Cataclysmic variable (CVs) are close interacting binaries in which a white dwarf accretes materials from a low mass main sequence companion. CVs can experience nova eruptions due to low mass transfer rates. In the standard theory of CV evolution, the ejected materials during nova eruptions are assumed to leave the system in the form of fast, isotropic, optically thick winds, which predicts that novae only result in positive variation (expansion) of orbital period (i.e. positive $ΔP$). In addition, the angular momentum losses (magnetic braking and gravitational radiation) only predicts a steady long-term decay in the orbital period of CVs, i.e. $\dot P$ is negative. Interestingly, an observation lasting over 30 years reveals positive and negative values for both $ΔP$ and $\dot P$ in CVs, strongly conflicting with the standard evolutionary patterns. However, it cannot be excluded that these observations originate from short-term phenomena caused by nova eruptions because of a short timescale of observations. In this paper, we model the effect of instantaneous nova eruptions on the evolution of CVs, considering three mechanisms associated with mass loss in nova eruptions, including fast wind, Frank jet and binary-driven mass loss. By assuming that the observed $ΔP$ and $\dot P$ are dominated by short-term phenomena, our results show that the binary-driven mass loss can explain almost all of the observations of normal CVs. However, the Frank jet may be needed for some of long-period CVs with evolved companions.
I report new orbital periods (P) for 13 classical novae, based on light curves from TESS, AAVSO, and other public archives. These new nova periods now constitute nearly one-seventh of all known nova periods. Five of my systems have P>1 day, which doubles the number of such systems that must have evolved companion stars. (This is simply because ground-based time series have neither the coverage nor the stability required to discover these small-amplitude long periods.) V1016 Sgr has a rare P below the period gap, and suddenly becomes useful for current debates on evolution of novae. Five of the…
Kepler high cadence data are used to measure the orbital periods and to determine the orbital waveforms of five dwarf novae. A significant improvement of the period of V1504 Cyg is achieved, while for the other systems periods are derived which are compatible with previous determinations. The orbital waveforms of the short period systems V1504 Cyg, V344 Lyr and V516 Lyr are very nearly sinusoidal, while the longer period dwarf nova V447 Lyr appears almost to be a twin of U Gem. The unusual system KIC 9202990 exhibits distinct variations of its waveform as a function of brightness during its ou…
I report on a large-scale search for the orbital periods (P) of most known nova systems, by looking for significant, coherent, and stable optical photometric modulation in two or more independent light curves taken mostly from the large surveys of TESS, Kepler, AAVSO, SMARTS, OGLE, ASAS, and ZTF. I have discovered 31 new orbital periods. Further, I have measured new periods for 18 novae with evolved companions, to 30 per cent accuracy, as based on their spectral energy distribution. Also, I have confirmed, improved, and rejected prior claims for P in 46 novae. (As part of this effort, I recogn…
The impact of nova eruptions on the long-term evolution of Cataclysmic Variables(CVs) is one of the least understood and intensively discussed topics in the field. Acrucial ingredient to improve with this would be to establish a large sample of post-novae with known properties, starting with the most easily accessible one, the orbitalperiod. Here we report new orbital periods for six faint novae: X Cir (3.71 h), ILNor (1.62 h), DY Pup (3.35 h), V363 Sgr (3.03 h), V2572 Sgr (3.75 h) and CQ Vel(2.7 h). We furthermore revise the periods for the old novae OY Ara, RS Car, V365Car, V849 Oph, V728 Sc…
Orbital Period Changes for Fourteen Novae and the Critical Failures of the Predictions of Standard Theories, the Hibernation Model, and the Magnetic Braking Model
The Optical Gravitational Lensing Experiment. Dwarf Novae in the OGLE Data. I. Three New Dwarf Novae: One in the Period Gap and Two Longer Period Objects
