A first look at cataclysmic variable stars from the 2dF QSO survey (original) (raw)

VLT/FORS spectroscopy of faint cataclysmic variables discovered by the Sloan Digital Sky Survey

Monthly Notices of the Royal Astronomical Society, 2006

We present medium-resolution VLT/FORS2 spectroscopy of six cataclysmic variables discovered by the Sloan Digital Sky Survey. We determine orbital periods for SDSS J023322.61+005059.5 (96.08 ± 0.09 min), SDSS J091127.36+084140.7 (295.74 ± 0.22 min), SDSS J103533.02+055158.3 (82.10 ± 0.09 min), and SDSS J121607.03+052013.9 (most likely 98.82 ± 0.16 min, but the one-day aliases at 92 min and 107 min are also possible) using radial velocities measured from their Hα and Hβ emission lines. Three of the four orbital periods measured here are close to the observed 75-80 min minimum period for cataclysmic variables, indicating that the properties of the population of these objects discovered by the SDSS are substantially different to those of the cataclysmic variables found by other means. Additional photometry of SDSS J023322.61+005059.5 reveals a periodicity of approximately 60 min which we interpret as the spin period of the white dwarf, suggesting that this system is an intermediate polar with a low accretion rate. SDSS J103533.02+055158.3 has a period right at the observed minimum value, a spectrum dominated by the cool white dwarf primary star and exhibits deep eclipses, so is an excellent candidate for an accurate determination of the parameters of the system. The spectroscopic orbit of SDSS J121607.03+052013.9 has a velocity amplitude of only 13.8 ± 1.6 km s −1 , implying that this system has an extreme mass ratio. From several physical constraints we find that this object must contain either a high-mass white dwarf or a brown-dwarf-mass secondary component or both.

Spatial distribution and galactic model parameters of cataclysmic variables

New Astronomy, 2008

The spatial distribution, galactic model parameters and luminosity function of cataclysmic variables (CVs) in the solar neighbourhood have been determined from a carefully established sample of 459 CVs. The sample contains all of the CVs with distances computed from the Period-Luminosity-Colours (PLCs) relation of CVs which has been recently derived and calibrated with 2MASS photometric data. It has been found that an exponential function fits best to the observational zdistributions of all of the CVs in the sample, non-magnetic CVs and dwarf novae, while the sech 2 function is more appropriate for nova-like stars and polars. The vertical scaleheight of CVs is 158±14 pc for the 2MASS J-band limiting apparent magnitude of 15.8. On the other hand, the vertical scaleheights are 128±20 and 160±5 pc for dwarf novae and nova-like stars, respectively. The local space density of CVs is found to be ∼ 3 × 10 −5 pc −3 which is in agreement with the lower limit of the theoretical predictions. The luminosity function of CVs shows an increasing trend toward higher space densities at low luminosities, implying that the number of short-period systems should be high. The discrepancies between the theoretical and observational population studies of CVs will almost disappear if for the zdependence of the space density the sech 2 density function is used.

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

We report spectroscopy and photometry of the cataclysmic variable stars ASASSN-14ho and V1062 Cyg. Both are dwarf novae with spectra dominated by their secondary stars, which we classify approximately as K4 and M0.5, respectively. Their orbital periods, determined mostly from the secondary stars' radial velocities, proved to be nearly identical, respectively 350.14 ± 0.15 and 348.25 ± 0.60 min. The Hα emission line in V1062 Cyg displays a relatively sharp emission component that tracks the secondary's motion, which may arise on the irradiated face of the secondary; this is not often seen and may indicate an unusually strong flux of ionizing radiation. Both systems exhibit double-peaked orbital modulation consistent with ellipsoidal variation from the changing aspect of the secondary. We model these variations to constrain the orbital inclination i, and estimate approximate component masses based on i and the secondary velocity amplitude K 2 .

The ASAS-SN catalogue of variable stars IX: The spectroscopic properties of Galactic variable stars

Monthly Notices of the Royal Astronomical Society

The All-Sky Automated Survey for Supernovae provides long baseline (∼4 yr) V-band light curves for sources brighter than V≲ 17 mag across the whole sky. We produced V-band light curves for a total of ∼61.5 million sources and systematically searched these sources for variability. We identified ∼426 000 variables, including ∼219 000 new discoveries. Most (${\sim }74{ per\ cent}$) of our discoveries are in the Southern hemisphere. Here, we use spectroscopic information from LAMOST, GALAH, RAVE, and APOGEE to study the physical and chemical properties of these variables. We find that metal-poor eclipsing binaries have orbital periods that are shorter than metal-rich systems at fixed temperature. We identified rotational variables on the main-sequence, red giant branch, and the red clump. A substantial fraction (${\gtrsim }80{ per\ cent}$) of the rotating giants have large vvvrot or large near-ultraviolet excesses also indicative of fast rotation. The rotational variables have unusual a...

