Fig 13 - uploaded by David K. Sing
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Extracted spectrum of the region containing the inner accretion disk and primary star. The spectrum is consistent with a ∼25000 K black body which has strong narrow absorption lines from H I, He I, Mg II, and Ca II.
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We report on the discovery of J0644+3344, a bright deeply eclipsing cataclysmic variable (CV) binary. Spectral signatures of both binary components and an accretion disk can be seen at optical wavelengths. The optical spectrum shows broad H I, He I, and He II accretion disk emission lines with deep narrow absorption components from H I, He I, Mg II...
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Citations
... The bright (V ∼ 13.5) novalike variable 1RXS J064434.5+334451 (hereafter J0644) was discovered to be an eclipsing binary by Sing et al. (2007). Their photometric observations over 16 nights between 2005 Feb 02 UT and 2006 Oct 13 UT revealed deep (1 − 1.2 mag) eclipses that recurred with an orbital period, P orb = 6.4649808 ± 0.0000060 hr. ...
... The most recent determination of the eclipse ephemeris was made by Hernández Santisteban et al. (2017). These authors acquired the original data for four eclipses from the work of Sing et al. (2007) and remeasured the times of mid-eclipse. They then combined these timings with a total of 10 additional timings that were obtained from eclipses observed in 2008 January and 2010 November and December finding HJD ecl = 2, 453, 403.759533 + 0.269 374 46 E, which is nearly identical to the earlier ephemeris. ...
... In this Research Note, we have compiled all previously published times of mid-eclipse (i.e., from Boyd (2012) and Hernández Santisteban et al. (2017)), including the 20 previously unpublished timings kindly provided by David Sing from his original work (Sing et al. 2007). We have used these timings, along with seven new eclipse timings that we have recently measured to update the ephemeris for J0644 and to check the stability of the orbital period. ...
We report seven new eclipse timings for the novalike variable 1RXS J064434.5+334451. An analysis of our data, along with all previously available timings (36 published and 16 unpublished), yields a best-fitting linear ephemeris of BJD$_\mathrm{ecl} = 2,453,403.7611(2) + 0.269~374~43(2)~\mathrm{E}$. We find a somewhat improved fit with a quadratic ephemeris given by: BJD$_\mathrm{ecl} = 2,453,403.7598 + 0.269~374~87~\mathrm{E} - 2.0\times10^{-11}~\mathrm{E}^2$, which suggests that the orbital period may be decreasing at a rate given by $\dot P \simeq -1.5\times10^{-10}$.
... (V ∼13.3 mag) was discovered by Woźniak et al. (2004) in the Northern Sky Variability Survey. Sing et al. (2007) reported this object as a deep eclipsing CV with the orbital period of Porb = 0.26937d and derived the physical parameters of the system, such as the WD mass M1 = 0.66M ⊙ , the mass ratio q = 0.78 and the WD temperature TWD∼25 000 K. They classified the system as a NL CV of the UX UMa-type or the SW Sex-type. Hernández Santisteban (2012), Echevarria (2015), and Hernández Santisteban et al. (2017) recently reported new time-resolved photometry and echelle spectroscopy of 1RXS J064434.5+334451. ...
... They constructed Doppler maps of the system in the Hα, Hβ, and He II 4686 emission lines and refined system parameters based on the obtained data. The WD with M1 = 0.82 ± 0.06M ⊙ and the mass ratio q = 0.96 ± 0.05 were proposed assuming the system inclination of i=78 • ± 2 in Hernández Santisteban et al. (2017) that is in a disagreement with Sing et al. (2007) and their own recent estimations: M1 = 0.91 ± 0.04M ⊙ , q = 0.91±0.09 from Hernández Santisteban (2012) and (2015). ...
... This allows us to determine exactly the phase 0.0 of the system and make an effort to identify the definite locations of emission-line sources. However, as we already noted, the system parameters determined by Sing et al. (2007), Hernández Santisteban (2012), Echevarria (2015), and Hernández Santisteban et al. (2017) for 1RXS J064434.5+334451 do not agree.. ...
