GRB170817A

This page lists all entries on GRB170817A in GRBweb

Summary Fermi GBM IPN GCN 21520 GCN 21528 GCN 21618 GCN 21641 GCN 21747 GCN 22206 GCN 22371 GCN 22372 GCN 22374 GCN 22763 GCN 34208

Summary table
Variable Value Source
GRB_name_Fermi GRB170817529
T0 12:41:06.283 UTC Fermi_GBM
ra 191.7500° IPN
decl -39.8000° IPN
pos_error 1.17e+01° IPN
T90 2.048 s Fermi_GBM
T90_error 0.466 s Fermi_GBM
T90_start 12:41:06.283 UTC Fermi_GBM
fluence 2.79e-07 erg/cm² Fermi_GBM
fluence_error 1.74e-08 erg/cm² Fermi_GBM
redshift 0.0093 IPN
T100 2.048 s
GBM_located False
mjd 57982.52854494213 Fermi_GBM
Fermi GBM table
GRB_name_Fermi GRB170817529
trigger_name bn170817529
ra 197.4500°
decl -23.3814°
pos_error 1.06e+01°
datum 2017-08-17
t_trigger 12:41:06.475 UTC
T90 2.048 s
T90_error 0.466 s
T90_start 12:41:06.283 UTC
fluence 2.79e-07 erg/cm²
fluence_error 1.74e-08 erg/cm²
flux_1024 1.77e+00 erg/cm²/s
flux_1024_error 1.98e-01 erg/cm²/s
flux_1024_time -3.20e-01 erg/cm²/s
flux_64 3.73e+00 erg/cm²/s
flux_64_error 9.26e-01 erg/cm²/s
IPN table
GRB_name GRB170817A
ra 191.7500°
decl -39.8000°
pos_error 1.17e+01°
redshift 0.0093
GCN 21520 table
GRB_name GRB170817A
GCN_number 21520
Detection_method Fermi GBM Det
t_trigger 12:41:06.470 UTC
ra 176.8000°
decl -39.8000°
Circular_text TITLE: GCN CIRCULAR NUMBER: 21520 SUBJECT: GRB 170817A: Fermi GBM detection DATE: 17/08/17 20:00:07 GMT FROM: Andreas von Kienlin at MPE A. von Kienlin (MPE), C. Meegan (UAH) and A. Goldstein (USRA) report on behalf of the Fermi GBM Team: "At 12:41:06.47 UT on 17 August 2017, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 170817A (trigger 524666471 / 170817529). The on-ground calculated location, using the GBM trigger data, is RA = 176.8, DEC = -39.8 (J2000 degrees, equivalent to 12 h 47 m, -39 d 48'), with an uncertainty of 11.6 degrees (radius, 1-sigma containment, statistical only; there is additionally a systematic error which we have characterized as a core-plus-tail model, with 90% of GRBs having a 3.7 deg error and a small tail suffering a larger than 10 deg systematic error. [Connaughton et al. 2015, ApJS, 216, 32] ). The angle from the Fermi LAT boresight at the GBM trigger time is 91 degrees. The GRB light curve shows a weak short pulse with a duration (T90) of about 2 s (50-300 keV). The time-averaged spectrum from T0-0.512 s to 2.048 s is well fit by a power law function with an exponential high-energy cutoff. The power law index is -0.89 +/- 0.5 and the cutoff energy, parameterized as Epeak, is 82 +/- 21 keV The event fluence (10-1000 keV) in this time interval is (2.3 +/- 0.4)E-07 erg/cm^2. The 1.024-sec peak photon flux measured starting from T0-0.32 s in the 8-1000 keV band is 1.9 +/- 0.2 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."
