- ID:
- ivo://CDS.VizieR/J/AJ/123/832
- Title:
- C star population in NGC 6822
- Short Name:
- J/AJ/123/832
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using the CFH12K camera, we apply the four-band photometric technique to identify 904 carbon stars in an area 28'x42' centered on NGC 6822. A few C stars outside of this area were also discovered with the Las Campanas Swope Telescope. The NGC 6822 survey employs two sets of observations obtained by rather different telescopes and with different procedures: the Swope Telescope on Las Campanas was used in 1999 October to secure images of NGC 6822 in Kron-Cousins R_KC_, CN (810nm), and TiO (770nm) filters. The 2048x2048 SITe No. 1 CCD yields a field of view of 23.7'x23.7'; NGC 6822 was also observed with the CFH12K at the beginning of one night in 2000 September. The camera consists of a 12Kx8K pixel mosaic covering a field of 42'x28', with each pixel corresponding to 0.206". Images were obtained through Mould I and R filters and through the CN and TiO filters. The NGC 6822 C star population has <I>=19.26 leading to an <M_I_>=-4.70, value essentially identical to the mean magnitude obtained for the C stars in IC 1613. Contrary to stars highlighting the optical image of NGC 6822, C stars are seen at large radial distances and trace a huge, slightly elliptical halo, which does not coincide with the huge H I cloud surrounding NGC 6822. The previously unknown stellar component of NGC 6822 has a exponential scale length of 3.0+/-0.1' and can be traced to 5 scale lengths. The C/M ratio of NGC 6822 is evaluated to be 1.0+/-0.2.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/436/91
- Title:
- C star population in outer disk of M31
- Short Name:
- J/A+A/436/91
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We employ the CFHT Megacam camera to survey ~1{deg}^2^ of the southern outer disc of M31, a region which includes the area where Battinelli et al. (2003, Cat. <J/AJ/125/1298>) have identified nearly one thousand C stars. In the outer M31 region not previously surveyed, we identify 361 new C star candidates, having similar photometric properties to the known ones, and confirm the slight decrease in the luminosity of C stars with galactocentric distances. We show that the Sloan g', r', i' filters are a viable approach, comparable to (CN-TiO), to identify C stars. We find that the (g'-r') colours of cool C stars can be so red that prohibitively long g' exposures are needed to acquire faint extragalactic C stars. This makes the Sloan filters a less promising approach to extend a C star survey to several Mpc. Our uniform large field survey detects the edge of M31 disk at ~35kpc. The intermediate-age population, represented by C stars, extends further to ~40kpc.
- ID:
- ivo://CDS.VizieR/J/AJ/125/1298
- Title:
- C star population in outer disk of M31
- Short Name:
- J/AJ/125/1298
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We employ the CFH12K mosaic to identify carbon stars, using the R, I, CN, and TiO photometric technique, in a 2240 arcmin2 area, ranging from 17 to 30kpc of the southwest disk of M31, barely reaching the edge of the observed H I disk. We found 945 C stars with <I_0_>=19.94mag and {sigma}=0.47. The surface density of C stars along the major axis of M31 follows an exponential profile with a scale length of 4.85+/-0.35kpc, in agreement with adopted values for the scale length of the disk population. Our survey partially overlaps with the recently discovered G1 density enhancement by Ferguson et al. We confirm that no AGB star excess is detectable in the surveyed part of the clump. The C/M ratio, along the major axis, is derived over a distance range of 7kpc. The strong C/M gradient seen contrasts with results of previous studies of the C stars in M31.
1464. C stars in IC 1613
- ID:
- ivo://CDS.VizieR/J/AJ/119/2780
- Title:
- C stars in IC 1613
- Short Name:
- J/AJ/119/2780
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results of a multifilter survey of the whole Magellanic-type galaxy IC 1613. Narrowband CN and TiO filters are used to identify carbon stars among red giants. We have identified 195 carbon stars, extending up to 15' from the center of the galaxy. We present well-calibrated R and I magnitudes for all stars. The large field surveyed allows a reliable foreground estimate of M stars, leading to a C/M ratio of 0.64, when giants as early as M0 are counted. Analysis of the photometric properties of the C star population reveals a narrow M_I_ distribution with a mean M_I_ of -4.69mag, with a dispersion of +/-0.28. IC 1613 has, for its absolute magnitude, a normal number of C stars.
- ID:
- ivo://CDS.VizieR/J/AJ/120/1801
- Title:
- C stars in Pegasus, DDO 210 and Tucana
- Short Name:
- J/AJ/120/1801
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the latest results of our ongoing four-filter photometric survey of C stars in Local Group dwarf irregular galaxies. Observations of the two low-luminosity dwarf irregular galaxies, Pegasus and DDO 210, revealed 40 and three C stars, respectively, assuming that the reddening of Pegasus is negligible. No C stars were identified in Tucana. Our observations permit the estimation of the color-magnitude diagram contamination by foreground M dwarfs thus yielding reliable C/M ratios. Our R and I photometry of the C stars cannot be used to solve the extinction controversy toward Pegasus. The three C stars in DDO 210 are quite bright when compared with C star populations in other dwarf galaxies. A larger, fainter population in that galaxy seems improbable, however. The statistics of C stars currently on hand for dwarf galaxies show a well-defined trend with the absolute magnitude of dwarf galaxies.