New time-resolved optical spectroscopic echelle observations of the nova-like cataclysmic variable RW Sextantis were obtained, with the aim to study the properties of emission features in the system. The profile of the H_alpha emission line can be clearly divided into two (`narrow' and `wide') components. Similar emission profiles are observed in another nova-like system, 1RXS~J064434.5+33445, for which we also reanalysed the spectral data and redetermined the system parameters. The source of the `narrow', low-velocity component is the irradiated face of the secondary star. We disentangled and removed the `narrow' component from the H_alpha profile to study the origin and structure of the region emitting the wide component. We found that the `wide' component is not related to the white dwarf or the wind from the central part of the accretion disc, but is emanated from the outer side of the disc. Inspection of literature on similar systems indicates that this feature is common for some other long-period nova-like variables. We propose that the source of the `wide' component is an extended, low-velocity region in the outskirts of the opposite side of the accretion disc, with respect to the collision point of the accretion stream and the disc.
We present a catalog containing 839 candidate post–common envelope systems. Common envelope evolution is very important in stellar astrophysics, particularly in the context of very compact and short-period binaries, including cataclysmic variables, as progenitors of, e.g., supernovae Type Ia or mergers of black holes and/or neutron stars. At the same time, it is a barely understood process in binary evolution. Due to limitations, since partially remedied, on direct simulation, early investigations were mainly focused on providing analytic prescriptions of the outcome of common envelope evolution. In recent years, detailed hydrodynamical calculations have produced deeper insight into the previously elusive process of envelope ejection. However, a direct link between the observations and theory of this relatively short-lived phase in binary evolution has not been forthcoming. Therefore, the main insight to be gained from observations has to be derived from the current state of systems likely to have gone through a common envelope. Here we present an extensive catalog of such observations as found in the literature. The aim of this paper is to provide a reliable set of data, obtained from observations, to be used in the theoretical modeling of common envelope evolution. In this catalog, the former common envelope donor star is commonly observed as a white dwarf or hot subdwarf star. This catalog includes period and mass estimates wherever obtainable. Some binaries are borderline cases to allow an investigation of the transition between a common envelope formation and other mass-transfer processes.
We report seven new eclipse timings for the novalike variable 1RXS J064434.5+334451. An analysis of our data, along with all previously available timings (36 published and 16 unpublished), yields a best-fitting linear ephemeris of BJD ecl = 2,453,403.7611(2) + 0.269,374,43(2) E . We find a somewhat improved fit with a quadratic ephemeris given by: BJD ecl = 2,453,403.7598 + 0.269,374,87 E − 2.0 × 10 ⁻¹¹ E ² , which suggests that the orbital period may be decreasing at a rate given by P ˙ ≃ − 1.5 × 10 − 10 .
We present a catalogue containing 839 candidate post common envelope systems. Common envelope evolution is very important in stellar astrophysics, particularly in the context of very compact and short-period binaries, including cataclysmic variables, as progenitors of e.g. supernovae type Ia or mergers of black holes and/or neutron stars. At the same time it is a barely understood process in binary evolution. Due to limitations, since partially remedied, on direct simulation, early investigations were mainly focused on providing analytic prescriptions of the outcome of common envelope evolution. In recent years, detailed hydrodynamical calculations have produced deeper insight into the previously elusive process of envelope ejection. However, a direct link between observations and theory of this relatively short-lived phase in binary evolution has not been forthcoming. Therefore, the main insight to be gained from observations has to be derived from the current state of systems likely to have gone through a common envelope. Here we present an extensive catalogue of such observations as found in the literature. The aim of this paper is to provide a reliable set of data, obtained from observations, to be used in the theoretical modelling of common envelope evolution. In this catalogue, the former common envelope donor star is commonly observed as a white dwarf star or as a hot sub-dwarf star. This catalogue includes period and mass estimates, wherever obtainable. Some binaries are border line cases to allow an investigation of the transition between a common envelope formation and other mass-transfer processes.
SW Sextantis systems are nova-like cataclysmic variables that have unusual spectroscopic properties, which are thought to be caused by an accretion geometry having part of the mass flux trajectory out of the orbital plane. Accretion onto a magnetic white dwarf is one of the proposed scenarios for these systems. To verify this possibility, we analyzed photometric and polarimetric time-series data for a sample of six SW Sex stars. We report possible modulated circular polarization in BO Cet, SW Sex, and UU Aqr with periods of 11.1, 41.2, and 25.7 minutes, respectively, and less significant periodicities for V380 Oph at 22 minutes and V442 Oph at 19.4 minutes. We confirm previous results that LS Peg shows variable circular polarization. However, we determine a period of 18.8 minutes, which is different from the earlier reported value. We interpret these periods as the spin periods of the white dwarfs. Our polarimetric results indicate that 15% of the SW Sex systems have direct evidence of magnetic accretion. We also discuss SW Sex objects within the perspective of being magnetic systems, considering the latest findings about the demography, formation, and evolution of cataclysmic variables.
