Z CamPaign Update February 2015

February 22, 2015

First, thank you to all the CCD and visual observers who have contributed to this campaign since 2009. With your help we have met all the original science goals, published several papers, unearthed a poorly understood group of anomalous Z Cams and whittled down the list of Z Cam suspects.

I'm happy to report there is still plenty to do.

All the bona fide Z Cams should be observed every night. They still have surprises in store for us and now that we have classified them unambiguously we need to maintain a historical record of their unique and interesting behavior. There are plenty of bright Z Cams that visual observers can follow throughout their range of variability. CCD observers should concentrate on Z Cams that get fainter than 15.0V.

The Z Cam List website lists all the bona fide and suspected Z Cams.

Z Cam suspects requiring close monitoring for 2015:

I'm adding a brand new Z Cam candidate for 2015, 1RXS J062954.6-033520. The ASAS light curve looks very promising. This bright Z Cam suspect can be followed by CCD and visual observers in both hemispheres. Something for everyone! Go get it.

(Click on light curves to enlarge)

PY Per- This star is one of the best remaining candidates for inclusion in the Z Cam family. In fact, it may be in a standstill right now! This one needs dense nightly snapshot photometry. Consider this a first order priority target for the 2015 Z CamPaign.

WZ CMa- This star has an outburst cycle of 57 days and each outburst lasts about 2 weeks. It's light curve resembles HP Nor, another southern Z Cam star. It's an active star, ranging from magnitude 14 to 17.5, so a good target for visual and CCD observers. This one is testing our patience. I think it is worth getting one more year of intense coverage just to see what happens.

V426 Oph- This pathological CV defies classification. It's an active system with a smallish amplitude, varying from 11.3- 13.3V most of the time. It has relatively frequent outbursts, but also has prolonged low states and fading events like a VY Scl star.

V416 Dra (HS 1857+7127)- This eclipsing system has a very active UGSS-looking light curve, which many Z Cams also have when not in standstill. The amplitude and period are right for a Z Cam, so let's keep chipping away at this one and see if it finally rewards us with a standstill.

V868 Cyg- I need to closely examine the data from 2013 to be sure it is not contaminated by the close companion to this dwarf nova. There could be a paper and a new bona fide Z Cam announced some time in the next few months, because it looks like a prolonged standstill occurred that year. Please continue to observe this star, but be sure to be careful identifying the variable and the nearby companion.

V1101 Aql- I thought this star was in standstill from September to December 2011, but there wasn't a lot of data coming in at that time. It does strike me that this apparent standstill was at the same level (14.7V) as the standstill reported in Masetti and Valle (1997). Since then it has looked more like a normal UGSS most of the time, which does not rule it out as a Z Cam candidate. I consider this a strong candidate for Z Cam-ness.

IS Del- There simply is not enough data to rule this out as a Z Cam. It looks like a typical UGSS, which of course, many Z Cams do when they are not in standstill.

HS 2133+0513- The CRTS light curve seems to hint at both a VY Scl fading and a potential standstill. I just can't take this one off the suspects list.

V1404 Cyg- This is another faint DN that looks like a UG with a cycle time of 50-60 days. There simply is not enough data over a long enough timespan to confidently rule it out as a Z Cam.

CSS 100624:220031+033431- The CRTS light curve seems to show a standstill around 18th magnitude. We need to devote more attention to this faint CV. If you have the aperture to cover the range 16 - 20V, please submit nightly snapshot data in V or CV to the AID.

HS 2325+8205 (NSV 14581)- There is not enough data to make the call either way. It's relatively bright (14-16.5V), so let's try to get denser coverage in 2015, please.

Z CamPaign stars to drop for 2015:

1RXS J015017.0+375614- Based on the available data, I am leaning towards classifying this one as a VY Scl star. It seems to have high and low states, with some impressive fading episodes.

HS 0139+0559, HS 0229+8016, HS 0642+5049- With no outbursts, no standstills, and a small amplitude of variation these three are almost certainly a Nova-like (NL) variables.

V392 Per- This dwarf nova has infrequent outbursts, and no evidence of standstills. Based on the anomalous long outburst in 2013, this star is worthy of further investigation, but I don't think it's going to end up being a Z Cam. We're dropping it from the Z CamPaign, but I would keep a watchful eye on this one.

V1505 Cyg- This looks like a NL system. The narrow range of variation and no obvious evidence of outbursts or standstills make it highly unlikely this is a Z Cam.

TT Ind- I think Josch Hambsch's excellent CCD data has shown this to be a simple UG, with an outburst cycle of about 166 days.

MN Lac- I think the outburst cycle time of 180 days is too long to be a Z Cam. This is likely a garden variety UG, and it is really faint, which makes it hard to observe. Let's concentrate on more promising candidates.

Here's wishing you clear skies and happy hunting,

Mike Simonsen