A catalog of 2249 white dwarfs which have been identified spectroscopically is presented complete through 1996 April. This compilation is the fourth edition of the Villanova Catalog of Spectroscopically Identified White Dwarfs. For each degenerate star, the following data entries with references are provided: (1) a catalog coordinate designation or WD number, in order of right ascension; (2) the right ascension and declination for epoch 1950.0; (3) the spectral type based upon the new system;(4) a catalog symbol denoting binary membership; (5) a list of most names known to exist for a given star; (6) proper motion and position angle; (7) broad-band UBV photometry, V, B-V, U-B; (8) multichannel spectrophotometry, V(MC), g-r; (9) Strömgren narrow-band photometry y, by , u-b; (10) an absolute visual magnitude based upon the best available color-magnitude calibration or trigonometric parallax; (11) the observed radial velocity uncorrected for gravitational redshift or solar motion; and (12) the trigonometric parallax with mean error when available. A Notes section for unusual or peculiar stars and a coded Reference Key alphabetized by the first author's last name are presented, as well as an expanded table cross-referencing all names to catalog WD number. An introduction and full descriptions of the entries are provided in the text.

We have conducted a detailed new survey of the local population of white dwarfs lying within 20 pc of the Sun. A new revised catalog of local white dwarfs containing 122 entries (126 individual degenerate stars) is presented. This list contains 27 white dwarfs not included in a previous list from 2002, as well as new and recently published trigonometric parallaxes. In several cases new members of the local white dwarf population have come to light through accurate photometric distance estimates. In addition, a suspected new double degenerate system (WD 0423+120) has been identified. The 20 pc sample is currently estimated to be 80% complete. Using a variety of recent spectroscopic, photometric, and trigonometric distance determinations, we re-compute a space density of 4.8 ± 0.5 × 10 −3 pc −3 corresponding to a mass density of 3.2 ± 0.3 × 10 −3 M pc −3 from the complete portion of the sample within 13 pc. We find an overall mean mass for the local white dwarfs of 0.665 M , a value larger than most other non-volume-limited estimates. Although the sample is small, we find no evidence of a correlation between mass and temperature in which white dwarfs below 13,000 K are systematically more massive than those above this temperature. Within 20 pc 25% of the white dwarfs are in binary systems (including double degenerate systems). Approximately 6% are double degenerates and 6.5% are Sirius-like systems. The fraction of magnetic white dwarfs in the local population is found to be 13%.

The most recent version of the Catalog of Spectroscopically Identified White Dwarfs lists 2249 white dwarf stars. Among these stars are 118 white dwarfs that have either reliable trigonometric parallaxes or color-based distance moduli which place them at a distance within 20 pc of the Sun. Most of these nearby white dwarfs are isolated stars, but 35 (30 % of the sample) are in binary systems, including such well known systems as Sirius A/B, and Procyon A/B. There are also three double degenerate systems in this sample of the local white dwarf population. The sample of local white dwarfs is largely complete out to 13 pc and the local density of white dwarf stars is found to be (5.5 +/- 0.8) x 10^-3 pc^-3 with a corresponding mass density of (3.7 +/- 0.5) x10^-3 M pc^-3.Comment: 20 pages, 3 Postscript figure

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Brief HST /STIS spectroscopic snapshot exposures of the cataclysmic variables 1RXS J232953.9+062814, CE315, BZ UMa and EY Cyg reveal very large N V/C IV line flux ratios, similar to those observed in AE Aqr. Such anomalous line flux ratios have so far been observed in 10 systems, and presumably reflect a different composition of the accreted material compared to the majority of cataclysmic variables. We discuss the properties of this small sample in the context of the recent proposal by Schenker et al. (2002) that a significant fraction of the present-day population of cataclysmic variables may have passed through a phase of thermal time-scale mass transfer.

