GRB180720B

This page lists all entries on GRB180720B in GRBweb

Summary Fermi GBM IPN Swift Fermi LAT GCN 22973 GCN 22975 GCN 22976 GCN 22977 GCN 22979 GCN 22980 GCN 22981 GCN 22983 GCN 22984 GCN 22985 GCN 22986 GCN 22988 GCN 22993 GCN 22996 GCN 22998 GCN 23004 GCN 23011 GCN 23017 GCN 23019 GCN 23020 GCN 23021 GCN 23023 GCN 23024 GCN 23033 GCN 23036 GCN 23037 GCN 23040 GCN 23041 GCN 23042 GCN 23073

Summary table
Variable Value Source
GRB_name_Fermi GRB180720598
T0 14:21:39 UTC Fermi_LAT
ra 0.5286° Swift
decl -2.9189° Swift
pos_error 4.53e-04° Swift
T90 48.897 s Fermi_GBM
T90_error 0.362 s Fermi_GBM
T90_start 14:21:44.006 UTC Fermi_GBM
fluence 2.99e-04 erg/cm² Fermi_GBM
fluence_error 9.03e-08 erg/cm² Fermi_GBM
redshift 0.6540 GCN_circulars,Konus-Wind Det
T100 53.903 s
GBM_located False
mjd 58319.59836805556 Fermi_LAT
Fermi GBM table
GRB_name_Fermi GRB180720598
trigger_name bn180720598
ra 0.5279°
decl -2.9169°
pos_error 2.48e+00°
datum 2018-07-20
t_trigger 14:21:39.654 UTC
T90 48.897 s
T90_error 0.362 s
T90_start 14:21:44.006 UTC
fluence 2.99e-04 erg/cm²
fluence_error 9.03e-08 erg/cm²
flux_1024 1.25e+02 erg/cm²/s
flux_1024_error 5.91e-01 erg/cm²/s
flux_1024_time 1.59e+01 erg/cm²/s
flux_64 1.71e+02 erg/cm²/s
flux_64_error 2.66e+00 erg/cm²/s
IPN table
GRB_name GRB180720B
ra 0.5292°
decl -2.9333°
pos_error 5.00e-02°
redshift 0.6540
Swift table
GRB_name GRB180720B
t_trigger 14:21:44 UTC
ra 0.5286°
decl -2.9189°
pos_error 4.53e-04°
fluence 8.60e-05 erg/cm²
redshift 0.6540
Fermi LAT table
GRB_name_Fermi GRB180720598
GRB_name GRB180720B
MET 553789304.0
datum 2018-07-20
t_trigger 14:21:39 UTC
ra 0.5286°
decl -2.9189°
pos_error 9.30e-04°
GCN 22973 table
GRB_name GRB180720B
GCN_number 22973
Detection_method Swift Det
t_trigger 14:21:44 UTC
ra 0.5300°
decl -2.9330°
Circular_text TITLE: GCN CIRCULAR NUMBER: 22973 SUBJECT: GRB 180720B: Swift detection of a burst DATE: 18/07/20 14:34:56 GMT FROM: David Palmer at LANL M. H. Siegel (PSU), D. N. Burrows (PSU), A. Deich (PSU), J.D. Gropp (PSU), J. A. Kennea (PSU), S. J. LaPorte (PSU), A. Y. Lien (GSFC/UMBC), M. J. Moss (George Washington University), K. L. Page (U Leicester), D. M. Palmer (LANL), B. Sbarufatti (PSU) and A. Tohuvavohu (PSU) report on behalf of the Neil Gehrels Swift Observatory Team: At 14:21:44 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 180720B (trigger=848890). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 0.530, -2.933 which is RA(J2000) = 00h 02m 07s Dec(J2000) = -02d 56' 00" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a multi-peaked structure with a duration of about 150 sec. The peak count rate was ~50000 counts/sec (15-350 keV), at ~11 sec after the trigger. The XRT began observing the field at 14:23:11.0 UT, 86.5 seconds after the BAT trigger. XRT found a bright, flaring and fading uncatalogued X-ray source located at RA, Dec 0.5279, -2.9170 which is equivalent to: RA(J2000) = +00h 02m 6.70s Dec(J2000) = -02d 55' 01.2" with an uncertainty of 5.0 arcseconds (radius, 90% containment). This location is 58 arcseconds from the BAT onboard position, within the BAT error circle. No event data are yet available to determine the column density using X-ray spectroscopy. The initial flux in the 0.1 s image was 6.59e-08 erg cm^-2 s^-1 (0.2-10 keV). No UVOT data is available yet. Burst Advocate for this burst is M. H. Siegel (siegel AT swift.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/too.html.) [GCN OPS NOTE(21jul18): In response to GCN Circular 22975, this archived copy of 22973 has been modified with the correct GRB maining "A" --> "B".]
GCN 22975 table
GRB_name GRB180720B
GCN_number 22975
Detection_method Swift Other
Circular_text TITLE: GCN CIRCULAR NUMBER: 22975 SUBJECT: Correction: Swift trigger #848890 is GRB 180720B (not GRB 180720A) DATE: 18/07/20 14:48:26 GMT FROM: Amy Lien at GSFC M. H. Siegel (PSU), D. N. Burrows (PSU), A. Deich (PSU), J.D. Gropp (PSU), J. A. Kennea (PSU), S. J. LaPorte (PSU), A. Y. Lien (GSFC/UMBC), M. J. Moss (George Washington University), K. L. Page (U Leicester), D. M. Palmer (LANL), B. Sbarufatti (PSU) and A. Tohuvavohu (PSU) report on behalf of the Neil Gehrels Swift Observatory Team: The GRB name in GCN Circ. #22973 should be GRB 180720B because of an earlier detection of GRB 180720A from AGILE/MCAL (GCN Circ. #22970). We apologize for the mistake and any confusion caused by this.
GCN 22976 table
GRB_name GRB180720B
GCN_number 22976
Detection_method Optical
ra 0.5286°
decl -2.9181°
Circular_text TITLE: GCN CIRCULAR NUMBER: 22976 SUBJECT: GRB 180720B: LCO Haleakala possible bright optical candidate DATE: 18/07/20 15:30:47 GMT FROM: Renato Martone at Universita' di Ferrara R. Martone, C. Guidorzi (U. Ferrara), S. Kobayashi (LJMU), C.G. Mundell (U. Bath), A. Gomboc (U. Nova Gorica), I.A. Steele (LJMU), A. Cucchiara, D. Morris (U. of Virgin Islands) on behalf of a large collaboration report: The LCO 2-m unit at Haleakala Observatory (Hawaii) began observing Swift GRB180720B (Siegel et al. GCN 22973) on July 20, 14:33:34 UT (11.8 minutes after the GRB trigger time) with the SDSS i' filter. On the border of the Swift-XRT error circle, we detect a 13-mag uncatalogued object at the following position: RA(J2000)= +00:02:06.87 DEC(J2000)= -02:55:05.2 with an error radius of ~1” as calibrated against nearby SDSS stars.
