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To: stefano@bicar.it
From: atel@astronomerstelegram.org
Subject: ATel  17233, 17234, 17235
Message-Id: <20250619071647.37144288092B@server.astronomerstelegram.org>
Date: Thu, 19 Jun 2025 03:16:47 -0400 (EDT)

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Posted: Within the last 24 hours
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ATEL #17233							     ATEL #17233

Title:	SVOM/ECLAIRs Detection of a possible photospheric radius expansion
		Type I X-ray burst from 4U 1850-086 in the globular cluster NGC 6712
Author:	F. Cangemi (APC, France), O. Godet (IRAP, F), S. Guillot (IRAP,
		F), J.-L. Atteia (IRAP, F), L. Zhang (IHEP, China)
Queries:	cangemi@apc.in2p3.fr
Posted:	18 Jun 2025; 07:52 UT
Subjects:X-ray, Binary, Neutron Star

On June 16th 2025 at 11:37:51.8 UTC (Tb), the onboard trigger of SVOM/ECLAIRs
detected a Type I thermonuclear X-ray burst at a position coincident with
the globular cluster NGC 6712 in which lies the known X-ray burster 4U
1850-086. The trigger localisation at RA=283.241 deg. and Dec=-8.727 deg.
is 2.2 arcminutes from 4U 1850-086, well within the 3.85 arcminutes uncertainty
on the position (90% confidence).

In the past, this source has exhibited a few X-ray bursts, mostly of several
minutes durations or longer (with RXTE, Galloway et al. 2020; with Swift-BAT,
ATel #5972, ATel #5978;  with MAXI, ATel #7500, and with MAXI+NICER, ATel
#16600), and three bursts with order 20-sec durations (with Integral JEM-X,
Galloway et al. 2020).

A preliminary time-resolved spectral analysis shows a decrease in the blackbody
temperature from kT = 2.7 +/- 0.2 keV (90% confidence)  to kT = 1.5 +/-0.5
keV over the ~10 seconds of the burst duration. A drop in temperature is
observed, decreasing from 2.8 +/- 0.2 keV to 2.0 +/- 0.2 keV keV between
Tb+8.02 seconds and Tb+10.02 seconds, while at the same time, the photospheric
radius increases from 0.80 +/- 0.07 km to 1.29 +/- 0.12 km, assuming a
distance of 7.4 +/- 0.6 kpc (Baumgardt & Vasiliev 2021). The increase in
blackbody normalization coincident with the drop in the temperature suggests
that the event could be a photospheric radius expansion (PRE) burst.

The integrated 4-30 keV flux is dropping from (7.8 +/- 0.5)e-08 erg/s/cm^2
(68% confidence) to (8.6 +/- 1.2)e-09 erg/s/cm^2 between Tb+4.02 and Tb+12.02
s. These fluxes correspond to a luminosity of 5.1e38 erg/s and 5.6e37 erg/s
assuming a distance of 7.4 kpc.

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. MXT has been developed jointly by CNES, CEA,
IJCLab, University of Leicester and MPE.

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Password Certification: Floriane Cangemi (cangemi@apc.in2p3.fr)
https://www.astronomerstelegram.org/?read=17233
==============================================================================
ATEL #17234							     ATEL #17234

Title:	A recent NuSTAR observation of the source GX 17+2
Author:	Aditya S  Mondal (Visva-Bharati)
Queries:	adityas.mondal@visva-bharati.ac.in
Posted:	18 Jun 2025; 16:26 UT
Subjects:X-ray, Binary, Neutron Star

In 2024, NuSTAR frequently observed the neutron star low-mass X-ray binary
GX 17+2. One of these observations, performed on 2024 March 16, is considered
for the present analysis. This observation (Obs ID: 30902026002) had an
exposure time of roughly 13 ks. The source was clearly detected in the
3-40 keV energy band, with an average count of ~500 counts/s. The light
curve showed some flaring at the initial part of the observation.

The 3-40 keV NuSTAR spectrum (FPMA and FPMB) was initially fitted with
an absorbed single-temperature blackbody (bbodyrad in Xspec) and a multi-temperature
blackbody component (diskbb in Xspec). A broad asymmetric Fe K-alpha emission
and a Compton hump were present in the spectrum. The red wing of the Fe
K-alpha emission line extends down to ~5 keV while the blue wing drops
around ~7 keV. A relativistic reflection model (relxillNS) was introduced
to model these spectral features. In addition, the spectrum showed the
presence of two absorption edges, indicating the presence of absorbing
material in the system. The whole combination of models gives a reduced
chi^2=1117 for 975 d.o.f.

The disk and the blackbody temperature were found to be kT_in=1.98+-0.01
keV and kT_bb=3.1+-0.02 keV, respectively. The reflection fit reveals an
inner disk radius of R_in=1.15+-0.04 R_ISCO and an inclination angle of
i=38+-1 deg. The X-ray flux during this observation was ~1.31e-8 erg/s/cm^2
in the 3-40 keV energy band. The absorption edges were found at the energies
of 8.20+-0.03 keV and 9.50+-0.05 keV. The R_in and inclination angle values
are consistent with the previous measurements done by Ludlam et al. 2017,
ApJ, 836, 140 from the analysis of the earlier NuSTAR observation.

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Password Certification: Aditya S. Mondal (adityas.mondal@visva-bharati.ac.in)
https://www.astronomerstelegram.org/?read=17234
==============================================================================
ATEL #17235							     ATEL #17235

Title:	Spectroscopic Classification of Optical Transients with the
		Lick Shane telescope
Author:	K. Taggart, R. J. Foley (UCSC)
Queries:	k.taggart@ucsc.edu
Posted:	18 Jun 2025; 22:43 UT
Subjects:Optical, Supernovae

Title: Spectroscopic Classification of Optical Transients with the Lick
Shane telescope 
Authors: K. Taggart, R. J. Foley (UCSC)

We report the following classifications of optical transients from spectroscopic
observations with the Kast spectrograph on the Shane telescope. The targets
were supplied by the Young Supernova Experiment and ZTF. All observations
were made on 2025 June 18 UT. Classifications were performed with SNID
(Blondin & Tonry, 2007, ApJ, 666, 1024).

Name         | IAU Name | RA (J2000)  | Dec (J2000) |   z   | Type  | Phase
| Notes 
PS25cxw      |  2025mbd | 17:07:28.15 | +34:34:04.11| 0.027 |  IIn  | peak
| (1) 
ZTF25aaufdhw |  2025nbz | 22:11:52.21 | +00:06:38.49| 0.033 |  II   | peak
| (2)

Notes: 
When the redshift is given to 2 decimal places, it is derived from the
SN spectrum. 
Otherwise, the redshift is determined from the host galaxy.

1) The recent spectrum exhibits broad H-alpha emission (FWHM 4,900 km/s)
consistent with a Type IIn supernova, and we therefore update the classification
from SN to Type IIn. 
2) We measure narrow H-alpha emission with absorption minimum -1,500 km/s
atop of a broader H-alpha emission component with absorption minimum -9,900
km/s.

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Password Certification: Kirsty Taggart (k.taggart@ucsc.edu)
https://www.astronomerstelegram.org/?read=17235
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