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To: stefano@bicar.it
From: atel@astronomerstelegram.org
Subject: ATel  17297, 17298
Message-Id: <20250722071057.945EA2880952@server.astronomerstelegram.org>
Date: Tue, 22 Jul 2025 03:10:57 -0400 (EDT)

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Posted: Within the last 24 hours
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ATEL #17297							     ATEL #17297

Title:	SVOM J195836+32283: a new galactic transient discovered by
		SVOM
Author:	D. Gotz, N. Dagoneau, A. Saccardi (CEA), D. Zhao, Y. Ma, L.
		Xin  (NAOC), J.-L. Atteia (IRAP)
Queries:	diego.gotz@cea.fr
Posted:	21 Jul 2025; 17:09 UT
Subjects:Optical, X-ray, Transient

On July 21th 2025 at 08:43:10 UTC  SVOM/ECLAIRs triggered on a source initially
identified as 4U 1954+31. SVOM slewed to the source location, and, due
to Earth occultation, MXT and VT could not observe the field right away.

As soon as MXT started the observation, about one hour later, at 09:32:37
UTC, its on board software detected an uncatalogued source in its field
of view, not consistent with the position of 4U 1954+31. The MXT observation
continued until 11:47:43 UTC.

Subsequent analysis of the entire MXT X-band data showed that the source
was not fading and, on the contrary, increased its flux by a factor about
two over the entire duration of the observation. In addition the source
presents a thermal spectrum, compatible with a black body of temperature
~0.2 keV. Based on these properties and on its position in the galactic
plane (l=69.03, b= 1.6) we propose to classify this source as a new galactic
transient, SVOM J195836+32283.

The J2000 X-ray coordinates are:

R.A. = 19h 58m 36s

Dec. = +32deg 28mm 20ss

with a 90% c.l. error radius of 30 arc sec (18 arc sec of statistical error).

The MXT error region was in the VT field of view during the SVOM second
orbit. A faint uncatalogued optical source was detected within the MXT
error region in VT_R band with a brightness of 22.2+/-0.4 mag, compared
to the PanSTARRS images, at the following J2000 coordinates

R.A. = 19h 58m 36.29s

Dec. = +32deg 28mm 25.7ss

with an error of 0.5 arc sec.

The VT images were obtained between 11:11:09 and 11:42:49 UTC with an effective
exposure time of 20x100 seconds. The VT magnitude is not corrected for
the Galactic extinction on the line of sight.

This source lies at 6 arc seconds from the MXT position, and we suggest
that it might be the counterpart of the X-ray source.

Follow-up observations at other wavelengths are encouraged.

The Space-based multi-band astronomical Variable Objects Monitor (SVOM)
is a China-France joint mission led by the Chinese National Space Administration
(CNSA), French Space Agency (CNES), and the Chinese Academy of Sciences
(CAS), which is dedicated to observing gamma-ray bursts and other transient
phenomena in the energetic universe. SVOM/ECLAIRs was developed jointly
by CNES, CEA-IRFU, CNRS-IRAP, CNRS-APC. SVOM/GRM was developed by the Institute
of High Energy Physics (IHEP) of CAS. SVOM/MXT was developed jointly by
CNES, CEA-IRFU, CNRS-IJCLab, University of Leicester, MPE. SVOM/VT was
jointly developed by Xi'an Institute of Optics and Precision Mechanics
(XIOPM), CAS and National astronomical observatories (NAOC), CAS.

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Password Certification: Diego Gotz (diego.gotz@cea.fr)
https://www.astronomerstelegram.org/?read=17297
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ATEL #17298							     ATEL #17298

Title:	A glitch in the Crab pulsar (PSR B0531+21)
Author:	Benjamin Shaw (University of Manchester), Danai Antonopoulou
		(UoM), Michael J. Keith (UoM), Andrew G. Lyne (UoM), Mitchell B. Mickaliger
		(UoM), Benjamin W. Stappers (UoM), Patrick Weltevrede (UoM)
Queries:	benjamin.shaw@manchester.ac.uk
Posted:	21 Jul 2025; 17:23 UT
Subjects:Radio, Pulsar, Magnetar

We report the detection of a small glitch event in the timing data of the
Crab pulsar (PSR B0531+21), which we monitor as part of the Jodrell Bank
Pulsar Timing Programme. The Crab pulsar is observed daily with the 42-ft
telescope using a 4 MHz wide band centred on 610 MHz. Additional short
observations are carried out with the Lovell telescope using a 384 MHz
wide band centred on 1532 MHz. This glitch is the 31st such event observed
in this pulsar and occurred on 2025 July 17; ~6 years after the previous
glitch in 2019. Preliminary analysis indicates a fractional rotational
spin-up of dF0/F0 = 2.33(9)E-09 and a fractional change to the spin-down
rate of dF1/F1 = 0.43(4)E-03 (1 sigma uncertainties). We currently measure
the glitch epoch to be MJD 60873.95(35). At present, we find no evidence
of any post-glitch transient behaviour; however we continue our daily monitoring
of the pulsar. Observations at other facilities are encouraged in order
to confirm the glitch and refine the measured parameters.

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Password Certification: Benjamin Shaw (benjamin.shaw@manchester.ac.uk)
https://www.astronomerstelegram.org/?read=17298
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