- ID:
- ivo://CDS.VizieR/J/AJ/162/102
- Title:
- LASSO; Robo-AO observation of 444 young stars
- Short Name:
- J/AJ/162/102
- Date:
- 14 Mar 2022 06:43:15
- Publisher:
- CDS
- Description:
- We present results from the Large Adaptive optics Survey for Substellar Objects, where the goal is to directly image new substellar companions (<70M_Jup_) at wide orbital separations (>~50au) around young (<~300Myr), nearby (<100pc), low-mass (~0.1-0.8 M{odot}) stars. We report on 427 young stars imaged in the visible (i') and near-infrared (J or H ) simultaneously with Robo-AO on the Kitt Peak 2.1m telescope and later the Maunakea University of Hawaii 2.2m telescope. To undertake the observations, we commissioned a new infrared camera for Robo-AO that uses a low-noise high-speed SAPHIRA avalanche photodiode detector. We detected 121 companion candidates around 111 stars, of which 62 companions are physically associated based on Gaia DR2 parallaxes and proper motions, another 45 require follow-up observations to confirm physical association, and 14 are background objects. The companion separations range from 2 to 1101 au and reach contrast ratios of 7.7 mag in the near-infrared compared to the primary. The majority of confirmed and pending candidates are stellar companions, with ~5 being potentially substellar and requiring follow-up observations for confirmation. We also detected a 43{+/-}9 M_Jup_ and an 81{+/-}5M_Jup_ companion that were previously reported. We found 34 of our targets have acceleration measurements detected using Hipparcos-Gaia proper motions. Of those, 58_-14_^+12^% of the 12 stars with imaged companion candidates have significant accelerations ({chi}^2^>11.8), while only 23_-6_^+11^% of the remaining 22 stars with no detected companion have significant accelerations. The significance of the acceleration decreases with increasing companion separation. These young accelerating low-mass stars with companions will eventually yield dynamical masses with future orbit monitoring.
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Search Results
- ID:
- ivo://CDS.VizieR/J/AJ/107/1556
- Title:
- Late B-type stars classification
- Short Name:
- J/AJ/107/1556
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In the fourth and final of a series of papers on the late B to the early F type stars, we refine the MK spectral classification system for the late B type stars and consider the effect of rotation on both spectral classification and Stromgren photometry of these stars. We extend the work of Morgan by establishing self-consistent sequences of narrow and broadlined standards. We reclassify a number of Bp stars, compare these classifications with Stromgren photometry and consider the question of whether all Bp stars are main-sequence objects.
7833. Late-G giants abundances
- ID:
- ivo://CDS.VizieR/J/PASJ/57/109
- Title:
- Late-G giants abundances
- Short Name:
- J/PASJ/57/109
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Towards clarifying the properties of late-G giants, for which we are currently conducting a planet-search project at Okayama Astrophysical Observatory, an extensive spectroscopic study has been performed for our first target sample of fifty-seven G6-G9 III stars, in order to establish the atmospheric parameters (Teff, logg, vt, and [Fe/H]), the stellar mass along with the evolutionary status, and the photospheric abundances of various elements. It was confirmed that the conventional spectroscopic method of parameter determination using Fe I / II lines with the assumption of LTE works successfully for these evolved stars. We determined the abundances (relative to the Sun) of 19 elements, and examined how their [X/Fe] ratios behave themselves with the run of [Fe/H].
- ID:
- ivo://CDS.VizieR/J/ApJS/247/50
- Title:
- Late-type contact binaries in CSS DR1
- Short Name:
- J/ApJS/247/50
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the physical parameters of 2335 late-type contact binary (CB) systems extracted from the Catalina Sky Survey (CSS). Our sample was selected from the CSS Data Release 1 by strictly limiting the prevailing temperature uncertainties and light-curve fitting residuals, allowing us to almost eliminate any possible contaminants. We developed an automatic Wilson-Devinney-type code to derive the relative properties of CBs based on their light-curve morphology. By adopting the distances derived from CB (orbital) period-luminosity relations (PLRs), combined with the well-defined mass-luminosity relation for the systems' primary stars and assuming solar metallicity, we calculated the objects' masses, radii, and luminosities. Our sample of fully eclipsing CBs contains 1530 W-, 710 A-, and 95 B-type CBs. A comparison with literature data and with the results from different surveys confirms the accuracy and coherence of our measurements. The period distributions of the various CB subtypes are different, hinting at a possible evolutionary sequence. W-type CBs are clearly located in a strip in the total mass versus mass-ratio plane, while A-type CBs may exhibit a slightly different dependence. There are no significant differences among the PLRs of A- and W-type CBs, but the PLR zero-points are affected by their mass ratios and fill-out factors. Determination of zero-point differences for different types of CBs may help us improve the accuracy of the resulting PLRs. We demonstrate that automated approaches to deriving CB properties could be a powerful tool for application to the much larger CB samples expected to result from future surveys.