GCN 21528 table
GRB_name GRB170817A
GCN_number 21528
Detection_method Fermi GBM Other
Circular_text TITLE: GCN CIRCULAR NUMBER: 21528 SUBJECT: LIGO/Virgo G298048 - Update on Fermi/GBM GRB 170817A Analysis DATE: 17/08/18 00:36:12 GMT FROM: Adam Goldstein at Fermi/GBM A. Goldstein (USRA), P. Veres (UAH), and A. von Kienlin (MPE) report on behalf of the GBM-LIGO Group: L. Blackburn (CfA), M. S. Briggs (UAH), J. Broida (Carleton College), E. Burns (NASA/GSFC), J. Camp (NASA/GSFC), T. Dal Canton (NASA/GSFC), N. Christensen (Carleton College), V. Connaughton (USRA), R. Hamburg (UAH), C. M. Hui (NASA/MSFC), P. Jenke (UAH), D. Kocevski (NASA/MSFC), N. Leroy (LAL), T. Littenberg (NASA/MSFC), J. McEnery (NASA/GSFC), R. Preece (UAH), J. Racusin (NASA/GSFC), P. Shawhan (UMD), K. Siellez (GATech), L. Singer (NASA/GSFC), J. Veitch (Glasgow), C. Wilson-Hodge (NASA/MSFC) The GBM trigger (Connaughton et al., LVC GCN 21506), which we determine to be a short GRB, occurred about 2 minutes before Fermi entered the South Atlantic Anomaly. To estimate the False Alarm Rate (FAR) of a chance coincident short GRB without using spatial information, we estimate the rate of short GRBs (defined as t90 <= 2 s) triggered by GBM. GBM has a total of 351 triggered short GRBs over an estimated triggering livetime of 3.23e8 s. This results in a FAR of one per 10.7 days. A simple estimate of the False Alarm Probability using only the temporal information of the two signals is 2.2e-6 (~4.5 sigma). The initial public report of the GRB (von Kienlin et al., GCN 21520) contained the spectral information using the maximum of the GBM localization posterior. Using the maximum of the updated LIGO/Virgo localization posterior (LVC, LVC GCN 21513), which is consistent with the GBM localization, we report the updated preliminary spectral information. The estimated GRB duration is ~ 2 s and is best fit by a power-law function with an exponential high-energy cutoff from T0-0.75 to T0+1.25 s. The power-law index is -0.88 +/- 0.44 and the cutoff energy, parametrized as Epeak, is 128.0 +/- 48.7 keV. The event fluence (10-1000 keV) in this time interval is (2.2 +/- 0.5)e-7 erg/cm^2, which we estimate to be near the 58th percentile of GBM-triggered short GRB fluences. The 64 ms peak photon flux estimated starting at T0 is 3.6 +/- 1.1 ph/s/cm^2 (10-1000 keV). The corresponding spectrum over this peak flux interval is fit by an exponential high-energy power law with index = -0.29 +/- 1.01 and Epeak = 124.2 +/- 52.6 keV. The event peak energy flux (10-1000 keV) is (7.3 +/- 2.4)e-7 erg/s/cm^2. Using this spectral information and the distance information provided by the LVC (40 +/- 8 Mpc) we estimate that the isotropic energy release in gamma-rays, Eiso ~ 4.3e46 erg in the 1 keV-10 MeV energy range and the isotropic peak luminosity, Liso ~1.4e47 erg/s. These results are preliminary and may be updated with further analysis.
