Neglected X-ray discovered polars

Abstract

We report results on the ROSAT-discovered noneclipsing short-period polars RX J0154.0−5947, RX J0600.5−2709, RX J0859.1+0537, RX J0953.1+1458, and RX J1002.2−1925 collected over 30 years. We present accurate linear orbital ephemerides that allow a correct phasing of data taken decades apart. Three of the systems show cyclotron and Zeeman lines that yield magnetic field strengths of 36 MG, 19 MG, and 33 MG for the last three targets, respectively. RX J0154.0−5947, RX J0859.1+0537, and RX J1002.2−1925 show evidence for part-time accretion at both magnetic poles, while RX J0953.1+1458 is a polar with a stable one-pole geometry. RX J1002.2−1925 shows large variations in the shapes of its light curves that we associate with an unstable accretion geometry. Nevertheless, it appears to be synchronized. We determined the bolometric soft and hard X-ray fluxes and the luminosities at the Gaia distances of the five stars. Combined with estimates of the cyclotron luminosities, we derived high-state accretion rates that range from Ṁ = 2.9 × 10−11 M⊙ yr−1 to 9.7 × 10−11 M⊙ yr−1 for white dwarf masses between 0.61 and 0.82 M⊙, in agreement with predictions based on the observed effective temperatures of white dwarfs in polars and the theory of compressional heating. Our analysis lends support to the hypothesis that different mean accretion rates appply for the subgroups of short-period polars and nonmagnetic cataclysmic variables.

A MeerKAT Survey of Nearby Novalike Cataclysmic Variables

“…We find that for IX Vel M ≈ 7 × 10 −9 M yr −1 shows good agreement with the observed SED. This is closer to the value of (7.9 ± 1.0) ×10 −9 M yr −1 which was proposed by Beuermann & Thomas (1990) than to 5 ×10 −9 M yr −1 which was proposed by Linnell et al (2007), however, they noted that their model only excludes estimates above 8 ×10 −9 M yr −1 , in which case our value is still consistent. .…”

“…IX Vel is the brightest CV in the night sky, with V ∼ 9.5. Extensive studies of this system have yielded numerous system parameters, including the masses of the WD (M 1 ) and secondary companion (M 2 ): M 1 = 0.80 +0.16 −0.11 M and M 2 = 0.52 +0.10 −0.07 M (Beuermann & Thomas 1990), a mass transfer rate of M = 5×10 −9 M yr −1 and an inclination of i = 57 • ± 2 • (Linnell et al 2007). Ultraviolet spectra Table 1.…”

“…RW Sex is well-studied and optically bright non-eclipsing NL with a derived mass ratio of q = 0.74 ± 0.10 and system inclination between 28 • < i < 40 • (Beuermann et al 1992). Linnell et al (2010) estimated a mass transfer rate of M ∼ 5 × 10 −9 M yr −1 .…”

Kepler K2 and TESS observations of two magnetic cataclysmic variables: The new asynchronous polar SDSS J084617.11+245344.1 and Paloma

“…J0846 is listed in the Catalina Survey Periodic Variable Star Catalog with a period of 0.1827862 d, with no uncertainty specified (Drake et al 2014). −170 pc above the Galactic plane, which is significantly larger than nearly every polar (Beuermann et al 2021).…”

“…ω is the WD's spin frequency and Ω is the binary orbital frequency.The Gaia EDR3(Gaia Collaboration et al 2016 distance to J0846 is 1230 +800 −290 pc (Bailer-Jones et al 2021). Its Galactic latitude of +35.4 • therefore places it 710 +460 −170 pc above the Galactic plane, which is significantly larger than nearly every polar(Beuermann et al 2021).…”