SWSex Stars, Old Novae, and the Evolution of Cataclysmic Variables

Acta Polytechnica CTU Proceedings, 2015

The population of cataclysmic variables with orbital periods right above the period gap are dominated by systems with extremely high mass transfer rates, the so-called SW Sextantis stars. On the other hand, some old novae in this period range which are expected to show high mass transfer rate instead show photometric and/or spectroscopic resemblance to low mass transfer systems like dwarf novae. We discuss them as candidates for so-called hibernating systems, CVs that changed their mass transfer behaviour due to a previously experienced nova outburst. This paper is designed to provide input for further research and discussion as the results as such are still very preliminary.

Discovery of a cataclysmic variable with a sub-stellar companion

Astronomy & Astrophysics, 2001

We find that the ROSAT source 1RXS J105010.3-140431 is a cataclysmic variable with orbital period of 88.6 minutes and a spectrum closely resembling WZ Sge. In particular, emission lines are flanked by Stark-broadened absorption wings probably originating in the photosphere of a compact object. The Balmer absorption lines can be modeled by the spectrum of a DA white dwarf with 13 000 <Teff<< T_{eff} <<Teff< 24 000 K. The strong absorption lines allowed us to obtain direct radial velocities of the white dwarf using the cross-correlation technique. We find an extremely low white dwarf radial velocity half amplitude, KwdK_{wd}Kwd = 4 pm\pmpm 1 km s$^{-1}$. This is consistent with the upper limit obtained from the H$\alpha$ emission line wing K < 20 km s$^{-1}$. The corresponding mass function is incompatible with a main sequence secondary, but is compatible with a post orbital period minimum cataclysmic variable with a brown dwarf-like secondary. The formal solution gives a secondary mass of 10-20 jovian masses. Doppler maps for the emission lines and the hypothesis of black-body emission indicate a steady state (T simr−3/4\sim r^{-3/4}simr−3/4) accretion disk mainly emitting in H$\alpha$ and an optically thicker hotspot with a strong contribution to the higher order Balmer lines and \ion{He}{I} 5875. As in other long cycle length dwarf novae, evidence for inner disk removal is found from the analysis of the emission lines.

The census of cataclysmic variables in the ROSAT Bright Survey

Astronomy and Astrophysics, 2002

We give an identification summary and results of polarimetric, photometric and spectroscopic follow-up observations of new, X-ray bright cataclysmic variables. These were identified as optical counterparts of high galactic latitude sources in the ROSAT All-Sky Survey. This optical identification programme is termed the ROSAT Bright Survey (RBS) and represents the first complete soft X-ray selected, flux-limited sample of CVs at high galactic latitude (survey area ∼ 20400 sq.deg.). The systems described here escaped previous identification programmes since these surveys were designed to identify even brighter than ours or particularly soft X-ray sources. Among the 11 new RBS-CVs we find 6 magnetic systems of AM Herculis type, 4 dwarf novae (among them one candidate), and one particularly bright system of uncertain nature, tentatively identified as dwarf nova or symbiotic binary. Orbital periods could be determined for all magnetic systems which range from 87.1 min to 187.7 min. Three of the new dwarf novae have moderate to high inclination and two of them might be eclipsing. Using non-magnetic systems only we derive a space density of CVs of ∼ 3 × 10 −5 pc −3 . This limit rests on the two new nearby, low-luminosity systems RBS0490 and RBS1955, with estimated distances of 30 pc only and luminosities below 10 30 erg s −1 .

SDSS unveils a population of intrinsically faint cataclysmic variables at the minimum orbital period

Monthly Notices of the Royal Astronomical Society, 2009

We discuss the properties of 137 cataclysmic variables (CVs) which are included in the Sloan Digital Sky Survey (SDSS) spectroscopic data base, and for which accurate orbital periods have been measured. 92 of these systems are new discoveries from SDSS and were followed-up in more detail over the past few years. 45 systems were previously identified as CVs because of the detection of optical outbursts and/or Xray emission, and subsequently re-identified from the SDSS spectroscopy. The period distribution of the SDSS CVs differs dramatically from that of all the previously known CVs, in particular it contains a significant accumulation of systems in the orbital period range 80-86 min. We identify this feature as the elusive "period minimum spike" predicted by CV population models, which resolves a long-standing discrepancy between compact binary evolution theory and observations. We show that this spike is almost entirely due to the large number of CVs with very low accretion activity identified by SDSS. The optical spectra of these systems are dominated by emission from the white dwarf photosphere, and display little or no spectroscopic signature from the donor stars, suggesting very low-mass companion stars. We determine the average absolute magnitude of these low-luminosity CVs at the period minimum to be < M g >= 11.6 ± 0.7. Comparison of the SDSS CV sample to the CVs found in the Hamburg Quasar Survey and the Palomar Green Survey suggests that the depth of SDSS is the key ingredient resulting in the discovery of a large number of intrinsically faint short-period systems.