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Re: VV Cep spectroscopy reference star ?

PostPosted: Fri Aug 11, 2017 1:44 pm
by Robin Leadbeater
Hi Thilo,

I am currently following VVCep (~3800-4100A). For relative flux calibration I am currently using Altair from the UVES POP "bright stars of the southern sky" and Vega from the CALSPEC list. This gives me measurements at two altitudes so I can calculate extinction more accurately if I need to but I have not bothered to do this yet. CALSPEC is not ideal though as it is at a significantly lower resolution than I am working at.

Cheers
Robin

Re: VV Cep spectroscopy reference star ?

PostPosted: Fri Aug 11, 2017 2:02 pm
by Robin Leadbeater
Note this is for calibration in relative flux only. I think calibration in absolute flux (spectrophotometry) is difficult in this part of the spectrum because of the large influence of atmospheric extinction. A better way to convert relative to absolute flux would be to use photometric B measurements but this can only be done accurately if the spectrum covers the full passband of the photometric filter. My spectra only cover part of the U and B bands so I cannot use this technique. If someone is making full spectrum measurements though (eg at low resolution) then these can be calibrated in absolute flux using Vmag values. (ISIS for example has the tools to do this)

Robin

Re: VV Cep spectroscopy reference star ?

PostPosted: Fri Aug 11, 2017 3:08 pm
by Thilo Bauer
Hi Robin,

I will take Altair into account. Sound reasonable. Appreciate your thoughts about this.

Thilo

Re: VV Cep spectroscopy reference star ?

PostPosted: Wed Aug 30, 2017 9:35 pm
by Phil Bennett
Hi Olivier,

I recommend mu Cep. It's a close spectral match to VV Cep (M2 Ia-ab), brighter and fairly close. It's never good to have a standard using up more observing time than the target star.

Phil