IW And is in a standstill, confirming its membership in the Z Cam class of stars This is not a newsbreak. Taichi Kato, Ryoko Ishioka and Makoto Uemura described this system as a Z Cam dwarf nova back in 2003, in the International Bulletin on Variable Stars (IBVS). http://www.konkoly.hu/cgi-bin/IBVSpdf?5376
Based on 55 observations made over a period of about four months this team caught IW And in a standstill, which is the defining characteristic of Z Cam dwarf novae.
Light curve of IW And from Kato et al, 2003, IBVS 5376
Since the earliest days of the Z CamPaign http://arxiv.org/abs/1104.0967 I had noticed that the light curve of IW And was unlike that of any other system in the Z Cam candidate sample. It exhibited a quasi-periodic behavior whose light curve looked more like an eclipsing system than a dwarf nova.
This never before seen behavior led me to believe that perhaps we had discovered some new animal in the CV Zoo. "This doesn't look like a Z Cam light curve," I told myself. "We may have stumbled on to something important here!" My ego quickly overruled the facts, and I have been hoping ever since that I had uncovered some unique, astrophysically interesting class of CVs. I convinced a lot of people to pay special attention to this system, hoping that my “discovery” would pan out.
Fortunately, the stars couldn’t care less about my ego, and IW Andromedae has once again gone into a prolonged standstill, as evidenced by the AAVSO light curve, confirming that it is indeed a member of the Z Cam class of dwarf novae.
AAVSO light curve of IW And, clearly showing the standstill after an active period of outbursts and quiescence. Welcome to the club, IW And. I still think you are special, and you will remain one of my favorite variable stars forever. As if to add to the lesson in humility, V513 Cas, my other "special case" appears to be in the early stages of a Z Cam standstill also! A Z CamPaign update will be coming soon. In the meantime, thank you to all who have made this campaign a success and keep up the excellent coverage. Humbly Yours, Mike Simonsen CVnet Coordinator -------------------------------------------- THE KEPLER LIGHT CURVES OF V1504 CYGNI AND V344 LYRAE: A STUDY OF THE OUTBURST PROPERTIES John Cannizzo et al  736 day light curve of V1504 Cyg  736 day light curve of V344 Lyr We examine the Kepler light curves of V1504 Cyg and V344 Lyr, encompassing ~736 d at 1 min cadence. During this span each system exhibited ~64-65 outbursts, including six superoutbursts. We find that, in both systems, the normal outbursts between two superoutbursts increase in duration over time by a factor ~1.2-1.9, and then reset to a small value after the following superoutburst. In both systems the trend of quiescent intervals between normal outbursts is to increase to a local maximum about half way through the supercycle - the interval from one superoutburst to the next - and then to decrease back to a small value by the time of the next superoutburst. This is inconsistent with Osaki's thermal-tidal model, which predicts a monotonic increase in the quiescent intervals between normal outbursts during a supercycle. (snip) Read the full abstract and pre-print here Authors: C.S. Froning, K.S. Long, B. Gaensicke, and P. Szkody  FUSE spectra of non-magnetic CVs During its lifetime, the Far Ultraviolet Spectroscopic Explorer (FUSE) was used to observe 99 cataclysmic variables in 211 separate observations. Here, we present a survey of the moderate resolution (R\simeq10,000), far-ultraviolet (905 - 1188 {\deg}A), time-averaged FUSE spectra of cataclysmic variables (CVs). The FUSE spectra are morphologically diverse. They show contributions from the accretion disk, the disk chromosphere, disk outflows, and the white dwarf, but the relative contribution of each component varies widely as a function of CV subtype, orbital period and evolutionary state, inclination, mass accretion rate, and magnetic field strength of the white dwarf. The data reveal information about the structure, temperature, density and mass flow rates of the disk and disk winds, the temperature of the white dwarf and the effects of ongoing accretion on its structure, and the long-term response of the systems to disk outbursts. The complete atlas of time-averaged FUSE spectra of CVs are available at the Multimission Archive at Space Telescope Science Institute as a High Level Science Product. RECENT PAPERS ON CVs For new papers on CV's see arxiv.org astro-ph Author: J. Echevarria Authors: Imamura & Tanabe Authors: Cohen et al Authors: Cannizzo et al Authors: Ruse II & Ringwald Authors: Shore et al Authors: Darnley et al | ACTIVITY AT A GLANCE New outbursts and unusual activity reported in the last 72 hours Last updated 13:35 UT January 27, 2012 DDMMYY 270112 X Leo 260112 HW Boo (HS1340+1524) V485 Cen V392 Hya DT Oct 250112 BF Ara AR Pic CSS101008:011517+245530 * indicates an unconfirmed outburst # indicates a noteworthy or unusual outburst 'Activity At A Glance' is gleaned from observations reported to AAVSO MyNewsFlash, BAAVSS-Alert, CVnet-Outburst, VSObs-share and VSNET-outburst. We sincerely thank all the observers who contribute timely observations and reports of activity to these email lists.
It’s all about the standstills, those episodes where the star gets stuck at a mid-point between maximum and minimum. If it doesn’t exhibit standstills it isn’t a Z Cam star. RECENT ZCamPAIGN ACTIVITY OF NOTE: AT Cnc re-entering standstill-  AT Cnc entering standstill at exactly the same magnitude as the prior standstill WW Cet entering faint state-  WW Ceti fading after a historical standstill  PY Per- 7 year light curve showing active and low states Recent (Nov-Dec 2011) standstill of HX Peg  Important to gather detailed long-term light curves for the
majority of these systems to better understand their nature.  AM Her stars in need of further investigation |
