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Z CamPaign Update December 2010

At the first quarter point of the second year of this campaign we have some interesting results and publications in print and in preparation. I’d like to take this opportunity to thank all the observers reporting their data on Z CamPaign stars. Your data is driving this project, and I appreciate the time and effort you have invested in it.

Most of the following light curves are roughly January 2009 to the present. They were all plotted using VStar.

WW Cet

WW Ceti is in standstill as of this writing. This is the first historical standstill of this CV, and as such has given us the chance to unambiguously classify this dwarf nova as a Z Cam. Our paper on this standstill and WW Ceti’s new classification has been accepted by the JAAVSO and is available on the arXiv pre-print server. Special thanks go to John Bortle and Rod Stubbings for their invaluable data.

The First Historical Standstill of WW Ceti

V513 Cas

This IW And star continues to exhibit quasi-periodic fades that resemble eclipses every 3-4 months, as well as brief maxima that have gone from ~60 days apart to ~45 days on average lately.

IW And

The cousin to V513 Cas, IW And exhibits a similar behavior, with eclipse-like features every 39 days or so and short outbursts every 40 days apart on average.


The pattern for this season changed to deep fades 11-16 days apart and outbursts every 20-30 days, but it looks like the star is transitioning into the prior behavior pattern in the last few weeks.

RX And

RX And has remained in UGSS mode, with outbursts every 2 weeks. No standstills in 2009 or 2010.


TW Tri

Nothing remarkable happening here, but coverage is improving. It appears this star has a similar outburst cycle to many Z Cams 12-15 days. If we do eventually observe a standstill I think it will get stuck around 15th magnitude. Keep the data coming!

AY Psc

AY Psc has outbursts approximately every three weeks. This star also exhibits eclipses, so it affords us the chance to determine orbital parameters, geometry of the system and masses of the components. It might be a worthwhile effort to observe eclipses while this is still well placed. The orbital period is 5.2 hours, so eclipse observations are a significant time investment.

TZ Per

The trend this season seems to indicate TZ Per’s outburst amplitude is damping down. This could be indication of a coming standstill. I’m going to go out on a limb and predict TZ Per will experience a standstill within the next 90 days, on or before March 15, 2011. We’ll see how that turns out. Predicting CV behavior is pretty risky.


PY Per

I am beginning to suspect this star might actually be a VY Scl star hiding amongst the Z Cams.

The recent prolonged low state is reminiscent of VY Scl. Does accretion just temporarily shut off for these stars? If so, what kicks it back on again?

Then again, RX And has been seen doing this kind of thing in the past. This is discussed in 2002A&A...384L...6S, RX And: An intermediate between Z Cam and VY Scl stars, Schreiber, M. R.; Gänsicke, B. T.; Mattei, J. A. You can see one example below from 1993.

Southern Observers, We Need You Too!


HL CMa is a bona fide Z Cam I found this standstill in the data from June 1999- January 2000.


It too seems to be damping down in preparation of an upcoming standstill. This effect is also seen in the light curve above. Note how the amplitude between max and min decreases leading up to the standstill.


Simply put, we need more data for this star. There isn’t enough current data to talk about and there isn’t enough historical data to make the call as to WZ CMa’s membership in the Z Cam class.

BX Pup

BX Pup is classified as a Z Cam and I have to agree based on the historical data. It appears there were standstill in 1992 and 1997.  We could certainly do with more coverage, and the standstill level is ~14.2, so its within reach of visual observers with moderate sized telescopes.

Z Cam

After being in standstill since August this year, it looks like Z Cam has dropped back down to quiescence and is ready to start the roller coaster ride all over again. Get your tickets for 2011 now folks. It will no doubt be another fun ride.

AT Cnc

Below is the light curve for the time covering the Z CamPaign, September 2009 to present. As you can see, we had a nice standstill last season, and AT Cnc is becoming well placed for observers now.

SY Cnc

The above light curve is the only solid evidence of a standstill in the historical data for SY Cnc. This is not much to hang a classification on, but there you have it. If we can unambiguously identify another standstill in the future it will be pretty important in solidifying this classification.

Interestingly, there may have been a standstill (or more than one) we missed due to the seasonal gap. This light curve (below) tempts me into thinking “just maybe”.


Suspected of being a Z Cam by Patrick Wils, the most recent AAVSOnet photometric data is currently embargoed, so we will have to wait for the paper to find out the rest of the story. Stay tuned…

V849 Her

The season is over for now, but this will become a morning object before long, so don’t forget about it. This may be another IW And star, so please observe it every clear night you can.

AH Her

What can I say? This fantastic star has given me much joy over the last three observing seasons. Everything that a Z Cam can do it has done in the last 36 months- standstills, mini-standstills, changes in maximum magnitude, damping down of outburst amplitudes- it’s done it all. Soon it will be a morning object again and who knows what it will be doing in 2011. Whatever it is, it will be interesting.

V426 Oph

I don't know what to make of this star. Its light curve certainly resembles a Z Cam at times over the past ten years. The jury is still out. It's an unpredictable and fun star to follow, visible to southern and northern observers and bright enough to be followed by visual observers. This one is for everyone. Stay on it.

UZ Ser

The last standstill of this Z Cam happened in 2005 (above). This star could stand more coverage also, but I don’t think we’ve missed anything. More data would help fill in the minima.

V391 Lyr

So far this looks to be a run of the mill UG. Nothing unusual or hinting at a standstill, but we’ll keep an eye on it for a while just in case.

HS 1857+7127

Looks like a UG or UGSS. Keep monitoring. Outburst cycle and orbital period suggest it could be UGZ, but don’t guarantee membership in the club.

V868 Cyg

Not enough data to comment, but coverage is improving as observers refine their techniques. This is a faint one.

V1505 Cyg

Seems to be almost continuously varying between 16 and 17.5V. Too chaotic to say anything meaningful, and still suffers from a lack of coverage. Keep this one on your list if you have it. If you can add it, please do, we need more data.

EM Cyg

During the campaign this one has been active, and had two distinct but brief standstills. A great star for everyone- bright, active and always varying.

FY Vul

The amplitude of the light changes for this one seem too narrow for a UGZ. I’ve been hoping more intense coverage would reveal something, but so far, no luck.

VW Vul

This star had a standstill in 2010 from March to April, and a short one again from mid-September to early October that might have been missed if not for the excellent coverage.

HS 2133+0513

The orphan star of the campaign so far. This star has yet to be adopted by observers. 

V1404 Cyg

This one is getting covered quite well. So far, all that has shown up is a fairly consistent outburst cycle of 25 days. It's possible that there was a brief standstill in April 2010.

HX Peg

This star had a standstill from December 2008 to January 2009. It looks like it may be heading for another one. This UGZ appears to have standstills almost annually.