(cba:news) (cba:chat) March stars

Joe Patterson jp42 at columbia.edu
Fri Mar 16 18:22:22 EDT 2018

Yes, I strongly recommend intense coverage of AT Cnc, for as many hours 
as you can get it. Best *morning* target for the next 1-2 weeks is AM 
CVn - also intensive.

Duplicating coverage on AM CVn isn't bad - in fact, it's highly 
desirable.  AM CVn has three periodicities: at 525 s, 1051 s, and 1028 
s.  The first two are generally the strongest; but because they're 
superhumps - not stable on long timescales - they have to be removed in 
order to track the orbital 1028 s signal.  Somewhat tricky, but can 
always be done if the data are DENSELY distributed.  That's the key - 
dense coverage.  This is true for most CBA programs, to some degree - 
but never as much as AM CVn, because separating these closely spaced 
frequencies is critical.


On 3/16/2018 5:03 PM, Shawn Dvorak wrote:

> As an extra incentive, AT Cnc is currently in a Z Cam standstill. The 
> AAVSO data shows it "got stuck" around mag 13.6 near the end of 
> January. Although the data is a bit sparse, it seems to be showing a 
> 0.4 mag amplitude variation with a ~6.5 day period. Interesting, but 
> possibly just a coincidence. It looks like I'll have mostly clear 
> skies tonight so I'll get a longish run on it from 0:30 - 06:30 UT
> Shawn
> On 03/04/2018 07:34 PM, Joe Patterson wrote:
>> Dear CBAers,
>> Muchas gracias for all the great data you've been sending, especially 
>> re the DQ Her stars which you've been covering so faithfully.  It's 
>> been a winter of ice and mishap and hard work - nothing really 
>> serious but maybe I got kind of soft after a semester off from work.
>> The DQs are relatively sparse in the (northern) springtime sky, so 
>> that program can rest - a little.  Here are my recommendations for 
>> northern observers:
>> 1. AT Cnc.  Probably a very ancient nova, and our last campaign 
>> showed a credible signal around 28 minutes.  Very desirable to get 
>> long runs now, the more the better.
>> 2. NY Ser.  Reputed to be in a standstill state now around 15.5 - I 
>> think the first such event observed in this star's sparse history. 
>> Excellent morning target.
>> 3. AM CVn.  Perhaps the least exciting star to observe (always within 
>> 0.15 mag of 14.2), but very important since it is the prototype of 
>> one of the most important classes - the mass-transferring double 
>> white dwarfs.  We have a TENTATIVE detection of period change through 
>> 2016, but a good 2018 season should nail it down.  This calls for 
>> steady coverage through April (especially) and March.
>> 4. HT Cam.  A DQ Her star for which we'd like to get a particularly 
>> accurate estimate of period change.
>> 5. BK Lyn.  What's it doing this year?  Pretty steady, or cycling 
>> like the ER UMa stars.  Spot checks will be fine, not necessarily 
>> time series.
>> And for southern observers:
>> 1. V598 Pup.  Lots of activity in this fascinating recent nova. 
>> Except for Berto, who always seems to spot the most interesting 
>> jewels, we've never observed it before.
>> 2. IM Nor.  Back in the sky now.  At 18.5, maybe only Gordon can work 
>> on it.  But some eclipse timings in the new season - i.e. maybe 20-25 
>> hours of coverage - would be great to add to our >95% completed paper 
>> on this star.
>> 3. V959 Mon.  Another recent nona for which we need the 2018 orbital 
>> light curve.  It's a long period, so your runs need to be at least 4 
>> hours.
>> 4. WX Pyx.  Keep going on this one, the Pdot is still kinda insecure.
>> (I think; Enrique would know for sure).
>> And both hemispheres: SW Sex.  We've never done a good job on it, and 
>> there's no excuse for it.  ALL the SW Sexers have been good to us... 
>> so let's give the prototype a chance!
>> Those are my recs.  Enrique may send his, of course.
>> joe
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