-36 telescope starting on 2021-03-23 (UT) 22:36:32. We obtained several images in Clear filter. We do not detect the afterglow candidate (Malesani et al., GCN 29703; Pozanenko et al., GCN 29708) within enhanced Swift-XRT position (Evans et al., GCN 29704). Preliminary photometry of the field is following Date, UT start, t-T0, Exp., Filter, OT, Err., UL (mid, days) 2021-03-23 22:36:32 0.02759 11*60 CR n/d n/d 16.6 The photometry is based on nearby USNO-B1.0 stars USNO-B1.0_id R2 1153-0524361 15.3 1153-0524625 14.44 1153-0524441 15.36 //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 29711 SUBJECT: GRB 210323A: Classification and redshift estimation DATE: 21/03/24 15:20:58 GMT FROM: Alexei Pozanenko at IKI, Moscow P. Minaev (IKI), A. Pozanenko (IKI) report on behalf of GRB IKI FuN: We analysed spectral data of GBM/Fermi of GRB 210323A (Hamburg et al., GCN 29709) which is initially reported in for GRB 210323A (Gropp et al., GCN 29699; Hamburg et al., GCN 29709) to classify the burst and estimate its redshift using EH-T90,i diagram [1,2]. The burst belongs to type I (short) population. We also estimate the lower limit on redshift of z = 0.42. See figure of EH-T90,i diagram for GRB 210323A at http://grb.rssi.ru/GRB210323A/GRB210323A_EH-T90.png [1] — Minaev et al., MNRAS, 492, 1919 (2020) [2] — Minaev et al., Astronomy Letters, 46, 573 (2020) //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 29712 SUBJECT: GRB 210323A: Swift/UVOT Upper Limits DATE: 21/03/24 15:26:43 GMT FROM: Alice Breeveld at MSSL-UCL A. A. Breeveld (UCL-MSSL) and J. D. Gropp (PSU) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 210323A 89 s after the BAT trigger (Gropp et al., GCN Circ. 29699). The optical afterglow detected by Malesani et al. (GCN Circ. 29703) and Pozanenko et al. (GCN Circ. 29708) and consistent with the XRT position (Evans et al. GCN Circ. 29704), is not 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 white_FC 89 239 147 >20.1 u_FC 302 552 246 >19.9 white 89 4948 569 >20.5 v 632 1423 97 >17.7 b 558 1522 97 >19.3 u 302 1497 324 >19.3 w1 681 1473 97 >18.5 m2 828 848 19 >18.8 w2 607 5034 136 >19.4 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.131 in the direction of the burst (Schlegel et al. 1998). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 29713 SUBJECT: Konus-Wind detection of GRB 210323A (short) DATE: 21/03/24 16:09:47 GMT FROM: Dmitry Frederiks at Ioffe Institute D. Frederiks, S. Golenetskii, A.Lysenko, A. Ridnaia, D. Svinkin, A. Tsvetkova, M. Ulanov, and T. Cline, on behalf of the Konus-Wind team, report: The short GRB 210323A (Swift-BAT detection: Gropp et al., GCN 29699; Fermi-GBM detection: Hamburg & Meegan, GCN 29709) triggered Konus-Wind (KW) at T0=79334.600 s UT (22:02:14.600). The burst light curve shows a single pulse with the total duration of ~0.45 s (20-1500 keV). The emission is seen up to ~2 MeV. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB210323_T79334/ As observed by Konus-Wind, the burst had a fluence of 1.57(-0.25,+0.50)x10^-6 erg/cm^2 and a 16-ms peak energy flux, measured from T0-0.016 s, of 1.23(-0.20,+0.36)x10^-5 erg/cm^2/s (both in the 20 keV - 10 MeV energy range). Since the brightest part of the burst emission was detected before the trigger, the spectral analysis was performed using the KW 3-channel light curve data. Modelling the time-integrated spectrum of the burst (measured from T0-0.128 to T0+0.320 s) by a power law with exponential cutoff model: dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep), yields alpha = -1.03(-0.17,+0.18) and Ep = 632(-167,+442) keV. All the quoted errors are estimated at the 68% confidence level. All the presented results are preliminary. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 29717 SUBJECT: Short GRB 210323A: GTC Observations DATE: 21/03/24 19:49:17 GMT FROM: Alexander Kann at IAA-CSIC A. de Ugarte Postigo (HETH/IAA-CSIC, DARK/NBI), D. A. Kann (HETH/IAA-CSIC), D. B. Malesani (DTU Space), N. R. Tanvir (Univ. Leicester), C. Thoene, M. Blazek, J. F. Agui Fernandez (all HETH/IAA-CSIC), and S. Geier (GTC, IAC) report: We observed the afterglow (Malesani et al., GCN #29703, Pozanenko et al., GCN #29708) of the short/hard GRB 210323A (Swift detection: Gropp et al., GCN #29699, Fermi GBM detection: Hamburg & Meegan, GCN #29709; Konus-Wind detection: Frederiks et al., GCN #29713) with OSIRIS at the 10.4m