David R. Skillman

THE 2001 SUPEROUTBURST OF WZ SAGITTAE

ABSTRACT We report the results of a worldwide campaign to observe WZ Sagittae during its 2001 superoutburst. After a 23 yr slumber at \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape

The remarkable rapid X-ray, ultraviolet, optical and infrared variability in the black hole XTE J1118+480

V=15.5

Superhumps in cataclysmic binaries. II: PG 0917+342

\end{document} , the star rose within 2 days to a peak brightness of 8.2, and showed a main eruption lasting 25 days. The return to quiescence was punctuated by 12 small eruptions, of ∼1 mag amplitude and 2 day recurrence time; these “echo outbursts” are of uncertain origin, but somewhat resemble the normal outbursts of dwarf novae. After 52 ...

SUPERHUMPS IN CATACLYSMIC BINARIES. XXIV. TWENTY MORE DWARF NOVAE

The transient black-hole binary XTE J1118+480 exhibited dramatic rapid variability at all wavelengths which were suitably observed during its 2000 April–July outburst. We examine time-resolved X-ray, ultraviolet, optical and infrared data spanning the plateau phase of the outburst. We find that both X-ray and infrared bands show large amplitude variability. The ultraviolet and optical variability is more subdued, but clearly correlated with that seen in the X-rays. The ultraviolet, at least, appears to be dominated by the continuum, although the lines are also variable. Using the X-ray variations as a reference point, we find that the ultraviolet (UV) variability at long wavelengths occurs later than that at short wavelengths. Uncertainty in the Hubble Space Telescope timing prohibits a determination of the absolute lag with respect to the X-rays, however. The transfer function is clearly not a delta-function, exhibiting significant repeatable structure. For the main signal we can rule out an origin in reprocessing on the companion star – the lack of variation in the lags is not consistent with this, given a relatively high orbital inclination. Weak reprocessing from the disc and/or companion star may be present, but is not required, and another component must dominate the variability. This could be variable synchrotron emission correlated with X-ray variability, consistent with our earlier interpretation of the infrared (IR) flux as due to synchrotron emission rather than thermal disc emission. In fact, the broad-band energy distribution of the variability from IR to X-rays is consistent with expectations of optically thin synchrotron emission. We also follow the evolution of the low-frequency quasi-periodic oscillation in X-rays, UV, and optical. Its properties at all wavelengths are similar, indicating a common origin.

The 1991 V603 Aquilae campaign - Superhumps and P-dots

We have found a 113.1 minute periodicity in the light curve of the nova-like variable PG 0917+342. The signal is of 0.027 mag semiamplitude and appears to change its period slightly (ΔP/P∼3×10 −4 ) over the 1 yr baseline of observations. As this period is ∼5% longer than the spectroscopically determined orbital period, it seems to be another example of the superhump phenomenon which afflicts cataclysmic variables of short orbital period and high accretion rate. The rate of period change is ∼500 times smaller than that seen in the familiar superhumps of dwarf novae, presumably because changes of the accretion disk in this binary are much milder than those occurring in a dwarf nova

BK Lyncis: the oldest old nova?... and a Bellwether for cataclysmic variable evolution

We report precise measures of the orbital and superhump period in 20 more dwarf novae. For 10 stars, we report new and confirmed spectroscopic periods—signifying the orbital period —as well as the P o

Superhumps and Accretion Disk Precession in TT Arietis

We report the results of an intensive program of photometry of the old nova V603 Aquilae during 1991. The coverage totaled 207 hr, spread over 66 nights. The mean value of the 3.5 hr photometric period was 0.14640 (±6) days, but the instantaneous value increased over the course of the 5 month observing season. This is a drift in the period rather than a truly secular effect, since the observed rate of increase is much too high to be consistent with period measurements in previous years. New spectroscopic observations confirm the radial velocity curve and O d .138 period found by Kraft in 1962. The low amplitude in v rad and the relatively narrow emission lines require a very low binary inclination; i∼20° is likely. The inequality of photometric and spectroscopic periods is thus established beyond doubt and is the outstanding puzzle

Superhumps in Cataclysmic Binaries. XIV. V592 Cassiopeiae

We summarize the results of a 20-year campaign to study the light curves of BK Lyn, a nova-like star strangely located below the 2-3 hour orbital-period gap in the family of cataclysmic variables (CVs). Two apparent superhumps dominate the nightly light curves with periods 4.6% longer, and 3.0% shorter, than the orbital period. The first appears to be associated with the star’s brighter states (V � 14), while the second appears to be present throughout and becomes very dominant in the low state (V � 15.7). It is plausible that these arise, respectively, from a prograde apsidal precession and a retrograde nodal precession of the star’s accretion disk.

Rapid Oscillations in Cataclysmic Variables. XIV. Orbital and Spin Ephemerides of FO Aquarii

We have been conducting a long-term (1988-1998) photometric study of the nova-like variable TT Arietis. The main periodic signal in the stars light curve normally occurs at a period that varies but averages ~0.1329 days, which is about 3.5% shorter than the orbital period of the binary. In 1997, this signal disappeared and was replaced by a stronger signal 8.5% longer than the orbital period. This new wave strongly resembles thesuperhumps commonly seen in SU UMa-type dwarf novae during superoutburst. In superhump parlance, we could say that a negative superhump was replaced by a positive superhump (P > Porb

Rapid Oscillations in Cataclysmic Variables. XV. HT Camelopardalis (=RX J0757.0+6306)

{r orb}