- ID:
- ivo://CDS.VizieR/J/AJ/153/92
- Title:
- Late-Type Extension to MoVeRS (LaTE-MoVeRS)
- Short Name:
- J/AJ/153/92
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the Late-Type Extension to the Motion Verified Red Stars (LaTE-MoVeRS) catalog, containing 46,463 photometric late-type (>M5) dwarfs within the Sloan Digital Sky Survey (SDSS) footprint. Proper motions were computed for objects combining astrometry from the SDSS Data Release 12 (DR12), the Two-micron All-Sky Survey (2MASS) Point Source Catalog, and the Wide-field Infrared Survey Explorer (WISE) AllWISE data sets. LaTE-MoVeRS objects were required to have significant proper motion . Using the LaTE-MoVeRS sample and Gaia Data Release 1, we estimate Gaia will be ~64% complete for very low-mass objects (>M5) in comparison to the combined SDSS+2MASS+WISE data set (i<21.3). We computed photometric distances and estimated stellar effective temperatures for the LaTE-MoVeRS catalog. The majority of the dwarfs in the sample have distances <150pc and T<3000K. Thirteen objects that have not been previously identified as nearby eff objects were identified within LaTE-MoVeRS with estimated photometric distances within 25pc. We also identified one new object that has not been previously identified with a large amount of excess mid-infrared flux (2MASS J11151597+1937266). This object appears to be an L2{gamma} at ~50pc showing spectroscopic signs of a flaring event (e.g., strong hydrogen Balmer emission lines). This object does not exhibit kinematics similar to any known kinematic association. The LaTE-MoVeRS catalog is available through SDSS CasJobs and VizieR.
- ID:
- ivo://CDS.VizieR/J/ApJ/681/1163
- Title:
- Late-type galaxies in Chandra deep fields
- Short Name:
- J/ApJ/681/1163
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report on the X-ray evolution over the last ~9Gyr of cosmic history (i.e., since z=1.4) of late-type galaxy populations in the Chandra Deep Field-North and Extended Chandra Deep Field-South (CDF-N and E-CDF-S, respectively; jointly CDFs) survey fields. Our late-type galaxy sample consists of 2568 galaxies, which were identified using rest-frame optical colors and HST morphologies. We utilized X-ray stacking analyses to investigate the X-ray emission from these galaxies, emphasizing the contributions from normal galaxies that are not dominated by active galactic nuclei (AGNs). Over this redshift range, we find significant increases (factors of ~5-10) in the X-ray-to-optical mean luminosity ratio (L_X_/L_B_) and the X-ray-to-stellar mass mean ratio (L_X_/M_*_) for galaxy populations selected by L_B_ and M_*_, respectively. When analyzing galaxy samples selected via SFR, we find that the mean X-ray-to-SFR ratio (L_X_/SFR) is consistent with being constant over the entire redshift range for galaxies with SFR=1-100M_{sun}_/yr, thus demonstrating that X-ray emission can be used as a robust indicator of star formation activity out to z~1.4. We find that the star formation activity (as traced by X-ray luminosity) per unit stellar mass in a given redshift bin increases with decreasing stellar mass over the redshift range z=0.2-1, which is consistent with previous studies of how star formation activity depends on stellar mass. Finally, we extend our X-ray analyses to Lyman break galaxies at z~3 and estimate that L_X_/L_B_ at z~3 is similar to its value at z=1.4.
