- ID:
- ivo://CDS.VizieR/J/AJ/132/866
- Title:
- New M dwarfs in solar neighborhood
- Short Name:
- J/AJ/132/866
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results from a spectroscopic study of 1063 nearby active M dwarfs, selected by correlating the Two Micron All Sky Survey and ROSAT catalogs. We have derived the spectral types and estimated distances for all of our stars. The spectral types range between K5 and M6. Nearly half of our stars lie within 50pc. We have measured the equivalent width of the H{alpha} emission line. Our targets show an increase in chromospheric activity from early to midspectral types, with a peak in activity around M5. Using the count rate and hardness ratios obtained from the ROSAT catalog, we have derived the X-ray luminosities. Our stars display a "saturation-type" relation between the chromospheric and coronal activity. The relation is such that log(LX/Lbol) remains "saturated" at a value of approximately -3 for varying H{alpha} equivalent width. We have found 568 matches in the USNO-B catalog and have derived the tangential velocities for these stars. There is a slight trend of decreasing chromospheric activity with age, such that the stars with higher vtan have lower H{alpha} equivalent widths. The coronal emission, however, remains saturated at a value of log(LX/Lbol)~-3 for varying tangential velocities, suggesting that the coronal activity remains saturated with age. We do not find any break in the saturation-type relation at the spectral type at which stars become fully convective (~M3.5). Most of the stars in our sample show more coronal emission than the dMe stars in the Hyades and Praesepe and have v_tan_<40km/s, suggesting a young population.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/421/643
- Title:
- New nearby stars in the LEHPMS
- Short Name:
- J/A+A/421/643
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a systematic search for new neighbourhood stars among the Liverpool-Edinburgh high proper motion survey which we cross-identified with the DENIS survey. Their high proper motions ensure that they are not giant stars. The distances are estimated using DENIS photometry and we found that 100 stars probably lie within 25 parsecs from the Sun. They are mostly M-dwarfs, and 10 are probably white dwarfs. This is the first distance estimate for 84 stars among them. 10 stars are estimated to be closer than 15 parsecs. In addition, one star, DENIS J2343155-241047, could also lie within 15pc if it belongs to the halo.
- ID:
- ivo://CDS.VizieR/J/AJ/134/252
- Title:
- New nearby white dwarf systems
- Short Name:
- J/AJ/134/252
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present spectra for 33 previously unclassified white dwarf systems brighter than V=17, primarily in the southern hemisphere. Of these new systems, 26 are DA, 4 are DC, 2 are DZ, and 1 is DQ. We suspect that three of these systems are unresolved double degenerates. We obtained VRI photometry for these 33 objects, as well as for 23 known white dwarf systems without trigonometric parallaxes, also primarily in the southern hemisphere. For the 56 objects, we converted the photometry values to fluxes and fit them to a spectral energy distribution using the spectroscopy to determine which model to use (i.e., pure hydrogen, pure helium, or metal-rich helium), resulting in estimates of Teff and distance.
- ID:
- ivo://CDS.VizieR/J/other/JAVSO/34.222
- Title:
- New Northern Hemisphere Variables
- Short Name:
- J/other/JAVSO/34
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A survey looking for previously unknown variable stars has been carried out in the declination range 30-39 degrees and in the R.A. range 0-24 hours. The survey was done in I-band, and was carried out from October 2003 to December of 2004. Seventy-five new and previously suspected variable stars were detected. This paper presents a brief description of the survey and identifies the new variables.
- ID:
- ivo://CDS.VizieR/J/MNRAS/450/3855
- Title:
- New OB star candidates in Carina Arm
- Short Name:
- J/MNRAS/450/3855
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- O and early B stars are at the apex of galactic ecology, but in the Milky Way, only a minority of them may yet have been identified. We present the results of a pilot study to select and parametrize OB star candidates in the Southern Galactic plane, down to a limiting magnitude of g=20. A 2 deg^2^ field capturing the Carina Arm around the young massive star cluster, Westerlund 2, is examined. The confirmed OB stars in this cluster are used to validate our identification method, based on selection from the (u-g, g-r) diagram for the region. Our Markov Chain Monte Carlo fitting method combines VPHAS+ u, g, r, i with published J, H, K photometry in order to derive posterior probability distributions of the stellar parameters log(Teff) and distance modulus, together with the reddening parameters A_0_ and R_V_. The stellar parameters are sufficient to confirm OB status while the reddening parameters are determined to a precision of {sigma}(A_0_)~0.09 and {sigma}(R_V_)~0.08. There are 489 objects that fit well as new OB candidates, earlier than ~ B2. This total includes 74 probable massive O stars, 5 likely blue supergiants and 32 reddened subdwarfs. This increases the number of previously known and candidate OB stars in the region by nearly a factor of 10. Most of the new objects are likely to be at distances between 3 and 6 kpc. We have confirmed the results of previous studies that, at these longer distances, these sight lines require non-standard reddening laws with 3.5<R_V_<4.
