Cynthia J. Taylor

LS Pegasi: A Low-Inclination SW Sextantis-Type Cataclysmic Binary with High-Velocity Balmer Emission-Line Wings 1

We present time-resolved spectroscopy and photometry of the bright cataclysmic variable LS Peg (=S193; V ≈ 13.0—Szkody et al.). The Balmer lines exhibit broad, asymmetric wings Doppler-shifted by about 2000 km s–1 at the edges, while the He i lines show phase-dependent absorption features strikingly similar to SW Sextantis stars, as well as emission through most of the phase. The C iii/N iii emission blend does not show any phase dependence. From velocities of Hα emission lines, we determine an orbital period of 0.174774±0.000003 days (=4.1946 hr), which agrees with Szkodys value of approximately 4.2 hr. No stable photometric signal was found at the orbital period. A noncoherent quasi-periodic photometric signal was seen at a period of 20.7±0.3 minutes.The high-velocity Balmer wings most probably arise from a stream reimpact point close to the white dwarf. We present simulated spectra based on a kinematic model similar to the modified disk-overflow scenario of Hellier & Robinson. The models reproduce the broad line wings, though some other details are unexplained.Using an estimate of dynamical phase based on the model, we show that the phasing of the emission- and absorption-line variations is consistent with that in (eclipsing) SW Sex stars. We therefore identify LS Peg as a low-inclination SW Sex star.Our model suggests i=30°, and the observed absence of any photometric signal at the orbital frequency establishes i < 60°. This constraint puts a severe strain on interpretations of the SW Sex phenomenon which rely on disk structures lying slightly out of the orbital plane.

Superhumps in Cataclysmic Binaries. XIV. V592 Cassiopeiae

ABSTRACT We report a spectroscopic and photometric study of the novalike variable V592 Cassiopeiae (=LS I 55° 8). The spectrum is that of a typical UX UMa–type star, with weak, narrow Balmer emission superposed on broad absorption. The 0.1–2.2 μm flux distribution also looks fairly normal, suggesting disk accretion at ∼10−8 M⊙ yr−1 and a distance of 330 pc. The emission lines move with P = 0.115063(1) days, which is presumably the underlying orbital period of the binary. Photometry reveals a different period, namely, 0.12228(1) days. The presence of this wave in a short‐period cataclysmic variable, and the value of the period excess at 6.3%, suggests identification as a “permanent superhump.” After subtraction of this large signal, the residual time series appears to contain a weak feature at 0.11193(5) days. The star evidently shows positive and negative superhumps simultaneously. Its binary period puts it among a modest number of nonmagnetic cataclysmic variables occupying the 2–3 hr period “gap.”

ORBITAL PERIODS FOR THE SU UMA-TYPE DWARF NOVAE UV PERSEI, VY AQUARII, AND V1504 CYGNI

We present mean spectra of three SU-UMa type dwarf novae and report orbital periods based on radial velocities taken near minimum light. For UV Per we find Porb = 0.06489 ± 0.00011 d (= 93.44 ± 0.16 min); for V1504 Cygni, 0.06951 ± 0.00005 (= 100.10 ± 0.07 min), and for VY Aqr, 0.06309 ± 0.00004 d (= 90.85 ± 0.06 min). The period for VY Aqr is slightly shorter than the period determined by Augusteijn from velocities during outburst, and is more consistent with expectations based on the superhump period. For UV Per we also present timeseries photometry obtained on two nights. A weak modulation may be present at a period near, but formally distinct from, the orbital period. A magnitude sequence is presented.

Orbital Periods for the Unusual Dwarf Novae ER Ursae Majoris and V1159 Orionis

ER UMa (PG 0943+521), V1159 Ori, and RZ LMi constitute a small recently- recognized group of dwarf novae, called the RZ LMi stars or the ER UMa stars. They share many features of the SU UMa-type, but have shorter outburst cycles than had been known previously. Here we establish orbital periods, based on emission-line radial velocities, for ER UMa (0.06366 ± 0.00003 d = 91.67 ± 0.04 min) and V1159 Ori (0.06217801 ± 1.3 × 10-7 d = 89.5363 ± 0.0002 min). The precise orbital period for V1159 Ori depends on an extrapolation of cycle count from 1991 to 1994, which is slightly uncertain, but the daily cycle count is reasonably secure. These orbital periods are similar to those of the more common, less frequently outbursting SU UMa stars. As is generally the case, the orbital periods derived here are slightly shorter than the periods of photometric superhumps which appear in superoutburst. The superhump period excesses found here are compatible with, but marginally larger than, those seen in other SU UMa stars of similar period. While the empirical link between ER UMa stars and SU UMa stars is generally strengthened by these results, the trend toward slightly larger period excesses (if true) can be interepreted as a tendency for systems with larger mass ratios to develop larger mass-transfer rates at a given orbital period.

