//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 27509 SUBJECT: GRB 200409A: Swift detection of a burst with an optical counterpart DATE: 20/04/09 03:30:47 GMT FROM: David Palmer at LANL J.D. Gropp (PSU), S. D. Barthelmy (GSFC), J. A. Kennea (PSU), N. J. Klingler (PSU), S. Laha (GSFC/UMBC/CRESST), A. Y. Lien (GSFC/UMBC), F. E. Marshall (NASA/GSFC), M. J. Moss (GWU), D. M. Palmer (LANL), M. H. Siegel (PSU) and A. Tohuvavohu (U Toronto) report on behalf of the Neil Gehrels Swift Observatory Team: At 03:19:59 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 200409A (trigger=965484). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 60.553, -50.247, which is RA(J2000) = 04h 02m 13s Dec(J2000) = -50d 14' 49" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve shows multiple peaks with a total duration of about 20 sec. The peak count rate was ~2000 counts/sec (15-350 keV), at ~1 sec after the trigger. The XRT began observing the field at 03:21:13.1 UT, 73.4 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source located at RA, Dec 60.53820, -50.22509 which is equivalent to: RA(J2000) = 04h 02m 09.17s Dec(J2000) = -50d 13' 30.3" with an uncertainty of 3.7 arcseconds (radius, 90% containment). This location is 85 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. We cannot determine whether the source is fading at the present time. A power-law fit to a spectrum formed from promptly downlinked event data gives a column density in excess of the Galactic value (1.27 x 10^20 cm^-2, Willingale et al. 2013), with an excess column of 5 (+4.06/-3.42) x 10^21 cm^-2 (90% confidence). UVOT took a finding chart exposure of 150 seconds with the White filter starting 77 seconds after the BAT trigger. There is a candidate afterglow in the rapidly available 2.7'x2.7' sub-image at RA(J2000) = 04:02:08.75 = 60.53646 DEC(J2000) = -50:13:28.4 = -50.22455 with a 90%-confidence error radius of about 0.77 arc sec. This position is 4.6 arc sec. from the center of the XRT error circle. The estimated magnitude is 19.14 with a 1-sigma error of about 0.16. No correction has been made for the expected extinction corresponding to E(B-V) of 0.01. 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: 27510 SUBJECT: GRB 200409A: Enhanced Swift-XRT position DATE: 20/04/09 08:49:18 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 2685 s of XRT Photon Counting mode data and 6 UVOT images for GRB 200409A, 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 = 60.53633, -50.22498 which is equivalent to: RA (J2000): 04h 02m 8.72s Dec (J2000): -50d 13' 29.9" 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: 27511 SUBJECT: GRB 200409A: Swift-XRT refined Analysis DATE: 20/04/09 10:11:45 GMT FROM: Phil Evans at U of Leicester D.N. Burrows (PSU), J. D. Gropp (PSU), A.P. Beardmore (U. Leicester), P.A. Evans (U. Leicester), J.P. Osborne (U. Leicester), T. Sbarrato (INAF-OAB), P. D'Avanzo (INAF-OAB), M.G. Bernardini (INAF-OAB), J.A. Kennea (PSU) and J.D. Gropp report on behalf of the Swift-XRT team: We have analysed 7.6 ks of XRT data for GRB 200409A (Gropp et al. GCN Circ. 27509), from 59 s to 18.1 ks after the BAT trigger. The data comprise 7 s in Windowed Timing (WT) mode (taken while Swift was slewing), with the remainder in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Evans et al. (GCN Circ. 27510). The light curve can be modelled with a series of power-law decays. The initial decay index is alpha=2.8 (+5.2, -0.8). At T+123 s the decay flattens to an alpha of -0.2 (+0.4, -0.7) before breaking again at T+441 s to a final decay with index alpha=0.80 (+0.34, -0.07). A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 1.94 (+0.17, -0.16). The best-fitting absorption column is 3.2 (+3.7, -1.9) x 10^20 cm^-2, consistent with the Galactic value of 1.3 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 3.3 x 10^-11 (3.6 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 3.2 (+3.7, -1.9) x 10^20 cm^-2 Galactic foreground: 1.3 x 10^20 cm^-2 Excess significance: <1.6 sigma Photon index: 1.94 (+0.17, -0.16) If the light curve continues to decay with a power-law decay index of 0.80, the count rate at T+24 hours will be 9.0 x 10^-3 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 3.0 x 10^-13 (3.2 x 10^-13) erg cm^-2 s^-1. The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00965484. This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 