GCN 21618 table
GRB_name GRB170817A
GCN_number 21618
Detection_method Optical
Circular_text TITLE: GCN CIRCULAR NUMBER: 21618 SUBJECT: LIGO/Virgo G298048: optical observations of CHILESCOPE observatory DATE: 17/08/20 14:24:47 GMT FROM: Alexei Pozanenko at IKI,Moscow A. Pozanenko (IKI), E. Mazaeva (IKI), A. Volnova (IKI), P. Minaev (IKI), M. Krugov (AFIF) report on behalf of IKI-GW follow-up collaboration: We observed the field of LIGO/Virgo trigger G298048 (LVC GCNs 21509, 21513) and the error circle of GMB/Fermi short burst GRB 170817A (Connaughton et al., GCN 21506) with RC-1000 and ASA-500 telescopes of CHILESCOPE observatory located at W 70d 34m S20d 27m. The observations started on Aug 17 (UT) 23:17:16 in clear filter. The last image was recorded on 2017-08-18T00:59:48. We cover central part of G298048 localization with typical limiting magnitude of 20m at 60 s exposure in each image. The covering map can be found in http://grb.rssi.ru/GRB170817A/bayestar_RC1000%20coverage.png The OT candidate found by Coulter et al. (LVC GCN 21529), the DLT17ck (Sheng Yang et al., GCN 21531) is out of the coverage in the first epoch of the observations. We also cover northern part of GBM/Fermi localization? 1-sigma containment, statistical only (Connaughton et al., GCN 21506). The coverage of the GBM localization is about 20%. Typical limiting magnitude of 17.5m at 60 s exposure in each image. The covering map can be found in http://grb.rssi.ru/GRB170817A/GRB170817A_GBM_coverage_ASA500.png The detailed investigation of the fields is underway. We are grateful to the remote staff of the observatory for timely observations.
GCN 21641 table
GRB_name GRB170817A
GCN_number 21641
Detection_method CALET
Circular_text TITLE: GCN CIRCULAR NUMBER: 21641 SUBJECT: LIGO/Virgo G298048: CALET Observations DATE: 17/08/22 09:36:51 GMT FROM: Takanori Sakamoto at Aoyama Gakuin U S. Nakahira (RIKEN), A. Yoshida, T. Sakamoto, Y. Kawakubo, M. Moriyama, Y. Yamada, A. Tezuka, S. Matsukawa (AGU), K. Yamaoka (Nagoya U), I. Takahashi (IPMU), Y. Asaoka, S. Ozawa, S. Torii (Waseda U), Y. Shimizu, T. Tamura (Kanagawa U), W. Ishizaki (ICRR), M. L. Cherry (LSU), S. Ricciarini (U of Florence), A. V. Penacchioni, P. S. Marrocchesi (U of Siena) and the CALET collaboration: The CALET Gamma-ray Burst Monitor (CGBM) was operating at the trigger time of G298048 (The LIGO Scientific Collaboration and the Virgo Collaboration, GCN Circ. 21509). No CGBM on-board trigger occurred at the time of the event. Based on the updated LVC localization sky map (preliminary-LALInference.fits.gz), none of the probability area was in the field-of-view of the CGBM/HXM. However, 99% of the summed probability was inside the field-of-view of the CGBM/SGM. The CGBM/SGM boresight position (R.A., Dec. = 223.8 deg, 43.4 deg) was 73 deg off-axis from the maximum LVC probability location (The LIGO Scientific Collaboration and the Virgo Collaboration, GCN Circ. 21527). Based on the analysis of the light curve data with 0.125 sec time resolution from -60 sec to 60 sec from the trigger time, we found no significant excess around the trigger time in either the HXM (7-3000 keV) or the SGM (40 keV -28 MeV) data. The incident angle of SGM to the position of SSS17a (Coulter et al., GCN Circ. 21529) was 71 deg. Assuming the association of GRB 170817A (Connaughton et al., GCN Circ. 21506) and SSS17a, we estimated the upper limit of the SGM. The 7-sigma upper limit of SGM using alpha=-0.9 and Epeak=130 keV (Goldstein et al., GCN Circ. 21528) is 5.5e-7 erg/cm2/s in the 10-1000 keV band at 1 s exposure assuming no shielding by ISS structures. This estimated upper limit is at the similar level to the reported peak flux, 7.3e-7 erg/cm2/s, of GRB 170817A by Fermi-GBM. We further noticed that the position of SSS17a was covered by the large structure of ISS at the time of the trigger. Because of this, the SGM sensitivity should be worse than what we reported above. Therefore, it is consistent that no signal of GRB 170817A is seen by the SGM data. The CALET Calorimeter (CAL) was operating in the high energy trigger mode at the trigger time of G298048. However, no LVC high probability region was included in the CAL's field of view at the time of the trigger.
