The period-gap cataclysmic variable CzeV404 Her: A link between SW Sex and SU UMa systems

Kára, Jan; Zharikov, S. V.; Wolf, M.; Kučáková, H.; Cagaš, P.; Rodriguez, A. L. Medina; Mašek, M.

doi:10.1051/0004-6361/202140958

“…Since Jacobian has a strong dependence on the radius (∝ r −3 ), an omission of Jacobian gives a biased impression that the emission from the outer disk much exceeds that from the inner disk. We note that the same issue has already been pointed out by Kato (2021) in figure 12 of Kára et al (2021). In figure A1, we show the copied Doppler map of Hα of Neustroev et al (2016) A.1.3 double-humped profile in quiescence of WZ Sge-type dwarf novae Amantayeva et al (2021) showed that the double-humped orbital profile of EZ Lyn in quiescence can be explained with a spiral arm structure in an accretion disk reaching the 2:1 resonance radius.…”

Section: A12 Jacobian In Conversion From Doppler Tomography To Spacia...supporting

confidence: 68%

“…Since Jacobian has a strong dependence on the radius (∝ r −3 ), an omission of Jacobian gives a biased impression that the emission from the outer disk much exceeds that from the inner disk. We note that the same issue has already been pointed out byKato (2021) in figure12ofKára et al (2021). In figureA1, we show the copied Doppler map of Hα of Neustroev et al (2016) using data observed in 2005 (upper left-hand panel).…”

supporting

confidence: 64%

2021 superoutburst of the WZ Sge-type dwarf nova V627 Pegasi lacks an early superhump phase

Tampo

¹

,

Kato

²

,

Kojiguchi

³

et al. 2023

Publications of the Astronomical Society of Japan

1

0

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Superoutbursts in WZ Sge-type dwarf novae (DNe) are characterized by both early superhumps and ordinary superhumps originating from the 2 : 1 and 3 : 1 resonances, respectively. However, some WZ Sge-type DNe show a superoutburst lacking early superhumps; it is not well established how these differ from superoutbursts with an early superhump phase. We report time-resolved photometric observations of the WZ Sge-type DN V627 Peg during its 2021 superoutburst. The detection of ordinary superhumps before the superoutburst peak highlights that this 2021 superoutburst of V627 Peg, like that in 2014, did not feature an early superhump phase. The duration of stage B superhumps was slightly longer in the 2010 superoutburst accompanied by early superhumps than that in the 2014 and 2021 superoutbursts, which lacked early superhumps. This result suggests that an accretion disk experiencing the 2 : 1 resonance may have a larger mass at the inner part of the disk and hence needs more time for the inner disk to become eccentric. The presence of a precursor outburst in the 2021 superoutburst suggests that the maximum disk radius should be smaller than that of the 2014 superoutburst, even though the duration of quiescence was longer than that before the 2021 superoutburst. This could be accomplished if the 2021 superoutburst was triggered as an inside-out outburst or if the mass transfer rate in quiescence changes by a factor of two, suggesting that the outburst mechanism and quiescence state of WZ Sge-type DNe may have more variety than ever thought.

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“…It could also provide insights on how the system changes during the small flares appearing during quiescence. Additionally, such spectra would permit a similar analysis to what what was done by Kára et al (2021), who used Doppler tomography (Marsh & Horne 1988) on the disc emission lines to obtain information on the velocity structure of the disc. Moreover, new spectra, especially in UV, could also help elucidate the nature of the primary and secondary.…”