Superhumps are among the abundant variable phenomena observed in the light curves of cataclysmic variables (CVs). They come in two flavours as positive and negative superhumps, distinguished by periods slightly longer or shorter, respectively, than the orbital periods of these interacting binary systems. Positive superhumps are ubiquitous in superoutbursting short period dwarf novae of the SU~UMa type but are less common in longer period systems with accretion disks in a permanent bright state such as novalike variables and most old novae. Negative superhumps do not seem not to have a preferen…
Changes in the supercycle lengths of some SU UMa-type dwarf novae have been detected by other studies, and indicate that the mass transfer rates noticeably decrease over time. We investigated the supercycle lengths of three SU UMa-type dwarf novae: AR Pic, QW Ser and V521 Peg, to determine if they have detectable changes in their supercycles. We present the results of optical spectroscopic and photometric observations of these sources. Our observations were conducted in 2016 and 2017 at the Boyden Observatory and the Sutherland station of the South African Astronomical Observatory. The quiesce…
Recurrent novae are star systems in which a massive white dwarf accretes material at such a high rate that it undergoes thermonuclear runaways every 1 - 100 years. They are the only class of novae in which the white dwarf can grow in mass, making some of these systems strong Type Ia supernova progenitor candidates. Almost all known recurrent novae are long-period (P_orb > 12 hrs) binary systems in which the requisite mass supply rate can be provided by an evolved (sub-)giant donor star. However, at least two recurrent novae are short-period (P_orb < 3 hrs) binaries in which mass transfer would…
High speed photometry of faint Cataclysmic Variables - VII. Targets selected from the Sloan Digital Sky Survey and the Catalina Real-time Transient Survey
A nova eruption irradiates and heats the donor star in a cataclysmic variable to high temperatures $T_{\rm irr}$, causing its outer layers to expand and overflow the Roche lobe. We calculate the donor's heating and expansion both analytically and numerically, under the assumption of spherical symmetry, and find that irradiation drives enhanced mass transfer from the donor at a rate $\dot{m}\propto T_{\rm irr}^{5/3}$, which reaches $\dot{m}\sim 10^{-6}\textrm{ M}_\odot\textrm{ yr}^{-1}$ at the peak of the eruption - about a thousand times faster than during quiescence. As the nova subsides and …
We present X-ray observations of novae V2491 Cyg and KT Eri about 9 years post-outburst, of the dwarf nova and post-nova candidate EY Cyg, and of a VY Scl variable. The first three objects were observed with XMM-Newton, KT Eri also with the Chandra ACIS-S camera, V794 Aql with the Chandra ACIS-S camera and High Energy Transmission Gratings. The two recent novae, similar in outburst amplitude and light curve, appear very different at quiescence. Assuming half of the gravitational energy is irradiated in X-rays, V2491 Cyg is accreting at $\dot{m}=1.4\times10^{-9}-10^{-8}M_\odot/yr$, while for KT…
Yunnan Observatories, Chinese Academy of Sciences (CAS)(中国科学院云南天文台);International Centre of Supernovae, Yunnan Key Laboratory(超新星国际中心,云南省重点实验室);University of Chinese Academy of Sciences(中国科学院大学);Center for Astronomical Mega-Science, Chinese Academy of Sciences(中国科学院天文大科学研究中心)
Accrete, Accrete, Accrete... Bang! (and repeat): The Remarkable Recurrent Novae
所有的新星都会复发,但只有少数几颗被观察到喷发不止一次。这些系统,复发新星(RNe),是新星的最极端的例子。RNe长期以来一直被认为是潜在的Ia型超新星祖先,最近他们对这一“荣誉”的要求得到了加强。在这篇简短的评论中,RNe将在最大震级下降率(MMRD)相空间的框架内提出。最近的工作整合到新星模型,以及随后的白矮星的增长,将被探讨。本文还介绍了RNe在银河系和河外的星群,包括新发现的“快速复发新星”子集(复发周期在10年或更短),以及迄今为止发现的最令人兴奋的新星系统-M31 N 2008- 12 a,它的年度爆发和巨大的超新星遗迹。在整个过程中,有关RNe的开放问题,以及一些预期的挑战和机遇,不久的将来将带来的解决。
The neutron star low mass X-ray binary (LMXB) AX J1745.6-2901 was detected an anomalously fast decrease of orbital period. The decreasing rate of orbital period exceeds the contribution of all processes extracting angular momentum from the binary star in standard model. Using SCENARIO MACHINE code we conducted a population synthesis study of X-ray novae with neutron stars to investigate a possible formation and evolution of such binaries. Such close LMXBs should experience a preceding common envelope stage, in which the magnetic fields of the low mass main-sequence donor stars can be dramatica…