Support ATel At Patreon

[ Previous | Next | ADS ]

EP-FXT detection of a possible new outburst from RX J0053.9-7226/SXP 46.6 in the SMC

ATel #16791; X. F. Zhao, Y. J. Xu, C. K. Li, Y. Chen, S. M. Jia, W. W. Cui, D. W. Han, M. Y. Ge, L. M. Song, J. Zhang, J. Guan, H. S. Zhao, J. J. Xu, H. Feng, S. N. Zhang (IHEP, CAS), D. Y. Li, Y. Liu, Z. X. Ling, C. C. Jin, W. Yuan, C. Zhang (NAOC, CAS), E. Kuulkers, A. Santovincenzo (ESA), P. O'Brien (Univ. of Leicester), K. Nandra, A. Rau, P. Friedrich, N. Meidinger, V. Burwitz (MPE), B. Cordier (CEA) on behalf of the Einstein Probe team
on 27 Aug 2024; 11:13 UT
Credential Certification: Yu-Peng Chen (chenyp@ihep.ac.cn)

Subjects: X-ray, Neutron Star, Pulsar

We report on the detection of X-ray brightening of the Be X-ray pulsar SXP 46.6 in the SMC by Einstein Probe (EP). The source was detected by the Follow-up X-ray Telescope (FXT) onboard EP in a single pointing observation (with an exposure time of 3.1 ks) beginning at 2024-08-26T18:13:01 (UTC). The position of the source is R.A. = 13.4773 deg, Dec. = -72.4469 deg, with an uncertainty of 10 arcsec (radius, 90% C.L. statistical and systematic). This position is consistent with that of SXP 46.6, a previously known X-ray source, with an angular separation of 6.0 arcsec.

Preliminary analysis shows that the FXT spectrum taken on August 26 can be modeled with an absorbed power-law model with a photon index of 0.82 (-0.12, +0.12) and a column density of 9.88 x 10^20 cm^-2. The derived unabsorbed flux in the 0.5-10 keV band is 1.38 (+0.05, -0.06) x 10^(-11) ergs/cm^2/s, giving an X-ray luminosity of ~1.4 x 10^36 erg/s for a distance of 65 kpc. The source was detected at a lower flux level of 1.1 x10^-12 ergs/cm^2/s, during a previous 1.4 ks FXT observation performed on August 22.

SXP 46.6 is a transient Be/X-ray binary in the SMC with a pulsation period of 46.6 s and an orbital period of ~137 d (Corbet et al. 1998; Galache et al. 2008). The source was not detected by FXT during its monitoring observations of the SMC starting on 2023-08-20T 04:27:57 (UTC) with an exposure of 3.1 ks. The upper limit is 1.25 x 10^-13 ergs/cm^2/s (90% confidence level). These observations suggest that SXP 46.6 is brightening and likely entering a new outburst. Multi-wavelength follow-up observations are encouraged.

Launched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics). EP is a mission of the Chinese Academy of Sciences in collaboration with ESA, MPE and CNES.