Two Long-period Cataclysmic Variable Stars: ASASSN-14ho and V1062 Cyg

Gasque, L. Claire; Hening, Callum A.; Hviding, Raphael E.; Thorstensen, J. R.; Paterson, K.; Breytenbach, H.; Motsoaledi, Mokhine; Woudt, P. A.

doi:10.3847/1538-3881/ab3e04

Cited by 8 publications

(11 citation statements)

References 22 publications

(19 reference statements)

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“…It has been already observationally known such a secondary is indeed present (Thorstensen 2015). Although such a result was apparently not present in model parameters in Knigge (2006) as stated in Gasque et al (2019), studies have shown that such systems can be formed if mass transfer occurs after the secondary has undergone significant nuclear evolution (e.g. Podsiadlowski et al 2003;Goliasch and Nelson 2015).…”

Section: Discussionmentioning

confidence: 92%

“…Quite recently, Gasque et al (2019) reported a radial velocity study of this object and obtained P orb of 0.24315(10) d. From the mass function, Gasque et al (2019) derived a constraint on the masses of the primary, secondary and the inclination. Their result favored a massive (∼1.0 M ⊙ ) white dwarf and an undermassive secondary for this P orb .…”

Section: Asassn-14homentioning

confidence: 99%

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ASASSN-14ho: Longest-period dwarf nova with multiple rebrightenings

Katô

2020

Publications of the Astronomical Society of Japan

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The post-outburst rebrightening phenomenon in dwarf novae and X-ray novae is still one of the most challenging subjects for theories of accretion disks. It has been widely recognized that post-outburst rebrightenings are a key feature of WZ Sge-type dwarf novae, which predominantly have short ( < ∼ 0.06 d) orbital periods. I found four post-outburst rebrightenings in ASASSN-14ho during its 2014 outburst, whose orbital period has recently measured to be exceptionally long [0.24315(10) d]. Using the formal solution of the radial velocity study in the literature, I discuss the possibility that this object can be an SU UMa-type dwarf nova near the stability border of the 3:1 resonance despite its exceptionally long orbital period. Such objects are considered to be produced if mass transfer occurs after the secondary has undergone significant nuclear evolution and they may be hidden in a significant number among dwarf novae showing multiple post-outburst rebrightenings.

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Section: Discussionmentioning

confidence: 92%

Section: Asassn-14homentioning

confidence: 99%

ASASSN-14ho: Longest-period dwarf nova with multiple rebrightenings

Katô

2020

Publications of the Astronomical Society of Japan

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“…This object showed four rebrightenings after the main superoutburst in 2014 (Kato 2020). The orbital period and mass ratio are 0.24315(10) d and 0.28, respectively (Gasque et al 2019). This orbital period is the longest one among known SU UMa-type DNe.…”

Section: Introductionmentioning

confidence: 77%

ASASSN-18aan: An Eclipsing SU UMa-type Cataclysmic Variable with a 3.6-hour Orbital Period and a Late G-type Secondary Star

Wakamatsu,

Thorstensen,

Kojiguchi

et al. 2021

Preprint

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We report photometric and spectroscopic observations of the eclipsing SU UMa-type dwarf nova ASASSN-18aan. We observed the 2018 superoutburst with 2.3 mag brightening and found the orbital period (P orb ) to be 0.149454(3) d, or 3.59 hr. This is longward of the period gap, establishing ASASSN-18aan as one of a small number of long-P orb SU UMa-type dwarf novae. The estimated mass ratio, (q = M 2 /M 1 = 0.278(1)), is almost identical to the upper limit of tidal instability by the 3:1 resonance. From eclipses, we found that the accretion disk at the onset of the superoutburst may reach the 3:1 resonance radius, suggesting that the superoutburst of ASASSN-18aan results from the tidal instability. Considering the case of long-P orb WZ Sge-type dwarf novae, we suggest that the tidal dissipation at the tidal truncation radius is enough to induce SU UMa-like behavior in relatively high-q systems such as SU UMatype dwarf novae, but that this is no longer effective in low-q systems such as WZ Sge-type dwarf novae. The unusual nature of the system extends to the secondary star, for which we find a spectral type of G9, much earlier than typical for the orbital period, and a secondary mass M 2 of around 0.18 M ⊙ , smaller than expected for the orbital period and the secondary's spectral type. We also see indications of enhanced sodium abundance in the secondary's spectrum. Anomalously hot secondaries are seen in a modest number of other CVs and related objects. These systems evidently underwent significant nuclear evolution before the onset of mass transfer. In the case of ASASSN-18aan, this apparently resulted in a mass ratio lower than typically found at the system's P orb , which may account for the occurrence of a superoutburst at this relatively long period.