GTC telescope at Roque de los Muchachos Observatory, in La Palma (Spain). The observation started at 05:31 UT (0.3118 days after the burst), and consisted of 3 x 600s with grism R1000B, covering the spectral range from 3700 to 7800 AA. Observations were taken at high airmass, near dawn. The 60 s acquisition image, with a seeing of 1".3, shows the afterglow at a magnitude of r' = 23.03 +/- 0.15 mag, using a nearby Pan-STARRS field star as photometric reference. This is in agreement with the NOT measurement. Spectral continuum is faintly detected above 5000 AA, and shows no clear evidence for any absorption or emission lines. We therefore place a weak upper limit of z < 3.1 on the redshift of GRB 210323A. There may be evidence for a low-significance emission line at 5110 AA, which is slightly offset from the continuum trace in the 2D spectrum. It is found using multiple reductions and analyses. Interpreting this line as [OII], the corresponding redshift would be z = 0.37. However, we do not find any evidence for other emission lines, such as Hbeta and [OIII], at the corresponding redshift, placing its reality in doubt. Further observations will be required to verify the reality of this feature and to attempt a redshift determination through host galaxy spectroscopy. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 29720 SUBJECT: GRB 210323A: Gemini-North Optical Source Detection DATE: 21/03/24 20:55:08 GMT FROM: Jillian Rastinejad at Northwestern Univ. J. Rastinejad, K. Paterson, W. Fong, C. D. Kilpatrick (Northwestern), T. Laskar (U. of Bath), A. Levan (Radboud U.), B. E. Cobb (GWU) report: We observed the location of the Swift and Fermi short GRB 210323A (Gropp et al., GCN 29699, Hamburg et al., GCN 29709) with the Gemini Multi-object Spectrograph (GMOS) mounted on Gemini-North. We obtained 15x90-sec imaging in r-band at a mid-time of 2021 March 24.637 UT (0.72 days post-burst). Just to the East, outside of the updated XRT position (90% confidence; Evans et al., GCN 29704), we detect faint emission consistent with the putative optical afterglow (Malesani et al., GCN 29703, Pozanenko et al, GCN 29708, de Ugarte Postigo et al., GCN 29717). However, there is also a clear extension from this position to the North, which we propose to be a faint underlying host galaxy. At present it is not possible to disentangle the contributions of faint afterglow and the underlying host. We measure a position for the source (or source complex) of RA = 21:11:47.34, Dec = +25:22:10.1 (J2000; 0.5'' uncertainty), ~0.7-0.9'' offset from the Mondy and NOT positions. After calibrating our stacked image to isolated stars detected in the PS1 photometric catalog (Chambers et al., 2016), we perform aperture photometry of the entire extended source, and measure r = 24.6 +/- 0.2 AB mag (not corrected for Milky Way extinction). Compared to the NOT and GTC measurements Malesani et al., GCN 29703; de Ugarte Postigo et al., GCN 29717), this indicates fading of ~1.7 magnitudes over ~9.5 hours, indicating a rapid rate of decay of F~t^-1.86. This decline rate is likely contaminated by the host galaxy and the true decline rate is potentially steeper, consistent with the steep X-ray afterglow decline rate (Beardmore et al., GCN 29705). Further observations are planned to assess any variability of the source. We thank Gemini staff Joan Font-Serra and Teo Mocnik for the rapid scheduling and execution of these observations. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 29721 SUBJECT: GRB 210323A: Swift-BAT refined analysis DATE: 21/03/24 22:17:51 GMT FROM: Sibasish Laha at GSFC S. D. Barthelmy (GSFC), J. R. Cummings (CPI), H. A. Krimm (NSF), S. Laha (GSFC/UMBC), A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC), 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-239 to T+963 sec from the recent telemetry downlink, we report further analysis of BAT GRB 210323A (trigger #1038247) (Gropp et al., GCN Circ. 29699). The BAT ground-calculated position is RA, Dec = 317.945, 25.352 deg which is RA(J2000) = 21h 11m 46.7s Dec(J2000) = +25d 21' 08.7" with an uncertainty of 1.4 arcmin, (radius, sys+stat, 90% containment). The partial coding was 76%. The BAT lightcurve showed complex structure with a duration less than 2 sec. T90 (15-350 keV) is 1.12 +- 0.32 sec (estimated error including systematics). The time-averaged spectrum from T-0.09 to T+1.26 