(cba:news) (cba:chat) POLARS... intermediate and full-fledged

Joe Patterson jp42 at columbia.edu
Wed Aug 1 17:03:25 EDT 2018

Aha, the critical question.

ASASSN-18ey is one of the two great success stories of the CBA (the 
other being WZ Sge in 2001). I watch greedily for each new message and 
salivate when it comes.  The present data will tell an eloquent story 
about black-hole superhumps.

But there's a statistical rule to consider.  If you have 10 nights of 
data, then to have a really *significant* increase in data, you need 20 
nights.  We have ~110 nights, so to learn a lot more, we need 110 more. 
We can't get that - the Sun will start killing us in another month 
(remember, the period is 17 hours).  So the moral is that we can back 
off the intensive coverage now.  Nevertheless, if you've been getting 
long nightly runs and can still do it, they will be very helpful for 
another month.

Botttom line: a good time to start thinking about (and observing) other 
targets.  I'll send a few more suggestions tonight.

joe p

On 8/1/2018 12:33 PM, David Cejudo wrote:
> Hello!
> Should i stop pointing ti ASASSN-18ey?
> I have a few nights’ worth of data to upload yet and the telescope is programmed to point to it again tonight.
> David Cejudo.
>> El 1 ago 2018, a las 17:49, Joe Patterson <jop at astro.columbia.edu> escribió:
>> Hi CBAers,
>> Something new!
>> We are preparing a proposal to observe a bunch of polars (AM Her stars) in hard X-rays (10-60 keV).  These energies are comparable to the free-fall energy onto a white dwarf.  And since the conventional model for polars invokes accreting gas falling directly to the surface, this observation can reveal the white-dwarf masses (more massive WDs are much smaller, and thus should produce much higher infall energies).
>> This experiment has been done successfully for a few of the celebrity polars.  We'd like to try it for some of the rank and file.  Here are the stars: VV Pup, UZ For, EP Dra, V834 Cen, V2301 Oph, HU Aqr, ST LMi. All these stars are known or at least likely to have high and low states, and it's important to know how bright they are now.  Probably the X-ray observation will only succeed if the star is in a high state. So at a minimum, is the star *currently* in a high state?
>> 1. This will probably require a 2-hour observation, since the stars vary strongly over an orbital cycle (generally 1.5-2.2 hours).
>> 2. Someone will need to estimate how long the star is likely to stay bright.  JUst a guess, of course... and I suppose that's my job (by consulting literature), but if anyone feels like doing that search of previous papers, I'd be grateful.
>> 3. Most of these stars are around 16-17 mag, and for that we always recommend unfiltered light.  But consider also a V filter.  Time resolution is of no great importance here, and unfiltered brings some problem, since these stars typically have very crazy colors (because of cyclotron radiation.  This is mitigated by V, which has a much narrower poassband and is the reference standard of most previously published studies.
>> Try to get as many as you can.  Not much need to do a *second* 2-hour light curve of a particular star.
>> Being faint and rapid large-amplitude flickerers, these stars tend to persuade the rookie observer that the data are no good.  But on a good night, it's likely the data are quite good.
>> We hope to submit this proposal, or part of it, soon... so see what you can do with this!
>> Re the intermediate polars, and the Star of the Year ASASSN-18ey, I'll write tomorrow.
>> joe p
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