Re: GSC 748-1618

[Tass Mailing List <tass@mail.alembic.net>]

Date: Wed, 21 Feb 2007 09:16:41 -0500
From: Doug Welch <welch@physics.mcmaster.ca>
To: Tass Mailing List <tass@mail.alembic.net>
Subject: Re: GSC 748-1618


Hi Mike,

DCEP-FO = delta Cepheid, first-overtone and I still agree with their
classification! :)

The first-overtone Cepheids are frequently single-mode pulsators. The
MACHO Project found that whenever the second-overtone mode was excited,
the star was a double-mode pulsator (first and second overtone).
However, the majority of first-overtone Cepheids only pulsate in one mode.

Cheers,
Doug

Tass Mailing List wrote:
>
> Date: Tue, 20 Feb 2007 22:55:32 -0600
> From: Michael Koppelman <lolife@bitstream.net>
> To: tass@tass-survey.org
> Subject: GSC 748-1618
>
> You guys remember this discussion?
>
>> On Sat, 1 Mar 2003, Patrick Wils wrote:
>>
>> >
>> > --- Doug Welch <welch@physics.mcmaster.ca> wrote:
>> > > I am a little curious why people have decided to ignore
>> > > my suggestion that this is a short-period, overtone
>> > > Cepheid. Perhaps it wouldn't seem so strange then!
>> >
>> > Yes, I agree now (I was quite sure it was an RR Lyrae star
>> before, but
>> > it doesn't fit in either of the RRab or RRc class, so it can't be).
>> > Aren't these overtone Cepheids always double mode pulsators ?  In
>> that
>> > case a frequency analysis should reveal a second period of about
>> 0.63
>> > days.
>> >
>> > Patrick
>> >
>
> Take a look at the attached PNG file. ASAS has since called this a
> "DCEP-FO". Does that make sense? I'm not even sure what that means.
> We've been thinking this was an RRab but it is too red at B-V~0.7 and
> V-I~0.8
>
> Cheers,
>
> M.
>
>
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