SVOM/ECLAIRs detection of an X-ray rebrightening from the BHXB AT2019wey
ATel #17680; S. Le Stum (APC, France), M. Brunet (IRAP, F), F. Cangemi (APC, F), A. Coleiro (APC, F), L. Tao (IHEP, China), L. Zhang (IHEP, C)
on 14 Feb 2026; 17:33 UT
Credential Certification: Floriane Cangemi (cangemi@apc.in2p3.fr)
Subjects: X-ray, Binary, Black Hole
Referred to by ATel #: 17686
We report on the detection of AT2019wey (=ATLAS 19bcxp) by the ECLAIRs coded-mask instrument on board the SVOM mission. The source was automatically detected by the Quicklook Analysis of the X band data received on the ground for the first time at 2026-02-12T12:16 after 5.2 ks of exposure. The source was detected with a SNR of 18 and a count rate of 11 counts/s (22 mCrab) in the 4-40 keV energy range. The ECLAIRs localization is R.A. = 68.9 deg, Dec = 55.3 deg (J2000) with a statistical uncertainty of 0.1 deg in radius (90% confidence level). The center of the ECLAIRs position is 0.08 deg away from AT2019wey, i.e., well within the position uncertainties.
A preliminary spectral analysis shows that the 4-100 keV spectrum can be suitably fitted (chi2/dof = 27.95/22) with a cutoffpl model with a photon index Gamma = 1.0 +/- 0.4, and a cut-off energy of 19 (+14 / -7) keV. The derived unabsorbed flux in the 4-100 keV band is [8.1 (-7.0 /+0.5)]e-10 erg/s/cm^2. Refined analysis is ongoing. The source was last reported in ATel #17190 in a soft spectral state, with no significant emission detected above 4 keV. The present detection suggests either the onset of a new outburst or a significant hardening of the X-ray spectrum. The source was not detected in earlier ECLAIRs pointings, supporting the interpretation of a recent change in its X-ray activity.
AT2019wey was first identified as an optical transient in December 2019 and subsequently detected in X-rays during an outburst in 2020 (ATels #13571, #13932, #13948, #13976, #14100). Based on its X-ray, optical, and radio properties, the source was later classified as a candidate black hole X-ray binary (Yao et al. 2021, ApJ, 920, 120). Further multi-wavelength follow-up observations are encouraged to follow the activity of the source.
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.
