- ID:
- ivo://CDS.VizieR/J/AJ/150/6
- Title:
- Solar neighborhood. XXXVI. VRI variability of M dwarfs
- Short Name:
- J/AJ/150/6
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an analysis of long-term photometric variability for nearby red dwarf stars at optical wavelengths. The sample consists of 264 M dwarfs south of decl.=+30 with V-K=3.96-9.16 and M_V_~~10-20, corresponding to spectral types M2V-M8V, most of which are within 25pc. The stars have been observed in the VRI filters for ~4-14yr at the CTIO/SMARTS 0.9m telescope. Of the 238 red dwarfs within 25pc, we find that only ~8% are photometrically variable by at least 20mmag (~2%) in the VRI bands. Only four stars have been found to vary by more than 50mmag, including GJ 1207 at 8.6pc, which experienced a single extraordinary flare, and GJ 2006 A, TWA 8 A, and TWA 8 B, which are all young stars beyond 25pc linked to moving groups. We find that high variability at optical wavelengths over the long term can in fact be used to identify young stars. Overall, however, the fluxes of most red dwarfs at optical wavelengths are steady to a few percent over the long term. The low overall rate of photometric variability for red dwarfs is consistent with results found in previous work on similar stars on shorter timescales, with the body of work indicating that most red dwarfs are only mildly variable. As expected, we find that the degree of photometric variability is greater in the V band than in the R or I bands, but we do not find any obvious trends in variability over the long term with red dwarf luminosity or temperature. We highlight 17 stars that show long-term changes in brightness, sometimes because of flaring activity or spots, and sometimes because of stellar cycles similar to our Sun's solar cycle. Remarkably, two targets show brightnesses that monotonically increase (G 169-029) or decrease (WT 460AB) by several percent over a decade. We also provide long-term variability measurements for seven M dwarfs within 25pc that host exoplanets, none of which vary by more than 20mmag. Both as a population, and for the specific red dwarfs with exoplanets observed here, photometric variability is therefore often not a concern for planetary environments, at least at the optical wavelengths where they emit much of their light.
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Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/325/1365
- Title:
- Solar neighbourhood metallicity distribution
- Short Name:
- J/MNRAS/325/1365
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a revised metallicity distribution of dwarfs in the solar neighbourhood. This distribution is centered on solar metallicity. We show that previous metallicity distributions, selected on the basis of spectral type, are biased against stars with solar metallicity or higher. A selection of G-dwarf stars is inherently biased against metal-rich stars and is not representative of the solar neighbourhood metallicity distribution. Using a sample selected on colour, we obtain a distribution where approximately half the stars in the solar neighbourhood have metallicities higher than [Fe/H]=0. The percentage of mid-metal-poor stars ([Fe/H}<-0.5) is approximately 4 per cent, in agreement with the present estimates of the thick disc.
- ID:
- ivo://CDS.VizieR/J/MNRAS/417/1823
- Title:
- Sombrero galaxy globular clusters
- Short Name:
- J/MNRAS/417/1823
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a large sample of over 200 integrated-light spectra of confirmed globular clusters (GCs) associated with the Sombrero (M104) galaxy taken with the Deep Imaging Multi-Object Spectrograph (DEIMOS) instrument on the Keck telescope. A significant fraction of the spectra have signal-to-noise ratio levels high enough to allow measurements of GC metallicities using the method of Brodie & Huchra. We find a distribution of spectroscopic metallicities in the range -2.2<[Fe/H]<+0.1 that is bimodal, with peaks at [Fe/H]~-1.4 and -0.6. Thus, the GC system of the Sombrero galaxy, like a few other galaxies now studied in detail, reveals a bimodal spectroscopic metallicity distribution supporting the long-held belief that colour bimodality reflects two metallicity subpopulations. This further suggests that the transformation from optical colour to metallicity for old stellar populations, such as GCs, is not strongly non-linear. We also explore the radial and magnitude distribution with metallicity for GC subpopulations but small number statistics prevent any clear trends in these distributions.
- ID:
- ivo://CDS.VizieR/J/A+AS/110/371
- Title:
- Southern binary galaxies. I.
