文件操作 - 1777619173.M340990P9192.mail.planetcloud-host.com,S=7406,W=7534:2,

文件: /var/vmail/bicar.it/stefano/cur/1777619173.M340990P9192.mail.planetcloud-host.com,S=7406,W=7534:2,

编辑文件内容

Received-SPF: Pass (sender SPF authorized) identity=mailfrom; client-ip=174.142.199.243; helo=server.astronomerstelegram.org; envelope-from=atel@astronomerstelegram.org; receiver=stefano@bicar.it 
To: stefano@bicar.it
From: atel@astronomerstelegram.org
Subject: ATel  17770, 17771
Message-Id: <20260501070537.84DF72880810@server.astronomerstelegram.org>
Date: Fri,  1 May 2026 03:05:37 -0400 (EDT)

------------------------------------------------------------------------------ 
The Astronomer's Telegram is free to read, free to publish, free to
use.  Thanks to the support of our patrons, we can continue to
keep it free. https://www.patreon.com/astronomerstel
------------------------------------------------------------------------------ 
The Astronomer's Telegram                   http://www.astronomerstelegram.org 
------------------------------------------------------------------------------
Posted: Within the last 24 hours
==============================================================================
ATEL #17770							     ATEL #17770

Title:	SVOM/ECLAIRs detection of the ongoing outburst from the HMXB
		XTE J1859+083
Author:	F. Cangemi (APC, France), A. Coleiro (APC, F), M. Dennefeld
		(IAP, F), O. Godet (IRAP, F), D. Götz (CEA, F), S. Guillot (IRAP,
		F), S. Le Stum (APC, F), H.-L. Li (NAOC, China), S. Schanne (CEA,
		F), L. Tao (IHEP, C), L.-P. Xin (NAOC, C), L. Zhang (IHEP, C)
Queries:	cangemi@apc.in2p3.fr
Posted:	30 Apr 2026; 09:35 UT
Subjects:X-ray, Binary, Neutron Star

On Monday, April 27, 2026, at 13:58:46.114 UT, the onboard trigger software
of the SVOM/ECLAIRs telescope detected and localized a source at R.A. =
284.818 deg and Dec. = 8.363 deg (J2000), with an uncertainty radius of
6.67 arcmin (90% confidence level) in the 5-20 keV energy band (SNR = 12.10).

Following this detection, SVOM autonomously slewed to the trigger direction,
and observations were performed with MXT (0.2-10 keV) starting at 14:11:52.222
UT, for a total exposure of 13.7 ks. The MXT position R.A. = 284.765 deg,
Dec. = 8.249 (J2000) deg with an uncertainty radius of 40.61 arcsec (90%
confidence level) consistent with the source XTE J1859+083.

A preliminary joint spectral analysis of the simultaneous ECLAIRs and MXT
data shows that the 0.6-100 keV spectrum is well fitted by an absorbed
cutoff power-law model (chi-square = 289.32/266 dof) with a photon index
of 1.33 (+/-0.16), a cutoff energy of 21 (+8, -4) keV and a hydrogen column
density of 1.92 (+/-0.16) e22 cm-2. The absorbed flux in the 0.6-100 keV
energy band is 2.0 (+/-0.4) e-09 erg/cm2/s. All errors are at the 90% confidence
level.

Preliminary SVOM/VT analysis does not reveal any significant variation
in the VT_B band flux of the Be-star companion candidate associated with
this source (Salganik et al. 2021) during the observations lasting for
about 8 hours. In the VT_R band, the flux also shows no variation; however,
the photometry is contaminated by a nearby star located at R.A. = 284.756792
deg, Dec. = 8.246000 deg (J2000).

The onset of the outburst was first reported by MAXI on March 24 (ATel
#17730). This is the first time the source has entered an outburst state
since 2015 (ATels #7034, #7037, #7045, #7425). XTE J1859+083 is a high-mass
X-ray binary (HMXB) hosting an accreting neutron star, identified as an
X-ray pulsar with a Be-type companion. The relatively hard spectrum and
the presence of a cutoff at about 20 keV are consistent with those typically
observed in accretion-powered pulsars of this class.

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.

------------------------------------------------------------------------------
Password Certification: Floriane Cangemi (cangemi@apc.in2p3.fr)
https://www.astronomerstelegram.org/?read=17770
==============================================================================
ATEL #17771							     ATEL #17771

Title:	NuSTAR detects hard-state decay and weak reflection in GS 1354-64
Author:	Oluwashina Adegoke (Caltech), Javier Garcia (NASA/GSFC, Caltech),
		Fiona Harrison (Caltech), Karl Forster (Caltech)
Queries:	oadegoke@caltech.edu
Posted:	1 May 2026; 04:43 UT
Subjects:X-ray, Black Hole, Transient

The onset of a new outburst from the black hole X-ray binary GS 1354-64
was triggered by the MAXI/GSC nova alert system on 2025 December 25 (ATel
#17563). Since then, the source has been followed up extensively across
multiple bands (ATel #17582, #17583, #17586, #17611, #17618, #17625, #17650,
#17673, #17697, #17724). The first NuSTAR observation of the source during
the current outburst was carried out on 2026 January 13 (ATel #17612).
At that time, the source was in a bright hard state, revealing strong relativistic
reflection features, with Gamma=1.76^+0.01_-0.02 and Ecut=49+/-1 keV. The
observed 1-100 keV flux was ~1.2 E-8 erg/cm^2/s. Several additional NuSTAR
observations have since been carried out through DDT requests as well as
GO/ToO programs.

With the source now fading and approaching the end of its visibility window
for NuSTAR, we obtained a ~15 ks NuSTAR DDT observation on 2026 April 29.
The 1-100 keV source flux has decreased to ~1 E-9 erg/cm^2/s. The spectrum
is hard and can be described by a powerlaw continuum with weak reflection
features. Relativistic reflection modeling yields Gamma=1.75^+0.06_-0.17,
while the coronal temperature remains unconstrained. These properties suggest
that the source is in the low-hard state during the decay phase and is
likely to return to quiescence in the near future.

------------------------------------------------------------------------------
Password Certification: Oluwashina Adegoke (oadegoke@caltech.edu)
https://www.astronomerstelegram.org/?read=17771
==============================================================================

==============================================================================
This is an automatically-generated notice.  You can remove yourself permanently
from receiving both the Daily Email Digest and Instant Email Notices from
The Astronomer's Telegram by following this link:
https://www.astronomerstelegram.org?unsubscribe&confirmation=a803d34e7ea924f9a4142bac00763549&address=stefano@bicar.it

文件操作 - 1777619173.M340990P9192.mail.planetcloud-host.com,S=7406,W=7534:2,

文件: /var/vmail/bicar.it/stefano/cur/1777619173.M340990P9192.mail.planetcloud-host.com,S=7406,W=7534:2,

编辑文件内容

修改文件时间

删除文件