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We have extended our detailed survey of the local white dwarf population from 20 to 25 pc, effectively doubling the sample volume, which now includes 232 stars. In the process, new stars within 20 pc have been added, a more uniform set of distance estimates as well as improved spectral and binary classifications are available. The present 25 pc sample is estimated to be about 68 per cent complete (the corresponding 20 pc sample is now 86 per cent complete). The space density of white dwarfs is unchanged at 4.8 ± 0.5 × 10 −3 pc −3 . This new study includes a white dwarf mass distribution and luminosity function based on the 232 stars in the 25 pc sample. We find a significant excess of single stars over systems containing one or more companions (74 per cent versus 26 per cent). This suggests mechanisms that result in the loss of companions during binary system evolution. In addition, this updated sample exhibits a pronounced deficiency of nearby 'Sirius-like' systems. 11 such systems were found within the 20 pc volume versus only one additional system found in the volume between 20 and 25 pc. An estimate of white dwarf birth rates during the last ∼8 Gyr is derived from individual remnant cooling ages. A discussion of likely ways new members of the local sample may be found is provided.Key words: binaries: close -white dwarfs. I N T RO D U C T I O NThere is considerable interest in establishing a complete census of the population of nearby stars, particularly for those of the lowest luminosity, such as white dwarfs (WDs), late M-stars and sub-stellar L and T dwarfs. For the WD stars, previous publications (Holberg et al. 2002, 2008a, hereafter LWD02 and LWD08, respectively) have discussed the sample extending to 20 pc from the Sun. Since 2008, the 20 pc sample has grown by 10 members and distance estimates have been improved for many other WDs in this range. In addition, Giammichele, Bergeron & Dufour (2012 -hereafter GBD) have conducted a thorough spectral analysis of most WDs within the existing 20 pc sample. These developments provide a firm basis for a more homogeneous and unbiased determination of spectral types and stellar parameters. Thus, an improved knowledge base now exists with which to characterize the 20 pc local sample, since its completeness now approaches 86 per cent. In this paper, our previous 20 pc (LS20) sample is updated and extended out to a distance of 25 pc (LS25). Our formal sample limit is actually 25.2 pc, since at this distance, the added volume is exactly twice that of the original LS20 sample, which facilitates direct comparisons between the two subsamples. For example, the higher completeness E-mail: holberg@argus.lpl.arizona.edu factor of LS20 permits extrapolation of population properties to the less complete LS25.The LS25 is a volume-limited sample in which distance is the fundamental criterion for inclusion. Such a sample has several properties that are not easily matched by magnitude-limited samples that include many more WDs. For example, LS25 is an all-sky survey th...

We have obtained HST /STIS data for a total of eleven polars as part of a program aimed to compile a homogeneous database of high-quality far-ultraviolet (FUV) spectra for a large number of cataclysmic variables (CVs). Of the eleven polars, eight were found in a state of low accretion activity (V347 Pav, VV Pup, V834 Cen, BL Hyi, MR Ser, ST LMi, RX J1554.2+2721 and V895 Cen) and three in a state of high activity (CD Ind, AN UMa and UW Pic). The STIS spectra of the low-state polars unambiguously reveal the photospheric emission of their white dwarf (WD) primaries. We have used pure hydrogen WD models to fit the FUV spectra of the low-state systems (except RX J1554.2+2721, which is a highfield polar) in order to measure the WD effective temperatures. In all cases, the fits could be improved by adding a second component, which is presumably due to residual accretion onto the magnetic pole of the WD. The WD temperatures obtained range from 10 800 K to 14 200 K for log g = 8.0. Our analysis more than doubles the number of polars with accurate WD effective temperatures. Comparing the WD temperatures of polars to those of non-magnetic CVs, we find that at any given orbital period the WDs in polars are colder than those in non-magnetic CVs. The temperatures of polars below the period gap are consistent with gravitational radiation as the only active angular momentum loss mechanism. The differences in WD effective temperatures between polars and non-magnetic CVs are significantly larger above the period gap, suggesting that magnetic braking in polars might be reduced by the strong field of the primary. We derive distance estimates to the low-state systems from the flux scaling factors of our WD model fits. Combining these distance measurements with those from the literature, we establish a lower limit on the space density of polars of 1.3 × 10 −6 pc −3 .