//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 22442 SUBJECT: GRB 180224A: Swift detection of a burst with an optical counterpart DATE: 18/02/24 22:32:57 GMT FROM: Scott Barthelmy at NASA/GSFC A. Y. Lien (GSFC/UMBC), S. D. Barthelmy (GSFC), J.D. Gropp (PSU), H. A. Krimm (NSF/USRA), S. J. LaPorte (PSU), F. E. Marshall (NASA/GSFC), K. L. Page (U Leicester), D. M. Palmer (LANL) and A. Tohuvavohu (PSU) report on behalf of the Neil Gehrels Swift Observatory Team: At 22:21:07 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 180224A (trigger=811561). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 202.661, +38.088 which is RA(J2000) = 13h 30m 39s Dec(J2000) = +38d 05' 17" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve shows a single FRED peak with a duration of about 15 sec. The peak count rate was ~2200 counts/sec (15-350 keV), at ~1 sec after the trigger. The XRT began observing the field at 22:22:28.1 UT, 80.5 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source located at RA, Dec 202.68324, 38.07881 which is equivalent to: RA(J2000) = 13h 30m 43.98s Dec(J2000) = +38d 04' 43.7" with an uncertainty of 3.8 arcseconds (radius, 90% containment). This location is 71 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. 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 consistent with the Galactic value of 8.24 x 10^19 cm^-2 (Willingale et al. 2013). UVOT took a finding chart exposure of 150 seconds with the White filter starting 85 seconds after the BAT trigger. There is a candidate afterglow in the rapidly available 2.7'x2.7' sub-image at RA(J2000) = 13:30:44.09 = 202.68370 DEC(J2000) = +38:04:44.6 = 38.07906 with a 90%-confidence error radius of about 0.63 arc sec. This position is 0.9 arc sec. from the center of the XRT error circle. The estimated magnitude is 18.94 with a 1-sigma error of about 0.15. No correction has been made for the expected extinction corresponding to E(B-V) of 0.01. Burst Advocate for this burst is A. Y. Lien (amy.y.lien AT nasa.gov). 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/too.html.) //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 22443 SUBJECT: GRB 180224A: Enhanced Swift-XRT position DATE: 18/02/25 00:57:27 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 1326 s of XRT Photon Counting mode data and 2 UVOT images for GRB 180224A, 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 = 202.68383, +38.07876 which is equivalent to: RA (J2000): 13h 30m 44.12s Dec (J2000): +38d 04' 43.5" with an uncertainty of 1.7 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: 22444 SUBJECT: GRB180224A: Global MASTER-Net bright OT detection DATE: 18/02/25 10:33:21 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs V.Vladimirov, V. Lipunov, E.Gorbovskoy, N.Tyurina, V.Kornilov, D.Zimnukhov, A.Krylov, I.Gorbunov, P.Balanutsa, A.Kuznetsov, V.Chazov, D. Kuvshinov (Lomonosov Moscow State University, SAI) A. Tlatov, V.Senik, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory) D.Buckley, S. Potter (South African Astronomical Observatory), O.Gres, N.M.Budnev (Irkutsk State University), V.Yurkov, A.Gabovich, Yu.Sergienko (Blagoveschensk Educational State University, Blagoveschensk), R.Podesta, C.Lopez, F. Podesta (Observatorio Astronomico Felix Aguilar (OAFA), National University of San Juan, Argentina), H. Levato, C. Saffe (Instituto de Ciencias Astronomicas,de la Tierra y del Espacio (ICATE), San Juan, Argentina), R. Rebolo, M. Serra, N. Lodieu, G. Israelian, L. Suarez-Andres (The Instituto de Astrofisica de Canarias), MASTER-Kislovodsk (Russia) robotic telescope (MASTER-Net: http://observ.pereplet.ru) located in Kislovodsk was pointed to the GRB180224.93 21 sec after notice time and 37 sec after trigger time at 2018-02-24 22:21:44 UT. On our unfiltered polarizing exposures set we found 1 bright optical transient within SWIFT error-box (ra=202.658 dec=38.0878 r=0.05) brighter then 18.1. RA,DEC = 13h 30m 44.057s , +38d 04m 44.55 s Error = 0.1 arcsec maximal magnitute ~ 16.7 The 5-sigma upper limit has been about 18.1mag The message may be