- ID:
- ivo://CDS.VizieR/J/ApJ/862/173
- Title:
- Nearby low-mass stars proper motions
- Short Name:
- J/ApJ/862/173
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper uses the multi-epoch astrometry from the Wide-field Infrared Survey Explorer (WISE) to demonstrate a method to measure proper motions and trigonometric parallaxes with precisions of ~4mas/yr and ~7mas, respectively, for low-mass stars and brown dwarfs. This method relies on WISE single exposures (Level 1b frames) and a Markov Chain Monte Carlo method. The limitations of Gaia in observing very low-mass stars and brown dwarfs are discussed, and it is shown that WISE will be able to measure astrometry past the 95% completeness limit and magnitude limit of Gaia (L, T, and Y dwarfs fainter than G~=19 and G=21, respectively). This method is applied to WISE data of 20 nearby (<=17pc) dwarfs with spectral types between M6-Y2 and previously measured trigonometric parallaxes. Also provided are WISE astrometric measurements for 23 additional low-mass dwarfs with spectral types between M6-T7 and estimated photometric distances <17pc. Only nine of these objects contain parallaxes within Gaia Data Release 2.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/AJ/126/2449
- Title:
- Nearby ultracool dwarfs in galactic plane
- Short Name:
- J/AJ/126/2449
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Surveys for nearby low-luminosity dwarfs tend to avoid the crowded regions of the Galactic plane. We have devised near-infrared color-magnitude and color-color selection criteria designed to identify late-type M and early-type L dwarfs within 12pc of the Sun. We use those criteria to search for candidates within the regions of the Galactic plane (|b|<10{deg}) covered by the Second Incremental Data Release from the Two Micron All Sky Survey (<II/241>). Detailed inspection of the available photographic images of the resulting 1299 candidates confirms only two as ultracool dwarfs. Both are known proper-motion stars, identified in the recent survey by Lepine et al. (2003, Cat. <J/AJ/125/1598>). Despite the low numbers, the inferred surface density is consistent with comparable surveys at higher latitudes. We discuss the implications for the luminosity function and consider means of improving the efficiency and scope of photometric surveys in the plane.
- ID:
- ivo://CDS.VizieR/J/MNRAS/452/173
- Title:
- Nearby young stars in Northern hemisphere
- Short Name:
- J/MNRAS/452/173
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a kinematically-unbiased search to identify young, nearby low-mass members of kinematic moving groups (MGs). Objects with both rotation periods shorter than 5 days in the SuperWASP All-Sky Survey and X-ray counterparts in the ROSAT All-Sky Survey were chosen to create a catalog of several thousand rapidly-rotating, X-ray active FGK stars. These objects are expected to be either genuinely young (<200Myr) single stars or tidally-locked spectroscopic binaries. We obtained optical spectra for a sub-sample of 146 stars to determine their ages and kinematics, and in some cases repeat radial velocity (RV) measurements were used to identify binarity. Twenty-six stars are found to have lithium abundances consistent with an age of 200Myr or younger and show no evidence for binarity, and in most cases measurements of Halpha and v sin i support their youthful status. Based on their youth, their radial velocities and estimates of their 3-dimensional kinematics, we find 11 objects that may be members of known MGs, 8 that do not appear associated with any young MG and a further 7 that are close to the kinematics of the recently proposed "Octans-Near" MG, and may be the first members of this MG found in the northern hemisphere. The initial search mechanism was ~18 per cent efficient at identifying likely-single stars younger than 200Myr, of which 80 per cent were early-K spectral types. A more complete survey may result in the detection of new nearby MGs, particularly in the comparatively little sampled northern hemisphere.
- ID:
- ivo://CDS.VizieR/J/A+A/562/A127
- Title:
- Near-IR integral field spectra of 15 M-L dwarfs
- Short Name:
- J/A+A/562/A127
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- At young ages, low surface gravity affects the atmospheric properties of ultracool dwarfs. The impact on medium-resolution near-infrared (NIR) spectra has only been slightly investigated at the M-L transition sofar. We present a library of near-infrared (1.1-2.45um) medium-resolution (R~1500-2000) integral field spectra of 15 young M6-L0 dwarfs. We aim at deriving updated NIR spectral type, luminosity and physical parameters (Teff, logg, M, L/L_{sun}_) of each source. This work also aims at testing the latest generation of BT-SETTL atmospheric models. We estimated spectral types using spectral indices and spectra of reference young objects classified in the optical. We used the 2010 and 2012 releases of the BT-SETTL synthetic spectral grid and cross-checked the results with the DRIFT-PHOENIX models to derive the atmospheric properties of the sources.
- ID:
- ivo://CDS.VizieR/J/ApJS/151/387
- Title:
- Near-IR spectral library of late-type stars
- Short Name:
- J/ApJS/151/387
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an empirical infrared spectral library of medium-resolution (R~2000-3000) H (1.6{mu}m) and K (2.2{mu}m) band spectra of 218 red stars, spanning a range of [Fe/H] from ~-2.2 to ~+0.3. The sample includes Galactic disk stars, bulge stars from Baade's window, and red giants from Galactic globular clusters. We report the values of 19 indices covering 12 spectral features measured from the spectra in the library. Finally, we derive calibrations to estimate the effective temperature, and diagnostic relationships to determine the luminosity classes of individual stars from near-infrared spectra. This paper is part of a larger effort aimed at building a near-IR spectral library to be incorporated in population synthesis models, as well as at testing synthetic stellar spectra.
