- ID:
- ivo://CDS.VizieR/J/A+A/568/A100
- Title:
- Photometric monitoring of halo C stars
- Short Name:
- J/A+A/568/A100
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Carbon stars are among the brightest intermediate-age stars. They are seen in nearly all galaxies of the Local Group. In the Milky Way they are members of the thin disk but over a hundred have been identified in the Galactic halo. Since the halo consists essentially of an old stellar population, these carbon stars warrant special attention. We believe that such stars are trespassers and belong to streams left over by disrupted dwarf spheroidal galaxies. By performing photometric monitoring we intend to identify Miras among the halo carbon stars. We obtained, over several semesters, K and J images centered on the carbon stars in order to determine their variation and periodicity.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/403/93
- Title:
- Photometry of AGB stars in NGC 185 and NGC 147
- Short Name:
- J/A+A/403/93
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The tables represent results of an ongoing photometric survey of Local Group galaxies, using a four filter technique based on the method of Wing (1971, Proc. of the Conference on Late-Type Stars, ed. G.W. Lockwood and H.M. Dyck, KPNO Contribution 554, 145) to identify and characterise the late-type stellar content. Two narrow band filters centred on spectral features of TiO and CN allow us to distinguish between AGB stars of different chemistries [M-type (O-rich) and C-type (C-rich)]. The major parts of two dwarf galaxies, NGC 185 and NGC 147, were observed; 154 new AGB carbon stars in NGC 185 and 146 in NGC 147 were identified. All detected stars (called sample 1 in the paper) are included in the tables, with coordinates and photometric properties. All stars of sample 1 have photometry in the filters V and i. For all stars, which are in addition included in the smaller sample 2 (and have also photometry in the narrowband filters TiO and CN) the colour index (TiO-CN) is provided, too. In the tables a chemistry flag F marks in which classification group the star falls. All stars of sample 2 can have "c" for Carbon star, "o" for oxygen-rich M-type star or "r" for the rest. This correspond to the selection areas in Figure 4 of the paper. The flag for all stars of sample 1, which are not already included in sample 2 (only Vi-photometry) is "u" for unclassified.
- ID:
- ivo://CDS.VizieR/J/A+A/410/795
- Title:
- Photometry of NGC 3109 carbon stars
- Short Name:
- J/A+A/410/795
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a CFH12K wide field survey of the carbon star population in and around NGC 3109. Carbon stars, the brightest members of the intermediate-age population, were found nearly exclusively in and near the disk of NGC 3109, ruling out the existence of an extensive intermediate-age halo like the one found in NGC 6822. Over 400 carbon stars identified have M_I_=-4.71, confirming the nearly universality of mean magnitude of C star populations in Local Group galaxies. Star counts over the field reveal that NGC 3109 is a truncated disk shaped galaxy without an extensive stellar halo. The minor axis star counts reach the foreground density between 4' and 5', a distance that can be explained by an inclined disk rather than a spheroidal halo. We calculate a global C/M ratio of 1.75+/-0.20, a value expected for such a metal poor galaxy.
- ID:
- ivo://CDS.VizieR/J/ApJ/775/45
- Title:
- PTI carbon star angular size survey
- Short Name:
- J/ApJ/775/45
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report new interferometric angular diameter observations of 41 carbon stars observed with the Palomar Testbed Interferometer. Two of these stars are CH carbon stars and represent the first such measurements of this subtype. Of these, 39 have Yamashita spectral classes and are of sufficiently high quality that we can determine the dependence of effective temperature on spectral type. We find that there is a tendency for the effective temperature to increase with increasing temperature index by ~120K per step, starting at T_eff_=~2500K for C3, y, although there is a large amount of scatter in this relationship. Overall, the median effective temperature of the carbon star sample is 2800+/-270 K and the median linear radius is 360+/-100R_{sun}_. We also find agreement, on average within 15K, with the T_eff_ determinations of Bergeat et al. (J/A+A/369/178) and a refinement of the carbon star angular size prediction based on V & K magnitudes is presented that is good to an rms of 12%. A subsample of our stars have sufficient {u, v} coverage to permit non-spherical modeling of their photospheres, and a general tendency for detection of statistically significant departures from sphericity with increasing interferometric signal-to-noise is seen. The implications of most -and potentially all- carbon stars being non-spherical is considered in the context of surface inhomogeneities and a rotation-mass-loss connection.
