//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 23908 SUBJECT: GRB 190220A: Swift detection of a burst with an optical counterpart DATE: 19/02/20 03:14:43 GMT FROM: Kim Page at U.of Leicester K. L. Page (U Leicester), N. J. Klingler (PSU), F. E. Marshall (NASA/GSFC), D. M. Palmer (LANL), M. H. Siegel (PSU) and A. Tohuvavohu (PSU) report on behalf of the Neil Gehrels Swift Observatory Team: At 02:59:34 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 190220A (trigger=889785). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 330.142, -76.691 which is RA(J2000) = 22h 00m 34s Dec(J2000) = -76d 41' 27" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a complex structure with a duration of about 10 sec. The peak count rate was ~1700 counts/sec (15-350 keV), at ~1 sec after the trigger. The XRT began observing the field at 03:00:55.5 UT, 80.8 seconds after the BAT trigger. The position determined from promptly downlinked data differs significantly from the on-board position, suggesting that the XRT may have centroided on a cosmic ray; the initial XRT position notice should be treated with caution. Using promptly downlinked data we find an uncatalogued, fading X-ray source located at RA, Dec 330.16325, -76.68047 which is equivalent to: RA(J2000) = 22h 00m 39.18s Dec(J2000) = -76d 40' 49.7" with an uncertainty of 3.7 arcseconds (radius, 90% containment). This location is 41 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 http://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 (1.10 x 10^21 cm^-2, Willingale et al. 2013), with an excess column of 4.9 (+3.65/-3.07) x 10^21 cm^-2 (90% confidence). UVOT took a finding chart exposure of 150 seconds with the White filter starting 86 seconds after the BAT trigger. There is a candidate afterglow in the rapidly available 2.7'x2.7' sub-image at RA(J2000) = 22:00:39.14 = 330.16309 DEC(J2000) = -76:40:50.4 = -76.68067 with a 90%-confidence error radius of about 0.66 arc sec. This position is 3.1 arc sec. from the center of the XRT error circle. The estimated magnitude is 19.29 with a 1-sigma error of about 0.16. No correction has been made for the expected extinction corresponding to E(B-V) of 0.13. Burst Advocate for this burst is K. L. Page (klp5 AT leicester.ac.uk). 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: 23912 SUBJECT: GRB 190220A: Enhanced Swift-XRT position DATE: 19/02/20 15:13:27 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 749 s of XRT Photon Counting mode data and 2 UVOT images for GRB 190220A, 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 = 330.16376, -76.68124 which is equivalent to: RA (J2000): 22h 00m 39.30s Dec (J2000): -76d 40' 52.5" with an uncertainty of 1.5 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: 23914 SUBJECT: GRB 190220A: Swift-BAT refined analysis DATE: 19/02/20 17:59:59 GMT FROM: Amy Lien at GSFC S. D. Barthelmy (GSFC), J. R. Cummings (CPI), H. A. Krimm (NSF/USRA), A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC), D. M. Palmer (LANL), K. L. Page (U Leicester), 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 190220A (trigger #889785) (Page et al., GCN Circ. 23908). The BAT ground-calculated position is RA, Dec = 330.128, -76.669 deg which is RA(J2000) = 22h 00m 30.7s Dec(J2000) = -76d 40' 10.1" with an uncertainty of 1.3 arcmin, (radius, sys+stat, 90% containment). The partial coding was 46%. The mask-weighted light curve shows a single-pulse structure that starts at ~T0, peaks at ~T+2 s, and ends at ~T+12 s. T90 (15-350 keV) is 10.0 +- 2.0 sec (estimated error including systematics). The time-averaged spectrum from T-0.12 to T+11.88 sec is best fit by a power law with an exponential cutoff. This fit gives a photon index 0.79 +- 0.77, and Epeak of 40.3 +- 6.7 keV (chi squared 60.03 for 56 d.o.f.). For this model the total fluence in the 15-150 keV band is 8.9 +- 1.0 x 10^-7 erg/cm2 and the 1-sec peak flux measured from T+1.88 sec in the 15-150 keV band is 2.6 +- 0.4 ph/cm2/sec. A fit to a simple power law gives a photon index of 2.03 +- 0.13 (chi squared 70.39 for 57 d.o.f.). 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/889785/BA/ //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 23917 SUBJECT: GRB 190220A: Swift-XRT refined Analysis DATE: 19/02/21 02:51:09 GMT FROM: Phil Evans at U of Leicester V. D'Elia (ASDC), A. D'Ai (INAF-IASFPA), A. Melandri (INAF-OAB), S. J. LaPorte (PSU), J.A. Kennea (PSU), B. Sbarufatti (INAF-OAB/PSU), A.P. Beardmore (U. Leicester), P.A. Evans (U. Leicester) and K.L. Page report on behalf of the Swift-XRT team: We have analysed 6.9 ks of XRT data for GRB 190220A (Page et al. GCN Circ. 23908), from 68 s to 80.7 ks after the BAT trigger. The data comprise 67 s in Windowed Timing (WT) mode (the first 8 s were 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. 23912). The light curve can be modelled with an initial power-law decay with an index of alpha=2.4 (+0.3, -0.4), followed by a break at T+173 s to an alpha of 1.10 (+/-0.08). A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 1.69 (+0.25, -0.23). The best-fitting absorption column is 3.9 (+1.5, -1.2) x 10^21 cm^-2, in excess of the Galactic value of 1.1 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 4.7 x 10^-11 (6.2 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 3.9 (+1.5, -1.2) x 10^21 cm^-2 Galactic foreground: 1.1 x 10^21 cm^-2 Excess significance: 3.7 sigma Photon index: 1.69 (+0.25, -0.23) If the light curve continues to decay with a power-law decay index of 1.10, the count rate at T+24 hours will be 1.9 x 10^-3 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 9.1 x 10^-14 (1.2 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/00889785. This circular is an official product of the Swift-XRT team.