Spectroscopy of the Cataclysmic Binaries CY Lyrae, TW Trianguli, and VW Vulpeculae 1

From Ha radial velocities taken in quiescence we find orbital periods of days, 0.1591 0.0004

Orbital Periods of the Dwarf Novae AR And, AM Cas, and PY Per

We present time-resolved spectroscopy of the dwarf-novae AR And, AM Cas, and PY Per. From velocities of H-alpha emission lines, we determine orbital periods of 0.16302 ± 0.00032 d (=3.91 h) for AR And and 0.15480 ± 0.00017 d (=3.72 h) for PY Per. Our period determination for AR And resolves a daily cycle-count ambiguity in a previous determination by Shafter, Veal, and Robinson (1995). No orbital period for PY Per has previously been published. The orbital period of Am Cas, determined here for hte first time, is constrained over a 46-night baseline to one of several precise values near 0.165 d (=3.96 h), the best of which are 0.16490 ± 0.00001 d and 0.16551 ± 0.0001 d. For PY Per, we use a single direct CCD exposure to extend the magnitude sequence of Misselt (1996). A comparison with the Downes & Shara atlas (1993) shows that PY Per had V ~ 19.8 when the Downes & Shara image was obtained, which is much fainter than the minimum listed in the General Catalogue of Variable Stars (Kholopov 1987). Our averaged spectra of all appear typical for dwarf novae, except that the Fe II lambda-5169 in AR And is unusally strong and weak features at lambda-5230, lambda-5270, and labmda-5322 (which we attribute to Fe II) also appear.

A Detailed Comparison of Hubble Space Telescope Faint Object Spectrograph and IUE Ultraviolet Spectra of Selected Seyfert Nuclei

Despite the contributions of the Hubble Space Telescope Faint Object Spectrograph (FOS) to the archive of UV observations of active galactic nuclei, the vast majority of UV reference data were obtained using the International Ultraviolet Explorer (IUE) satellite. These data remain important since they provide historical information about the intensities of the UV continua and emission lines that is needed to constrain models of the active nucleus. A detailed comparison of the FOS and IUE data is critical to understanding how the measurable quantities depend on the individual instrumental calibrations, and how any conclusions derived from modeling the observations may vary depending on the source of the UV data. Rigorous comparison of FOS and IUE spectra have so far been performed only for spectrophotometric standard star observations that are acquired accurately and have high signal-to-noise ratios. We compare typical FOS spectra that were not acquired and observed with the strict regimen that is used for standard-star observations, especially in the pre-COSTAR era. All nonproprietary UV FOS spectrophotometric archival data for the Seyfert 1 galaxies Mrk 509, NGC 3783, and NGC 5548 that have near-simultaneous (within 24 hr) IUE observations are used in the analysis. These data demonstrate that the absolute photometric calibrations of the FOS and IUE agree within ~5% in absolute flux for two of the objects. For NGC 5548, the FOS and IUE flux data disagree by ~50% in the 1200-2000 A region. In this object there may be evidence for flux nonlinearity of the IUE detector and a contribution from the host galaxy redward of 2800 A. Cross-correlation of the FOS and IUE spectra reveals no zero-point wavelength shift larger than the IUE wavelength calibration errors. Comparison of line flux measurements from both the FOS and IUE spectra show that for strong emission lines (e.g., Lyα, C IV, and Mg II) the measured intensities always agree within 15%, while for moderately strong lines (e.g., N V, Si IV/O IV, He II, and C III]) the agreement is ~30% (1 σ). Weak lines (e.g., O I, C II, N IV], O III], and N III]) may not even be detected in the IUE spectra, and when they are detected the disagreement between the measured fluxes can be very large.