1RXH J082623.6–505741: A New Long-period Cataclysmic Variable with an Evolved Donor and a Low Mass-transfer Rate

Abstract

We report the discovery of 1RXH J082623.6−505741, a 10.4 hr orbital period compact binary. Modeling extensive optical photometry and spectroscopy reveals a ∼0.4 M ⊙ K-type secondary transferring mass through a low-state accretion disk to a nonmagnetic ∼0.8 M ⊙ white dwarf. The secondary is overluminous for its mass and dominates the optical spectra at all epochs and must be evolved to fill its Roche Lobe at this orbital period. The X-ray luminosity L X ∼ 1–2 × 1032 erg s−1 derived from both new XMM-Newton and archival observations, although high compared to most CVs, still only requires a modest accretion rate onto the white dwarf of M ̇ ∼ 3 × 10−11 to 3 × 10−10 M ⊙ yr−1, lower than expected for a cataclysmic variable with an evolved secondary. No dwarf nova outbursts have yet been observed from the system, consistent with the low derived mass-transfer rate. Several other cataclysmic variables with similar orbital periods also show unexpectedly low mass-transfer rates, even though selection effects disfavor the discovery of binaries with these properties. This suggests the abundance and evolutionary state of long-period, low mass-transfer rate cataclysmic variables are worthy of additional attention.

An X-Ray-dim “Isolated” Neutron Star in a Binary?

“…However, there is no evidence for the dwarf nova outburst in our long time-series archives data (see Figure 1). We also note that the fraction of dwarf novae above the period gap can remain in quiescence due to the low accretion rates or large accretion disk (Sokolovsky et al 2022). If we consider that approximately half of the gravitational energy of the accreting gas is liberated through X-rays in the boundary layer, then for an M c ∼ 1.00 M e white dwarf, the inferred accretion rate of  ~´-M 1.63 10 11 M e yr −1 implies the X-ray luminosity of ∼1.38 × 10 32 erg s −1 .…”

The multi-wavelength view of shocks in the fastest nova V1674 Her

“…We searched for periodicities in photon arrival times using the 2 code (Sokolovsky et al 2022b) constructing the ' periodogram' (de Jager et al 1989;de Jager & Büsching 2010;Kerr 2011). No periodicities were identified in the trial period range of 1 to 1000 s that would satisfy the following criteria: (i) be significant at < 0.05 level ( § 1); (ii) be present in both FPMA and FPMB data; (iii) not be a multiple of the NuSTAR orbital period.…”

From Active Stars to Black Holes: A Discovery Tool for Galactic X-Ray Sources

“…It also undergoes regular, triangularshaped outbursts, which last ∼200 days, in contrast to typical dwarf nova outbursts which last ∼10 days. At its orbital period, the donor must be an evolved subgiant (e.g., Sokolovsky et al 2022). The optical spectrum is indeed dominated by the FGtype donor, albeit with He II 4686 and the rare CIII/NIII Figure 9.…”