GCN 22977 table
GRB_name GRB180720B
GCN_number 22977
Detection_method Optical
Circular_text TITLE: GCN CIRCULAR NUMBER: 22977 SUBJECT: GRB 180720B: Kanata 1.5m optical/NIR observation DATE: 18/07/20 16:21:08 GMT FROM: Koji Kawabata at HASC,Hiroshima U M. Sasada, T. Nakaoka, M. Kawabata, N. Uchida, Y. Yamazaki, K. S. Kawabata (Hiroshima Univ.) report on behalf of Kanata team: We performed optical and NIR imaging polarimetry to the field of the GRB 180720B (Siegel et al. GCN 22973; Martone et al. GCN 22976) from 2018-07-20 14:22:57 UT (73 seconds after the trigger) with HOWPol and HONIR attached to the 1.5-m Kanata telescope at Higashi-Hiroshima Observatory, Japan. We detected a bright optical counterpart of the GRB within the the Swift-XRT error circle of the X-ray afterglow. The magnitude of the optical counterpart was R~9.4 mag in our first frame taken with 30 second exposure and then smoothly declined. Further analysis is ongoing.
GCN 22979 table
GRB_name GRB180720B
GCN_number 22979
Detection_method Optical
Circular_text TITLE: GCN CIRCULAR NUMBER: 22979 SUBJECT: GRB 180720B : TSHAO optical observations DATE: 18/07/20 21:36:57 GMT FROM: Alexei Pozanenko at IKI, Moscow I. Reva (FAPHI), A. Pozanenko (IKI), A. Volnova (IKI), E. Mazaeva (IKI), A. Kusakin (FAPHI), M. Krugov (FAPHI) report on behalf of larger GRB follow-up collaboration: We observed the field of GRB 180720B (Siegel et al., GCN 22973) with Zeiss-1000 telescope of Tien Shan Astronomical Observatory starting on July 20 (UT) 19:46:17. We obtained several images in R and B-filters. The optical afterglow (Martone et al. GCN 22976; Sasadaet al., GCN 22977) is clearly detected in both filters. Preliminary photometry of the afterglow at (UT, mid time) 19:59 is R =17.1 +/- 0.1. The photometry is based on nearby USNO-B1.0 (R2) stars.
GCN 22980 table
GRB_name GRB180720B
GCN_number 22980
Detection_method Fermi LAT Det
t_trigger 14:21:44.550 UTC
ra 0.5800°
decl -2.9500°
Circular_text TITLE: GCN CIRCULAR NUMBER: 22980 SUBJECT: GRB 180720B : Fermi-LAT detection DATE: 18/07/20 22:28:56 GMT FROM: Elisabetta Bissaldi at INFN,Bari E. Bissaldi (Politecnico & INFN Bari) and J. L. Racusin (NASA/GSFC) report on behalf of the Fermi-LAT team: "At 14:21:44.55 UT on July 20, 2018, Fermi-LAT detected high-energy emission from GRB 180720B, which was also detected by Swift (Siegel et al. 2018, GCN 22973) and by Fermi-GBM (trigger 553789304 / 180720598). The best LAT on-ground location is found to be RA, Dec = 0.58, -2.95 (J2000) with an error radius of 0.11 deg (90 % containment, statistical error only). This was 50 deg from the LAT boresight at the time of the trigger. The data from the Fermi-LAT show a significant increase in the event rate that is spatially and temporally correlated with the trigger with very high significance. The highest-energy photon is a 5 GeV event which is observed 137 seconds after the GBM trigger. Given that GRB 180720B is detected by both Swift and Fermi, and it is very bright in the LAT, we encourage follow-up observations. The Fermi-LAT point of contact for this burst is Elisabetta Bissaldi (elisabetta.bissaldi@ba.infn.it). The Fermi-LAT is a pair conversion telescope designed to cover the energy band from 20 MeV to greater than 300 GeV. It is the product of an international collaboration between NASA and DOE in the U.S. and many scientific institutions across France, Italy, Japan and Sweden."
GCN 22981 table
GRB_name GRB180720B
GCN_number 22981
Detection_method Fermi GBM Det
t_trigger 14:21:39.650 UTC
Circular_text TITLE: GCN CIRCULAR NUMBER: 22981 SUBJECT: GRB 180720B: Fermi GBM observation DATE: 18/07/20 22:50:18 GMT FROM: Oliver J Roberts at USRA/NASA O.J. Roberts (USRA/NASA) and C. Meegan (UAH) report on behalf of the Fermi GBM Team: "At 14:21:39.65 UT on 20 July 2018, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 180720B (trigger 553789304 / 180720598), which was also detected by Swift (Siegel et al. 2018, GCN 22973/22975) and the LAT (Bissaldi et al., GCN 22980). The GBM on-ground location is consistent with the Swift position. The angle from the Fermi LAT boresight at the GBM trigger time using the Swift-XRT position is 50 degrees. The GBM light curve consists of a very bright, FRED-like peak with numerous overlapping pulses with a duration (T90) of 49 s (50-300 keV). The time-averaged spectrum from T0 to T0+55 s is best fit by a Band function with Epeak = 631 +/- 10 keV, alpha = -1.11 +/- 0.01 and beta = -2.30 +/- 0.03. The event fluence (10-1000 keV) over the T90 interval is (2.985 +/- 0.001)E-04 erg/cm^2. The 1-sec peak photon flux measured starting from T0+4.4 s in the 10-1000 keV band is 125 +/- 1 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."