1466. C stars in SMC
- ID:
- ivo://CDS.VizieR/J/A+AS/97/603
- Title:
- C stars in SMC
- Short Name:
- J/A+AS/97/603
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Accurate positions and charts for 1707 carbon stars in the Small Magellanic Cloud identified on GRISM plates are presented. The catalog provides data on magnitudes, colors, and carbon-abundance measurements and can be used for selecting carbon stars with special characteristics.
- ID:
- ivo://CDS.VizieR/J/A+A/416/111
- Title:
- C stars in Wolf-Lundmark-Melotte galaxy
- Short Name:
- J/A+A/416/111
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We used the CFH12K wide field camera to survey the carbon star population of the Wolf-Lundmark-Melotte system using the CN-TiO technique. 149 C stars are identified with a mean <I>=20.28, corresponding to <M_I_>=-4.65, a mean luminosity similar to what we found in other irregular galaxies. Star counts in and around the main body of WLM reveal that its stellar distribution is quite elliptical ({epsilon}=0.58) with major and minor axes of 26' and 11'. Comparison of the density profile of C stars and old red giants shows that their scale lengths differ by only 15% pointing to mixed populations. Wolf-Lundmark-Melotte is found to be unique among dwarf irregular galaxies by having essentially a handful of early-type AGB M stars thus leading to an extreme C/M ratio.
- ID:
- ivo://CDS.VizieR/J/A+A/534/A111
- Title:
- CT Her differential BV photometry and RV
- Short Name:
- J/A+A/534/A111
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a multi-site photometric campaign carried out in 2004-2008 for the Algol-type eclipsing binary system CT Her, the primary component of which shows delta Scuti-type oscillations. Our data consist of differential light curves collected in the filters B and V which have been analysed using the method of Wilson-Devinney (Phoebe). After identification of an adequate binary model and removal of the best-matching light curve solution, we performed a Fourier analysis of the residual B and V light curves to investigate the pulsational behaviour.
- ID:
- ivo://CDS.VizieR/J/AJ/121/2020
- Title:
- CTIO and WFPC2 photometry in NGC 6822
- Short Name:
- J/AJ/121/2020
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate the massive star population of NGC 6822 with ground-based UBV photometry covering the whole of the galaxy and HST WFPC2 photometry with filters F255W, F336W, F439W, and F555W of two fields containing very rich and crowded OB associations. The four-band WFPC2 photometry is used to derive Teff and E(B-V). H-R diagrams are constructed for the OB associations included in our fields. These show that 10Myr old populations are present in OB 9 and OB 6, while more recent star formation have occurred in OB 8, OB 13, OB 15, and OB 7. Two particularly interesting H II regions, Hubble V and Hubble X, are included in our fields. The luminous massive stars that power these bright H II regions (H{alpha} luminosity several times that of the Orion nebula), could be resolved even in their dense cores thanks to the HST spatial resolution. Our data reveal very young (a few million years), apparently coeval populations, with several massive star candidates.
- ID:
- ivo://CDS.VizieR/J/ApJ/892/112
- Title:
- CTIO/DECam LCs for Galactic bulge variable stars
- Short Name:
- J/ApJ/892/112
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- With the advent of the Legacy Survey of Space and Time, time-domain astronomy will be faced with an unprecedented volume and rate of data. Real-time processing of variables and transients detected by such large-scale surveys is critical to identifying the more unusual events and allocating scarce follow-up resources efficiently. We develop an algorithm to identify these novel events within a given population of variable sources. We determine the distributions of magnitude changes (dm) over time intervals (dt) for a given passband f, p_f_^(dm|dt)^, and use these distributions to compute the likelihood of a test source being consistent with the population or being an outlier. We demonstrate our algorithm by applying it to the DECam multiband time-series data of more than 2000 variable stars identified by Saha+ (2019, J/ApJ/874/30) in the Galactic Bulge that are largely dominated by long-period variables and pulsating stars. Our algorithm discovers 18 outlier sources in the sample, including a microlensing event, a dwarf nova, and two chromospherically active RS CVn stars, as well as sources in the blue horizontal branch region of the color-magnitude diagram without any known counterparts. We compare the performance of our algorithm for novelty detection with the multivariate Kernel Density Estimator and Isolation Forest on the simulated PLAsTiCC data set. We find that our algorithm yields comparable results despite its simplicity. Our method provides an efficient way for flagging the most unusual events in a real-time alert-broker system.
