The Big List of SW Sextantis Stars

(v5.3.0 – Oct 2016)


The SW Sextantis stars are a sub-class of cataclysmic variables (CVs) that share a number of characteristic observational properties (e.g., transient absorption in their emission line cores that appears at specific orbital phases, single-peaked emission lines rather than the double-peaked lines characteristic of disk-accreting CVs, indications of very high mass transfer rate, etc. – follow this link for a more complete and detailed list of the observational characteristics of the SW Sex stars). Although studied individually for a number of years, the SW Sex stars were first identified as an observationally similar group in the early 1990s.

Establishing a complete census of membership in the SW Sex class is a difficult task, as our understanding of the range and possible origins of the SW Sex syndrome has evolved over the past two decades. For example, original defining characteristics of being a high inclination (i.e., eclipsing) CV and having He II λ4686 emission comparable in strength to that of Hβ have been relaxed as it has become apparent that these were likely selection effects that influenced the discovery of the first SW Sex stars. Meanwhile, some recent work has suggested that the SW Sex stars might be the weakest magnetic CVs with the highest mass transfer rates (follow this link for a discussion of the magnetic scenario for the SW Sex stars), while other theories utilize complex accretion disk structural models (e.g., tilted, warped, precessing disks).

Townsley & Gänsicke (2009) make the following interesting statement about the possible origin of the SW Sex syndrome: “Speculating that high [white dwarf effective temperature] and [mean mass transfer rate] are a common characteristic to all VY Scl/SW Sex stars suggests that these systems represent an exceptional phase in CV evolution. One possible explanation is that these are systems that just evolved into a semi-detached configuration, as the mass transfer goes through a short peak during turn-on (e.g., D'Antona et al. 1989), and that CVs are preferentially born within the 3-4 hr period range, which would be the case if the initial mass distribution is peaked toward equal masses in the progenitor MS binaries (de Kool 1992).”

Consequently, determining the full census of the SW Sex stars is important, as the SW Sex syndrome appears to be widespread among the CV population, and possibly has important implications related to the secular evolution of CVs. A full understanding of the SW Sex syndrome will likely depend on a complete census of the number and range of CVs that are afflicted with it. To this end, I have compiled The Big List of SW Sextantis Stars. It is not necessarily intended to be the definitive SW Sex star census, but it is exhaustive in the sense that it contains all CVs that have been linked to the SW Sex stars in published sources.

The Big List of SW Sextantis Stars is complete to the best of my knowledge (as of the version date listed above). During each update of the Big List, I locate new SW Sex stars by running a NASA-ADS search, with a publication window starting 1 month prior to the last Big List update, for text strings “SW Sex” and “cataclysmic” in paper abstracts, cross-correlated with a full-text ADS search for just “SW Sex” anywhere in the body of the paper. If you know of a new SW Sex star that I've missed, please email its name or other identifying information to me, and I'll add it to the list. Some of the information shown here is unavoidably subjective (mainly the assessment of a CV as a Definite, Probable, or Possible SW Sex star). If you disagree with any of my assessments, you can also email me and I will consider changing the appropriate entry, based on your persuasiveness!

Citation Text

If the material presented here has aided in the completion of your research project, then I would appreciate the inclusion of the following citations in any corresponding publications:

  • A citation to my paper in which the Big List is first described:

\bibitem[Hoard et al.(2003)]{hsf03} Hoard, D.~W., Szkody, P., Froning, C.~S., Long, K.~S., \& Knigge, C.\ 2003, \aj, 126, 2473

  • A footnote giving this URL, located near the usage of Big List data in the publication text; for example,

\footnote{See D.~W.\ Hoard's Big List of SW Sextantis Stars at \url{} (Hoard et al.\ 2003).}

The following papers cite the Big List of SW Sex Stars (thank you!):

  • 2017NewA...50...30H – “NSV 1907 - A new eclipsing, nova-like cataclysmic variable” by Hümmerich et al.
  • 2015arXiv150307992S – “Faint-state transitions in the SW Sextantis nova-like variable, HS 0455+8315” by Shears et al. (also see JBAA, 126, 42)
  • 2014AJ....147...68T – “On the SW Sex-Type Eclipsing Cataclysmic Variable SDSS0756+0858” by Tovmassian et al.
  • 2013AJ....145..168W – “Far-Ultraviolet Spectroscopy of the Nova-Like Variable KQ Monocerotis: A New SW Sextantis Star?” by Wolfe et al.
  • 2013MNRAS.428.3559D – “The SW Sex Enigma” by Dhillon et al.
  • 2011MNRAS.410..963N – “Dark Spot, Spiral Waves, and the SW Sextantis Behaviour: It is all about UX Ursae Majoris” by Neustroev et al.
  • 2010AJ....140.1313H – “Simultaneous X-ray and Ultraviolet Observations of the SW Sextantis Star DW Ursae Majoris” by Hoard et al.
  • 2009ApJ...697.1717B – “On the Accretion Rates of SW Sextantis Nova-like Variables” by Ballouz & Sion
  • 2009A&A...496..765K – “Nova-like Cataclysmic Variable TT Arietis. QPO Behaviour Coming Back from Positive Superhumps” by Kim et al.
  • 2007MNRAS.377.1747R – “SW Sextantis Stars: The Dominant Population of Cataclysmic Variables with Orbital Periods Between 3 and 4 hours” by Rodríguez-Gil et al.
  • 2004ApJ...615L.129K – “Time-Resolved Ultraviolet Spectroscopy of the SW Sex Star DW UMa: Confirmation of a Hidden White Dwarf and the Ultraviolet Counterpart to Phase 0.5 Absorption Events” by Knigge et al.
  • 2003PASP..115.1118W – “Investigating the Sloan Digital Sky Survey Cataclysmic Variable SDSS J132723.39+652854.2” by Wolfe et al.

Orbital Period Distribution of the SW Sex Stars

Orbital period distribution of the SW Sex Stars

Note: sometimes the version number of this plot lags behind the version number of the Big List (top of this page); this happens when information added or revised on the list does not affect the orbital period distribution.

Counting Statistics for the Big List