GCN 22983 table
GRB_name GRB180720B
GCN_number 22983
Detection_method MITSuME
Circular_text TITLE: GCN CIRCULAR NUMBER: 22983 SUBJECT: GRB 180720B: MITSuME Akeno optical observations DATE: 18/07/21 02:16:27 GMT FROM: Ryosuke Itoh at Tokyo Institute of Tech. R. Itoh, K. L. Murata, Y. Tachibana, S. Harita, K. Morita, K. Shiraishi, K. Iida, M. Oeda, R. Adachi, S. Niwano, Y. Yatsu, and N. Kawai (Tokyo Tech) report on behalf of the MITSuME collaboration: We observed the optical counterpart of GRB 180720B (Siegel et al., GCN 22973) with the optical three color (g', Rc, and Ic) CCD cameras attached to the MITSuME 50cm telescope of Akeno Observatory, Yamanashi, Japan. The observation started on 2018-07-20 18:08:46 UT, (~3.8 hours after the burst). We detected the previously reported afterglow (Martone et al., GCN 22976, Sasada et al., GCN 22977, Reva et al., GCN 22979) in the g', Rc and Ic band. The photometric results of the OT are listed below. We used UCAC-4 catalog for flux calibration. #T0+[hour] MID-UT T-EXP[sec] g' Rc Ic ------------------------------------------------------------------- 3.8 18:14:30 540 16.53+/-0.06 16.67+/-0.06 16.25+/- 0.08 ------------------------------------------------------------------- T0+ : Elapsed time after the burst [hour] T-EXP: Total Exposure time [sec]
GCN 22984 table
GRB_name GRB180720B
GCN_number 22984
Detection_method Swift-XRT Other
ra 0.5286°
decl -2.9189°
Circular_text TITLE: GCN CIRCULAR NUMBER: 22984 SUBJECT: GRB 180720B: Swift-XRT refined Analysis DATE: 18/07/21 02:17:13 GMT FROM: Phil Evans at U of Leicester K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester), V. D'Elia (ASDC), A. D'Ai (INAF-IASFPA), A. Melandri (INAF-OAB), A. Tohuvavohu (PSU), S. J. LaPorte (PSU), J.A. Kennea (PSU), P.A. Evans (U. Leicester) and M.H. Siegel report on behalf of the Swift-XRT team: We have analysed 7.2 ks of XRT data for GRB 180720B (Siegel et al. GCN Circ. 22973), from 90 s to 19.4 ks after the BAT trigger. The data comprise 3.3 ks in Windowed Timing (WT) mode with the remainder in Photon Counting (PC) mode. The refined XRT position is RA, Dec = 0.5286, -2.9189 which is equivalent to: RA (J2000): 00 02 06.86 Dec(J2000): -02 55 08.1 with an uncertainty of 3.5 arcsec (radius, 90% confidence). The late-time light curve (from T0+5.6 ks) can be modelled with an initial power-law decay with an index of alpha=1.18 (+0.16, -0.28), followed by a break at T+7030 s to an alpha of -0.17 (+0.26, -1.33). A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 1.770 (+/-0.011). The best-fitting absorption column is 1.42 (+/-0.04) x 10^21 cm^-2, in excess of the Galactic value of 3.9 x 10^20 cm^-2 (Willingale et al. 2013). The PC mode spectrum has a photon index of 1.85 (+/-0.07) and a best-fitting absorption column of 1.75 (+0.23, -0.22) x 10^21 cm^-2. The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.8 x 10^-11 (4.9 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 1.75 (+0.23, -0.22) x 10^21 cm^-2 Galactic foreground: 3.9 x 10^20 cm^-2 Excess significance: 10.1 sigma Photon index: 1.85 (+/-0.07) If the light curve continues to decay with a power-law decay index of -0.17, the count rate at T+24 hours will be 21 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 8.4 x 10^-10 (1.1 x 10^-9) erg cm^-2 s^-1. The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00848890. This circular is an official product of the Swift-XRT team. [GCN OPS NOTE(21jul18): In response to GCN Circular 22986, this archived copy of 22984 has been modified with the correct GRB maining "A" --> "B".]
GCN 22985 table
GRB_name GRB180720B
GCN_number 22985
Detection_method Fermi LAT Det
Circular_text TITLE: GCN CIRCULAR NUMBER: 22985 SUBJECT: GRB 180720B: OSN detection, fading slower? DATE: 18/07/21 02:51:06 GMT FROM: Alexander Kann at IAA-CSIC D. A. Kann, L. Izzo (both HETH/IAA-CSIC), V. Casanova (IAA-CSIC), and A. de Ugarte Postigo (HETH-IAA/CSIC and DARK/NBI) report on behalf of HETH: We observed the position of the extremely bright GRB 180720B (Swift-BAT detection: Siegel et al., GCN #22973, GCN #22975; Fermi-LAT detection: Bissaldi and Racusin, GCN #22980; Fermi-GBM detection: Roberts et al., GCN #22981) with the T90 telescope of the Observatorio Sierra Nevada (OSN) near Granada, Spain. The optical afterglow (Martone et al., GCN #22976; Sasada et al., GCN #22977; Reva et al., GCN #22979; Itoh et al., GCN #22983) is clearly detected in single 180 s images. For an Rc image at mid-time 0.455188 days after the INTEGRAL SPI/ACS trigger (14:21:40 UT), we derive Rc = 17.53 +/- 0.03 mag. We note that this is only ~0.4 mag fainter than the value found by Reva et al. at 0.23 days after the GRB, indicating the decay may have slowed down. This feature also seems to be seen in the XRT light curve (Page et al., GCN #22984). Further observations, even with smaller telescopes, are strongly encouraged. Magnitudes were obtained against SDSS standard stars transformed following the equations of Lupton (2005). [GCN OPS NOTE(21jul18): Due to a processing problem with some in-line UTF formatting characters, the "slower?" was deleted from the SUBJECT-line in the distributed circulars. It has been replaced in these archived copies.] [GCN OPS NOTE(21jul18): Per author's request, A. de U.P. was added to the author list.]
GCN 22986 table
GRB_name GRB180720B
GCN_number 22986
Detection_method Swift-XRT Other
Circular_text TITLE: GCN CIRCULAR NUMBER: 22986 SUBJECT: GCN 22984 was for GRB 180720B DATE: 18/07/21 02:59:07 GMT FROM: Phil Evans at U of Leicester P. A. Evans (U Leicester) reports on behalf of the Swift-XRT team : The XRT refined analysis reported in GCN Circ. 22984 was the analysis of GRB 180720B, not A as reported in the circular. Apologies for the confusion.
GCN 22988 table
GRB_name GRB180720B
GCN_number 22988
Detection_method Optical
Circular_text TITLE: GCN CIRCULAR NUMBER: 22988 SUBJECT: GRB 180720B: LCO optical afterglow observations DATE: 18/07/21 04:59:42 GMT FROM: Daniele Malesani at Dark Cosmology Centre, Niels Bohr Inst Nicolas Crouzet (IAC) and Daniele B. Malesani (DAWN/NBI and DARK/NBI) report: We observed the optical afterglow of GRB 180720B (Siegel et al., GCN 22973; Martone et al., GCN 22976) using the 0.4-m telescope located at the Teide Observatory, part of the Las Cumbres Observatory (LCO) telescope network. A single 600-s exposure in the SDSS r band was obtained with mean time July 21.094 UT (0.495 days after the GRB). The PSF of the image is not optimal, being double-peaked. Aperture photometry, compared to nearby stars from the Pan-STARRS catalog, provides for the afterglow a preliminary magnitude r = 17.85 +- 0.10 AB.