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.46 +- 0.17. The fluence in the 15-150 keV band is 2.4 +- 0.3 x 10^-07 erg/cm2. The 1-sec peak photon flux measured from T-0.10 sec in the 15-150 keV band is 2.9 +- 0.3 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/1038247/BA/ //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 29724 SUBJECT: GRB 210323A: MASTER optical observation DATE: 21/03/24 23:16:11 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs N.Tiurina, V. Lipunov, V.Kornilov, E.Gorbovskoy,P.Balanutsa,F.Balakin, V.Vladimirov, A.Kuznetsov,K.Zhirkov,D. Vlasenko, I.Gorbunov, D.Zimnukhov, V.Senik, A.Chasovnikov,A.Pozdnyakov,V.Topolev, D.Cheryasov(Lomonosov Moscow State University, SAI, Physics Department), D. Buckley (South African Astronomical Observatory), O.A. Gres, N.M. Budnev (Irkutsk State University, API), R. Podesta, C.Lopez, F. Podesta, C.Francile (Observatorio Astronomico FelixAguilar OAFA), R. Rebolo, M. Serra(The Instituto de Astrofisica de Canarias), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity) MASTER Global robotic net (MASTER-Net:http://observ.pereplet.ru Lipunov et al.,2010,Advances in Astronomy,2010,30L) automatically started Swift GRB 210323A (Gropp et al. GCN 29699, Ttrigger=22:02:18UT, https://gcn.gsfc.nasa.gov/other/210323A.gcn3) optical observations at MASTER-Tunka (in ~100km of Mondy , Pozanenko et al. GCN 29708) at 2021-03-23 22:03:12UT with 10s expositions by MASTER-600 twin robotic telescope and by MASTER-VWFC (very wide field cameras)at sunrise. The Sun altitude at MASTER-Tunka and Mondy was -9.6, see alert location and conditions of observation at http://observ.pereplet.ru/images/tunka2021-03-23-22-03-13.jpg (webcamera). The distance to Sun of GRB coordinates was 49.6deg., that made 18.4m OT detection little likelihood for the telescopes at this location and at this time. MASTER observed this alert's error-box also at MASTER-Tavrida (2021-03-24 02:07:41 UT, with upper limit 18.2), MASTER-IAC (2021-03-24 03:40:27 UT, Lipunov et al. 29702), and MASTER-OAFA (started at 2021-03-24 09:40:18UT), see cover map, limits and altitudes at https://master.sai.msu.ru/site/master2/observ.php?id=1575256 Reduction and analyses will continue. This message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 29726 SUBJECT: GRB 210323A: Insight-HXMT/HE detection DATE: 21/03/25 03:15:20 GMT FROM: Y Q Zhang at IHEP Y. Q. Zhang, C. Cai, J. C. Liu, Q. Luo, S. Xiao, W. C. Xue, Q. B. Yi, C. Zheng，Y. Huang, C. K. Li, G. Li, X. B. Li, J. Y. Liao, X. Y. Song, 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 2021-03-23T22:02:18.40 (T0), Insight-HXMT/HE detected GRB 210323A (trigger ID: HEB210323918) in a routine search of the data, which also triggered Swift/BAT (Gropp J.D. et al., GCN #29699) and Fermi/GBM (Hamburg R. et al., GCN #29709). The Insight-HXMT/HE light curve mainly consists of a single pulse with a duration (T90) of 0.33 s measured from T0-0.03 s. The 1-ms peak rate, measured from T0+0.05 s, is 9821 cnts/sec. The total counts from this burst is 1842 counts. URL_LC: http://twiki.ihep.ac.cn/pub/HXMT/GRBList/HEB210323918_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: 30000 SUBJECT: Short GRB 210323A: likely host galaxy detection DATE: 21/05/12 14:38:46 GMT FROM: Daniele B Malesani at DTU Space Daniele B. Malesani (DTU Space), Luca Izzo (DARK/NBI) and Andrea Rossi (INAF/OAS) report on behalf of a larger collaboration. We observed again the field of the short GRB 210323A (Gropp et al., GCN 29699). We used the ALFOSC camera at the Nordic Optical Telescope (NOT). Observations were carried out during the night of 2021 May 4, approximately 42.3 days after the GRB, and consisted of 5x600 s exposure in the r band. The optical source detected in our earlier observation (Malesani et al., GCN 29703; see also Pozanenko et al., GCN 29708; de Ugarte Postigo et al., GCN 29717; Rastinejad et al., GCN 29720) has clearly faded, confirming it is the afterglow of GRB 210323A. Directly underneath the position of the optical transient, a faint source is visible in the stack of our images, which is likely the host galaxy of the GRB (see also Rastinejad et al., GCN 29720). We measure for the host an AB magnitude r = 24.6 +- 0.3, calibrated against nearby stars from the Pan-STARRS catalogue. We acknowledge expert help from the support astronomer at the NOT, Amanda Djupvik.