Pulsation properties of C stars in the Small Magellanic Cloud

Abstract

Abstract.A sample of carbon-rich stars (C-stars) in the Small Magellanic Cloud (SMC) was selected from the combined 2MASS and DENIS catalogues on the basis of their J − K s colour. This sample was extended to include confirmed C-stars from the Rebeirot et al. (1993) spectroscopic atlas. In this combined sample (N = 1149), a smaller number (N = 1079) were found to have MACHO observations. For this sub-sample, light curves were determined and 919 stars were found to have high quality light-curves with amplitudes of at least 0.05 mag. Of these stars, only 4% have a well-defined single period -most of these have multiple well-defined periods, while 15% have highly irregular light-curves. The distribution of the logarithm of the period versus magnitude, colour, period ratio (if applicable), and amplitude was analyzed and compared with previous works. Variable C-stars are distributed in three sequences: B, C, and D from Wood et al. (1999), and do not populate sequences with periods shorter than log P ∼ 1.5. Stellar ages and masses were estimated using stellar evolutionary models.

Characterizing the Population of Bright Infrared Sources in the Small Magellanic Cloud

“…Even more intriguing, the 2MASS point source at this location is associated with RAW 631, a carbon star (Rebeirot et al 1993;Raimondo et al 2005).…”

“…However, it also has a very deep acetylene absorption feature (Q branch) at 13.7 µm and a possible (weak) silicon carbide emission feature. In the optical, Raimondo et al (2005) and Soszyński et al (2011) photometrically classified it as a carbon star. Our optical spectrum confirms the carbonrich chemistry of the source (Figure 3).…”

“…We adhered to these rules unless background gradients or additional sources in the slits forced us to search for a more suitable background image. Differenced images were then cleaned using the rogue pixel masks supplied by the SSC and the imclean pixel-replacement algorithm developed Pojmański (1997Pojmański ( , 2014; G09, Groenewegen et al (2009); S11, Soszyński et al (2011) b Optical spectral type references: B80, (Blanco et al 1980); E80, Elias et al (1980); P83, Prevot et al (1983); W83, Wood et al (1983), R93, Rebeirot et al (1993); R05, Raimondo et al (2005); G98, Groenewegen & Blommaert (1998);G15, González-Fernández et al (2015); K16, this work; Multiple=in five or more of the references. Additional, multiply used references: Sanduleak (1989); Elias et al (1985); Massey & Olsen (2003); Levesque et al (2006).…”

Near-IR observations of NGC 6822: AGB stars, distance, metallicity and structure

“…The use of this selection criterion may be a conservative approach in defining the number of C-rich AGB stars (cf. Raimondo et al 2004) but intrinsic C-rich AGB stars are usually brighter than TRGB stars and those C-rich stars below the TRGB are either extrinsic carbon stars (they belong to a binary system and have been polluted by AGB winds) or are sources with larger photometric errors that should instead be on to the O-rich branch. Therefore we adopted J −K s = 1.36 as the colour that distinguishes between sources of different chemical types.…”

Oxygen- and carbon-rich variable red giant populations in the Magellanic Clouds from EROS, OGLE, MACHO, and 2MASS photometry

“…All yielded catalogues of numerous variable stars. In these data the period-luminosity relations of the LPV's on the AGB are well documented for both the Large and Small Magellanic Clouds (Wood et al 1999;Wood 2000;Cioni et al 2001Noda et al 2002Noda et al , 2004Lebzelter & Hinkle 2002;Ita et al 2004a,b;Kiss & Bedding 2003, 2004Soszynski et al 2004aSoszynski et al ,b, 2005Groenewegen 2004;Fraser et al 2005;Raimondo et al 2005).…”