GCN 21747 table
GRB_name GRB170817A
GCN_number 21747
Detection_method Optical
Circular_text TITLE: GCN CIRCULAR NUMBER: 21747 SUBJECT: LIGO/Virgo G298048: ALMA observations DATE: 17/08/29 12:37:56 GMT FROM: Rhaana Starling at U.of Leicester S. Schulze (Weizmann Institute of Science), S. Kim (PUC Chile), S. Martin (JAO), F. E. Bauer (PUC Chile), M. Bremer (IRAM), S. Campana (INAF Brera), Z. Cano (IAA Granada), J. Corral-Santana (ESO Chile), P. D'Avanzo (INAF Brera), C. De Breuck (ESO), I. de Gregorio-Monsalvo (JAO), M. de Pasquale (Istanbul University), J. P. U. Fynbo (Dark Cosmology Centre), D. Garcia-Appadoo (JAO), D. Hartman (U. Clemson), J. Hjorth (Dark Cosmology Centre), P. Jakobsson (U. Iceland), D. A. Kann (IAA Granada), T. Kruehler (MPE Garching), R. Lekshmi (ARIES), A. J. Levan (U Warwick), A. Lundgren (JAO), D. Malesani (Dark Cosmology Centre), M. Michalowski (Adam Mickiewicz University), B. Milvang-Jensen (Dark Cosmology Centre), K. Misra (ARIES), S. R. Oates (U. Warwick), R. Sanchez-Ramirez (IAA Granada), M. Sparre (Heidelberg Institute for Theoretical Studies), R. L. C. Starling (U. Leicester), N. R. Tanvir (U. Leicester), C. C. Thoene (IAA Granada) and D. J. Watson (Dark Cosmology Centre) report: We have used the Atacama Large Millimeter/submillimeter Array, ALMA, to observe the field of LIGO/Virgo candidate G298048 (The LIGO Scientific Collaboration and the Virgo Collaboration GCN Circ. 21509) and GRB 170817A (Connaughton et al. GCN Circ. 21506; Svinkin et al. GCN Circ. 21515), centered on the position of the optical transient reported in Coulter et al. (GCN Circ. 21529). Observations were taken at four epochs: 2017-08-18, 2017-08-20, 2017-08-21 and 2017-08-25 and have been carried out in the B7 band centred at 338.5 GHz (central wavelength 0.89 mm). The field of view covered an area of 18.3 arcsec. Data processing is underway. We thank ALMA for their excellent support.
GCN 22206 table
GRB_name GRB170817A
GCN_number 22206
Detection_method Other
Circular_text TITLE: GCN CIRCULAR NUMBER: 22206 SUBJECT: LIGO/Virgo G298048: Brightening X-ray Emission from GW170817/GRB170817A/SSS17a DATE: 17/12/07 22:11:17 GMT FROM: Phil Evans at U of Leicester Daryl Haggard, John J. Ruan, Melania Nynka (McGill/MSI), Vicky Kalogera (Northwestern/CIERA), and Phil Evans (Leicester) report: We have performed a detailed analysis of new Chandra X-ray observations of GW170817 obtained via Chandra Director's Discretionary Time (PI: Wilkes, Program Number 18408601). The X-ray counterpart to GW170817/GRB170817A/SSS17a is clearly detected in the new observations. This program acquired two exposures of GRB170817A: (1) a 74.09 ks exposure (ObsID 20860) beginning at 2017 December 2.08 UT, approximately 108 days post-burst, and (2) a 24.74 ks exposure (ObsID 20861) beginning at 2017 December 6.45 UT, approximately 111 days post-burst. Since the two new exposures are close in time and the X-ray emission of GRB170817A is not expected to vary significantly over ~4 day timescales, we co-add the two data sets into one 98.83 ks exposure at 109.2 days post-burst. We perform spectral extractions assuming an absorbed power-law spectral model with fixed NH = 7.5e20 cm^−2 and find that the X-ray flux of GRB170817A has an absorbed flux of f(0.3−8 keV) = 1.58e−14 +/- 0.14 erg s^−1 cm^−2 (Gamma = 1.62 +/- 0.27) at 109.2 days post-burst, which corresponds to an unabsorbed luminosity of L(0.3−10 keV) = 42.5e38 +/- 3.7 erg s^−1 (see also Troja et al. GCN 22201 and Margutti et al. GCN 22203). This represents significant X-ray brightening compared to Chandra observations at 15.6 days post-burst, for which we find an absorbed flux of