Paloma: A Magnetic Cv Between Polars and Intermediate Polars

Abstract

We present analyses of archival X-ray data obtained from the XMM-Newton satellite and optical photometric data obtained from 1 m class telescopes of ARIES, Nainital of a magnetic cataclysmic variable (MCV) Paloma. Two persistent periods at 156 ± 1 minutes and 130 ± 1 minutes are present in the X-ray data, which we interpret as the orbital and spin periods, respectively. These periods are similar to those obtained from the previous as well as new optical photometric observations. The soft-X-ray excess seen in the X-ray spectrum of Paloma and the averaged X-ray spectra are well fitted by two-temperature plasma models with temperatures of 0.10 +0.02 −0.01 and 13.0 +0.5 −0.5 keV with an Fe Kα line and an absorbing column density of 4.6 × 10 22 cm -2 . This material partially covers 60 ± 2 % of the X-ray source. We also present the orbital and spin-phase-resolved spectroscopy of Paloma in the 0.3 − 10.0 keV energy band and find that the X-ray spectral parameters show orbital and spin-phase dependencies. New results obtained from optical and X-ray studies of Paloma indicate that it belongs to a class of a few magnetic CVs that seem to have the characteristics of both the polars and the intermediate polars.

Hard X-ray cataclysmic variables

“…These have been recently improved with a long optical campaign resulting in P Ω =1.393 h and P ω =1.355 h (Tovmassian et al, 2017). The spin-to-orbit period ratio is remarkably high, P ω /P Ω = 0.97 making IGR J19552+0044 the IP with the lowest degree of asynchronism, and joining "Paloma" which has a spin-to-orbit period ratio ∼0.83 (Joshi et al, 2016). These two systems are likely in their way to become polars and represent test cases for mCV evolution.…”

X-Ray and Optical Study of the Gamma-ray Source 3FGL J0838.8–2829: Identification of a Candidate Millisecond Pulsar Binary and an Asynchronous Polar

“…Other CVs with more complex light curves and multiple periods have also been proposed as extreme asynchronous polars, most notably RX J0524+42, dubbed "Paloma" (Schwarz et al 2007;Joshi et al 2016), and IGR J19552+0044 (Bernardini et al 2013;Thorstensen & Halpern 2013). Paloma is suggested to have an orbital period of 157 minutes, and a spin period that is either 136 or 146 minutes, which are asynchronous by 14% or 7% respectively (Schwarz et al 2007).…”

X-Ray Emissions from Accreting White Dwarfs: A Review

“…Finally, the difference between the orbital and spin periods of the object "Paloma" (156 minutes and 130 minutes, respectively Schwarz et al 2007, Joshi et al 2016 are too large for it to be a short-lived deviation. Since the well-established asynchronous polars are thought to synchronize within several centuries (Littlefield et al 2015), this transitional object may be best classified as a low luminosity diskless IP, with the highest ratio of P s to P o .…”