SW Sextantis systems are nova-like cataclysmic variables that have unusual spectroscopic properties, which are thought to be caused by an accretion geometry having part of the mass flux trajectory out of the orbital plane. Accretion onto a magnetic white dwarf is one of the proposed scenarios for these systems. To verify this possibility, we analysed photometric and polarimetric time-series data for a sample of six SW Sex stars. We report possible modulated circular polarization in BO Cet, SW Sex, and UU Aqr with periods of 11.1, 41.2 and 25.7 min, respectively, and less significant periodicities for V380 Oph at 22 min and V442 Oph at 19.4 min. We confirm previous results that LS Peg shows variable circular polarization. However, we determine a period of 18.8 min, which is different from the earlier reported value. We interpret these periods as the spin periods of the white dwarfs. Our polarimetric results indicate that 15% of the SW Sex systems have direct evidence of magnetic accretion. We also discuss SW Sex objects within the perspective of being magnetic systems, considering the latest findings about cataclysmic variables demography, formation and evolution.
p>We present measurements of the component masses in 15 Cataclysmic Variables (CVs) - 6 new estimates and 9 improved estimates. We provide new calibrations of the relationship between superhump period excess and mass ratio, and use this relation to estimate donor star masses for 225 superhumping CVs. With an increased sample of donor masses we revisit the implications for CV evolution. We confirm the high mass of white dwarfs in CVs, but find no trend in white dwarf mass with orbital period. We argue for a revision in the location of the orbital periodminimum of CVs to 79.6±0.2min, significantly shorter than previous estimates. We find that CV donors below the gap have an intrinsic scatter of only 0.005 R⊙ around a common evolutionary track, implying a correspondingly small variation in angular momentum loss (AML) rates. In contrast to prior studies, we find that standard CV evolutionary tracks - without additional AML - are a reasonable fit to the donor masses just below the period gap, but that they do not reproduce the observed period minimum, or fit the donor radii below 0.1M⊙.</p
We present measurements of the component masses in 15 Cataclysmic Variables (CVs) - 6 new estimates and 9 improved estimates. We provide new calibrations of the relationship between superhump period excess and mass ratio, and use this relation to estimate donor star masses for 225 superhumping CVs. With an increased sample of donor masses we revisit the implications for CV evolution. We confirm the high mass of white dwarfs in CVs, but find no trend in white dwarf mass with orbital period. We argue for a revision in the location of the orbital period minimum of CVs to $79.6 \pm 0.2$ min, significantly shorter than previous estimates. We find that CV donors below the gap have an intrinsic scatter of only 0.005 R$_{\odot}$ around a common evolutionary track, implying a correspondingly small variation in angular momentum loss rates. In contrast to prior studies, we find that standard CV evolutionary tracks - without additional angular momentum loss - are a reasonable fit to the donor masses just below the period gap, but that they do not reproduce the observed period minimum, or fit the donor radii below 0.1 M$_{\odot}$.
We have obtained simultaneous photometric and spectroscopic observations of the cataclysmic variable 1RXS J064434.5+334451. We have calibrated the spectra for slit losses using the simultaneous photometry allowing to construct reliable Doppler images from H$\alpha$ and HeII 4686 emission lines. We have improved the ephemeris of the object based on new photometric eclipse timings, obtaining $HJD = 2453403.759533 + 0.26937446E$. Some eclipses present a clear internal structure which we attribute to a central HeII emission region surrounding the white dwarf, a finding supported by the Doppler tomography. This indicates that the system has a large inclination angle $i=78 \pm 2^{\circ}$. We have also analysed the radial velocity curve from the emission lines to measure its semi--amplitude, $K_1$, from H$\alpha$ and HeII 4686 and derive the masses of the components: $M_1=0.82\pm0.06$ M$_{\odot}$, $M_2=0.78\pm0.04$ M$_{\odot}$ and their separation $a=2.01\pm0.06$ $R_{\odot}$. The Doppler tomography and other observed features in this nova-like system strongly suggests that this is a SW Sex-type system.