f(0.3−8 keV) = 0.36e−14 +/- 0.1 erg s^−1 cm^−2 (Gamma = 2.4 +/- 0.8) and an unabsorbed luminosity of L(0.3−10 keV) = 10.4e38 +/- 2.0 erg s^−1 (Haggard et al. 2017). We also examine the three previously-detected X-ray sources CXOU J130948, CXOU 130946, and the host galaxy NGC 4993. The fluxes of CXOU 130946 and the host-galaxy NGC 4993 are consistent with our previous deep Chandra observations, while CXOU J130948 appears to be variable in X-rays (Margutti et al. 2017; Haggard et al. 2017). The origin of the X-ray emission from the NS-NS coalescence GW170817/GRB170817A is an important diagnostic for all post-merger interpretations, and different scenarios predict distinct evolution in its X-ray light curve. These observations support scenarios in which the X-ray and radio emission share a common origin, i.e., the X-ray light curve is consistent with outflow models which may be either a cocoon shocked by the jet or dynamical ejecta from the merger. Further deep X-ray monitoring can place powerful constraints on the physical parameters of these models. The X-ray brightening strengthens the argument that simple top-hat jet models are not consistent with the latest observations. However, more advanced models of structured jets with off-axis viewing angles should be pursued and cannot yet be ruled out. We thank Belinda Wilkes and the Chandra scheduling, data processing, and archive teams for making these observations possible.
GCN 22371 table
GRB_name GRB170817A
GCN_number 22371
Detection_method Other
Circular_text TITLE: GCN CIRCULAR NUMBER: 22371 SUBJECT: LIGO/Virgo GW170817: Chandra X-ray Emission Continues to Rise ~156 Days Post-Merger DATE: 18/01/29 19:21:22 GMT FROM: Daryl Haggard at McGill U Daryl Haggard, Melania Nynka, John J. Ruan (McGill/MSI), Phil Evans (Leicester), and Vicky Kalogera (Northwestern/CIERA) report: We have obtained new X-ray observations of GW170817 via Chandra Director's Discretionary Time (PI: Wilkes, Program Number 19408607). The X-ray counterpart to GW170817/GRB170817A/SSS17a continues to be detected and the X-ray emission continues to brighten approximately 156 days after the neutron star merger. This contradicts previous claims of the X-ray fading of GW170817 in XMM-Newton observations at 135 days (D'Avanzo et al. 2018, arXiv: 1801.06164). This new Chandra program acquired several exposures of GRB170817A: ObsID, ExpTime, StartDate, Days Post-Burst ----- ------- --------- --------------- 20936 31.75 ks 2018-01-17 21:55:17 153.5 days 20938 15.86 ks 2018-01-21 13:45:18 157.1 days 20939 22.25 ks 2018-01-24 08:18:48 159.9 days Since these new Chandra exposures are close in time and the X-ray emission of GRB170817A is not expected to vary significantly over <10 day timescales, we co-add these three data sets into one 69.86 ks exposure at 156.4 days post-burst. We perform spectral extractions assuming an absorbed power-law spectral model with fixed NH = 7.5e20 cm^−2 and find that the X-ray flux of GRB170817A has an absorbed flux of f(0.3−8 keV) = 1.93(+0.39/-0.32)e−14 erg s^−1 cm^−2 (with Gamma ~ 1.67) at 156.4 days post-burst, which corresponds to an unabsorbed luminosity of L(0.3−10 keV) = 5.23(+1.30/-0.95)e39 erg s^−1 (assuming a luminosity distance of 42.5 Mpc). This represents continued X-ray brightening compared to Chandra observations at 15.6 and 109.2 days post-burst, for which we find an absorbed flux of f(0.3−8 keV) = 0.36(+0.1/-0.07)e−14 erg s^−1 cm^−2 (with Gamma = 2.4 +/- 0.8, unabsorbed L(0.3−10 keV) = 10.4(+2.0/-1.6)e38 erg s^−1; Haggard et al. 2017) and f(0.3−8 keV) = 1.58(+0.14/-0.13)e−14 erg s^−1 cm^−2 (with Gamma = 1.6 +/- 0.3, unabsorbed L(0.3−10 keV) = 