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To: stefano@bicar.it
From: atel@astronomerstelegram.org
Subject: ATel 17385, 17386, 17387
Message-Id: <20250912071736.D076D28808E4@server.astronomerstelegram.org>
Date: Fri, 12 Sep 2025 03:17:36 -0400 (EDT)

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Posted: Within the last 24 hours
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ATEL #17385							     ATEL #17385

Title:	SVOM/ECLAIRs detection of a thermonuclear burst in Terzan 1
Author:	M. Brunet (IRAP, France), F. Cangemi (APC, F), S. Guillot
		(IRAP, F), A. Coleiro (APC, F), L. Zhang (IHEP, China)
Queries:	marius.brunet@irap.omp.eu
Posted:	11 Sep 2025; 08:47 UT
Subjects:X-ray, Binary, Globular Cluster, Neutron Star, Transient

We report on the detection of a type I thermonuclear burst located in the
globular cluster Terzan 1 by the ECLAIRs coded-mask instrument (4-150 keV)
on board the SVOM mission. The source was detected by the offline trigger
at 2025-09-05T10:20:02.2 on a timescale of 10.24 seconds.

The source has been located at R.A. = 263.973 deg, Dec = -30.462 deg (J2000)
with a 90% statistical uncertainty of 6.7' in radius. We associate the
ECLAIRs trigger source with XB 1732-30 (1RXS J173546.9-302859), whose coordinates
are located 1.9' away from the trigger location.

The 4-20 keV time-integrated spectrum can be well fitted (chi2/dof = 12.67/9)
using a bbodyrad model, with a temperature of kT = 2.44 +/- 0.07 keV and
a radius of 7.66 +0.50/-0.44 km, assuming a distance of 6.7 kpc (Baumgardt
et al, MNRAS 482-4, 2019). The derived unabsorbed flux in the 4-20 keV
band is 3.21 +0.15/-0.09 photons/s/cm^2, or (4.26 +0.16/-0.13)e-8 erg/s/cm^2.

The lightcurve shows a double peak structure in the 8-12 keV energy band,
not visible in the 4-8 keV energy band. This could indicate that ECLAIRs
detected a photospheric radius expansion (PRE) burst. However, a preliminary
time-resolved spectral analysis does not show the characteristic signatures
of a PRE burst, namely a significant drop in blackbody temperature (kT)
together with a strong increase in the emission radius (blackbody normalisation)
during the expansion phase, followed by a contraction back to the neutron
star radius.

The source XB 1732-30 is a known burster that was in quiescence for over
20 years until the 20th May 2025 when ECLAIRs detected a type I burst from
this sources (Atel #17201). A decline in the source's activity had since
been observed by NICER (ATel #17215). 
This new burst could indicate that the source is exhibiting renewed activity.
Moreover, MAXI has detected an apparent increase in the X-ray flux from
Terzan 1, similar to what was observed during a previous period of activity
reported in ATel #16124 (http://maxi.riken.jp/star_data/J1734-304/J1734-304.html).

Further multi-wavelength observations are encouraged.

The Space Variable Objects Monitor (SVOM) is a China-France joint mission
led by the Chinese National Space Administration (CNSA, China), National
Center for Space Studies (CNES, France), and the Chinese Academy of Sciences
(CAS, China), which is dedicated to observing gamma-ray bursts and other
transient phenomena in the energetic universe. ECLAIRs was developed jointly
by APC, CEA, CNES and IRAP.

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Password Certification: Sebastien Guillot (Sebastien.guillot@gmail.com)
https://www.astronomerstelegram.org/?read=17385
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ATEL #17386							     ATEL #17386

Title:	Two new impact events during total lunar eclipse on 7th September,
		2025 by Indian Centre for Space Physics telescope located at IERCOO
Author:	 Mohit Bisht, Kuldeep Belwal, Sandip K. Chakrabarti, D. Bhowmick,
		S. Chakrabarti, D. Bisht (Indian Centre for Space Physics)
Queries:	sandipchakrabarti9@gmail.com
Posted:	11 Sep 2025; 14:21 UT
Subjects:Optical, Solar System Object

At 2025-09-07 18:49:47.280UT, while monitoring the impact of meteorites
during the total lunar eclipse, we clearly observed a signature of impact,
creating two bright regions near Mare Tranquilltatis. Fig. 1 (http://csp.res.in/images/fig1.jpg)
shows our observed frame. Fig. 2 (http://csp.res.in/images/fig2.jpg) shows
the subtracted from the earlier frame taken 3s prior to this. Fig. 3 (http://csp.res.in/images/fig3.jpg)
shows approximate locations of the event. We used 10 inch Meade reflector
located at IERCOO, Sitapur (87.79E, 22.51N) with an ATIK camera (1391x1039)
and an exposure of 1s.

The simultaneous impacts indicate a possible grazing incidence of a meteorite
with a valley on its path. Size of each pixel is about 2.4km which limits
the width of possible craters. We encourage LRO 
to observe formations of possible new craters in these locations. We encourage
other observers to check if any event was seen in other wavelengths.

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Password Certification: Sandip Kumar  Chakrabarti (sandipchakrabarti9@gmail.com)
https://www.astronomerstelegram.org/?read=17386
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ATEL #17387							     ATEL #17387

Title:	Correction to ATel #17384
Author:	Jianhua Fang(ZL), Pei Wang(NAOC), Dengke Zhou(ZL), Huaxi Chen(ZL),
		Yi Feng(ZL),  Kuang Mao(ZL), Qi Wang(ZL), Zhaorong Tang(ZL), Qiuhong
		Pan(ZL), Dantong Jin(ZL), Di Li(THU/NAOC)
Queries:	wangpei@nao.cas.cn
Posted:	11 Sep 2025; 15:05 UT
Subjects:Radio, Gamma Ray, Neutron Star, Pulsar

In ATel #17384, the reported pulsar parameters were quoted without uncertainties.

We provide the parameters with uncertainties here.

PSR J1904-0708 (associated with 4FGL J1904.7-0708):

DM = 87.15 &plusmn; 0.05 pc cm-3, 
P = 2.05794 &plusmn; 0.00003 ms. 
</li>

PSR J1730-0359 (associated with 4FGL J1730.4-0359):

DM = 22.45 &plusmn; 0.05 pc cm-3, 
P = 5.08991 &plusmn; 0.00001 ms. 
</li>

PSR J1827+1141 (associated with 4FGL J1827.5+1141):

DM = 45.10 &plusmn; 0.05 pc cm-3, 
P = 2.65838 &plusmn; 0.00002 ms. 
</li>

These updates do not alter the scientific conclusions presented in
the original telegram.

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Password Certification: Pei Wang (wangpei@nao.cas.cn)
https://www.astronomerstelegram.org/?read=17387
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