cited. ==================================================================== The observations made on zenit distance = 23 degrees, galaxy latitude b = 76 degree. The moon (68 % bright part) is 16 degrees above the horizon. The distance between moon and object is 97 degrees. The sun altitude is -53.0 degree. The object can be observed till sunrise at 2018-02-25 03:53:29 UT. MASTER-SAAO robotic telescope (MASTER-Net: http://observ.pereplet.ru) located in SAAO was pointed to the GRB180224.94 92 sec after notice time and 176 sec after trigger time at 2018-02-24 22:24:12 UT. On our first set we not found optical transient within SWIFT error-box (ra=202.638 dec=38.0819 r=0.1) brighter then 15.8. The 5-sigma upper limit has been about 15.8 mag The message may be cited. The observations made on high zenit distance = 82 degrees, galaxy latitude b = 76 degree. The moon (68 % bright part) is 6 degrees above the horizon. The distance between moon and object is 97 The sun altitude is -48.3 degree. The object can be observed till sunrise at 2018-02-25 04:21:26. This message can be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 22445 SUBJECT: GRB 180224A: Swift-XRT refined Analysis DATE: 18/02/25 13:55:08 GMT FROM: Phil Evans at U of Leicester A. Melandri (INAF-OAB), P. D'Avanzo (INAF-OAB), B. Sbarufatti (INAF-OAB/PSU), D.N. Burrows (PSU), A. Tohuvavohu (PSU), S.L. Gibson (U. Leicester), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), V. D'Elia (ASDC) and A.Y. Lien report on behalf of the Swift-XRT team: We have analysed 7.2 ks of XRT data for GRB 180224A (Lien et al. GCN Circ. 22442), from 84 s to 47.4 ks after the BAT trigger. The data comprise 35 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. 22443). The light curve can be modelled with an initial power-law decay with an index of alpha=0.70 (+/-0.08), followed by a break at T+3451 s to an alpha of 2.00 (+0.30, -0.25). A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 1.65 (+0.17, -0.16). The best-fitting absorption column is 9.2 (+5.4, -4.7) x 10^20 cm^-2, in excess of the Galactic value of 8.2 x 10^19 cm^-2 (Willingale et al. 2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 4.1 x 10^-11 (4.6 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 9.2 (+5.4, -4.7) x 10^20 cm^-2 Galactic foreground: 8.2 x 10^19 cm^-2 Excess significance: 2.9 sigma Photon index: 1.65 (+0.17, -0.16) If the light curve continues to decay with a power-law decay index of 2.00, the count rate at T+24 hours will be 5.7 x 10^-4 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 2.3 x 10^-14 (2.6 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/00811561. This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 22446 SUBJECT: GRB 180224A: RATIR Optical Observations DATE: 18/02/25 17:01:05 GMT FROM: Alan M. Watson at Instituto de Astronomia 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 180224A (Lien et al., GCN 22442) 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 2018/02 25.23 to 2018/02 25.53 UTC (7.24 to 14.42 hours after the BAT trigger), obtaining a total of 3.91 hours exposure in the r and i bands. We detect a source at 13:30:44.11 38:04:44.2 (J2000, ± 0.5 arcsec), within the Swift-XRT error circle, in comparison with the SDSS DR9, with the following magnitudes: r = 22.94 +/- 0.13 i = 22.08 +/- 0.06 These magnitudes are in the AB system and are not corrected for Galactic extinction in the direction of the GRB. The position and magnitudes of this source are consistent with the SDSS DR9 galaxy SDSS J133044.06+380443.0, which has r = 22.56 +/- 0.18 and i = 21.83 +/- 0.14. We suggest that this might be the host galaxy of the GRB. Vladimirov et al. (GCN 22444) report a early 16.1 mag transient in the Swift XRT error circle. Our non-detection 7 hours later suggests that the afterglow faded extremely quickly. We thank the staff of the Observatorio Astronómico Nacional in San Pedro Mártir. