(cba:news) (cba:chat) Up and Running---AM CVn

Joe Patterson jop at astro.columbia.edu
Wed Mar 12 06:30:16 EDT 2014


Hi Shawn and Jim, and dog-lovers everywhere...

You bet - it's the most prolific periodic-signal producer in captivity! 
  My recollection is that we measured 22 periodic signals in our 
Skillman et al. 1999 study.  At most, maybe 6 of them "are understood".

Now granted, some of the single (non-accreting) pulsating white dwarfs 
have *hundreds* of periodic signals - mostly very close sidebands, only 
resolvable with long time series (esp. by the Whole Earth Telescope). 
But these are actual pulsations of the white dwarf, which has had more 
than a billion years to get its pulsations organized.  AM CVn's signals 
come from the accretion disk, which gas flows through on a timescale of 
days-to-weeks.  So it wins by that yardstick.

A worthy competitor is V455 And (nee HS2331+3905) which has at least 10 
signals, plus one complex at ~5 minutes, which may host dozens of 
components if it could only be resolved.  We may try a campaign to 
resolve it, one of these years.  The first paper ever written on this 
star, by Araujo-Betancor in 2005, is now a classic.  Great star, great 
research, excellent writing.  Helena is now polishing up our first paper 
on this amazing star.

I've been mining CBA data every year to time AM CVn's orbital wave, 
which is very weak at 0.0035 mag semi-amplitude.  We're now finally able 
to see, with a baseline of 36 years (the last 21 from CBA), the period 
change which can test the hypothesis that the star is powered by the 
removal of angular momentum by gravitational waves.  It's a theory 
universally assumed, but not yet tested.  That's the goal - but we need 
a few more weeks of coverage to nail it down, or fail.

HP Lib is another important star of this type, which has received 
surprisingly little attention.  Great target for April through June.

Well, if summer knocks out Shawn, we'll just have to settle for those 
exquisite long light curves we've been seeing from Oregon in recent years.

joe


On 3/11/2014 9:29 PM, Shawn Dvorak wrote:
> Always a good sign when there's no smoke!  I usually shut down my
> observatory during the hot, rainy summer here in Florida and am always
> worried when I hit the power buttons after hauling everything back out
> to the observatory in the fall.
>
> AM CVn's light curve is not the most exciting I've seen but I suppose
> with enough data some periodic signals can be teased out.
>
> Shawn
>
>
> On 03/11/2014 09:17 PM, Jim Jones wrote:
>> After a long, long winter, I powered up the observatory this afternoon
>> and nothing caught on fire.
>>
>> So I will give AM CVn a shot tonight...all night.  But I will be
>> surprised if the wheels don't fall off.
>>
>> Jim Jones
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