- Short Name:
- J/A+AS/110/371
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- (no description available)
- ID:
- ivo://CDS.VizieR/J/A+A/380/609
- Title:
- Southern emission-line stars multiphotometry
- Short Name:
- J/A+A/380/609
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper presents a catalogue of previously unpublished optical and infrared photometry for a sample of 162 emission-line objects and shell stars visible from the southern hemisphere. The data were obtained between 1978 and 1997 in the Walraven (WULBV), Johnson/Cousins UBV(RI)_c_ and ESO and SAAO near-infrared (JHKLM) photometric systems. Most of the observed objects are Herbig Ae/Be (HAeBe) stars or HAeBe candidates appearing in the list of HAeBe candidates of The et al. (1994, Cat. <J/A+AS/104/315>), although several B[e] stars, LBVs and T Tauri are also included in the sample. For many of the stars the data presented here are the first photo-electric measurements in the literature. The resulting catalogue consists of 1809 photometric measurements. Optical variability was detected in 66 out of the 116 sources that were observed more than once. 15 out of the 50 stars observed multiple times in the infrared showed variability at 2.2 microns (K band). Table 1 contains the stars identifiers, positions, types and a summary of the observational data on each star. Tables 2, 3 and 4 contain all obtained photometry in the Walraven WULBV, Johnson/Cousins UBV(RI)_c and ESO and SAAO near-infrared (JHKLM) photometric systems.
- ID:
- ivo://CDS.VizieR/J/AZh/77/569
- Title:
- Southern isolated triple systems of galaxies
- Short Name:
- J/AZh/77/569
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using the ESO/SERC and POSS-I surveys we selected 76 isolated triple systems of galaxies with DE<-3{deg}. For each triplet the equatorial coordinates, type of configuration, angular diameters, apparent angular separation of the components, morphological types, total magnitudes and other characteristics are presented.
- ID:
- ivo://CDS.VizieR/III/179
- Title:
- Southern MK Standards 5800-10200A
- Short Name:
- III/179
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Spectra are presented for MK standards in the wavelength range 580-1020nm. The stars cover the normal spectral types O to M and luminosity types I, III, and V. In addition, a small number of peculiar stars are included. The data are in 137 FITS files, in the "fits" subdirectory. The list of the 137 stars is included in the "stars.dat" file; note that the list is not identical to the stars listed in Table1 of the paper.
- ID:
- ivo://CDS.VizieR/J/A+A/440/1061
- Title:
- Southern red high proper motion objects
- Short Name:
- J/A+A/440/1061
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of spectroscopic follow-up observations for a sample of 71 red objects with high proper motions in the range 0.08-1.14 arcsec/yr as detected using APM and SuperCOSMOS Sky Surveys (SSS) measurements of multi-epoch photographic Schmidt plates. Red objects were selected by combining the photographic BjRI magnitudes with 2MASS near-infrared JHKs magnitudes. Some 50 of the 71 spectroscopically classified objects turn out to be late-type (>M6) dwarfs and in more detail, the sample includes 35 ultracool dwarfs with spectral types between M8 and L2, some previously reported, as well as five M-type subdwarfs, including a cool esdM6 object, SSSPM J0500-5406. Distance estimates based on the spectral types and 2MASS J magnitudes place almost all of the late-type (>M6) dwarfs within 50pc, with 25 objects located inside the 25pc limit of the catalogue of nearby stars. Most of the early-type M dwarfs are located at larger distances of 100-200pc, suggesting halo kinematics for some of them. All objects with Halpha equivalent widths larger than 10 Angstroms have relatively small tangential velocities (<50km/s). Finally, some late-type but blue objects are candidate binaries.
- ID:
- ivo://CDS.VizieR/VII/142A
- Title:
- Southern Redshifts Catalogue
- Short Name:
- VII/142A
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This catalogue provides a "best-estimate" of the heliocentric radial velocities of some 13000 galaxies south of Declination 0 degrees. It is based on over 17000 redshift measurements, from over 200 sources, either published or otherwise made public. Aside from redshift references, each entry includes flags as to whether the velocity is from optical or radio observations, or both, as well as an indication of the nature of any optical emission lines. Galaxies with velocities beyond 75000 km/s are not included. All entries have been made interactively, by one person (A.P.F.). The interaction was necessary because different investigators may use different names, quote slightly different positions, and obtain slightly different velocities for the same galaxy. Thus duplicate entries for the same galaxy are avoided (although a few may inevitably be included).
- ID:
- ivo://CDS.VizieR/J/AJ/119/241
- Title:
- South Galactic cap MCT blue objects
- Short Name:
- J/AJ/119/241
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Results for the south Galactic cap region of the Montreal-Cambridge-Tololo survey of blue subluminous stars are presented. This region overlaps the 840 deg^2^ region studied almost three decades ago by Slettebak & Brundage (1971AJ.....76..338S). We present a list of equatorial coordinates, photographic photometry, and spectroscopic identifications, as well as finding charts, for 188 blue objects [(U-B)_pg_<=-0.6] brighter than B_pg_=16.5 in this area. Completeness of the survey and comparisons with other similar efforts are discussed.
