VV Cep spectroscopy reference star ?

VV Cep 2017-2019 Campaign
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Re: VV Cep spectroscopy reference star ?

Postby Robin Leadbeater » Fri Aug 11, 2017 1:44 pm

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
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http://www.threehillsobservatory.co.uk
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Re: VV Cep spectroscopy reference star ?

Postby Robin Leadbeater » Fri Aug 11, 2017 2:02 pm

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
LHIRES III #29 ATIK314 ALPY 600/200 ATIK428 Star Analyser 100/200 C11 EQ6
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Re: VV Cep spectroscopy reference star ?

Postby Thilo Bauer » Fri Aug 11, 2017 3:08 pm

Hi Robin,

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

Thilo
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Re: VV Cep spectroscopy reference star ?

Postby Phil Bennett » Wed Aug 30, 2017 9:35 pm

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
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