Hubble Space Telescope Ultraviolet Light Curves Reveal Interesting Properties of CC Sculptoris and RZ Leonis

Szkody, Paula; Mukadam, Anjum S.; Toloza, Odette; Gänsicke, B. T.; Dai, Zhenwen; Pala, A. F.; Waagen, Elizabeth O.; Godon, Patrick; Sion, E. M.

doi:10.3847/1538-3881/aa5c88

Cited by 12 publications

(7 citation statements)

References 40 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Throughout the duration of the individual HST observations (typically a few hours), CVs can show different types of variability, such as eclipses, modulations due to the white dwarf rotation, white dwarf pulsations, double humps and brightenings (e.g. Szkody et al 2002b;Araujo-Betancor et al 2003;Szkody et al 2017;Toloza et al 2016;Pala et al 2019). Eclipses are particularly important since they allow a white dwarf mass measurement based only on geometrical assumptions to be obtained.…”

Section: Light Curve Analysismentioning

confidence: 99%

Constraining the Evolution of Cataclysmic Variables via the Masses and Accretion Rates of their Underlying White Dwarfs

Pala,

Gänsicke,

Belloni

et al. 2021

Preprint

View full text Add to dashboard Cite

We report on the masses (𝑀 WD ), effective temperatures (𝑇 eff ) and secular mean accretion rates ( 𝑀 ) of 43 cataclysmic variable (CV) white dwarfs, 42 of which were obtained from the combined analysis of their Hubble Space Telescope ultraviolet data with the parallaxes provided by the Early Third Data Release of the Gaia space mission, and one from the white dwarf gravitational redshift. Our results double the number of CV white dwarfs with an accurate mass measurement, bringing the total census to 89 systems. From the study of the mass distribution, we derive 𝑀 WD = 0.81 +0.16 −0.20 M , in perfect agreement with previous results, and find no evidence of any evolution of the mass with orbital period. Moreover, we identify five systems with 𝑀 WD < 0.5M , which are most likely representative of helium-core white dwarfs, showing that these CVs are present in the overall population. We reveal the presence of an anti-correlation between the average accretion rates and the white dwarf masses for the systems below the 2 − 3 h period gap. Since 𝑀 reflects the rate of system angular momentum loss, this correlation suggests the presence of an additional mechanism of angular momentum loss that is more efficient at low white dwarf masses. This is the fundamental concept of the recently proposed empirical prescription of consequential angular momentum loss (eCAML) and our results provide observational support for it, although we also highlight how its current recipe needs to be refined to better reproduce the observed scatter in 𝑇 eff and 𝑀 , and the presence of helium-core white dwarfs.

show abstract

Section: Light Curve Analysismentioning

confidence: 99%

Constraining the Evolution of Cataclysmic Variables via the Masses and Accretion Rates of their Underlying White Dwarfs

Pala,

Gänsicke,

Belloni

et al. 2021

Preprint

View full text Add to dashboard Cite

show abstract

“…However, the K2 mission supplied an opportunity to study variable stars with uninterrupted, high-cadence photometry. Kepler observed only a small number of weakly magnetized CVs and IPs during its lifetime, including FO Aqr (Kennedy et al 2016), RZ Leo (Szkody et al 2017), MV Lyr (Scaringi et al 2017), and 1RXS J180431.1-273932 (Sanne et al 2021).…”

Section: K2 Observationsmentioning

confidence: 99%

Searching for Diamagnetic Blob Accretion in the 74 day K2 Observation of V2400 Ophiuchi

Langford,

Littlefield,

Garnavich

et al. 2021

Preprint

Self Cite

View full text Add to dashboard Cite

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 disk-less 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 lightcurve. 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 quasi-periodic oscillations, which make the beat and spin signals inconspicuous on short timescales. Notably, a log-log full power spectrum shows a break frequency at ∼ 10 2 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 seconds and 927.7 ± 0.1 seconds respectively. A power spectrum of the entire K2 observation demonstrates beat period dominance. However, time-resolved power spectra reveals a strong dependence between observation length and the dominant frequency of the light curve. For short observations (2-12 hrs) 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.

show abstract

“…Finally, we note that very few observations of IPs by either the Kepler spacecraft or the Transiting Exoplanet Survey Satellite (TESS) have been published. FO Aqr (Kennedy et al 2016) and RZ Leo (Szkody et al 2017) are two exceptions. MV Lyr, whose magnetic field is so weak that it can channel the accretion flow only at very low accretion rates, is another such system (Scaringi et al 2017).…”

Section: Introductionmentioning

confidence: 96%

Quasi-periodic Oscillations in the TESS Light Curve of TX Col, a Diskless Intermediate Polar on the Precipice of Forming an Accretion Disk

Scaringi

Garnavich

Szkody

et al. 2021

Self Cite

View full text Add to dashboard Cite

One of the fundamental properties of an intermediate polar is the dynamical nature of the accretion flow as it encounters the white dwarf's (WD's) magnetosphere. Many works have presumed a dichotomy between disk-fed accretion, in which the WD accretes from a Keplerian disk, and stream-fed accretion, in which the matter stream from the donor star directly impacts the WD's magnetosphere without forming a disk. However, there is also a third, poorly understood regime in which the accretion flow consists of a torus of diamagnetic blobs that encircles the WD. This mode of accretion is expected to exist at mass-transfer rates below those observed during disk-fed accretion, but above those observed during pure stream-fed accretion. We invoke the diamagnetic-blob regime to explain the exceptional Transiting Exoplanet Survey Satellite light curve of the intermediate polar TX Col, which transitioned into and out of states of enhanced accretion during Cycles 1 and 3. Power-spectral analysis reveals that the accretion was principally stream fed. However, when the mass-transfer rate spiked, large-amplitude quasiperiodic oscillations (QPOs) abruptly appeared and dominated the light curve for weeks. The QPOs have two striking properties: they appear in a stream-fed geometry at elevated accretion rates, and they occur preferentially within a well-defined range of frequencies (∼10-25 cycle day −1 ). We propose that during episodes of enhanced accretion, a torus of diamagnetic blobs forms near the binary's circularization radius and that the QPOs are beats between the white dwarf's spin frequency and unstable blob orbits within the WD's magnetosphere. We discuss how such a torus could be a critical step in producing an accretion disk in a formerly diskless system.Unified Astronomy Thesaurus concepts: DQ Herculis stars (407); Cataclysmic variable stars (203); White dwarf stars (1799); Stellar magnetic fields (1610)

show abstract

Hubble Space Telescope Ultraviolet Light Curves Reveal Interesting Properties of CC Sculptoris and RZ Leonis

Cited by 12 publications

References 40 publications

Constraining the Evolution of Cataclysmic Variables via the Masses and Accretion Rates of their Underlying White Dwarfs

Constraining the Evolution of Cataclysmic Variables via the Masses and Accretion Rates of their Underlying White Dwarfs

Searching for Diamagnetic Blob Accretion in the 74 day K2 Observation of V2400 Ophiuchi

Quasi-periodic Oscillations in the TESS Light Curve of TX Col, a Diskless Intermediate Polar on the Precipice of Forming an Accretion Disk

Contact Info

Product

Resources

About