- ID:
- ivo://CDS.VizieR/J/MNRAS/369/783
- Title:
- Radial velocities & distances of carbon stars
- Short Name:
- J/MNRAS/369/783
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Optical radial velocities have been measured for 38 C-type Mira variables (C-Miras). These data together with others in the literature are used to study the differences between optical and CO millimetre (mm) observations for C-Miras and the necessary corrections to the optical velocities are derived in order to obtain the true radial velocities of the variables. The difference between absorption and emission-line velocities is also examined. A particularly large difference (+30km/s) is found in the case of the H{alpha} line. A catalogue is given of 177 C-Miras with estimated distances and radial velocities. The distances are based on bolometric magnitudes derived in Paper I (Whitelock et al., 2006, Cat. <J/MNRAS/369/751>) using South African Astronomical Observatory (SAAO) observations or (for 60 of the stars) using non-SAAO photometry. In the latter case, the necessary transformations to the SAAO system are derived. These data will be used in Paper III (Feast et al., 2006MNRAS.369..791F) to study the kinematics of the C-Miras.
- ID:
- ivo://CDS.VizieR/J/A+A/473/143
- Title:
- Radial velocities of C stars near Galactic plane
- Short Name:
- J/A+A/473/143
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The availability, from 2MASS, of a large homogeneous sample of Galactic C stars and the recognition that their absolute magnitude can be accurately determined offer the possibility to use them as kinematical probes to investigate motions in the thin or thick disks. Our aims is to determine the radial velocities for 70 C stars, a few degrees from the Galactic plane and distributed in longitudes from 60{deg} to 220{deg}.
- ID:
- ivo://CDS.VizieR/J/MNRAS/462/3376
- Title:
- Radial velocities of NGC 6822 carbon stars
- Short Name:
- J/MNRAS/462/3376
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using spectra taken with the AAOmega spectrograph, we measure the radial velocities of over 100 stars, many of which are intermediate age carbon stars, in the direction of the dwarf irregular galaxy NGC 6822. Kinematic analysis suggests that the carbon stars in the sample are associated with NGC 6822, and estimates of its radial velocity and galactic rotation are made from a star-by-star analysis of its carbon star population. We calculate a heliocentric radial velocity for NGC 6822 of -51+/-3km/s and show that the population rotates with a mean rotation speed of 11.2+/-2.1km/s at a mean distance of 1.1kpc from the galactic centre, about a rotation axis with a position angle of 26{deg}+/-13{deg}, as projected on the sky. This is close to the rotation axis of the HI gas disc and suggests that NGC 6822 is not a polar ring galaxy, but is dynamically closer to a late-type galaxy. However, the rotation axis is not aligned with the minor axis of the AGB isodensity profiles and this remains a mystery.
- ID:
- ivo://CDS.VizieR/J/A+A/321/236
- Title:
- Reddening and fluxes of carbon stars
- Short Name:
- J/A+A/321/236
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This table contains our CV-classification (see Subsec. 3.3 in the paper) for 133 carbon variables and their colour excess E(B-V) as determined by the method described in Sec. 4.
- ID:
- ivo://CDS.VizieR/J/A+A/447/473
- Title:
- R I CN TiO photometry of DDO190 carbon stars
- Short Name:
- J/A+A/447/473
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have carried out deep R, I, CN, TiO observations of the dwarf irregular galaxy DDO 190. We confirm the existence intermediate-age population around this galaxy. The identification of 47 carbon stars seen up to 5 arcmin from the centre of the galaxy implies that the population distribution of DDO 190 is similar to those found in some other Local Group dIrr galaxies. An estimate of the metallicity, [Fe/H]=-1.55+/-0.12, is obtained based on the observed C/M ratio. From the analysis of star counts, corrected for the radial variation of the incompleteness level, we determine a scale-length {alpha}=40+/-5", in agreement with the recent literature.
- ID:
- ivo://CDS.VizieR/J/A+A/418/33
- Title:
- RI photometry of C stars in NGC 147
- Short Name:
- J/A+A/418/33
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have imaged a 42'x28' field centered on the spheroidal galaxy NGC 147 to study its AGB population and determine the main structural properties of this M31 companion. This field was observed through two broadband (R and I) and two narrowband (CN and TiO) filters, following the standard approach of our systematic survey of C stars in nearby galaxies. We identified 288 C stars in NGC 147. The average I-magnitude of such sample of C stars is <I>=20.31 with {sigma}=0.40. If we adopt a distance modulus {mu}0=24.39, derived from the luminosity of both the tip of the red giant branch (TRGB) and the horizontal branch (HB) by Han et al. (1997, Cat. <J/AJ/113/1001>, we conclude that the average absolute I-magnitude of C stars is <M_I_>=-4.39, thus slightly under luminous with respect to what was found for other galaxies in our survey.
