GRB 220501A

A. D'Ai (INAF-IASFPA), E. Ambrosi (INAF-IASFPA),
V. D'Elia (SSDC & INAF-OAR), C. Gronwall (PSU), A. Y. Lien (U Tampa),
K. L. Page (U Leicester) and D. M. Palmer (LANL) report on behalf of
the Neil Gehrels Swift Observatory Team:

At 19:51:51 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 220501A (trigger=1104842).  Swift did not slew to the
burst location due to an observing constraint. 
The BAT on-board calculated location is 
RA, Dec 85.577, +14.033 which is 
   RA(J2000) = 05h 42m 18s
   Dec(J2000) = +14d 02' 00"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a single-peaked
structure with a duration of about 60 sec.  The peak count rate
was ~2500 counts/sec (15-350 keV), at ~0 sec after the trigger. 

Due to a Sun observing constraint, Swift cannot slew to the BAT
position until 07:38 UT on 2022 August 04. There will thus be no XRT or
UVOT data for this trigger before this time. 

Burst Advocate for this burst is A. D'Ai (antonino.dai AT inaf.it). 
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/)

The Fermi GBM team reports the detection of a likely LONG GRB

At 19:51:50 UT on 1 May 2022, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 220501A (trigger 673127515.736396 / 220501828).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 71.8, Dec = 11.5 (J2000 degrees, equivalent to J2000 04h 47m, 11d 30'), with a statistical uncertainty of 6.3 degrees.

The angle from the Fermi LAT boresight is 89.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2022/bn220501828/quicklook/glg_skymap_all_bn220501828.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/bn220501828/quicklook/glg_healpix_all_bn220501828.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2022/bn220501828/quicklook/glg_lc_medres34_bn220501828.gif

A. Klotz (CNRS-OMP-IRAP), A. de Ugarte Postigo, S. Antier (both 
CNRS-OCA-ARTEMIS), D. Dornic (CPPM), A. Sabahaddin (ShaO),T. Midavaine 
(KNC), V. Rupchandani (AUS), P. A. Duverne (IJCLAB), Y. Rajabov (UBAI), 
X. Song (BJP), X. F. Wang (THU/BJP), J. Zhu (BJP), L. Wang,  X. Zeng, A. 
Iskandar (XAO), and D. A. Kann (IAA-CSIC) report on behalf of the 
GRANDMA collaboration:

We observed the BAT error circle of GRB 220501A (D'Ai et al., GCN 31982
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 ; 
Fermi GBM Team, GCN 31983
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 ) with the TJML 11" Celestron telescope 
installed at Guitalens observatory. We recorded a stack of 8 x 60 s 
unfiltered images in the range from 28.8 to 38.9 minutes after the 
trigger.

We did not detect any optical counterpart of GRB 220501A in the BAT 
error circle to a limiting magnitude r(AB) > 16.0 mag. Photometry was 
calibrated against the Pan-STARRS catalog.

GRANDMA is a worldwide telescope network (grandma.ijclab.in2p3.fr) 
devoted to the observation of transients in the context of 
multi-messenger astrophysics (Antier et al. 2020 MNRAS 497, 5518). 
Kilonova-Catcher (KNC) is the citizen science program of GRANDMA 
(http://kilonovacatcher.in2p3.fr/).

O.J. Roberts (USRA) and C. Meegan (UAH)
report on behalf of the Fermi GBM Team:

"At 19:51:50.74 UT on 01 May 2022, the Fermi Gamma-Ray Burst Monitor (GBM)
triggered and located GRB 220501A (trigger 673127515 / 220501828), which
was also detected by Swift/BAT (A. D'Ai et al. 2022, GCN 31982
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 ). The
Fermi GBM Final Real-time Localization (GCN 31983
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 ) is consistent with the
Swift position.

The angle from the Fermi LAT boresight at the GBM trigger time is 94 degrees.

The GBM light curve shows a FRED-like burst
with a duration (T90) of about 51 s (50-300 keV).
The time-averaged spectrum from T0-3.6 s to T0+47.6 s is
best fit by a power law function with an exponential
high-energy cutoff. The power law index is -0.49 +/- 0.18 and
the cutoff energy, parameterized as Epeak, is 114 +/- 11 keV

The event fluence (10-1000 keV) in this time interval is
(3.53 +/- 0.24)E-06 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+2.0 s in the 10-1000 keV band
is 2.5 +/- 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/"

Y.-D. Hu, E. Fernandez-Garcia, T.-R. Sun, A. J. Castro-Tirado, M. D. Caballero-Garcia, R. Sanchez-Ramirez, I. Perez-Garcia (IAA-CSIC),  C. Perez del Pulgar,  A. Castellon, I. Carrasco, A. Reina (Univ. de Malaga) and F. Rendon (IAA-CSIC and INTA-CEDEA) on behalf of a larger collaboration, report:

Following the detection of GRB 220501A by Swift (D'Ai et al., GCNC 31982) and Fermi (Fermi GBM team, GCNC 31983, Roberts et al. GCNC 31988), the 0.3m BOOTES-1B robotic telescope in Mazagon (Huelva), southern Spain, automatically responded to this burst on May 1 at 20:14 UT (~22.3 min after trigger), right after the twilight and at high airmass. In the co-added frame (38 x 10 s, clear filter), no source is detected within the BAT error position (D'Ai et al., GCNC 31982) down to 17.5 mag, which is consistent with the non-detection reported by Klotz et al. (GCNC 31984).

We thank the staff at INTA-CEDEA for their excellent support.

H. A. Krimm (NSF),S. D. Barthelmy (GSFC),
A. D'Ai (INAF-IASFPA), S. Laha (GSFC/UMBC),
A. Y. Lien (U Tampa), C. B. Markwardt (GSFC),
D. M. Palmer (LANL), T. Parsotan (GSFC/UMBC),
T. Sakamoto (AGU), M. Stamatikos (OSU)
(i.e. the Swift-BAT team):

Using the data set from T-239 to T+816 sec from the recent telemetry
downlink, we report further analysis of BAT GRB 220501A (trigger #1104842)
(D'Ai et al., GCN Circ. 31982
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 ).  The BAT ground-calculated position is
RA, Dec = 85.583, 14.010 deg which is
   RA(J2000)  =  05h 42m 20.0s
   Dec(J2000) = +14d 00' 36.5"
with an uncertainty of 1.6 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 92%.

The mask-weighted light curve shows a FRED-like pulse that starts
at ~T-1 s and peaks at ~T+5 s. It is followed by a second weak pulse
at ~T+200 s. T90 (15-350 keV) is 202.24 +- 20.60 sec (estimated error
including systematics).

The time-averaged spectrum from T-1.21 to T+224.20 sec is best fit
by a power law with an exponential cutoff.  This fit gives a photon
index 0.64 +- 0.62, and Epeak of 72.3 +- 28.6 keV (chi squared 44.65
for 56 d.o.f.).  For this model the total fluence in the 15-150 keV
band is 2.2 +- 0.2 x 10^-6 erg/cm2 and the 1-sec peak flux measured
from T+4.28 sec in the 15-150 keV band is 1.2 +- 0.2 ph/cm2/sec.
 A fit to a simple power law gives a photon index of 1.54 +- 0.13
(chi squared 52.35 for 57 d.o.f.).  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/1104842/BA/