- ID:
- ivo://CDS.VizieR/J/MNRAS/443/2327
- Title:
- New proper motion objects from UKIDSS GPS
- Short Name:
- J/MNRAS/443/2327
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The UKIDSS Galactic Plane Survey (GPS) began in 2005 as a seven year effort to survey ~1800deg^2^ of the northern Galactic plane in the J, H, and K passbands. The survey included a second epoch of K-band data, with a baseline of two to eight years, for the purpose of investigating variability and measuring proper motions. We have calculated proper motions for 167 million sources in a 900deg^2^ area located at l>60{deg} in order to search for new high proper motion objects. Visual inspection has verified 617 high proper motion sources (>200mas/yr) down to K=17, of which 153 are new discoveries. Among these, we have a new spectroscopically confirmed T5 dwarf, an additional T dwarf with estimated type T6, 13 new L dwarf candidates, and two new common proper motion systems containing ultracool dwarf candidates. We provide improved proper motions for an additional 12 high proper motion stars that were independently discovered in the WISE data set during the course of this investigation.
- ID:
- ivo://CDS.VizieR/J/AJ/133/2898
- Title:
- New proper-motion stars (-90<DE< -47)
- Short Name:
- J/AJ/133/2898
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report 1606 new proper-motion systems in the southern sky (declinations -90{deg} to -47{deg}) with 0.40"/yr>{mu}>=0.18"/yr. This effort is a continuation of the SuperCOSMOS-RECONS (SCR) proper-motion search to lower proper motions than reported in Papers VIII, X, XII, and XV in this series. Distance estimates are presented for the new systems, assuming that all stars are on the main sequence. We find that 31 systems are within 25pc, including two systems (SCR 0838-5855 and SCR 1826-6542) that we anticipate to be within 10pc. These new discoveries constitute a more than 10-fold increase in new systems found in the same region of sky searched for systems with mu>=0.40"/yr, suggesting a happy hunting ground for new nearby slower proper-motion systems in the region just north (declinations -47{deg} to 0{deg}), much of which has not been rigorously searched during previous efforts.
- ID:
- ivo://CDS.VizieR/J/AJ/142/92
- Title:
- New proper motion stars with pm>=0.18"/yr
- Short Name:
- J/AJ/142/92
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Here we present 1584 new southern proper motion systems with {mu}>=0.18"/yr and 16.5>R_59F_>=18.0. This search complements the six previous SuperCOSMOS-RECONS (SCR) proper motion searches of the southern sky for stars within the same proper motion range, but with R_59F_<=16.5. As in previous papers, we present distance estimates for these systems and find that three systems are estimated to be within 25pc, including one, SCR 1546-5534, possibly within the RECONS 10pc horizon at 6.7pc, making it the second nearest discovery of the searches. We find 97 white dwarf candidates with distance estimates between 10 and 120pc, as well as 557 cool subdwarf candidates.
- ID:
- ivo://CDS.VizieR/J/AJ/142/10
- Title:
- New proper motion stars 0.40"/yr>pm>=0.18"/yr
- Short Name:
- J/AJ/142/10
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present 2817 new southern proper motion systems with 0.40"/yr>{mu}>=0.18"/yr and declination between -47{deg} and 00{deg}. This is a continuation of the SuperCOSMOS-RECONS (SCR) proper motion searches of the southern sky. We use the same photometric relations as previous searches to provide distance estimates based on the assumption that the objects are single main-sequence stars. We find 79 new red dwarf systems predicted to be within 25pc, including a few new components of previously known systems.
- ID:
- ivo://CDS.VizieR/J/AJ/154/57
- Title:
- New SDSS and Washington photometry in Segue 3
- Short Name:
- J/AJ/154/57
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new SDSS and Washington photometry of the young outer-halo stellar system Segue 3. Combined with archival VI-observations, our most consistent results yield Z=0.006+/-0.001, log(Age)=9.42+/-0.08, (m-M)_0_=17.35+/-0.08, and E(B-V)=0.09+/-0.01, with a high binary fraction of 0.39+/-0.05 derived using the Padova models. We confirm that mass-segregation has occurred, supporting the hypothesis that this cluster is being tidally disrupted. A three-parameter King model yields a cluster radius of r_cl_=0.017{deg}+/-0.007{deg}, a core radius of r_c_=0.003{deg}+/-0.001{deg}, and a tidal radius of r_t_=0.04{deg}+/-0.02{deg}. A comparison of Padova and Dartmouth model-grids indicates that the cluster is not significantly {alpha}-enhanced, with a mean [Fe/H]=-0.55_-0.12_^+0.15^dex, and a population age of only 2.6+/-0.4Gyr. We rule out a statistically significant age spread at the main-sequence turnoff because of a narrow subgiant branch, and discuss the role of stellar rotation and cluster age, using Dartmouth and Geneva models: approximately 70% of the Seg 3 stars at or below the main-sequence turnoff have enhanced rotation. Our results for Segue 3 indicate that it is younger and more metal-rich than all previous studies have reported to date. From colors involving Washington C and SDSS-u filters, we identify several giants and a possible blue straggler for future follow-up spectroscopic studies, and we produce spectral energy distributions of previously known members and potential Segue 3 sources with Washington (CT_1_), Sloan (ugri), and VI-filters. Segue 3 shares the characteristics of unusual stellar systems that have likely been stripped from external dwarf galaxies as they are being accreted by the Milky Way, or that have been formed during such an event. Its youth, metallicity, and location are all inconsistent with Segue 3 being a cluster native to the Milky Way.