Section: Discussionmentioning

confidence: 93%

OGLE-BLG504.12.201843: A possible extreme dwarf nova

Landri¹,

Pejcha²,

Pawlak³

et al. 2022

Preprint

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We present the analysis of existing optical photometry and new optical spectroscopy of the candidate cataclysmic variable star OGLE-BLG504.12.201843. As was shown previously, this object has an orbital period of 0.523419 days and exhibits year-long outbursts with a mean period of 973 days. Using digitized photographic archives, we show that the earliest recorded outburst occurred in 1910. We propose that this object is a U Gem-type dwarf nova with extreme properties. The orbital variability of the system in outburst shows clear signs of an accretion disc, from which the outburst likely originates. During quiescence, the object slowly brightens by up to 0.75 mag in the 𝐼 band over 600 days before the outburst and exhibits small flares with amplitude 0.2 mag in the 𝐼 band. We interpret the gradual brightening as an increase in the luminosity and temperature of the accretion disc, which is theoretically predicted but only rarely seen in DNe. The origin of small flares remains unexplained. The spectra shows Balmer absorption lines both in quiescence and outburst, which can be associated with a bright secondary star or a cold accretion disc. During outbursts, emission lines with FWHM of about 450 km s −1 appear, but they lack typical double-peaked profiles. We suggest that either these lines originate in the disc winds or the orbital inclination is low, the latter being consistent with constrains obtained from the orbital variability of the system. Due to its extreme properties and peculiarities, OGLE-BLG504.12.201843 is an excellent object for further follow-up studies.

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“…To do this, we attempt to reproduce the collected photometric observations of the system eclipse light curves in quiescence, standstill, and during an outburst using the tool developed by Zharikov et al (2013). The detailed description of the model can be found in our recent papers of Subebekova et al (2020) and Kára et al (2021). Here we note only that the light curve is a superposition of the flux contribution of four main components: the white dwarf primary, the secondary star, and the accretion disk with the bright spot formed at the disk/ stream impact region.…”

Section: Eclipse Light-curve Modeling and System Parametersmentioning

confidence: 99%

“…The disk limb darkening also includes the following Eddington approximation (Mayo et al 1980;Paczynski & Schwarzenberg-Czerny 1980). We also used the complex model for the bright spot described in detail in Kára et al (2021; see Figure 9 therein) where all definitions of parameters can be found.…”

Section: Eclipse Light-curve Modeling and System Parametersmentioning

confidence: 99%

The Z Camelopardalis-type Star AY Piscium: Stellar and Accretion Disk Parameters

Kára

¹

,

Zharikov

²

,

Wolf

³

et al. 2023

ApJ

Self Cite

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We present a new study of the Z Cam-type eclipsing cataclysmic variable AY Piscium with the aim of determining the fundamental parameters of the system and the structure of the accretion flow therein. We use time-resolved photometric observations supplemented by spectroscopy in the standstill, to which we applied our light-curve modeling techniques and the Doppler tomography method, to update system parameters. We found that the system has a massive white dwarf M WD = 0.90(4) M ☉, a mass ratio q = 0.50(3), and the effective temperature of a secondary T 2 = 4100(50) K. The system inclination is i = 74.°8(7). The orbital period of the system P orb = 0.217320523(8) day is continuously increasing at a rate of P ̇ orb = + 7.6 ( 5 ) × 10 − 9 day yr−1. The mass-transfer rate varies between 2.4 × 10−10 M ⊙ yr−1 in quiescence up to 1.36 × 10−8 M ⊙ yr−1 in outburst. The accretion disk transitions from the cooler, flared, steady-state disk to a warmer state with a practically constant and relatively high disk height. The mass-transfer rate is about 1.6 × 10−9 M ⊙ yr−1 in the standstill. The Balmer emission lines show a multicomponent structure similar to that observed in long-orbital-period nova-like systems. Out of standstill, the system exhibits outburst bimodality, with long outbursts being more prominent. We conclude that the Balmer emission lines in AY Psc are formed by the combination of radiation from the irradiated surface of the secondary, from the outflow zone, and from winds originating in the bright spot and the disk’s inner part.

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The period-gap cataclysmic variable CzeV404 Her: A link between SW Sex and SU UMa systems

Cited by 7 publications

References 53 publications

2021 superoutburst of the WZ Sge-type dwarf nova V627 Pegasi lacks an early superhump phase

2021 superoutburst of the WZ Sge-type dwarf nova V627 Pegasi lacks an early superhump phase

OGLE-BLG504.12.201843: A possible extreme dwarf nova

The Z Camelopardalis-type Star AY Piscium: Stellar and Accretion Disk Parameters

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