AI CMi light curve

AI CMi is a strange star. It has been classified as a RCB-type in the past but now it is known as an L irregular variable.

Eggen (1983) defined it as a pseudocepheid ("supergiants in the Hertzsprung gap with light variations more erratic than those of the cepheids") with a cycle length of less than 100 days.

It turns out that AI CMi seems to be a planetary nebula precursor, a post-AGB star on its way to becoming a white dwarf.

Its spectral type has been classified as G5Iab (MacConnell and Bidelman, 1976). As a bona-fide post-AGB star, it seems to be surrounded by a dust shell that explains its B-V around +1.6.

It shows deep minima alternating with brighter cycles and also show double maxima. It reminds me of R Doradus and a mix of a double peaked mira and a RV Tau star. It's not surprising given its position in the H-R diagram!

NOW: AI Canis Minoris is in a very bright state. According to ASAS-3 data and my visual observations, it is at V= 7.86 on May 10, 2003. (See light curve above)

Lightcurve from Eggen's paper ("Pseudocepheids. I. R Puppis, HR 4441, HR 4511, and AI CMi", Astron. J. 88, 386-403, 1983)

Total lightcurve including data from the Mark III camera of the TASS project. (yellow dots)

AI Canis Minoris es una estrella muy vieja, post-AGB, en camino a convertirse en enana blanca.
En estos días se la puede ver inusitadamente brillante. El 10 de mayo estaba en 7.86 de acuerdo a los datos de ASAS-3.
Esta estrella fue catalogada como RCB en el pasado, actualmente se la considera como una L.
Su tipo espectral es G5Iab y su B-V de 1.6 (variable), fuertemente enrojecido por material interestelar, eyectado por la estrella en su fase AGB.
Es que AI CMi es una precursora de nebulosa planetaria.
Eggen (1983) la incluye en su lista de "pseudocefeidas" ("supergigantes en el vacío de Hertzsprung con variaciones de luz más erráticas que las de las cefeidas.") con un ciclo de variación de menos de 100 días.