- ID:
- ivo://CDS.VizieR/J/A+A/479/131
- Title:
- Near-IR spectra of inner red giants
- Short Name:
- J/A+A/479/131
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The existence in the Milky Way of either a long thin bar with a half length of 4.5kpc and a position angle of around 45{deg} with respect to the Sun-Galactic centre line or a bulge+bar complex, thicker and shorter, with a smaller tilt respect to the Sun-GC line, has been a matter of discussion in recent decades. In this paper, we present low resolution (R=500) near-infrared spectra for selected and serendipitous sources in six inner in-plane Galactic fields at l=7{deg}, 12{deg}, 15{deg}, 20{deg}, 26{deg} and 27{deg}, with the aim of analysing the stellar content present in those fields.
- ID:
- ivo://CDS.VizieR/J/A+A/325/1115
- Title:
- Near-simultaneous ROSAT and Mt Wilson data
- Short Name:
- J/A+A/325/1115
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Table 1 lists near-simultaneous X-ray data and Ca II H&K line-core emission data from the ROSAT All-Sky Survey and from the Mt. Wilson H&K spectrometer, respectively. The stars in this sample are 215 bright F-, G-, and K-type stars. Table 2 lists the derived excess Ca II H&K line-core and the X-ray flux densities for the same stars.
- ID:
- ivo://CDS.VizieR/J/ApJ/817/112
- Title:
- NEOWISE/AllWISE high proper motion objects
- Short Name:
- J/ApJ/817/112
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Wide-field Infrared Survey Explorer (WISE) was reactivated in 2013 December (NEOWISE) to search for potentially hazardous near-Earth objects. We have conducted a survey using the first sky pass of NEOWISE data and the AllWISE catalog to identify nearby stars and brown dwarfs with large proper motions ({mu}_total_>~250mas/yr). A total of 20548 high proper motion objects were identified, 1006 of which are new discoveries. This survey has uncovered a significantly larger sample of fainter objects (W2>~13mag) than the previous WISE motion surveys of Luhman (2014, J/ApJ/781/4) and Kirkpatrick et al. (2014, J/ApJ/783/122). Many of these objects are predicted to be new L and T dwarfs based on near- and mid-infrared colors. Using estimated spectral types along with distance estimates, we have identified several objects that likely belong to the nearby solar neighborhood (d<25pc). We have followed up 19 of these new discoveries with near-infrared or optical spectroscopy, focusing on potentially nearby objects, objects with the latest predicted spectral types, and potential late-type subdwarfs. This subset includes six M dwarfs, five of which are likely subdwarfs, as well as eight L dwarfs and five T dwarfs, many of which have blue near-infrared colors. As an additional supplement, we provide 2MASS and AllWISE positions and photometry for every object found in our search, as well as 2MASS/AllWISE calculated proper motions.
- ID:
- ivo://CDS.VizieR/J/A+A/503/541
- Title:
- Neutral Li in late-type stars non-LTE calculations
- Short Name:
- J/A+A/503/541
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We perform non-LTE calculations of lithium in late-type stars for a wide range of stellar parameters, including quantum mechanical cross-sections for collisions with neutral hydrogen and the negative hydrogen ion. Non-LTE abundance corrections for the lithium resonance line at 670.7nm and the subordinate line at 610.3nm, are calculated using 1D MARCS model atmospheres spanning a large grid in effective temperature, surface gravity, and metallicity, and lithium abundance. The competing effects of ultraviolet over-ionization and photon losses in the resonance line govern the behaviour of the non-LTE effects with stellar parameters and lithium abundance. The size and sign of the non-LTE abundance corrections vary significantly over the grid for the 670.7nm line, but are typically positive and below 0.15dex for the 610.3nm line. The new collisional data play a significant role in determining the abundance corrections.
- ID:
- ivo://CDS.VizieR/J/MNRAS/450/3490
- Title:
- 15 new brown dwarfs in Orion OB1a/25 Ori group
- Short Name:
- J/MNRAS/450/3490
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a study of 15 new brown dwarfs belonging to the ~7Myr old 25 Orionis group and Orion OB1a subassociation with spectral types between M6 and M9 and estimated masses between ~0.07 and ~0.01M_{sun}_. By comparing them through a Bayesian method with low-mass stars (0.8<~M/M_{sun}_ <~0.1) from previous works in the 25 Orionis group, we found statistically significant differences in the number fraction of classical T Tauri stars, Weak T Tauri stars, class II, evolved discs and purely photospheric emitters at both sides of the substellar mass limit. Particularly, we found a fraction of 3.9^+2.4^_-1.6_ percent low-mass stars classified as Classic T Tauri star and class II or evolved discs, against a fraction of 33.3^+10.8^_-9.8_ percent in the substellar mass domain. Our results support the suggested scenario in which the dissipation of discs is less efficient for decreasing mass of the central object.