- ID:
- ivo://CDS.VizieR/J/ApJ/348/253
- Title:
- Late type giants and supergiants in X-Ray
- Short Name:
- J/ApJ/348/253
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Results are presented of an extensive X-ray survey of 380 giant and supergiant stars of spectral types from F to M, carried out with the Einstein Observatory. It was found that the observed F giants or subgiants (slightly evolved stars with a mass M less than about 2 solar masses) are X-ray emitters at the same level of main-sequence stars of similar spectral type. The G giants show a range of emission more than 3 orders of magnitude wide; some single G giants exist with X-ray luminosities comparable to RS CVn systems, while some nearby large G giants have upper limits on the X-ray emission below typical solar values. The K giants have an observed X-ray emission level significantly lower than F and F giants. None of the 29 M giants were detected, except for one spectroscopic binary.
- ID:
- ivo://CDS.VizieR/J/MNRAS/246/54
- Title:
- Late-type giants in Baade's window
- Short Name:
- J/MNRAS/246/54
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Radial velocities have been measured for an unbiased sample of 239 late-type M giants in the b=-4{deg} galactic bulge window (Baade's window). The radial velocities were acquired at the AAT Observatory.
- ID:
- ivo://CDS.VizieR/J/AJ/83/1090
- Title:
- Late-type M dwarfs towards the SGP
- Short Name:
- J/AJ/83/1090
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A catalog, including finding charts, is presented which contains 282 faint stars of spectral type M3 and later, located in an area of 173 square degrees near the South Galactic Pole. The catalog is based on a spectroscopic survey undertaken with the Curtis Schmidt at CTIO and provides a finding list of M stars free of any possible kinematic bias. The majority of these stars are expected to be dwarfs. To the same limiting magnitude, the observed surface density is comparable to that of the faint M stars in the direction of the North Galactic Pole, named 273 over 190 square degrees.
- ID:
- ivo://CDS.VizieR/J/A+A/631/A43
- Title:
- Late-type stars FeI & FeII NLTE line formation
- Short Name:
- J/A+A/631/A43
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Iron plays a crucial role in studies of late-type stars. In their atmospheres, neutral iron is the minority species and lines of FeI are subject to the departures from local thermodynamic equilibrium (LTE). In contrast, one believes that LTE is a realistic approximation for FeII lines. The main source of the uncertainties in the non-LTE (NLTE) calculations for cool atmospheres is a treatment of inelastic collisions with hydrogen atoms. We investigate the effect of FeI+HI and FeII+HI collisions and their different treatment on the FeI/FeII ionisation equilibrium and iron abundance determinations for Galactic halo benchmark stars HD 84937, HD 122563, and HD 140283 and a sample of 38 very metal-poor (VMP) giants in the dwarf galaxies with well known distances. We perform the NLTE calculations for FeI-FeII with applying quantum-mechanical rate coefficients for collisions with HI from recent papers of Barklem (2018, Cat. J/A+A/612/A90B18), Yakovleva, Belyaev, and Kraemer (2018CP....515..369Y, YBK18), and Yakovleva, Belyaev, and Kraemer (2019MNRAS.483.5105Y , YBK19). We find that collisions with HI serve as efficient thermalisation processes for FeII, such that the NLTE abundance corrections for FeII lines do not exceed 0.02dex, in absolute value, for [Fe/H]~>-3 and reach +0.06dex at [Fe/H]~-4. For a given star, different treatments of FeI+HI collisions by B18 and YBK18 lead to similar average NLTE abundances from the FeI lines, although there exist discrepancies in the NLTE abundance corrections for individual lines. With using quantum-mechanical collisional data and the Gaia based surface gravity, we obtain consistent abundances from the two ionisation stages, FeI and FeII, for a red giant HD 122563. For a turn-off star HD 84937 and a subgiant HD 140283, we analyse the iron lines in the visible and the ultra-violet (UV, 1968 to 2990{AA}) range. For either FeI or FeII, abundances from the visible and UV lines are found to be consistent in each star. The NLTE abundances from the two ionisation stages agree within 0.10dex, when using the YBK18 data, and 0.13dex in case of B18. The FeI/FeII ionisation equilibrium is achieved for each star of our stellar sample in the dwarf galaxies, with the exception of stars at [Fe/H]~<-3.7.