Multiwavelength report on LXT 221107A

ATel #15756; A. C. Rodriguez (Caltech), S. R. Kulkarni (Caltech)
on 11 Nov 2022; 20:31 UT
Credential Certification: Shri Kulkarni (srk@astro.caltech.edu)

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We summarize multi-wavelength archival data for the X-ray transient LXT 221107A (ATel #15748,15754) which is plausibly associated with ROSAT detection 2RXS J060415.1+124554 and HD 251108. We downoaed ASAS-SN and TESS datasets for HD 251108 and found a periodicity of 42.2 days (and less likely 22 days). The Gaia counterpart Gaia DR3 3342754943193083392 hasa parallax, radial and tangential velocities of 1.94 +/- 0.02 milliarcsecond, -57 +/- 23 km/s, 11.9 +/- 0.1 km/s, respectively. HD 251108 is above the main sequence on the Gaia color magnitude diagram, and thus evolved. Finally, HD 251108 is detected (8.8 mJy, 2–4 GHz) by both Epochs of the VLA Sky Survey (VLASS). The quiescent X-ray luminosity based on the ROSAT measurement, is 2E32 erg/s. The peak X-ray luminosity reported from LEIA is 1E34 erg/s, lasting for ~3 days (ATel #15754). We suggest HD 251108 system is an RS CVn-type active binary star. The peak luminosity, outburst duration, and X-ray to optical flux ratio place this star among the most luminous and longest lasting RS CVn outbursts (e.g. Figure 10 of Karmakar et al. 2022, accepted by MNRAS).