J. W. Robertson

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

RZ LEONIS MINORIS, PG 0943+521, AND V1159 ORIONIS: THREE CATACLYSMIC VARIABLES WITH SIMILAR AND UNUSUAL OUTBURST BEHAVIOR

V=15.5

The 65 Day Period in 3C 66A during Bright State

\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 ...

Post-Common-Envelope Binary Stars and the Precataclysmic Binary PG 1114+187

We call attention to a small group of cataclysmic variable stars (whose prototype might be considered RZ LMi) that have complex light curves fo similar shape which repeat with typical periods of a few weeks. The predictability of the time of each superoutburst and the stability of the shape of the light curve is unexpectedly high for cataclysmic variables, which are well-known for erratic variations in both the timing and the shape of their outbursts. The phenomenon appears to be closely related to SU Ursae Majoris-type superoutbursts, especially since superhumps appear in these stars. The similiarities and differences between these RZ LMi stars and SU UMa systems are summerized and discussed in the context of extant models for the superoutbursts of SU UMa-type dwarf novae.

New Complexities in the Low-State Line Profiles of AM Herculis

Historically, 3C 66A has been considered a relative quiescent blazar. For that reason, 3C 66A was selected as a comparison source for OJ 287 in the OJ-94 project. However, after more detailed observation it turns out that the variability of 3C 66A itself is very interesting. We have analyzed the entire project data set of 3C 66A from fall of 1993 to spring of 1998 by using structure function analysis, Deeming periodograms, Scargle periodograms, and the folded light curves. Here we present the first preliminary evidence for the 65 day period in 3C 66A observed during the bright state. Our analysis indicates that this period is slowly slowing down. We will also discuss the possible physical mechanism producing the observed periodicity.

Are Z Camelopardalis–Type Dwarf Novae Brighter at Standstill?

We present orbit-resolved spectroscopy and orbit-sampled photometry of the binary system PG 1114+187. Both photometry and radial velocity studies reveal a period P = 1.75992 days, which is taken to be the orbital period of the binary. Strong modulation of emission-line strength with the same period is also present. A preliminary mass ratio, M2/M1 ≈ 0.7, is found from primary- and secondary-star radial velocity amplitudes. No evidence is seen for either an accretion disk or mass transfer, leading to the conclusion that PG 1114+187 is not a cataclysmic variable (CV) but is in a pre-CV state, before the initiation of mass transfer. The short orbital period also leads to the conclusion that the system passed through a common-envelope phase at some time in the past. The current list of known post–common-envelope and precataclysmic binary stars is also reviewed and the general properties of this class of star are discussed.

RXTE, ROSAT, EUVE, IUE, and Optical Observations through the 45 Day Supercycle of V1159 Orionis

When accretion temporarily ceases in the polar AM Her, the emission-line profiles are known to develop several distinct components, whose origin remains poorly understood. The new low-state spectra reported here have a more favorable combination of spectral resolution (R ~4500), time resolution (~3 minute exposures), and S/N than earlier work, revealing additional details of the orbital dependence of the line profiles. The central strong feature of Hα is found to be composed of two components of similar strength, one having K ~ 100 km s^−1 and phased with the motion of the secondary star, the other having little or no detectable radial velocity variations. We attribute the central line component to gas near the coupling region, perhaps with a contribution from irradiation of the secondary star. The two satellite components have radial velocity offsets of ~±250 km s^−1 on either side of the central strong Hα peak. These satellites most likely arise in large loops of magnetically confined gas near the secondary star due to magnetic activity on the donor star and/or interactions of the magnetic fields of the two stars. Doppler maps show that these two satellite features have concentrations at velocities that match the velocity locations of L4 and L5 in the system.

Low-State Flaring Events in AM Herculis

Average V-band brightnesses over multiple outbursting and standstill intervals are computed for the light curves of five Z Cam-type dwarf novae: RX And, Z Cam, SY Cnc, AH Her, and HX Peg. Both CCD photometry from RoboScope and AAVSO visual estimates are used in the analysis, with consistent results from the two databases for the stars in common. In four of the five stars, the standstills are as bright as or brighter than the mean V-band brightness during outbursting intervals. This is consistent with Z Cam stars being near the upper stability boundary in for operation of the thermal limit cycle that is thought to be responsible for ˙ M dwarf nova outbursts. However, the unusual standstills or hesitations observed in SY Cnc are sometimes fainter than the mean brightness during outbursting intervals. From several well-observed examples we describe the light curves of Z Cam stars as they enter standstill. During this characteristic damped oscillation the amplitude decreases with a timescale approximately equal to the mean outburst recurrence interval, and the period of the oscillation decreases with as standstill is approached. The exits from standstill usually change abruptly ˙ P. 20.4 into outbursting mode by emerging from standstill into a decline from outburst.

Light Curve of CR Bootis 1990-2012 from the Indiana Long-Term Monitoring Program

A complete 45 day supercycle of the cataclysmic variable V1159 Ori comprising a superoutburst and eight normal outbursts was observed. Coverage included ground-based optical observations as well as observations with RXTE for 38 days, ROSAT for 34 days, IUE for 27 days, and Extreme Ultraviolet Explorer (EUVE) for 10 days. The resulting light curves reveal that the optical and UV light variations are inversely correlated with the RXTE and ROSAT fluxes, with the largest change in intensity occurring in the ROSAT bandpass. There is no evidence for a strong EUV/soft X-ray component during outburst. An outflowing wind is evident from the C IV line profile during each brief outburst as well as the superoutburst. The transitions from outburst states of the disk to quiescent states take place on timescales of hours. Accretion disk models can fit the UV line and continuum energy distributions near outburst only if the disk radial temperature profile is modified from the standard case to produce a hotter distribution in the outer annuli. The high mass transfer rate, the hot disk distribution, and the similarity of outbursts and superoutbursts argue for outside-in outbursts in this system.

THE DWARF NOVA OUTBURSTS OF NOVA HER 1960 (=V446 HER)

A photometric monitoring campaign has been conducted in order to investigate the character and origin of flaring events occasionally seen in the long-term low-state light curve of the polar prototype AM Her. Four telescopes employed during 2004 May?July revealed that the events have typical duty cycles of 2%?35%, amplitudes of 0.2?0.6 mag, and typical durations of 15?90 minutes. A striking concentration of the 2004 events appears near inferior and superior conjunction of the secondary star. Interestingly, in the long-term RoboScope-monitored light curve (1990?2003), similar events are uniformly distributed in phase. AM Hers accretion geometry and the nature of its low states allow for two likely origins for the observed events, namely, residual accretion during low states and activity (flares) on the secondary star. Considering that AM Her is likely a one-pole accretor in the low states, the former requires irregular mass transfer from the secondary, resulting in random accretion bursts, with cyclotron beaming concentrating the flares into two phase intervals. On the other hand, considering the stability of the magnetic poles, this cannot address the random distribution of the events during the long-term light curve. Drifting active regions on the secondary star could explain the random distribution of the events; however, coincidence must be invoked to explain their occurrence at the observed phases of orbital conjunction. A combination of the two ideas is also discussed, in which stellar activity on the secondary star induces random accretion bursts, with cyclotron beaming then concentrating the flares into two phase intervals.