42.5(+3.7/-3.5)e38 erg s^−1; Ruan et al. 2018), respectively. Our findings here contradict recent reports of dimming in the X-ray flux from XMM Newton at 135 days (D'Avanzo et al. 2018), which was reported to be 2.1(+0.7/-0.5)e-15 erg s^−1 cm^−2 (0.3-10 keV unabsorbed). However, this reported flux value is a typo, and should be 2.1(+0.7/-0.5)e-14 erg s^−1 cm^−2 (D’Avanzo 2018, private communication). Taking this corrected flux and rescaling to a 0.3-8 keV absorbed flux for comparison to the previous Chandra measurements above gives 1.67(+0.87/-0.64)e-14 erg s^−1 cm^−2. Thus, the recent X-ray data at 15.6 days (Chandra), 109.2 days (Chandra), 135 days (XMM), and 156.4 days (Chandra) are all consistent with continued X-ray brightening. We provide a light curve table summarizing these measurements: Days, Telescope, Flux* (0.3-8 abs), Ref ---- --------- ---------------- --- 15.6 Chandra 0.36(+0.10/-0.07)e−14 Haggard et al. (2017) 109.2 Chandra 1.58(+0.14/-0.13)e−14 Ruan et al. (2018) 135 XMM 1.67(+0.87/-0.64)e-14 D'Avanzo et al. (2018) 156.4 Chandra 1.93(+0.39/-0.32)e-14 This work *Flux units: erg s^−1 cm^−2; all uncertainties are 90% confidence interval Current post-merger models suggest that the origin of the X-rays could be afterglow emission from either a mildly-relativistic cocoon or a structured jet. For a cocoon, the continued rise of X-ray emission suggest that the cocoon has not yet reached a deceleration phase. For a structured jet, the rising X-ray emission suggest emission from the jet core has not yet entered the observed line of sight. Continued monitoring of GW170817 will be critical for discriminating between these and other models. Note that another ~30 ks of Chandra observations during this same time interval are forthcoming. We thank Belinda Wilkes and the Chandra scheduling, data processing, and archive teams for making these observations possible.
GCN 22372 table
GRB_name GRB170817A
GCN_number 22372
Detection_method Other
Circular_text TITLE: GCN CIRCULAR NUMBER: 22372 SUBJECT: GW170817/GRB170817A: Preliminary results of Chandra monitoring DATE: 18/01/29 20:42:49 GMT FROM: Eleonora Troja at GSFC E. Troja (UMD/GSFC) and L. Piro (INAF/IAPS) report on behalf of a larger collaboration: The Chandra X-ray Observatory re-observed the field of GW170817 starting on January 17th, 2018, and performed five short exposures observations as part of its on-going monitoring program (PI: Wilkes). Only three of these exposures (ObsID: 20936, 20938, 20939) are currently archived and available to the public. Here we report the preliminary findings from these observations. The X-ray afterglow is detected with high significance in all the exposures at an average count rate of 0.0016 cts/s in the 0.5-8.0 keV energy band. A preliminary inspection of the hardness ratio does not show any significant spectral variation. Therefore, we perform a spectral analysis using an absorbed power-law model with absorption column fixed at the Galactic value of 7.5E20 cm^-2 and a photon index Gamma=1.575 as derived from our broadband analysis (Troja et al. 2018, arXiv:1801.06516). We derive an unabsorbed X-ray flux of (3.2 +/- 0.3)E-14 erg/cm2/s in the 0.3-10 keV energy band. The quoted error is at the 68% confidence level. This new measurement is higher than the value measured by Chandra at ~110 days (~2.5E-14 erg/cm2/s, Troja et al. 2018), and higher than the value measured by XMM-Newton at ~135 days (D'Avanzo et al., 2018). The latest measurement is consistent with a rising afterglow with F~t^0.8, although, within the errors, a slow turn-over of the X-ray light curve cannot be excluded. Further analysis is on-going.