GCN 22993 table
GRB_name GRB180720B
GCN_number 22993
Detection_method MAXI Det
t_trigger 14:28:15 UTC
ra 0.4670°
decl -2.8460°
Circular_text TITLE: GCN CIRCULAR NUMBER: 22993 SUBJECT: GRB 180720B: MAXI/GSC detection DATE: 18/07/21 11:19:21 GMT FROM: H. Negoro at Nihon U. H. Negoro (Nihon U.), A. Tanimoto (Kyoto U.), M. Nakajima, W. Maruyama, A. Sakamaki (Nihon U.), T. Mihara, S. Nakahira, F. Yatabe, Y. Takao, M. Matsuoka (RIKEN), N. Kawai, M. Sugizaki, Y. Tachibana, K. Morita (Tokyo Tech), T. Sakamoto, M. Serino, S. Sugita, Y. Kawakubo, T. Hashimoto, A. Yoshida (AGU), S. Ueno, H. Tomida, M. Ishikawa, Y. Sugawara, N. Isobe, R. Shimomukai (JAXA), Y. Ueda, T. Morita, S. Yamada (Kyoto U.), Y. Tsuboi, W. Iwakiri, R. Sasaki, H. Kawai, T. Sato (Chuo U.), H. Tsunemi, T. Yoneyama (Osaka U.), M. Yamauchi, K. Hidaka, S. Iwahori (Miyazaki U.), T. Kawamuro (NAOJ), K. Yamaoka (Nagoya U.), M. Shidatsu (Ehime U.) report on behalf of the MAXI team: The MAXI/GSC nova alert system triggered on GRB 180720B (Siegel et al., GCN 22973/20975; Bissaldi et al., GCN 22980; Roberts et al., GCN 22981) at 14:28:15 UT on 2018 July 20, 396 sec after the Fermi/GRB trigger. Assuming that the source flux was constant over the transit, we obtain the source position at (R.A., Dec) = (0.467 deg, -2.846 deg) = (00 01 52, -02 50 45) (J2000) with a statistical 90% C.L. elliptical error region with long and short radii of 0.21 deg and 0.16 deg, respectively. The roll angle of the long axis from the north direction is 166.0 deg counterclockwise. There is an additional systematic uncertainty of 0.1 deg (90% containment radius). The above position is 5.6 arcminutes from the Swift/XRT position of GRB 180720B (Siegel et al. GCN 22973). The X-ray flux averaged over the scan was 191 +- 27 mCrab (4.0-10.0keV, 1 sigma error). MAXI/GSC also detected the source at 25 +/- 12 mCrab in the next scan transit at 16:01. The 2-20 keV GSC spectrum obtained in the scan transit at 14:28 is well described by an absorbed power-law with a photon index of 2.11 +/- 0.25 with n_H fixed at the total Galactic column density to the direction of 3.5e20 atoms/cm2.
GCN 22996 table
GRB_name GRB180720B
GCN_number 22996
Detection_method Optical
Circular_text TITLE: GCN CIRCULAR NUMBER: 22996 SUBJECT: GRB 180720B: VLT/X-shooter redshift DATE: 18/07/21 14:34:50 GMT FROM: Daniele Malesani at Dark Cosmology Centre, Niels Bohr Inst P. M. Vreeswijk (Radboud Univ. Nijmegen), D. A. Kann (HETH/IAA-CSIC), K. E. Heintz (Univ. Iceland and DAWN/NBI), A. de Ugarte Postigo (HETH-IAA/CSIC and DARK/NBI), B. Milvang-Jensen (DAWN/NBI), D. B. Malesani (DARK/NBI and DAWN/NBI), S. Covino (INAF/Brera), A. J. Levan (Univ. Warwick), G. Pugliese (Amsterdam), report on behalf of the Stargate collaboration: We observed the optical counterpart of GRB 180720B (Siegel et al., GCN 22973; Martone et al., GCN 22976) with the ESO VLT UT2 equipped with the X-shooter spectrograph. Two spectra of 600 s each were secured starting on 2018 July 21.384 UT (0.786 days after the GRB), covering the wavelength range 3000-25000 AA. A bright continuum is detected across the entire observed range. Several absorption features are detected, which can be identified as due to Fe II, Mg II, Mg I, and Ca II, all at z = 0.654. We also identify fine-structure transitions due to both Fe II* and Ni II**, thus making the redshift association with the GRB secure. We acknowledge the ESO observing staff at Paranal, in particular Juan Carlos Munoz, Emanuela Pompei, and Luca Sbordone.
GCN 22998 table
GRB_name GRB180720B
GCN_number 22998
Detection_method Swift-BAT Det
ra 0.5280°
decl -2.9250°
Circular_text TITLE: GCN CIRCULAR NUMBER: 22998 SUBJECT: GRB 180720B: Swift-BAT refined analysis DATE: 18/07/21 17:11:45 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), T. Sakamoto (AGU), M. H. Siegel (PSU), M. Stamatikos (OSU), T. N. Ukwatta (LANL) (i.e. the Swift-BAT team): Using the data set from T-240 to T+962 sec from the recent telemetry downlink, we report further analysis of BAT GRB 180720B (trigger #848890) (Siegel et al., GCN Circ. 22973). The BAT ground-calculated position is RA, Dec = 0.528, -2.925 deg which is RA(J2000) = 00h 02m 06.8s Dec(J2000) = -02d 55' 31.3" with an uncertainty of 1.2 arcmin, (radius, sys+stat, 90% containment). The partial coding was 8%. The mask-weighted light curve shows a multi-peaked structure, with the main peak occurs around ~T+11 s. The burst emission starts around ~T-20 s, although there might be additional emission before the GRB came into the BAT FOV at ~T-57 s. The burst lasts beyond the available event data range (until T+962 s). Analysis using the BAT survey data shows that the burst emission extends at least till ~ T+2000 s, when Swift went into SAA and no more data were collected. The burst came back into the BAT FOV at ~ T0+5626 s, and the burst was no longer detected (signal-to-noise ratio < 3 sigma). The time-averaged spectrum from T-20.0 to T+961.1 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.36 +- 0.03. The fluence in the 15-150 keV band is 8.6 +- 0.1 x 10^-05 erg/cm2. The 1-sec peak photon flux measured from T+10.94 sec in the 15-150 keV band is 67.9 +- 2.6 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/848890/BA/
GCN 23004 table
GRB_name GRB180720B
GCN_number 23004
Detection_method MITSuME
Circular_text TITLE: GCN CIRCULAR NUMBER: 23004 SUBJECT: GRB 180720B: MITSuME Ishigaki optical observations DATE: 18/07/22 00:04:42 GMT FROM: Ryosuke Itoh at Tokyo Institute of Tech. T. Horiuchi, H. Hanayama, M. Honma (IAO, NAOJ), R. Itoh, K. L. Murata, Y. Tachibana, S. Harita, K. Morita K. Shiraishi, K. Iida, M. Oeda, R. Adachi, S. Niwano, Y. Yatsu, and N. Kawai (Tokyo Tech) report on behalf of the MITSuME collaboration: We observed the optical counterpart of GRB 180720B (Siegel et al., GCN 22973) with the optical three color (g', Rc, and Ic) CCD cameras attached to the Murikabushi 1m telescope of Ishigakijima Astronomical Observatory, Japan. The observation started on 2018-07-20 17:11:26 UT, (~2.8 hours after the burst). We detected the previously reported afterglow (Martone et al., GCN 22976, Sasada et al., GCN 22977, Reva et al., GCN 22979) in the Rc and Ic band. The photometric results of the OT are listed below. We used UCAC-4 catalog for flux calibration. #T0+[hour] MID-UT T-EXP[sec] Rc Ic ------------------------------------------------------------------- 2.8 17:14:58 240 16.23+/-0.03 16.24+/-0.05 ------------------------------------------------------------------- T0+ : Elapsed time after the burst [hour] T-EXP: Total Exposure time [sec]
