Variable Star Spectra Compared

Maurice Gavin

Adjacent selection of low-res spectra (4.15nm/pixel) of mostly variable stars captured during a two and half hour session in poor transparency (lvm~3) on 1999 March 18. The targets in an 'equatorial' strip of sky from south through to SW from Sky Cat 2000 and located via the LX200's autopointing facility. M-type stars immediately identified on download by their 'bead-like' spectrum. The relative efficiency of the spectroscope may be gauged by the brevity of exposures (alpha Ori =1/100 second !) ensuring capture of fainter spectra in a few seconds.

Note the 'carbon' stars T Cnc and RV Mon have a triple absorption band between A line and H-alpha. RV Mon (9.7 -11.9) is unseemly bright for the brief exposure and Megastar lists GSC 161:2696 (m6.2) at same position but only one star recorded at this location. The top pair (RZ Hya+W Cnc) are very faint currently (2m exposure) and their spectra has shifted almost entirely in IR (to right) as have T Hya and RT Cnc immediately below. Compare RZ Hya to S Hya - both are of similar spectral class but presumably at a different phase of their respective light cycle. S Hya and Betelgeuse (alpha Ori) currently have similar spectra although of somewhat different spectral class.

Progressively 'hotter' stars KM Hya [type-A], KX Hya [type-B] and Plaskett's Star (HD 47129 in Mon; type-O8e) included - the latter appears to show one (and maybe a second) emission line near, but not coincident with, H-beta.

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