Re: HD 145913

[Arne Henden <aah@nofs.navy.mil>]

I seriously doubt it is a CV, with a quiescent magnitude of ~7.7,
since that would imply naked eye visibility if it ever went into
outburst.  A5 is also quite red if we were dealing with a run-of-the-mill
CV.  My guess is that Mira's photometric estimate is in
error or not being used correctly.  I presume you looked long
enough to confirm that there could not be eclipses at John's
period?  The TASS Welch-Stetson statistic is quite high, so I
would look at the original data and see if there was any discrepant
data that gave such a high value if the star is "constant" (at least
within the error limits of Tom's camera).
Arne

Michael Koppelman wrote:
> OK, I looked at HD 145913 last night. Check out my data here:
> 
> http://www.lolife.com/astronomy/hd145913/
> 
> I have some multicolor data, too. What I did was do BVRI for an hour 
> then high time resolution in R for an hour, and then another hour in 
> BVRI. My S/N was very high. For the program star it was (according to 
> Mira) 800 or so. It was not saturated. The integrations in Rc was 30 
> seconds. The standard deviation in the comp stars was 0.005. The 
> standard deviation of the program star was 0.008.
> 
> There is a slight period to this flicker (13 minutes and 4.5 minutes), 
> but it could just be noise. I would for sure call it noise except that, 
> according to Mira, the errors are very low. The standard deviation in 
> the comp stars is 0.005. The amplitude of the program star is 0.04, 
> which is damn small but still 8 times the 1-sigma error and almost 3 
> times the 3-sigma error. So maybe it is flickering. I had an exchange 
> with Joe Patterson of the CBA (on another matter) and he had stated 
> "Virtually all CVs flicker erratically on timescales of 1-3 minutes, so 
> if your time resolution is much worse than ~40 s, you become blind to 
> this and it appears merely as unwanted noise (which can be quite large, 
> even ~0.2 mag)." This is what caused me to look at such short periods. 
> This star is A5, so it's not red. I'm not claiming it's a CV and it's 
> probably just noise and can be crossed off the list for a short period 
> 0.2 mag eclipser that John thought it might be (see below). I don't know.
> 
> Cheers,
> Michael Koppelman
> 
> 
> 
>> Info from Aladin:
>> ICRS 2000.0 coordinates      16 13 18.7377 +06 02 15.537
>> B magn, V magn               7.97, 7.76
>> Spectral type                A5
>>
>>
>>
>>
>>
>> John Greaves, 2002 July 12
>>
>>
>> Okay, if somebody like Michael K. fancies a change from EW stars, this
>> one has a possibility of being a delta Scutid.
>>
>> HD 145913 is spectrum A5, mag around V 7.8.  Welch-Stetson Index is 18.
>> Amplitude appears quite low, maybe 0.2 V at very most.
>>
>> Not much on lightcurve structure on a per night basis from Tom's data,
>> but the one good night looks interesting, though of short duration, and
>> structured enough to look like a true lightcurve shape rather than an
>> artefact.  Period may be very short if pulsator, around 0.2 or so days.
>>
>> Hipparcos (HIP 79493) noted a small 0.05 Hp mag range (5th and 95th
>> percentile), but it's in neither the NSVs or GCVS or a New Tycho
>> Variable for that matter.
> 
> 
> 
> Begin forwarded message:
> 
>> From: Patrick Wils <patrickwils@yahoo.com>
>> Date: Sat May 3, 2003  6:10:01 PM US/Central
>> To: Michael Koppelman <lolife@bitstream.net>
>> Subject: Re: new stars and such
>>
>> Hi Michael,
>>
>> --- Michael Koppelman <lolife@bitstream.net> wrote:
>>
>>> OK, data divers, I need a new star. Hopefully something where 14h <
>>> RA > < 18h or so.
>>
>>
>> HD 145913 (from the July data set, I think) might be a possibility as
>> well, RA near 16h, see
>> http://www.tass-survey.org/tass/data/july_2002/hd145913.html
>>
>> Patrick
>>
>>
>> __________________________________
>> Do you Yahoo!?
>> The New Yahoo! Search - Faster. Easier. Bingo.
>> http://search.yahoo.com
> 
> 
> 
> 
>