GCN 23011 table
GRB_name GRB180720B
GCN_number 23011
Detection_method Konus-Wind Det
t_trigger 14:21:45.261 UTC
redshift 0.6540
Circular_text TITLE: GCN CIRCULAR NUMBER: 23011 SUBJECT: Konus-Wind observation of GRB 180720B DATE: 18/07/22 13:43:39 GMT FROM: Dmitry Frederiks at Ioffe Institute D. Frederiks, S. Golenetskii, R.Aptekar, A. Kozlova, A.Lysenko, D. Svinkin, A. Tsvetkova, M. Ulanov, and T. Cline, on behalf of the Konus-Wind team, report: The long, extremely bright GRB 180720B (Swift-BAT detection: Siegel et al., GCN 22973, GCN 22975; Fermi-LAT detection: Bissaldi and Racusin, GCN 22980; Fermi-GBM detection: Roberts et al., GCN 22981) triggered Konus-Wind at T0=51705.261 s UT (14:21:45.261). The burst light curve shows a multi-peaked structure with a total duration (T100) of ~125 s. The emission is seen up to ~15 MeV. As observed by Konus-Wind, the burst had a fluence of (5.43 ± 0.26)x10^-4 erg/cm2 and a 64-ms peak energy flux, measured from T0+15.168, of (9.70 ± 0.52)x10^-5 erg/cm2 (both in the 20 keV - 10 MeV energy range). The time-integrated spectrum (measured from T0 to T0+119.808 s) is best fit in the 20 keV - 15 MeV range by the GRB (Band) function with the following model parameters: the low-energy photon index alpha = -1.01 (-0.06,+0.06), the high energy photon index beta = -2.07 (-0.08,+0.07), the peak energy Ep = 451 (-45,+52) keV, chi2 = 102/97 dof. The spectrum near the peak count rate (measured from T0+14.592 s to T0+15.360 s) is best fit in the 20 keV - 15 MeV range by the GRB (Band) function with the following model parameters: the low-energy photon index alpha = -0.82 (-0.09,+0.10), the high energy photon index beta = -2.27 (-0.22,+0.13), the peak energy Ep = 779 (-127,+169) keV, chi2 = 92/76 dof. Assuming the redshift z=0.654 (Vreeswijk et al., GCN 22996) and a standard cosmology model with H_0 = 70 km/s/Mpc, Omega_M = 0.30, and Omega_Lambda = 0.70, we estimate the following rest-frame parameters: the isotropic energy release E_iso is ~6.0x10^53 erg, the peak luminosity L_iso is ~1.8x10^53 erg/s, and the rest-frame peak energy of the time-integrated spectrum, Ep,z, is ~746 keV. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB180720_T51705/ All the quoted errors are estimated at the 90% confidence level. All the presented results are preliminary.
GCN 23017 table
GRB_name GRB180720B
GCN_number 23017
Detection_method Optical
Circular_text TITLE: GCN CIRCULAR NUMBER: 23017 SUBJECT: GRB 180720B: COATLI Optical Detection DATE: 18/07/22 20:52:09 GMT FROM: Alan M. Watson at Instituto de Astronomia UNAM Alan M. Watson (UNAM), Nat Butler (ASU), Rosa L. Becerra (UNAM), William H. Lee (UNAM), Carlos Román-Zúñiga (UNAM), Alexander Kutyrev (GSFC), and Eleonora Troja (GSFC) report: We observed the field of GRB 180720B (Siegel et al., GCN Circ. 22973) with the COATLI 50-cm telescope and interim imager at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir (http://coatli.astroscu.unam.mx) from 2018-07-22 06:25 to 11:23 UTC (from 40.07 to 45.03 hours after the trigger), obtaining a total of 4.06 hours of exposure in the w filter. We detect the optical counterpart (Martone et al., GCN Circ. 22976) with w = 20.07 +/- 0.02 These magnitudes are calibrated against the USNO-B1 catalog (adjusted to an approximate AB system) and are not corrected for Galactic extinction in the direction of the GRB. We thank the COATLI technical team (Fernando Ángeles, Oscar Chapa, Salvador Cuevas, Alejandro Farah, Jorge Fuentes, Rosalía Langarica, Fernando Quirós, and Carlos Tejada) and the staff of the Observatorio Astronómico Nacional.
GCN 23019 table
GRB_name GRB180720B
GCN_number 23019
Detection_method Optical
redshift 0.6540
Circular_text TITLE: GCN CIRCULAR NUMBER: 23019 SUBJECT: GRB 180720B: Testing the universality of the newly born neutron star in BdHNe DATE: 18/07/22 22:30:27 GMT FROM: Remo Rufinni at ICRA R. Ruffini, Y. Aimuratov, C. L. Bianco, Y. C. Chen, D. M. Fuksman, M. Karlica, R. Moradi, D. Primorac, J.A. Rueda, N. Sahakyan, Y. Wang, on behalf of the ICRANet team, report: GRB 180720B (Siegel et al., GCN 22973) is a long GRB with isotropic energy ~6.0e53 erg (Frederiks et al., GCN 23011). It belongs to the long GRB subclass of Binary Driven Hypernovae (BdHNe) (Ruffini et al., 2016, ApJ, 832, 136), with energies larger than 1e52 erg and GeV radiation, which allows the determination of the black hole mass (Ruffini et al., arXiv:1803.05476). It includes GRB 130427A associated to SN 2013cq (Ruffini et al., GCN 14526, Xu et al., GCN 14646), as well as GRB 160625B (Troja et al., 2017). The comparison of X-ray light-curves is attached [1], plotted in the rest frame of the sources. These sources are polar views from the normal to the plane of the binary progenitor (Ruffini et al., arXiv:1803.05476). In GRB 180720B, which has redshift z = 0.654 (GCN 22996), being a BdHN, a supernova is expected to peak, using the averaged observed value (Cano et al., 2016), at 21.8 +/ 4.3 day after the trigger (11 August 2018, uncertainty from August 7th to August 15th): the prolonged observations of the afterglow in all bands, especially the optical band, is recommended to further probe the nature of the supernova and of the newly born neutron star, strikingly constant in all BdHNe (see also Becerra et al., arXiv:1803.04356). [1] Link: http://www.icranet.org/documents/20180721.jpg Caption of figure: Three BdHNe with polar views from the normal to the plane of the binary progenitor, pointing to the similarities. GRB 130427A with redshift z=0.34 is associated to the companion supernova SN 2013cq. GRB 160625B has redshift z=1.406, which is too far for the optical observation of the associated supernova (Woosley & Bloom, 2006). GRB 180720B with redshift z=0.654 is expected to have the observation of an associated supernova.
