Re: HD 145913

["Jim Bedient" <bedient@hawaii.rr.com>]

Hey Michael,

I still have the PEP gear laying here.  I'll try a run on this star Saturday
night, weather permitting - from 8 UT or so to about 12UT

Jim B.

>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
>>>
>>>
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>> 
>> 
>> 
>> 
>> 
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