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 22447 SUBJECT: GRB 180224A: Swift-BAT refined analysis DATE: 18/02/25 18:19:11 GMT FROM: Amy Lien at GSFC T. Sakamoto (AGU), 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), 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 180224A (trigger #811561) (Lien et al., GCN Circ. 22442). The BAT ground-calculated position is RA, Dec = 202.675, 38.073 deg which is RA(J2000) = 13h 30m 41.9s Dec(J2000) = +38d 04' 23.0" with an uncertainty of 1.3 arcmin, (radius, sys+stat, 90% containment). The partial coding was 93%. The mask-weighted light curve shows a FRED-like pulse that starts at ~ T0, peaks at ~ T+1 s, and ends at ~T+15 s. T90 (15-350 keV) is 10.9 +- 3.6 sec (estimated error including systematics). The time-averaged spectrum from T-0.48 to T+14.57 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 2.11 +- 0.18. The fluence in the 15-150 keV band is 4.7 +- 0.5 x 10^-7 erg/cm2. The 1-sec peak photon flux measured from T+0.40 sec in the 15-150 keV band is 1.4 +- 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/811561/BA/ //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 22448 SUBJECT: GRB 180224A: AbAO optical observations DATE: 18/02/25 20:06:13 GMT FROM: Alexei Pozanenko at IKI, Moscow E. Mazaeva (IKI), A. Pozanenko (IKI), A. Volnova (IKI), R. Inasaridze (AbAO), V. Ayvazian (AbAO), O. Kvaratskhelia (AbAO), G. Inasaridze (AbAO), I. Molotov (KIAM), report on behalf of larger GRB follow-up collaboration: We observed the field of GRB 180224A (Lien et al., GCN 22442) with AS-32 (0.7m) telescope of Abastumani Observatory starting on Feb. 25 (UT) 01:07:37. The afterglow of GRB 180224A (Lien et al., GCN 22442; Vladimirov et al., GCN 22444) is clearly detected in a stacked image. Preliminary photometry is following. Date UT start t-T0 Filter Exp. OT Err. UL (mid, days) (s) 2018-02-25 01:07:37 0.15162 CR 60*60 21.88 0.15 22.6 The photometry is based on nearby SDSS DR9 stars SDSS_id R_Lupton J133038.17+380528.6 17.45 J133040.16+380535.7 17.10 J133051.85+380146.4 17.91 We confirm the fast decay of the afterglow and possible host galaxy association SDSS DR9 J133044.06+380443.0 with the afterglow source (Watson et al., GCN 22446). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 22452 SUBJECT: GRB 180224A: OASDG optical observations DATE: 18/02/26 10:10:08 GMT FROM: Luca Izzo at IAA-CSIC L. Izzo (IAA-CSIC), A. Noschese (AC-OASDG) report: We observed the field of GRB 180224A (Lien et al. GCN 22442) with the 0.5m telescope of the Osservatorio Astronomico S. Di Giacomo located in Agerola, Italy ( http://acgo.it/oa ). We obtained a series of 9x180 s images in the Rc filter, starting at 23:33:36 UT, ~ 1.21 hrs after the GRB detection. In our stacked image, we find no source at the position of the observed optical counterpart (Vladimirov et al. GCN 22444, Watson et al. GCN 22446, Mazaeva et al. GCN 22448) down to a 3-sigma limit of Rc (Vega) > 20.2. The calibration was performed using nearby stars in the USNO B1 catalog. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 22454 SUBJECT: GRB 180224A: Swift/UVOT Detection DATE: 18/02/26 17:54:14 GMT FROM: Sam LaPorte at PSU GRB 180224A: Swift/UVOT Detection S. J. LaPorte (PSU) and A. Y. Lien (GSFC/UMBC) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 180224A 85 s after the BAT trigger (Lien et al., GCN Circ. 22442). A fading source consistent with the XRT position (Evans et al. GCN Circ. 22443) also detected by (Lipunov et al. GCN Circ. 22444; Watson et al. GCN Circ. 22446; Pozanenko et al. GCN Circ. 22448) is detected in the initial UVOT exposures. The preliminary UVOT position is: RA (J2000) = 13:30:44.10 = 202.68377 (deg.) Dec (J2000) = +38:04:44.5 = 38.07902 (deg.) with an estimated uncertainty of 0.46 arc sec. (radius, 90% confidence). Preliminary detections and 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the early exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag white 61 211 294 18.9 +/- 0.07 white 553 5337 287 20.7 +/- 0.33 v 603 1397 97 >18.4 b 552 1348 78 >19.5 u 273 5063 500 >20.3 w1 652 1446 97 >18.7 m2 824 844 19 >18.2 w2 751 771 19 >17.6 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.01 in the direction of the burst (Schlegel et al. 1998).