Abstract
Abstract Since its discovery in 1995, V2400 Ophiuchi (V2400 Oph) has stood apart from most known intermediate polar cataclysmic variables due to its proposed magnetic field strength (9–27 MG) and diskless accretion. To date, the exact accretion mechanism of the system is still unknown, and standard accretion models fail to accurately predict the peculiar behavior of its light curve. We present the K2 Campaign 11 light curve of V2400 Oph recording 74.19 days of photometric data cadenced at 1 minute. The light curve is dominated by aperiodic flickering and quasiperiodic oscillations, which make the beat and spin signals inconspicuous on short timescales. Notably, a log–log full power spectrum shows a break frequency at ∼102 cycles d−1 similar to some disk-fed systems. Through power-spectral analysis, the beat and spin periods are measured as 1003.4 ± 0.2 s and 927.7 ± 0.1 s, respectively. A power spectrum of the entire K2 observation demonstrates beat period dominance. However, time-resolved power spectra reveal a strong dependence between observation length and the dominant frequency of the light curve. For short observations (2–12 hr) the beat, spin, or first beat harmonic can be observed as the dominant periodic signal. Such incoherence and variability indicate a dynamical accretion system more complex than current intermediate polar theories can explain. We propose that a diamagnetic blob accretion model may serve as a plausible explanation for the accretion mechanism.
Highlights
Cataclysmic variable stars (CVs) offer astronomers the rare chance to observe accretion events over very short timescales.CV systems consist of two closely orbiting stars, a white dwarf primary and a red dwarf companion
CVs that contain white dwarf (WD) with significant (>1 MG) magnetic fields fall into two categories: polars, the strongest magnetic WDs, and intermediate polars (IPs), more moderate magnetic WDs
Standard IP theory predicts that if a white dwarf possesses a moderate magnetic field strength (∼1–10 MG), an accretion disk can form around the white dwarf (Patterson 1994)
Summary
Cataclysmic variable stars (CVs) offer astronomers the rare chance to observe accretion events over very short timescales. Known as “pole flipping,” this process is present in V2400 Oph; X-ray data implies that only 25% of the accretion stream participates in pole flipping (Hellier & Beardmore 2002) This evidence suggests there is some continual flow to each magnetic pole at all times, similar to a disk-fed accretion system. Joshi et al (2019) provide the most recent observational study of V2400 Oph Their Suzaku X-ray observations in 2014 showed the spin period to dominate the power spectrum, indicating the system had changed from a stream-fed to diskfed dominant accretion mechanism. Theoretically by King (1993) and Wynn & King (1995) This model predicts that in IPs, the accretion flow might consist of discrete blobs traveling along non-Keplerian orbits in the outer regions of the white dwarf’s Roche lobe. The long 74 day K2 light curve supplies ample data to constrain the accretion mechanism guided by previously proposed models and new investigative techniques
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