GCN 22374 table
GRB_name GRB170817A
GCN_number 22374
Detection_method Other
Circular_text TITLE: GCN CIRCULAR NUMBER: 22374 SUBJECT: GW170817/GRB170817A: Updated results from the full Chandra dataset DATE: 18/01/30 13:00:12 GMT FROM: Eleonora Troja at GSFC E. Troja (UMD/GSFC) and L. Piro (INAF/IAPS) report on behalf of a larger collaboration: We analyzed the full set of five observations of GW170817 performed by the Chandra X-ray Observatory between January 17th and January 28th, 2018, i.e. ~153 and ~164 days after the merger. A log of observations is reported below: ObsID Exposure [ks] 0.5-8.0 keV count rate [cts/s] 20936 31.75 0.0018 +/- 0.0002 20937 20.77 0.0014 +/- 0.0003 20938 15.86 0.0019 +/- 0.0003 20939 22.25 0.0011 +/- 0.0002 20945 14.22 0.0010 +/- 0.0003 The average net count-rate is 0.00148 +/- 0.00011 cts/s, consistent with the value of 0.00145 +/- 0.00014 observed at 110 days (Troja et al. 2018, arXiv:1801.06516). The average spectrum, obtained by coadding the five exposures, is well described by an absorbed power-law model with N_H=7.5E20 cm^-2 and photon index Gamma=1.65+/-0.16 (68% c.l.), consistent with the value derived from the broadband spectrum at earlier times (Troja et al. 2018, arXiv:1801.06516). Based on this new analysis, we estimate an unabsorbed X-ray flux of (2.6 +/- 0.3)E-14 erg/cm2/s (68% c.l.) in the 0.3-10 keV band, consistent with the X-ray flux measured at 110 days. Our results do not support the claim of a decreasing X-ray flux, as suggested by D'Avanzo et al. (2018, arXiv:1801.06164), and are consistent either with a slowly rising afterglow or a slow turn-over of the X-ray light curve expected when the afterglow reaches its peak (e.g. Lazzati et al. 2017, arXiv:1712.03237; Troja et al. 2018, arXiv:1801.06516). We note that the X-ray afterglow displays a marginal level of variability on timescales of a few days, being the count-rate from the last two exposures (20939,20945) consistently lower. The spectrum from these two observations is characterized by a photon index Gamma= 1.9 +/- 0.3 (68% c. l.), slightly softer than the value measured in the first three exposures (20936,20937, and 20938) Gamma = 1.59+/-0.17 (68% c. l.), yet consistent within the large uncertainties. The lower count-rate and soft spectral shape could be indicative of the cooling frequency entering the X-ray band, although the limited statistics prevent us to draw any firm conclusion.
