2016/11/30 by N. Rea, F. Coti Zelati, P. Esposito +31 · 1 citation
Physics and Astronomy · #Astronomy #Astrophysical Phenomena and Observations #Astrophysics #Astrophysics and Cosmic Phenomena #Cataclysmic variable star #Millisecond #Millisecond pulsar #Physics #Pulsar #Pulsars and Gravitational Waves Research #Stars #Variable star #White dwarf #astro-ph.HE #astro-ph.SR
paper · pdf · doi:10.1093/mnras/stx1560
19 pages, 14 figures. MNRAS accepted (submitted on November 10th, 2016)
arxiv created 2017/06/21 · openalex publication_date 2017/06/22 · arxiv updated 2017/08/23 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
In a search for the counterpart to the Fermi-LAT source 3FGL J0838.8−2829, we performed a multiwavelength campaign: in the X-ray band with Swift and XMM–Newton; in the infrared and optical with OAGH, ESO-NTT and IAC80; and in the radio with ATCA observations. We also used archival hard X-ray data obtained by INTEGRAL. We report on three X-ray sources consistent with the position of the Fermi-LAT source. We confirm the identification of the brightest object, RX J0838−2827, as a magnetic cataclysmic variable that we recognize as an asynchronous system (not associated with the Fermi-LAT source). RX J0838−2827 is extremely variable in the X-ray and optical bands, and timing analysis reveals the presence of several periodicities modulating its X-ray and optical emission. The most evident modulations are interpreted as being caused by the binary system orbital period of ∼1.64 h and the white dwarf spin period of ∼1.47 h. A strong flux modulation at ∼15 h is observed at all energy bands, consistent with the beat frequency between spin and orbital periods. Optical spectra show prominent Hβ, He i and He ii emission lines that are Doppler-modulated at the orbital period and at the beat period. Therefore, RX J0838−2827 accretes through a disc-less configuration and could be either a strongly asynchronous polar or a rare example of a pre-polar system on its way to reaching synchronism. Regarding the other two X-ray sources, XMM J083850.4−282759 showed a variable X-ray emission, with a powerful flare lasting for ∼600 s, similar to what is observed in transitional millisecond pulsars during the subluminous disc state: this observation possibly means that this source can be associated with the Fermi-LAT source.