First Detection of an X-ray Outburst from the CV PNV J06483343+0656236 by Einstein Probe
ATel #17026; H. Q. Cheng, R. D. Liang (NAO, CAS), X.-Y. Zhou (PRIC), S. F. Zhu (USTC), D. Y. Li and C. C. Jin (NAO, CAS) report on behalf of the Einstein Probe team
on 11 Feb 2025; 09:56 UT
Credential Certification: Yuan Liu (liuyuan@bao.ac.cn)
Subjects: Cataclysmic Variable
We report on the Einstein Probe (EP)'s detection of a new X-ray outburst, namely EP J064833.4+065624, which is associated with the cataclysmic variable (CV) PNV J06483343+0656236. The outburst was first detected by the Wide-field X-ray Telescope (WXT) on board EP in a single pointing observation with an exposure time of 3.1 ks at 2025-02-05T13:01:30 (UTC). The position of the source is R.A. = 102.133 deg, Dec.= 6.913 deg, with an uncertainty of 2.9 arcmin (radius, 90% C.L. statistical and systematic). The WXT spectrum can be fitted by an absorbed power law with a photon index of 4.5 (+2.7, -2.1), with the column density N_H fixed at the Galactic value of 5.5e+21 cm^-2. The derived absorbed flux in 0.5-4 keV is 6.0 (+6.6, -3.2) e-12 ergs/s/cm^2.
A backward search by data stacking finds that the source has brightened since January 30th, 2025. The X-ray flux of the source remained relatively stable since the first detection, with a recently detected value of ~1.5e-11 ergs/s/cm^2 at 2025-02-09T09:54:25 (UTC).
We performed an observation with the Follow-up X-ray Telescope (FXT) on board EP at 2025-02-10T18:11:45. A bright X-ray source was detected at R.A.= 102.1393 deg, Dec. = 6.9401 deg, with an uncertainty of 10 arcsec (radius, 90% C.L. statistical and systematic), consistent with the WXT source position. This position is consistent with that of the CV PNV J06483343+0656236, with an angular separation of 1.3 arcsec. Preliminary analysis shows that the average 0.5-10 keV FXT spectrum can be modeled by an absorbed power law with a photon index of 1.54 (+0.15, -0.11) and a column density N_H of < 6.5e+20 cm^-2. The derived unabsorbed 0.5-10 keV flux is 1.36 (+0.13, -0.12) e-11 ergs/s/cm^2, which is more than one order of magnitude higher than that from the ROSAT All Sky Survey (~3.5e-13 ergs/s/cm^2).
This is the first time that an X-ray outburst is detected from PNV J06483343+0656236. We note that this CV also exhibits a contemporaneously prominent outburst in the optical band since January 29th, 2025, with its g-band brightness increased by ~4.8 magnitudes measured by the All-Sky Automated Survey for Supernovae (ASAS-SN).
More 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.
