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Free keywords:
LARGE-MAGELLANIC-CLOUD; X-RAY SOURCES; PHOTON IMAGING CAMERA; DEPTH
SURVEY EFEDS; XMM-NEWTON; AM CVN; OPTICAL COUNTERPART; INTERMEDIATE
POLARS; RX J1914.4+2456; MODELAstronomy & Astrophysics; white dwarfs; Magellanic Clouds; X-rays: binaries; X-rays: individuals:
eRASSU J060839.5-704014;
Abstract:
Context. During four all-sky surveys (eRASS1-4), eROSITA, the soft X-ray instrument aboard Spektrum-Roentgen-Gamma (SRG) detected a new supersoft X-ray source, eRASSU J060839.5-704014, in the direction of the Large Magellanic Cloud (LMC). Aims. We arranged follow-up observations in the X-ray and optical wavelengths and further searched in archival observations to reveal the nature of the object. Methods. Using X-ray observations with XMM-Newton we investigated the temporal and spectral behaviour of the source. Results. We discover pulsations at 374 s with a pulse profile consistent with 100% modulation. We identify two other periodicities in the eROSITA data, which we establish as aliases due to the sampling of the eROSITA light curve. We identify a multi-wavelength counterpart to the X-ray source in UVW1 and g, r, i, and z images obtained by the optical/UV monitor on XMM-Newton and the Dark Energy Camera at the Cerro Tololo Inter-American Observatory. The timing and spectral characteristics of the source are consistent with a double degenerate ultra-compact binary system in the foreground of the LMC. eRASSU J060839.5-704014 belongs to a rare class of AM CVns, which are important to study in the context of progenitors of SN Ia and for persistent gravitational wave detection. Conclusions. We identify eRASSU J060839.5-704014 as a new double degenerate ultra-compact binary located in the foreground of the LMC.