GCN 23020 table
GRB_name GRB180720B
GCN_number 23020
Detection_method Optical
Circular_text TITLE: GCN CIRCULAR NUMBER: 23020 SUBJECT: GRB 180720B: ISON-Castelgrande optical observations DATE: 18/07/22 23:39:09 GMT FROM: Alexei Pozanenko at IKI, Moscow S. Schmalz (KIAM), F. Graziani (GAUSS). A. Pozanenko (IKI), A. Volnova (IKI), E. Mazaeva (IKI), I. Molotov (KIAM) report on behalf of larger GRB follow-up collaboration: We observed the field of GRB 180720B (Swift-BAT detection: Siegel et al., GCN 22973, GCN 22975; Fermi-LAT detection: Bissaldi and Racusin, GCN 22980; Fermi-GBM detection: Roberts et al., GCN 22981; MAXI/GSC detection: Negoro et al., GCN 22993; Konus-Wind detection: Frederiks et al., GCN 23011) with ORI-22 (22 cm) telescope of ISON-Castelgrande observatory starting on July 20 (UT) 23:04:30. We obtained 150 images of 60 s exposure in Clear filter. The optical afterglow (e.g. Martone et al. GCN 22976; Sasada et al., GCN 22977; Reva et al., GCN 22979; Itoh et al., GCN 22983; Kann et al., GCN 22985) is detected in separate images up to the end of series. The coordinates of the optical afterglow are (J2000) :02:06.792 -02:55:04:99 with uncertainties of about 0.5 arcsec in both coordinates. Preliminary photometry of the afterglow at (UT, mid time) 23:22:21 is R =17.40 +/- 0.15. The photometry is based on nearby USNO-B1.0 (R2) stars.
GCN 23021 table
GRB_name GRB180720B
GCN_number 23021
Detection_method Optical
Circular_text TITLE: GCN CIRCULAR NUMBER: 23021 SUBJECT: GRB 180720B: REM photometry DATE: 18/07/23 09:43:43 GMT FROM: Stefano Covino at Brera Astronomical Observatory S.Covino, D. Fugazza (INAF/OAB), on behalf of the REM team, report: We observed the field of GRB180720B (Siegel et al. GCN 22973) with the REM 60cm robotic telescope located at the ESO premise of La Silla (Chile). The observations were performed starting from about 13.5 hours after the event and were carried in the g, r, i, z, J, H and K bands. The optical counterpart (Martone et al. GCN 22976) is still detected in the optical and in the NIR bands. A preliminary photometry on the first H band set of frame gives: H = 15.65 +- 0.22 at 13.7 hours from the GRB time. Magnitudes are calibrated against the 2MASS catalogue.
GCN 23023 table
GRB_name GRB180720B
GCN_number 23023
Detection_method Optical
ra 0.5288°
decl -2.9182°
Circular_text TITLE: GCN CIRCULAR NUMBER: 23023 SUBJECT: GRB 180720B: MASTER Global Net OT observations DATE: 18/07/23 11:57:20 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs V. Lipunov, E. Gorbovskoy, N.Tiurina, D.Vlasenko, V.Kornilov, A.Kuznetsov, V.Chazov, I. Gorbunov, D.Zimnukhov, D.Kuvshinov, P.Balanutsa, V.Vladimirov, Lomonosov Moscow State University,SAI D. Buckley, South African Astronomical Observatory (SAAO) R. Rebolo, M. Serra, N. Lodieu, G. Israelian, L. Suarez-Andres The Instituto de Astrofisica de Canarias (IAC) A. Tlatov, V.Senik, D. Dormidontov Kislovodsk Solar Station of the Pulkovo Observatory R. Podesta, F. Podesta, C. Lopez, C.Francile Observatorio Astronomico Felix Aguilar (OAFA) H.Levato, Instituto de Ciencias Astronomicas, de la Tierra y del Espacio (ICATE) O. Gres, N.M.Budnev , Yu.Ishmuhametova Irkutsk State University (ISU) A. Gabovich, V. Yurkov, Yu. Sergienko Blagoveschensk Educational State University (BSPU) MASTER-Amur robotic telescope (MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Russia (Blagoveschensk State Pedagogical University) was pointed to the Swift GRB180720B (Siegel et al., GCN Circ #22973) 113 sec after trigger time at 2018-07-20 14:23:37 UT. So as the GRB was 4.6 degrees above the horizont, the good observations started on 2018-07-20 15:21:50UT. Galaxy latitude b = -63.07 degree. The moon (58 % bright part) is 9 degrees above the horizon. The distance between moon and object was 143. The sun altitude was -17.19 degree. The object observed till 2018-07-20 15:47:58 MASTER-SAAO robotic telescope (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 GRB180720B 27260 sec after trigger time at 2018-07-19 20:56:09 UT as MASTER's LAT (Bissaldi et al GCN22980)alert inspection with polarization filters. MASTER-SAAO auto-detection system ( Lipunov et al., "MASTER Global Robotic Net", Advances in Astronomy, 2010, 30L ) discovered bright OT source at (RA, Dec) = 00h 02m 06.92s -02d 55m 05.6s on 2018-07-19 20:56:09 UT. The OT magnitude is ~16.8m . There is no minor planet at this place. We have reference image on 2016-05-04.12293 UT with unfiltered mlim = 18.1m. The observations made on zenit distance = 16.7 degrees, galaxy latitude b = -74.37 degree. The moon (61 % bright part) was 24 degrees above the horizon.The sun altitude was -63.7 degree. MASTER-SAAO reobserved this area on 2018-07-21 22:28:10-22:54:51UT as MASTER's MAXI (Negoro et al GCN 22993) alert inspection with mlim=20.2 and unfiltered m_OT~19.1 The discovery and reference images are http://master.sai.msu.ru/static/OT/MASTERGRB180720B.jpg MASTER-Kislovodsk robotic telescope (MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Russia (Pulkovo Solar Station) was pointed to the GRB180720B (Siegel et al., GCN Circ #22973) 27457 sec after trigger time at 2018-07-20 21:59:21 UT . On our first (180s exposure) set MASTER-Kislovodsk auto-detection system discovered OT with m_OT~17.0, automatical mlim~17.6. The observations made on zenit distance = 25.66 degrees, galaxy latitude b = -63.07 degree. The moon (61 % bright part) is below the horizon(The altitude of Moon is -8). The distance between moon and object is 138 The sun altitude is -24.87 degree. The object observed till 2018-07-20 22:19:52 MASTER-IAC robotic telescope (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 GRB180720B (Siegel et al., GCN Circ #22973) 44691 sec after trigger time at 2018-07-21 02:46:35 UT . On our first (60s exposure) MASTER-IAC auto-detection system discovered optical transient within Swift error-box with automatical magnitude ~18.0. The observations made on zenit distance = 43.01 degrees, galaxy latitude b = -63.07 degree. The moon (63 % bright part) is below the horizon(The altitude of Moon is -15). The distance between moon and object is 136 The sun altitude is -36.01 degree. The object observed till 2018-07-21 03:03:36 The visibility GRB error box (coord:0.5279, -2.9170 error_box: 0.05) at trigger time at different MASTER sites: obj: -47.70 sun: 29.73 - Tavrida (Crimea, Russia) obj: -41.62 sun: 72.28 - IAC, Teide, (Tenerife, Spain) obj: -54.25 sun: 15.39 - SAAO (Sutherland, SA) obj: -46.85 sun: 23.59 - Kislovodsk (Russia) obj: -29.98 sun: 15.28 - Ural(Kourovka, Russia) obj: -10.74 sun: -8.46 - Tunka (near Baykal Lake, Russia) obj: 4.55 sun: -17.19 - Amur(Blagoveschensk) obj: 6.72 sun: 27.64 - OAFA (Argentina) The message may be cited.
