Detection of X-ray brightening from the CV LAMOST J015016.17+375618.9 by Einstein Probe

ATel #16896; D. Y. Li (NAO, CAS), R.-Z. Li (YNAO, CAS), S. Q. Jiang (NAO, CAS), H. Zhou (PMO, CAS), X. L. Chen (YNU), K. Chatterjee (YNU) and C. C. Jin (NAO, CAS) report on behalf of the Einstein Probe team:
on 7 Nov 2024; 09:52 UT
Credential Certification: Yuan Liu (liuyuan@bao.ac.cn)

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We report on the detection of X-ray brightening of the CV LAMOST J015016.17+375618.9 by the Einstein Probe (EP). The source was first detected by the Wide-field X-ray Telescope (WXT) on board EP in a single pointing observation (with an exposure time of 11.8 ks) at 2024-11-05T07:13:32 (UTC). The position of the source is R.A. = 27.556 deg, Dec. = 37.937 deg, with an uncertainty of 2.3 arcmin. A backwards search by data stacking finds that the source has brightened since 28th Oct. An upper limit to the flux of ~2e-12 ergs/s/cm^2 is set by the non-detection of stacking data taken by EP-WXT on 7th Sep.

The WXT spectrum of the last observation can be fitted by an absorbed power law with a photon index of 1.3 (+0.7, -0.4), with the NH fixed at the Galactic value of 5.2e+20 cm^-2. The derived unabsorbed flux in 0.5-4 keV is 7.2 (+/-2.7) e-12 ergs/s/cm^2.

With the observation of the Follow-up X-ray Telescope (FXT) on board EP performed at 2024-11-06T08:52:05, a bright X-ray source was detected at R.A.= 27.5677 deg, Dec.= 37.9381 deg (with an uncertainty of 10 arcsec), consistent with the WXT source position. This position is consistent with that of the CV LAMOST J015016.17+375618.9, a previously known X-ray source, with an angular separation of 1.9 arcsec. Preliminary analysis shows that the FXT spectrum can be modeled by an absorbed power law with a photon index of 1.53 (+0.1, -0.08), and the derived unabsorbed 0.5-10 keV flux is 7.83 (+0.21, -0.21) e-12 ergs/s/cm^2, which is more than one order of magnitude higher than that from the ROSAT All Sky survey (~2e-13 ergs/s/cm^2).

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.