GRB 240215A

James DeLaunay (PSU), Aaron Tohuvavohu (U Toronto), Samuele Ronchini (PSU), Gayathri Raman (PSU), Jamie A. Kennea (PSU), Tyler Parsotan (NASA GSFC)  report:

Swift/BAT did not localize GRB 240215A onboard (T0: 2024-02-15T15:33:00.41 UTC, Fermi/GBM trigger 729703985).

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 by this notice, GUANO sent a command to the Swift Burst Alert Telescope (BAT) to save 200 seconds of BAT event-mode data from [-50,+150] seconds around the time of the burst. All the requested event mode data was delivered to the ground.

In ground analysis of the available TTE data, we find the position of
the burst with SNR 13.9 in the image domain.

At the time of the trigger, Swift did not have a lock on its star tracker so positions may be inaccurate by up to a few tenths of a degree. 

The BAT position is
RA, Dec = 132.237, -6.4058, which is:
    RA (J2000)     08h 48m 56.88s
    Dec (J2000)  -06d 24' 20.88"
with an estimated statistical uncertainty of 3 arcminutes plus ~15 arcminutes due to loss of star tracker loss

XRT and UVOT follow-up has been requested.
Results of follow-up observations will be reported in future circulars.

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/

P. A. Evans (U. Leicester) reports on behalf of the Swift team:

Swift has initiated a series of observations, tiled on the sky, of the
Swift/BAT GRB 240215A. Automated analysis of the XRT data will
be presented online at http://www.swift.ac.uk/xrt_products/TILED_GRB00123

Any uncatalogued X-ray sources detected in this analysis will be
reported on this website and via GCN COUNTERPART notices. The probability of finding
serendipitous sources, unrelated to the Swift/BAT event is high: any X-ray source
considered to be a probable afterglow candidate will be reported via a GCN Circular
after manual consideration.

Details of the XRT automated analysis methods are detailed in Evans et
al. (2007, A&A, 469, 379; 2009, MNRAS, 397, 1177 and 2014, ApJS, 210, 8).

This circular is an official product of the Swift-XRT team.

L. Scotton (UAH) and C. Meegan (UAH) report on behalf of
the Fermi Gamma-ray Burst Monitor Team:

"At 15:33:00.41 UT on 15 February 2024, the Fermi Gamma-ray Burst Monitor (GBM)
triggered and located GRB 240215A (trigger 729703985/240215648),
which was also detected by Swift/BAT-GUANO (J. DeLaunay et al. 2024, GCN 35733
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 ).
The Fermi GBM on-ground location is consistent with the Swift/BAT-GUANO position.

The angle from the Fermi LAT boresight is 67 degrees.

The GBM light curve consists of a pulse followed by weak emission with a duration (T90)
of about 57 s (50-300 keV). The time-averaged spectrum
from T0-4.1 to T0+60.4 s is best fit by
a simple power law function with index -1.77 +/- 0.06.

The event fluence (10-1000 keV) in this time interval is
(3.6 +/- 0.3)E-06 erg/cm^2. The 1-sec peak photon flux measured
starting from T0-0.064 s in the 10-1000 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:
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/"

D.N. Burrows (PSU), J.P. Osborne (U. Leicester), K.L. Page (U.
Leicester), A.P. Beardmore (U. Leicester), C. Salvaggio (INAF-OAB), M.
Ferro (INAF-OAB), R. Brivio (INAF-OAB), J. D. Gropp (PSU), S. Dichiara
(PSU) and P.A. Evans (U. Leicester) reports on behalf of the Swift-XRT
team:

Swift-XRT has performed follow-up observations of the
Swift/BAT-detected burst GRB 240215A in a series of observations tiled
on the sky. The total exposure time is 4.4 ks, distributed over 4
tiles; the maximum exposure at a single sky location was 2.7 ks. The
data were collected between T0+44.5 ks and T0+1384.7 ks, and are
entirely in Photon Counting (PC) mode. 

Four uncatalogued X-ray sources are detected, of which one ("Source 2")
is fading with >3-sigma significance, and is therefore likely the GRB
afterglow.  The position of this source is RA, Dec=132.0101, -6.5099
which is equivalent to:

RA (J2000): 08:48:2.42
Dec(J2000): -06:30:35.5

with an uncertainty of 8.1 arcsec (radius, 90% confidence).  This
position is 14.9 arcmin from the Swift/BAT position.  The source is
fading with alpha >0.5.

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00021670.
The results of the full analysis of the tiled XRT observations are
available at https://www.swift.ac.uk/xrt_products/TILED_GRB00123.

This circular is an official product of the Swift-XRT team.