Detection of the optical counterpart of the proposed double degenerate polar RX J1914+24

Abstract

We have detected the optical counterpart of the proposed double degenerate polar RX J1914124. The I-band light curve is modulated on the 9.5-min period seen in X-rays. There is no evidence for any other periods. No significant modulation is seen in J. The infrared colours of RX J1914124 are not consistent with a main-sequence dwarf secondary star. Our ASCA spectrum of RX J1914124 is typical of a heavily absorbed polar and our ASCA light curve also shows only the 9.5-min period. We find that the folded I band and X-ray light curves are out of phase. We attribute the I-band flux to the irradiated face of the donor star. The long-term X-ray light curve shows a variation in the observed flux of up to an order of magnitude. These observations strengthen the view that RX J1914124 is indeed the first double degenerate polar to be detected. In this light, we discuss the synchronizing mechanisms in such a close binary and other system parameters.

Ultra-Short Period Double-Degenerate Binaries

“…The same was found in the optical by Ramsay et al (2000). A similar analysis of RX J0806.3+1527 X-ray data by Israel et al (1999) and optical data by Israel et al (2002) and Ramsay et al (2002a) also found only one period with its harmonics (but see below for further discussions).…”

“…No hard component was evident in the ROSATdata (Motch & Haberl 1995). Much deeper hard X-ray observations of RX J1914.4+2456 were carried out by Ramsay et al (2000) with ASCA: they measured an upper limit of the bolometric luminosity of this component of 10~7 with respect to the terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1017/S0252921100002281 …”

“…The accretion had to be far from symmetric about the rotation axis in order to prevent a lower region rotating into view as the upper rotated over the limb of the star; they considered absorption could not be the cause, and that pole-switching would not be possible on the observed short timescales in the system. Ramsay et al (2000) examined the long-term brightness of RX J1914.4+2456 and found that its measured brightness varied between 0.03 and 0.3 HRI cts s _ 1 in the X-ray and between / = 16.6 and / = 18.2 in the red over a period of 6 years. Such variability in X-rays is also evident in RX J0806.3+1527 (Israel et al 1999) and in the optical even on short time scales (Ramsay et al 2002a, Israel et al 2002.…”

“…In order to characterise the nature of the secondary in RX J1914.4+2456, Ramsay et al (2000) Ramsay et al (2002b) where the magnitudes are with respect to Star 'B' of Motch et al (1996).…”

“…Since then the optical counterpart has been identified (Ramsay et al 2000) and significant progress has been made in elucidating the nature of the system. In 1999, another soft source, RX J0806.3+1527, was identified with a pulsation period of 321s (Israel et al 1999, also Beuermann et al 1999, again classified as an IP.…”