GCN 23024 table
GRB_name GRB180720B
GCN_number 23024
Detection_method Optical
Circular_text TITLE: GCN CIRCULAR NUMBER: 23024 SUBJECT: GRB 180720B: D50 optical observations DATE: 18/07/23 20:21:57 GMT FROM: Jan Strobl at AI AS CR,Ondrejov M. Jelinek, J. Strobl, R. Hudec, C. Polasek (ASU CAS Ondrejov) report: We observed the position of the bright GRB 180720B (Siegel et al., GCN 22973 & GCN 22975) with the D50 telescope of the Astronomical Institute Ondrejov, near Prague, Czech Republic. We performed a series of ~300x 20s unfiltered exposures as soon as the position became accessible above local horizon, between 9.8 and 12h after the trigger. The optical afterglow (Martone et al., GCN 22976; Sasada et al., GCN 22977; Reva et al., GCN 22979; Itoh et al., GCN 22983) is clearly detected in single 20 s images. We confirm the stationary behaviour during our observations as reported by Kann et al. (GCN 22985) - the afterglow might have faded as few as 0.04 mag between 10 and 11h after the GRB trigger.
GCN 23033 table
GRB_name GRB180720B
GCN_number 23033
Detection_method Optical
Circular_text TITLE: GCN CIRCULAR NUMBER: 23033 SUBJECT: GRB 180720B: KAIT Optical Observations DATE: 18/07/25 00:12:38 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, observed the field of Swift GRB 180720B (Siegel et al., GCN 22973) each night from 21 to 24 UT, at a mean time of 0.855, 1.886, 2.883 and 3.874 days, respectively, after the burst. Observations were performed with a sequence in the B, V, R, I and clear (roughly R) filters, and the exposure time was 60 s per image. The optical afterglow (Martone et al., GCN 22976) was clearly detected and we measure its clear band mag to be 18.5, 19.6, 20.5 and 20.9, respectively, calibrated to the SDSS catalog.
GCN 23036 table
GRB_name GRB180720B
GCN_number 23036
Detection_method Fermi LAT Det
Circular_text TITLE: GCN CIRCULAR NUMBER: 23036 SUBJECT: GRB 180720B long follow up requested DATE: 18/07/25 08:52:55 GMT FROM: Arnon Dar at Technion-Israel Inst. of Tech Long follow up of the afterglow of the extremely bright GRB 180720B (Swift-BAT detection: Siegel et al., GCN #22973, GCN #22975; Fermi-LAT detection: Bissaldi and Racusin, GCN #22980; Fermi-GBM detection: Roberts et al., GCN #22981; Konus Wind detection: Frederiks et al. GCN 23011) is urged. It will provide another critical test of GRB theories. Its current late-time X-ray afterglow, measured with Swift XRT, decays like a single power-law with a temporal index alpha=1.34+/-0.01 and an unabsorbed spectral index beta=0.82+/-0.04 (Evans et al. Swift-XRT GRB lightcurve repository). It satisfies well the Cannonball model closure relation alpha=beta+1/2 (e.g., Dado and Dar, PhRvD, 94, 3007 (2016)) for the late time unabsorbed afterglows of SN-GRBs (while those of SN-less GRBs satisfy alpha=2, e.g., Dado and Dar arXiv:1807.08726). An SN akin to SN1998bw may be resolved from the optical afterglows around day ~15. An achromatic break in the late time afterglow is expected only if the host galaxy is aligned near face on. [GCN OPS NOTE(26jul18): The operator has corrected the GRB name in the Subject-line; and corrected Frederiks reference from 230110 to 23011.]
GCN 23037 table
GRB_name GRB180720B
GCN_number 23037
Detection_method Other
ra 0.5292°
decl -2.0000°
Circular_text TITLE: GCN CIRCULAR NUMBER: 23037 SUBJECT: GRB 180720B: AMI-LA 15.5 GHz observation DATE: 18/07/25 09:12:00 GMT FROM: Itai Sfaradi at Hebrew U of Jerusalem Itai Sfaradi (HUJI), Joe Bright (Oxford), Assaf Horesh (HUJI), Rob Fender (Oxford) , Sara Motta (Oxford), David Titterington, Yvette Perrott (MRAO, Cambridge) report: We observed the position of GRB180720B (GCN CIRCULAR #22973) with the Arcminute Microkelvin Imager Large Array (AMI-LA; Zwart et al. 2008; Hickish et al. 2018) at 15.5 GHz on 2018-07-22.21 for 3.9 hours. We clearly detect a source at the phase center, fitting the source with the CASA task IMFIT provides an integrated flux density of ~ 1 mJy and a position of RA: 00:02:07.02, Dec: -02 55 02.224 with a synthesized beam major and minor FWHM of 93’’ and 27’’ respectively (consistent with the position reported in GCN CIRCULAR #22973). The custom pipeline REDUCE_DC (e.g. Perrott et al. 2015) was used to calibrate and flag the data, with 3C286 as the absolute flux calibrator and J2357-0152 as the interleaved phase calibrator. We plan to continue monitoring this source, and would like to thank the MRAO staff for carrying out these observations.
