Renewed X-ray activity in the decline phase of 4U 0614+091 observed with SVOM/ECLAIRs
ATel #17528; D. Rawat (OBAS, France), F. Cangemi (APC, F), S. Le Stum (APC, F), S. Guillot (IRAP, F), M. Brunet (IRAP, F), A. Coleiro (APC, F), L. Zhang (IHEP, China)
on 6 Dec 2025; 11:25 UT
Credential Certification: Floriane Cangemi (cangemi@apc.in2p3.fr)
Subjects: X-ray, Binary, Neutron Star
We report the detection of a renewed X-ray activity from the neutron-star low-mass X-ray binary 4U 0614+09 with the ECLAIRs coded-mask instrument on board the SVOM mission. Beginning on 24th September, the source has exhibited a significant increase in X-ray flux, rising from about 14 counts per second to about 40 counts per second (in the 4-10 keV band) on 28th November 2025.
A preliminary spectral analysis of the 1st December observation (during which the ECLAIRs light curve already shows signs of decline, with the 4-10 keV count rate decreasing from 36 counts per second to 30 counts per second within a day) was performed over an exposure time of 15.7 ks. The resulting spectrum is well fitted (chi2 = 17.07 for 19 dof) by a model consisting of an unabsorbed blackbody with a temperature of kT = 1.3 (+0.1/-0.1) keV (90% confidence level) and a radius of Rbb = 1.92 (+0.55/-0.56) km, assuming a distance of 3 kpc (Galloway et al. 2020), together with a power-law component characterized by a photon index gamma = 2.9 (+0.2/-0.4) and a normalization of 2.7 (+3.0/-1.9). The derived unabsorbed flux in the 4-50 keV band is 2.17 (+0.09/-0.07) 10-9 erg/s/cm^2.
The light curve further shows a decreasing trend, but an increase in flux from 20 to about 28 counts per second was observed between 4th and 5th December in the 4-10 keV band. This source is known to exhibit outbursts with highly variable recurrence times, as well as oscillations associated with type-I thermonuclear bursts. No type-I burst has been detected with ECLAIRs throughout the rising phase, starting on 24th September.
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.
