V1460 Her: A fast spinning white dwarf accreting from an evolved donor star

Abstract

We present time-resolved optical and ultraviolet spectroscopy and photometry of V1460~Her, an eclipsing cataclysmic variable with a 4.99\,h orbital period and an overluminous K5-type donor star. The optical spectra show emission lines from an accretion disc along with absorption lines from the donor. We use these to measure radial velocities, which, together with constraints upon the orbital inclination from photometry, imply masses of $M_1=0.869\pm 0.006{\mathrm{M}}_{\odot }$ and $M_2=0.295\pm 0.004{\mathrm{M}}_{\odot }$ for the white dwarf and the donor. The radius of the donor, $R_2=0.43\pm 0.002{\mathrm{R}}_{\odot }$, is $\approx 50$ per cent larger than expected given its mass, while its spectral type is much earlier than the M3.5 type that would be expected from a main sequence star with a similar mass. HST spectra show strong $\mathrm{N}\mathrm{V}$ 1240 A emission but no $\mathrm{C}\mathrm{IV}$ 1550 A emission, evidence for CNO-processed material. The donor is therefore a bloated, over-luminous remnant of a thermal-timescale stage of high mass transfer and has yet to re-establish thermal equilibrium. Remarkably, the HST ultraviolet data also show a strong 30 per cent peak-to-peak, $38.9$s pulsation that we explain as being due to the spin of the white dwarf, potentially putting V1460 Her in a similar category to the propeller system AE Aqr in terms of its spin frequency and evolutionary path. AE Aqr also features a post-thermal timescale mass donor, and V1460 Her may therefore be its weak magnetic field analogue since the accretion disc is still present, with the white dwarf spin-up a result of a recent high accretion rate.

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Cited by in corpus (16)

• A catalogue of cataclysmic variables from 20 years of the Sloan Digital Sky Survey with new classifications, periods, trends and oddities
• Birth of the ELMs: a ZTF survey for evolved cataclysmic variables turning into extremely low-mass white dwarfs
• Found: a rapidly spinning white dwarf in LAMOST J024048.51+195226.9
• Reversing the verdict: Cataclysmic variables could be the dominant progenitors of AM CVn binaries after all
• LAMOST J0140355+392651: An evolved cataclysmic variable donor transitioning to become an extremely low mass white dwarf
• Radio and optical observations of the possible AE Aqr twin, LAMOST J024048.51+195226.9
• A faint companion around CrA-9: protoplanet or obscured binary?
• Confirmation of a Second Propeller: A High-Inclination Twin of AE~Aquarii
• The interacting double white dwarf population with LISA; stochastic foreground and resolved sources
• Optical detection of the rapidly spinning white dwarf in V1460 Her
• Mass limits of the extremely fast-spinning white dwarf CTCV J2056-3014
• Periodicity from X-ray sources within the inner Galactic disk
• Searching for cataclysmic variable stars in unidentified X-ray sources
• Testing the third body hypothesis in the Cataclysmic Variables LU Camelopardalis, QZSerpentis, V1007 Herculis and BK Lyncis
• Prospects for the Observation of Continuous Gravitational Waves from Deformed Fast-spinning White Dwarfs
• Gravitational Wave Emission by Accretion of Matter and Magnetic Deformation in Fast Rotating White Dwarfs