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“…In Figure 13, we compare the objects in our sample to these objects, and to the canonical donor sequence for unevolved donors (black dashed line). The other objects are QZ Ser (Thorstensen et al 2002a), EI Psc (also called 1RXS J232953.9+062814; Thorstensen et al 2002b), SDSS J170213.26 + 322954.1 (Littlefair et al 2006, BF Eridani (Neustroev & Zharikov 2008), CSS J134052.0 + 151341 (Thorstensen 2013), HS 0218+3229 (Rodríguez-Gil et al 2009), SDSS J001153.08-064739.2 (Rebassa-Mansergas et al 2014, ASAS-SN 13cl (Thorstensen 2015), ASAS-SN 15cm (Thorstensen et al 2016), ASAS-SN 14ho (Gasque et al 2019), V1460 Her (Ashley et al 2020, and ASAS-SN 18aan (Wakamatsu et al 2021). To our knowledge, this represents a near-complete inventory of currently known evolved CV donors, though new systems are regularly being discovered.…”

Section: Comparison To Other Evolved Cvsmentioning

confidence: 99%

Birth of the ELMs: a ZTF survey for evolved cataclysmic variables turning into extremely low-mass white dwarfs

El-Badry,

Rix,

Quataert

et al. 2021

Preprint

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We present a systematic survey for mass-transferring and recently-detached cataclysmic variables (CVs) with evolved secondaries, which are progenitors of extremely low mass white dwarfs (ELM WDs), AM CVn systems, and detached ultracompact binaries. We select targets below the main sequence in the Gaia color-magnitude diagram with ZTF light curves showing large-amplitude ellipsoidal variability and orbital period 𝑃 orb < 6 hr. This yields 51 candidates brighter than 𝐺 = 18, of which we have obtained many-epoch spectra for 21. We confirm all 21 to be completely-or nearly-Roche lobe filling close binaries. 13 show evidence of ongoing mass transfer, which has likely just ceased in the other 8. Most of the secondaries are hotter than any previously known CV donors, with temperatures 4700 < 𝑇 eff /K < 8000. Remarkably, all secondaries with 𝑇 eff 7000 K appear to be detached, while all cooler secondaries are still mass-transferring. This transition likely marks the temperature where magnetic braking becomes inefficient due to loss of the donor's convective envelope. Joint fitting of spectral energy distributions, light curves, radial velocities, and parallaxes constrains system parameters robustly. Most of the proto-WD secondaries have masses near 0.15 𝑀 ; their companions have masses near 0.8 𝑀 . We infer a space density of ∼ 60 kpc −3 , roughly 80 times lower than that of normal CVs and three times lower than that of ELM WDs. The implied Galactic birth rate, R ∼ 60 Myr −1 , is half that of AM CVn binaries. Most systems are well-described by MESA models for CVs in which mass transfer begins only as the donor leaves the main sequence. All are predicted to reach minimum periods 5 𝑃 orb /min 30 within a Hubble time, where they will become AM CVn binaries or merge. This sample triples the known evolved CV population, includes far hotter donors than previous studies, and offers broad opportunities for improving understanding of the compact binary population.

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Two Long-period Cataclysmic Variable Stars: ASASSN-14ho and V1062 Cyg

Cited by 8 publications

References 22 publications

ASASSN-14ho: Longest-period dwarf nova with multiple rebrightenings

ASASSN-14ho: Longest-period dwarf nova with multiple rebrightenings

ASASSN-18aan: An Eclipsing SU UMa-type Cataclysmic Variable with a 3.6-hour Orbital Period and a Late G-type Secondary Star

Birth of the ELMs: a ZTF survey for evolved cataclysmic variables turning into extremely low-mass white dwarfs

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