Spectra of two long-period variable red giant stars - XY Lyr and V465 Cas (Johannes D. Clausen)

Spectra of two long-period variable red giant stars - XY Lyr and V465 Cas

Looking at these two spectra you'd be forgiven to think that I had mistakenly pasted the same spectrum twice. But, indeed, these are separate spectra of two very similar M-class red giant stars. As is typical for the cool M-class stars, the spectra are dominated by molecular bands of titanium oxide, which can survive in the stellar atmosphere because of the relatively low surface temperature.

XY Lyr and V465 Cas are of M4-M5II class and are both long-period variable (LPV) stars, also called Mira-variables. According to data from AAVSO.org, V465 Cas has a period of ~2½ years, whereas that of XY Lyr is a lot shorter at around 6 months.

XY Lyr (red symbols, R-band; green symbols, V-band):

V465 Cas (only V-band data available):

The setup used to capture the spectra can be seen here: https://astrob.in/n7u78t/0/. The spectrum of XY Lyr was created from a stack of 21 individual 30-s subs calibrated with darks. The V465 Cas spectrum was created from 31 individual 20-s subs calibrated with darks. The spectra are shown corrected for instrument response.

Final
Original
B
C

B

Title: Field of XY Lyr (HD 172380) from the guide camera

Uploaded: ...

C

Title: Field of V465 Cas (HD 7733) from the guide camera

Uploaded: ...

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