THE ASTROPHYSICAL JOURNAL, 521 : 362È375, 1999 August 10 1999. The American Astronomical Society. All rights reserved. Printed in U.S.A. ( RXT E, ROSAT , EUV E, IUE, AND OPTICAL OBSERVATIONS THROUGH THE 45 DAY SUPERCYCLE OF V1159 ORIONIS PAULA SZKODY,1,2 A. LINNELL,2 KENT HONEYCUTT,3 JEFF ROBERTSON,4 ANDREW SILBER,2,5 D. W. HOARD,2,6 L. PASTWICK,2 V. DESAI,2 IVAN HUBENY,7 JOHN CANNIZZO,8 WILLIAM LILLER,9 RONALD ZISSELL,10 AND GARY WALKER11 Received 1999 January 11 ; accepted 1999 March 22 ABSTRACT 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 RXT E for 38 days, ROSAT for 34 days, IUE for 27 days, and Extreme Ultraviolet Explorer (EUV E) for 10 days. The resulting light curves reveal that the optical and UV light variations are inversely correlated with the RXT E and ROSAT Ñuxes, 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 outÑowing wind is evident from the C IV line proÐle during each brief outburst as well as the superoutburst. The transitions from outburst states of the disk to quiescent states take place on time- scales of hours. Accretion disk models can Ðt the UV line and continuum energy distributions near out- burst only if the disk radial temperature proÐle is modiÐed 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. Subject headings : novae, cataclysmic variables È stars : individual (V1159 Orionis) È ultraviolet : stars È X-rays : stars 1. INTRODUCTION Dwarf novae are characterized by the presence of out- bursts of 2È9 mag amplitude that last for 1È15 days and recur at intervals from weeks to months. Early theories to explain these outbursts involved increased mass transfer from the late main-sequence companion to the primary white dwarf (Bath 1975 ; Verbunt 1986), and recent ideas have centered on an increasing surface density of the accre- tion disk during quiescence, which results in a transition from a low- to a high-viscosity state (Cannizzo 1993 ; Osaki 1996). Because the dwarf novae span a wide range of orbital periods (from 80 minutes to days), the mass transfer rates and subsequent accretion rates through the disk and onto the white dwarf have a large range (Warner 1995). However, in order for an outburst to occur, the accretion rate must be below a critical value for the orbital period (Shafter, Wheeler, & Cannizzo 1986), and the resulting disks are usually optically thin and difficult to parameterize. At high accretion rates during outbursts, the disks are similar to 1 Based on observations with the Apache Point Observatory (APO) 3.5 m telescope, which is owned and operated by the Astrophysical Research Consortium (ARC). 2 Department of Astronomy, Box 351580, University of Washington, Seattle, WA 98195. 3 Department of Astronomy, Indiana University, Bloomington, IN 47405. 4 Department of Physical Sciences, Arkansas Tech University, Russell- ville, AR 72801. 5 Present address : NeoPath, Inc., 8271 154th Avenue NE, Redmond, WA 98052. 6 Present address : CTIO, Casilla 603, La Serena, Chile. 7 Laboratory for Astronomy and Solar Physics, Code 681, NASA/ GSFC, Greenbelt, MD 20771. 8 Laboratory for High-Energy Astrophysics, Code 662, NASA/GSFC, Greenbelt, MD 20771. 9 Casilla 5022, Renaca Bajo, Chile. 10 Mt. Holyoke College, 161 North Main Street, South Hadley, MA 01075. 11 179 South Main Street, Sherborn, MA 01770. what is predicted for steady state, optically thick models, as evidenced by the Ñux distribution being close to F j P j~2.3 (Szkody 1985). For systems below the period gap (the normal SU UMa stars), the mass transfer rates are usually low (\10~10 M _ yr~1), the outbursts are the inside-out variety (Smak 1984), and the tidal stresses on the eccentric disks produced in these systems with extreme mass ratios lead to super- outbursts (SOBs), which are longer lasting and of larger amplitude than normal dwarf nova outbursts. Di†erences in the mass transfer rates and/or the viscosity parameters can result in outside-in outbursts, such as evident in OY Car (Vogt 1983). The combination of disk instability and tidal instability can explain the wide range of behavior evident in dwarf novae (Osaki 1996), but the details of the physical condition of the disk material during the outburst and SOB cycles remain to be solved. Simple accretion theory predicts that one-half of the luminosity should emerge from viscous interaction in the disk, while the other one-half should come out at the boundary layer where the Keplerian velocities of the inner disk material meet the more slowly rotating white dwarf (Shakura & Sunyaev 1973). The disk has temperatures suffi- cient for it to emit in the optical and UV, while the higher temperatures in the boundary layer result in X-ray emis- sion. Early Einstein surveys (Patterson & Raymond 1985) formulated a picture of quiescent dwarf novae with physi- cally thin disks and hard X-ray emission from optically thin boundary layers, while outbursting dwarf novae had thick disks and EUV/soft X-ray emission from an optically thick boundary layer. However, subsequent, more detailed studies revealed large variations among systems. U Gem showed an increase of both hard and soft X-rays from quiescence to outburst (Cordova & Mason 1984), SS Cyg showed the expected decrease in hard and increase in soft X-ray (Jones & Watson 1992 ; Ponman et al. 1995), while SU UMa and RU Peg showed a decrease in hard X-ray Ñux 362