//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 32482 SUBJECT: GRB 220825A: Fermi GBM Final Localization DATE: 22/08/25 16:46:46 GMT FROM: Joshua Wood at MSFC/Fermi-GBM The Fermi GBM team reports the detection of a likely LONG GRB At 01:57:48.50 UT on 25 Aug 2022, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 220825A (trigger 683085473 / 220825082). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 87.9, Dec = -10.8 (J2000 degrees, equivalent to J2000 05h 52m, -10d 48'), with a statistical uncertainty of 5.7 degrees. The angle from the Fermi LAT boresight is 115.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2022/bn220825082/quicklook/glg_skymap_all_bn220825082.png The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2022/bn220825082/quicklook/glg_healpix_all_bn220825082.fit The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2022/bn220825082/quicklook/glg_lc_medres34_bn220825082.gif //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 32483 SUBJECT: GRB 220825A: Swift/BAT-GUANO detection DATE: 22/08/26 04:07:21 GMT FROM: Aaron Tohuvavohu at U Toronto James DeLaunay (UAlabama), Aaron Tohuvavohu (U Toronto), Gayathri Raman (PSU), Jamie A. Kennea (PSU), report: Swift/BAT did not localize GRB 220825A onboard (T0: 2022-08-25T01:57:48 UTC, Fermi/GBM trig #683085473). The Fermi 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, GUANO sent a command to the Swift Burst Alert Telescope (BAT) to save 200 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. The BAT likelihood search, NITRATES (DeLaunay + Tohuvavohu, arXiv:2111.01769), detects the burst with a sqrt(TS) of 9.1 in a 16.384 s analysis time bin. NITRATES results, independently, are ambiguous with respect to whether this burst originates from in or outside the BAT FOV, with a borderline DeltaLLHOut of 7.7 and no specific location in the FOV significantly preferred. Independent spectral and/or fluence measurements of this burst from other instruments could help determine the preferred spatial origin. See Section 9.1 and Figure 20 in the NITRATES paper for brief descriptions and interpretation of sqrt(TS), DeltaLLHPeak, and DeltaLLHOut. 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/ //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 32490 SUBJECT: GRB 220825A: Fermi GBM observation DATE: 22/08/26 20:30:29 GMT FROM: Sarah Dalessi at UAH S. Dalessi (UAH), C. Fletcher (USRA), C. Meegan (UAH), and J. Wood (NASA MFSC) report on behalf of the Fermi GBM Team: "At 01:57:48.50 UT on 25 August 2022, the Fermi Gamma-Ray Burst Monitor (GBM) triggered and located GRB 220825A (trigger 683085473 / 220825082), which was also detected by the Swift/BAT-GUANO (J. DeLaunay et al. 2022, GCN 32483). The angle from the Fermi LAT boresight at the GBM trigger time is 115.0 degrees. The GBM light curve consists of a single peak burst with a duration (T90) of about 14.1 s (50-300 keV). The time-averaged spectrum from T0-4.1 s to T0+8.2 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -1.24 +/- 0.19 and the cutoff energy, parameterized as Epeak, is 56.6 +/- 7.0 keV The event fluence (10-1000 keV) in this time interval is (1.83 +/- 0.14)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0-1.98 s in the 10-1000 keV band is 4.96 +/- 0.37 ph/s/cm^2. A Band function fits the spectrum equally well with Epeak= 46.2 +/- 9.5 keV, alpha = -0.96 +/- 0.37 and beta = -2.48 +/- 0.32. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog: https://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html For Fermi GBM data and info, please visit the official Fermi GBM Support Page: https://fermi.gsfc.nasa.gov/ssc/data/access/gbm/"