GCN 22763 table
GRB_name GRB170817A
GCN_number 22763
Detection_method Optical
Circular_text TITLE: GCN CIRCULAR NUMBER: 22763 SUBJECT: GW170817/GRB170817A: LBT optical detection DATE: 18/06/05 14:03:37 GMT FROM: Andrea Rossi at INAF A. Rossi (INAF-OAS), M. Cantiello (INAF-OA Abruzzo) V. Testa, D. Paris (INAF-OAR), A. Melandri, S. Covino, O. S. Salafia, P. D'Avanzo, S. Campana (INAF-OAB), L. Nicastro, E. Palazzi, F. Cusano (INAF-OAS), G. Stratta (Urbino University/INFN Firenze), R. Carini, S. Piranomonte, E. Brocato (INAF-OAR), V. D'Elia (ASDC), and M. Branchesi (GSSI) report on behalf of the GRAWITA collaboration and its partners: We observed the optical counterpart of GRB 170817A (Kienlin et al., GCN 21520) associated to GW 170817 (LVC GCN Circ. 21509, 21513) with the LBC imager mounted on the Large Binocular Telescope (Mt Graham, AZ, USA). Observations were performed in the r-sloan filter on 2018-01-23, i.e., ~160 days after the GW/GRB trigger. At the location of the optical transient (e.g., Coulter et al., GCN 21529; Adams et al., 21816) we detect the optical afterglow of GRB 170817A with magnitude r-sloan=26.2+-0.4, calibrated against Pan-STARRS field stars. Image analysis was performed after preliminary removal of an elliptical model of the underlying host galaxy from each single frame. However, some residual emission is left which contributes for ~0.2 mags to the uncertainty of the photometry. Our detection is the first one from a ground-based optical telescope. It is in agreement with a turnover/flattening in the optical light curve of GW 170817/GRB 170817A as inferred by Alexander at al. 2018 (arXiv:1805.02870) and with the overall flattening/declining temporal evolution observed in the X-ray and radio bands (D'Avanzo et al. 2018, A&A, 613 L1; Hajela et al. GCN Circ. 22692; Troja et al. GCN Circ. 22693; Dobie et al. arXiv:1803.06853; Alexander at al. 2018; arXiv:1805.02870). We acknowledge the excellent support from the LBT staff in obtaining these observations.
GCN 34208 table
GRB_name GRB170817A
GCN_number 34208
Detection_method Swift Other
Circular_text TITLE: GCN CIRCULAR NUMBER: 34208 SUBJECT: IceCube-230708A: Upper limits from Swift/BAT-GUANO DATE: 23/07/13 03:09:49 GMT FROM: Samuele Ronchini at PSU Samuele Ronchini (PSU), Gayathri Raman (PSU), Aaron Tohuvavohu (U Toronto), James DeLaunay (U Alabama), Jamie A. Kennea (PSU), Tyler Parsotan (NASA GSFC) report: The neutrino candidate (GCN 34203) was inside the coded BAT field of view. The IceCube notice, distributed in near real-time, triggered the Swift Mission Operations Center operated Gamma-ray Urgent Archiver for Novel Opportunities (GUANO; Tohuvavohu et al. 2020, ApJ, 900, 1). Upon trigger by this notice, GUANO sent a command to the Swift Burst Alert Telescope (BAT) to save 90 seconds of BAT event-mode data from [-45,+45] seconds around the time of the burst. All the requested event mode data was delivered to the ground. Using the NITRATES analysis (DeLaunay + Tohuvavohu 2022, ApJ, 941, 169), we searched for emission on 8 timescales from 0.128s to 16.384s in the interval [-20,+20] seconds around the merger time. We find no evidence for a signal, and derive the following upper limits. We quote the 5-sigma flux upper limits in the 15-350 keV band, considering IceCube localization, for four spectral templates (soft, normal, and hard GRB-like templates described in [arXiv:1612.02395], and spectral shape from GRB170817A [arXiv:1710.05446]) and for four time bins. In units of 10^-8 erg/s/cm^2: Bin duration (s) | hard normal soft GRB 170817A ---------------------------------------------------- 0.256 | 10.4 15.0 13.8 15.9 1.024 | 5.3 7.7 7.1 8.1 4.096 | 2.9 4.2 3.8 4.4 16.384 | 1.8 2.6 2.4 2.8 The upper limits as function of sky position are plotted here: https://doi.org/10.5281/zenodo.8141103 The corresponding fits file can be found here: https://doi.org/10.5281/zenodo.8140900 GUANO is a fully autonomous, extremely low latency, spacecraft commanding pipeline designed for targeted recovery of BAT event mode data around the times of compelling astrophysical events to enable more sensitive GRB searches. A live reporting of Swift/BAT event data recovered by GUANO can be found at: https://www.swift.psu.edu/guano/