Mon. Not. R. Astron. Soc., 471, 2902-2916 (2017/November-1)
Multiband study of RX J0838-2827 and XMM J083850.4-282759: a new asynchronous magnetic cataclysmic variable and a candidate transitional millisecond pulsar.
REA N., COTI ZELATI F., ESPOSITO P., D'AVANZO P., DE MARTINO D., ISRAEL G.L., TORRES D.F., CAMPANA S., BELLONI T.M., PAPITTO A., MASETTI N., CARRASCO L., POSSENTI A., WIERINGA M., DE ONA WILHELMI E., LI J., BOZZO E., FERRIGNO C., LINARES M., TAURIS T.M., HERNANZ M., RIBAS I., MONELLI M., BORGHESE A., BAGLIO M.C. and CASARES J.
Abstract (from CDS):
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.
© 2017 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society
accretion, accretion discs - novae, cataclysmic variables - pulsars: general - white dwarfs - X-rays: individual: RX J0838-2827 - X-rays: individual: XMM J083850.4 -282759 - X-rays: individual: XMM J083850.4 -282759
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