GCN 23040 table
GRB_name GRB180720B
GCN_number 23040
Detection_method Optical
Circular_text TITLE: GCN CIRCULAR NUMBER: 23040 SUBJECT: GRB 180720B: OAJ optical observations DATE: 18/07/26 08:56:58 GMT FROM: Luca Izzo at IAA-CSIC L. Izzo, D. A. Kann (HETH/IAA-CSIC), A. de Ugarte Postigo (HETH/IAA-CSIC, DARK/NBI), C. C. Thoene, K. Bensch, M. Blazek (HETH/IAA-CSIC), M. C. Diaz-Martin, and S. Rodriguez-Llano (OAJ) report: We observed the field of the Swift-BAT GRB 180720B (Siegel et al. GCN 22973), detected also by Fermi-LAT (Bissaldi et al. GCN 22980), with the 0.8m telescope of the Observatorio Astrofisico de Javalambre (Teruel, Spain). Observations consisted of a series of 3x300 s griz exposures, starting at 01:12:55 UT (10.85 hr after the GRB trigger). The afterglow is clearly detected at a position consistent with the one reported by Martone et al. (GCN 22976). We measure a magnitude of r(AB) = 17.77+/- 0.05 mag at an average time of 01:37:14 UT (11.26 hr after the GRB trigger), as compared to nearby SDSS stars.
GCN 23041 table
GRB_name GRB180720B
GCN_number 23041
Detection_method Swift-BAT Det
Circular_text TITLE: GCN CIRCULAR NUMBER: 23041 SUBJECT: NuSTAR observations of GRB 180720B DATE: 18/07/26 16:39:39 GMT FROM: Eric C Bellm at UW E. C. Bellm (UW) and S. B. Cenko (GSFC) report: We have analyzed 38 ksec of NuSTAR data for GRB 180720B (M. H. Siegel et al., GCN Circ. 22973), from 243 ksec to 318 ksec after the BAT trigger. NuSTAR detects emission from the X-ray afterglow to approximately 30 keV. The NuSTAR spectrum can be well-modeled from 3-30 keV by an absorbed power law with spectral index 1.80+/-0.06, consistent with the value reported by XRT (K. L. Page et al., GCN Circ. 22984). The 3-30 keV flux was 4.8+/-0.2 x 10^-12 erg cm^-2 s^-1. We thank Karl Forster and the NuSTAR operations team for their assistance executing these TOO observations.
GCN 23042 table
GRB_name GRB180720B
GCN_number 23042
Detection_method CALET
redshift 0.6540
Circular_text TITLE: GCN CIRCULAR NUMBER: 23042 SUBJECT: GRB 180720B: CALET Gamma-Ray Burst Monitor detection DATE: 18/07/27 04:11:45 GMT FROM: Takanori Sakamoto at AGU M. L. Cherry (LSU), A. Yoshida, T. Sakamoto, V. Pal'shin, S. Sugita, Y. Kawakubo, A. Tezuka, S. Matsukawa, H. Onozawa, T. Ito, H. Morita, Y. Sone (AGU), K. Yamaoka (Nagoya U), S. Nakahira (RIKEN), I. Takahashi (IPMU), Y. Asaoka, S. Ozawa, S. Torii (Waseda U), Y. Shimizu, T. Tamura (Kanagawa U), W. Ishizaki (ICRR), S. Ricciarini (U of Florence), A. V. Penacchioni, P. S. Marrocchesi (U of Siena) and the CALET collaboration: The extremely bright, long GRB 180720B (Swift-BAT trigger #848890: Siegel et al., GCN Circ. 22973, Barthelmy et al. GCN Circ. 22998; Fermi-LAT detection: Bissaldi and Racusin, GCN Circ. 22980; Fermi-GBM observation: Roberts and Meegan, GCN Circ. 22981; MAXI/GGS detection: Negoro et al., GCN Circ. 22993; Konus-Wind observation: Frederiks et al., GCN Circ. 23011) triggered the CALET Gamma-ray Burst Monitor (CGBM) at 14:21:40.948 UTC on 20 July 2018. Because of a problem in one of the ground alert processing script, the GCN notice was not distributed automatically for this event. The burst signal was seen by all CGBM detectors. The CGBM data cover the time interval from T-243 sec to T+1449 sec (when the HV was on and the source was in the CGBM FoV). The burst light curve shows the main emission episode comprised of several bright overlapped pulses which starts at T-2.9 sec, peaks at 15.3 sec, and ends at T+54.0 sec, followed by the weak tail seen at least up to T+120.1 sec. The T90 and the T50 durations measured by the SGM data are 51.1 +- 3.0 sec and 15.4 +- 1.4 sec (40-1000 keV), respectively. No any precursor is seen in the time interval from T-243 sec to T-2.9 sec. The time-averaged spectrum of the main episode (measured by the SGM from T+0.8 sec to T+52.8 sec) is best fit in the 30 keV - 20 MeV range by a GRB (Band) model with alpha = -1.29 +- 0.04, Epeak = 686(-77, +88) keV, and beta = -2.23(-0.12, +0.09) (chi2 = 254.4/236 dof). The emission is seen up to ~20 MeV. The resulting fluence in the 30 keV - 10 MeV range is 5.79(-0.19, +0.20)x10^-4 erg/cm2 . Assuming a redshift of z=0.654 (Vreeswijk et al., GCN 22996) and a FlatLambdaCDM cosmology with H0=68 km/s/Mpc and Omega_M=0.308 (Planck Collaboration 2016, A&A, 594, A13 (Paper XIII)), the isotropic energy release, Eiso, is 6.82(-0.22, 0.24)x10^53 erg. The quoted errors are at the 90% CL. The ground processed light curve is available at http://cgbm.calet.jp/cgbm_trigger/ground/1216131585/ All the quoted values are preliminary. The CALET data used in this analysis are provided by the Waseda CALET Operation Center located at the Waseda University.
GCN 23073 table
GRB_name GRB180720B
GCN_number 23073
Detection_method Optical
Circular_text TITLE: GCN CIRCULAR NUMBER: 23073 SUBJECT: GMRT radio detection of GRB 180720B DATE: 18/08/03 09:23:31 GMT FROM: Poonam Chandra at TIFR Poonam Chandra (NCRA-TIFR), A. J. Nayana (NCRA-TIFR), Dipankar Bhattacharya (IUCAA), S. Bradley Cenko (NASA) and Alessandra Corsi (Texas-Tech) report: We observed GRB 180720B (Siegel et al. GCN 22973) with the Giant Metrewave Radio Telescope at the 1.4 GHz band on 2018 Jul 29.99 UT. We detect a radio afterglow with the flux density of ~370+/-59 uJy at the optical position (Martone et al. GCN 22976). We thank the staff of the GMRT that made these observations possible. GMRT is run by the National Centre for Radio Astrophysics of the Tata Institute of Fundamental Research. More observations are planned.