27512 SUBJECT: Swift GRB 200409A: Global MASTER-Net observations report DATE: 20/04/09 17:32:31 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-SAAO robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in South Africa (South African Astronomical Observatory) was pointed to the Swift GRB 200409A ( J.D. Gropp et al., GCN 27509) errorbox 49717 sec after notice time and 49742 sec after trigger time at 2020-04-09 17:09:01 UT, with upper limit up to 19.1 mag. Observations started at twilight. The observations began at zenith distance = 44 deg. The sun altitude is -10.2 deg. The galactic latitude b = -47 deg., longitude l = 259 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=1333122 We obtain a following upper limits. Tmid-T0 | Site |Filt.| Expt. | Limit| Comment _________|_____________________|_____|_______|______|________ 49832 | MASTER-SAAO | C | 180 | 19.1 | 49834 | MASTER-SAAO | C | 180 | 19.0 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 27514 SUBJECT: Fermi GBM Sub-Threshold Detection of GRB 200409A DATE: 20/04/09 18:58:23 GMT FROM: Eric Burns at GSFC E. Burns (GSFC), M. S. Briggs (UAH), C. M. Hui (MSFC), C. Malacaria (MSFC), and P. Veres (UAH) reports on behalf of the Fermi-GBM Team Swift-BAT detected GRB 200409A at 03:19:59 UT (GCN 27509). There was no Fermi-GBM onboard trigger around the event. An automated, blind search for short gamma-ray bursts below the onboard triggering threshold in Fermi-GBM identified GRB 200904A with high reliability [1], with a localization consistent with the Swift-BAT location, and a discovery timescale of 0.703 s. The GBM targeted search [2], the most sensitive, coherent search for GRB-like signals, was run from +/-30 s around BAT trigger time. A transient source was identified whose most significant timescale according to the search is 1.024 s, with a log likelihood ratio of 62, with a consistent location, and is consistent with a soft spectrum for a GRB. Preliminary spectral analysis statistically prefers a power-law fit over models that constrain Epeak. Using T0-0.320 to T0+0.320 as the source interval gives an alpha of -1.84 +/- 0.06, a photon flux of 3.3 +/- 0.4 ph/s/cm^2, and a fluence of (2.0+/-0.2)E-7 erg/s/cm^2. [1] https://gcn.gsfc.nasa.gov/notices_gbm_sub/608095205.fermi [2] Goldstein et al. 2019 arXiv:1903.12597 //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 27519 SUBJECT: GRB 200409A: Swift-BAT refined analysis DATE: 20/04/10 03:56:27 GMT FROM: Amy Lien at GSFC S. D. Barthelmy (GSFC), J. R. Cummings (CPI), H. A. Krimm (NSF), J.D. Gropp (PSU), 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-240 to T+963 sec from the recent telemetry downlink, we report further analysis of BAT GRB 200409A (trigger #965484) (Gropp et al., GCN Circ. 27509). The BAT ground-calculated position is RA, Dec = 60.555, -50.243 deg which is RA(J2000) = 04h 02m 13.3s Dec(J2000) = -50d 14' 36.4" with an uncertainty of 2.7 arcmin, (radius, sys+stat, 90% containment). The partial coding was 75%. The mask-weighted light curve shows several overlapping pulses that start at ~T0 and ends at~T+19 s. The main peak occurs at ~T0. T90 (15-350 keV) is 17.91 +- 5.20 sec (estimated error including systematics). The time-averaged spectrum from T+0.01 to T+19.01 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 2.14 +- 0.44. The fluence in the 15-150 keV band is 2.3 +- 0.6 x 10^-7 erg/cm2. The 1-sec peak photon flux measured from T+0.01 sec in the 15-150 keV band is 1.2 +- 0.2 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/965484/BA/ //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 27521 SUBJECT: GRB 200409A: No detection of radio emission 5 hours post-burst DATE: 20/04/10 04:09:36 GMT FROM: Dougal Dobie at VAST Dougal Dobie (USYD/CSIRO), Tara Murphy (USYD), David Kaplan (UWM) While performing follow-up of GRB 200405B (GCN 27497, 27516) we received notification of the detection of GRB 200409A and the associated optical and X-ray candidate counterpart (GCN 27509). We added it to our schedule and carried out observations of it from 2020-04-09 07:00-09:30 UTC, approximately 5 hours post-burst. We make no detection of radio emission at 5.5 or 9 GHz with 3-sigma upper limits of 90 uJy and 81 uJy respectively. Thank you to CSIRO staff for supporting these observations during these especially difficult times.