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GCN Circular 34208

Subject
IceCube-230708A: Upper limits from Swift/BAT-GUANO
Date
2023-07-13T03:09:49Z (10 months ago)
From
Samuele Ronchini at PSU <sjs8171@psu.edu>
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/
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