Spectroscopic search for new SW Sextantis stars in the 3-4 h orbital period range - I

Rodríguez‐Gil, P.; Schmidtobreick, L.; Gänsicke, B. T.

doi:10.1111/j.1365-2966.2006.11245.x

Cited by 61 publications

(95 citation statements)

References 69 publications

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“…The results obtained are reminiscent of the radial velocity curve of the SW Sex star V380 Oph, displayed in fig. 13 of Rodríguez‐Gil, Schmidtobreick & Gänsicke (2007a), which shows a shorter time‐scale variation superimposed on the sinusoidal orbital modulation. If the same behaviour is displayed by Hα075648 and Hα122105, then we observed less than one orbital cycle in any one night.…”

Section: Results For Individual Systemsmentioning

confidence: 96%

An Hα-selected sample of cataclysmic variables – I. Observations of newly discovered systems

Pretorius¹,

Knigge²

2008

Monthly Notices RAS

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Strong selection effects are present in observational samples of cataclysmic variables (CVs), complicating comparisons to theoretical predictions. The selection criteria used to define most CV samples discriminate heavily against the discovery of short‐period, intrinsically faint systems. The situation can be improved by selecting CVs for the presence of emission lines. For this reason, we have constructed a homogeneous sample of CVs selected on the basis of Hα emission. We present discovery observations of the 14 CVs and two additional CV candidates found in this search. The orbital periods of 11 of the new CVs were measured; all are above 3 h. There are two eclipsing systems in the sample, and one in which we observed a quasi‐periodic modulation on a ∼1000 s time‐scale. We also detect the secondary star in the spectrum of one system, and measure its spectral type. Several of the new CVs have the spectroscopic appearance of nova‐like variables, and a few display what may be SW Sex star behaviour. In a companion paper, we discuss the implications of this new sample for CV evolution.

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Section: Results For Individual Systemsmentioning

confidence: 96%

An Hα-selected sample of cataclysmic variables – I. Observations of newly discovered systems

Pretorius¹,

Knigge²

2008

Monthly Notices RAS

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“…All the features described above are defining characteristics of the SW Sex stars (see Thorstensen et al 1991b; Rodríguez‐Gil, Schmidtobreick & Gänsicke 2007). Even though each system exhibits its own peculiarities (e.g.…”

Section: Sw Sex Membershipmentioning

confidence: 99%

SW Sextantis stars: the dominant population of cataclysmic variables with orbital periods between 3 and 4 h

Rodríguez‐Gil

Gänsicke

Hagen

et al. 2007

Monthly Notices of the Royal Astronomical Society

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We present time‐series optical photometry of five new cataclysmic variables (CVs) identified by the Hamburg Quasar Survey (HQS). The deep eclipses observed in HS 0129+2933 (= TT Tri), HS 0220+0603 and HS 0455+8315 provided very accurate orbital periods of 3.35129827(65), 3.58098501(34) and 3.56937674(26) h, respectively. HS 0805+3822 shows grazing eclipses and has a likely orbital period of 3.2169(2) h. Time‐resolved optical spectroscopy of the new CVs (with the exception of HS 0805+3822) is also presented. Radial velocity studies of the Balmer emission lines provided an orbital period of 3.55 h for HS 1813+6122, which allowed us to identify the observed photometric signal at 3.39 h as a negative superhump wave. The spectroscopic behaviour exhibited by all the systems clearly identifies them as new SW Sextantis (SW Sex) stars. HS 0220+0603 shows unusual N ii and Si ii emission lines suggesting that the donor star may have experienced nuclear evolution via the CNO cycle. These five new additions to the class increase the number of known SW Sex stars to 35. Almost 40 per cent of the total SW Sex population do not show eclipses, invalidating the requirement of eclipses as a defining characteristic of the class and the models based on a high orbital inclination geometry alone. On the other hand, as more SW Sex stars are identified, the predominance of orbital periods in the narrow 3–4.5 h range is becoming more pronounced. In fact, almost half the CVs which populate the 3–4.5 h period interval are definite members of the class. The dominance of SW Sex stars is even stronger in the 2–3 h period gap, where they make up 55 per cent of all known gap CVs. These statistics are confirmed by our results from the HQS CVs. Remarkably, 54 per cent of the Hamburg nova‐like variables have been identified as SW Sex stars with orbital periods in the 3–4.5 h range. The observation of this pile‐up of systems close to the upper boundary of the period gap is difficult to reconcile with the standard theory of CV evolution, as the SW Sex stars are believed to have the highest mass‐transfer rates among CVs. Finally, we review the full range of common properties that the SW Sex stars exhibit. Only a comprehensive study of this rich phenomenology will prompt to a full understanding of the phenomenon and its impact on the evolution of CVs and the accretion processes in compact binaries in general.

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“…The ingress to the eclipse is steeper than the egress. Such an eclipse shape is very common for SW Sex stars (Thorstensen et al 1991) and was a defining feature of the class until it was later revealed that there are also non-eclipsing SW Sex stars (Rodríguez-Gil et al 2007b).…”

Section: Photometrymentioning

confidence: 99%

On the Sw Sex-Type Eclipsing Cataclysmic Variable Sdss0756+0858

Tovmassian

Hernández

González–Buitrago

et al. 2014

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We conducted a spectroscopic and photometric study of SDSS J075653.11+085831. X-ray observations were also attempted. We determined the orbital period of this binary system to be 3.29 hr. It is a deep eclipsing system, whose spectra show mostly single-peaked, Balmer emission lines and a rather intense He ii line. There is also the presence of faint (often double-peaked) He i emission lines as well as several absorption lines, Mg i being the most prominent. All of these features point toward the affiliation of this object with the growing number of SW Sex-type objects. We developed a phenomenological model of an SW Sex system to reproduce the observed photometric and spectral features.

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Spectroscopic search for new SW Sextantis stars in the 3-4 h orbital period range - I

Cited by 61 publications

References 69 publications

An Hα-selected sample of cataclysmic variables – I. Observations of newly discovered systems

An Hα-selected sample of cataclysmic variables – I. Observations of newly discovered systems

SW Sextantis stars: the dominant population of cataclysmic variables with orbital periods between 3 and 4 h

On the Sw Sex-Type Eclipsing Cataclysmic Variable Sdss0756+0858

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