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Start Over Subject infrared photometry Subject late-type stars
1. Absolute magnitudes for late-type dwarfs
ID:
ivo://CDS.VizieR/J/AN/326/321
Title:
Absolute magnitudes for late-type dwarfs
Short Name:
J/AN/326/321
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a new formula for absolute magnitude determination for late-type dwarf stars as a function of (g-r) and (r-i) for Sloan photometry (as defined by Abazajian et al., 2003AJ....126.2081A). The absolute magnitudes estimated by this approach are brighter than those estimated by colour-magnitude diagrams, and they reduce the luminosity function rather close to the luminosity function of Hipparcos.
2. A catalog of cool dwarf targets for the TESS
ID:
ivo://CDS.VizieR/J/AJ/155/180
Title:
A catalog of cool dwarf targets for the TESS
Short Name:
J/AJ/155/180
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a catalog of cool dwarf targets (V-J>2.7, T_eff_~<4000 K) and their stellar properties for the upcoming Transiting Exoplanet Survey Satellite (TESS), for the purpose of determining which cool dwarfs should be observed using two minute observations. TESS has the opportunity to search tens of thousands of nearby, cool, late K- and M-type dwarfs for transiting exoplanets, an order of magnitude more than current or previous transiting exoplanet surveys, such as Kepler, K2, and ground-based programs. This necessitates a new approach to choosing cool dwarf targets. Cool dwarfs are chosen by collating parallax and proper motion catalogs from the literature and subjecting them to a variety of selection criteria. We calculate stellar parameters and TESS magnitudes using the best possible relations from the literature while maintaining uniformity of methods for the sake of reproducibility. We estimate the expected planet yield from TESS observations using statistical results from the Kepler mission, and use these results to choose the best targets for two minute observations, optimizing for small planets for which masses can conceivably be measured using follow-up Doppler spectroscopy by current and future Doppler spectrometers. The catalog is available in machine readable format and is incorporated into the TESS Input Catalog and TESS Candidate Target List until a more complete and accurate cool dwarf catalog identified by ESA's Gaia mission can be incorporated.
3. Ackermann red stars
ID:
ivo://CDS.VizieR/II/260
Title:
Ackermann red stars
Short Name:
II/260
Date:
21 Oct 2021
Publisher:
CDS
Description:
In the late 1960s Gerhard Ackermann published two lists of extremely red stars (1968ZA.....69..130A and 1970A&A.....8..315A), including what appeared to be reliable spectral classifications for a few hundred stars. The two published papers provide details of the observing and analysis, made between June and October 1968 at the Heidelberg observatory with the 25cm f/3.6 Schmidt camera together with a 10-degree UBK7 prism yielding a dispersion of 3500 {AA}/mm at the atmospheric A band (7700{AA}). Exposures on ammonia-hypersensitized Kodak I-N emulsion + RG665 filter were obtained along with direct plates on I-N emulsion as well as 103a-E + OG550, totalling 101 exposures in all. The spectra were classified by following the precepts of Cameron & Nassau (1955ApJ...122..177C) and Nassau & Velghe (1964ApJ...139..190N). Ackermann initiated photoelectric observations at I and K, but obviously the Heidelberg weather was not conducive to pursuing this. Because the calibration of the photometry on the direct plates was by necessity rather crude, Ackermann's photometric results are not reported here -- the procedures used were sufficient to identify the reddest stars, but not for much else. Approximate V magnitudes were added for all the stars -- for the most part these are merely averages of the photo-blue and -red magnitudes in both GSC-2.2 and USNO-B1.0, but their zero-point and scale should be reliable at the few-tenths magnitude level in this range. Coordinates were drawn from either UCAC2 or 2MASS depending mainly on Declination, since UCAC2 extends only to about +40 Dec in this area. The UCAC2 positions should be good to better than 0.1", and those from 2MASS to 0.2". In a few cases, such as gross overexposure in 2MASS, positions are from various Schmidt survey catalogues, as indicated with each entry. The first 13 stars of the catalog come from the concluding volume of the ZA paper; in the 1970 paper, Ackermann refers to these stars using the acronym HDK, which is adopted here. The published table gave rather rough arcminute-precision positions (for equinox 1965). Star 6 was recovered 1 degree east of the nominal place, and identified with the variable star WX CMi. Along with the positions and IDs, the table shows V magnitudes and the spectral types given in the original paper. Some of the stars are within the region covered by the ASAS-3 survey, so reliable V magnitudes are available along with beautiful lightcurves. Ackermann's second much longer list contains rough photometry from the POSS-I prints for some 400 very red stars in the Cygnus starcloud, and for 254 of these spectral types were also determined. The stars without spectral classifications comprise a diverse group including both red/reddened late-type stars and greatly obscured hotter stars, but no real astrophysical information is given for any of them beyond sheer redness -- these stars are omitted from the catalog. In consultation with Prof Ackermann, the following changes have been made to the spectral types: for stars shown in the original table with a hyphen between two types (e.g. M5-M6), this was to show that the type was uncertain to that degree (i.e. M5 or M6), for which the 'slash' notation of Nancy Houk was preferred, and thus M5-M6 becomes M5/6. One star, 78-0-144, exhibited a range in types, and it is shown as M7-M9. Ackermann also indicated a number of stars as being of very-late type with VO present (separable from the A-band), but where the star was too faint to classify accurately. He agrees these are likely to be in the range M7 to M9, and again these are shown in the slash-style notation as M7/9:, with the colon added to indicate uncertainty since the types were not explicit in the original, and sometimes a question mark for those already marked as uncertain in the original. These changes were made so that machine parsing schemes will be better able to handle the classifications.
4. A grid of MARCS model atmospheres for S stars
ID:
ivo://CDS.VizieR/J/A+A/601/A10
Title:
A grid of MARCS model atmospheres for S stars
Short Name:
J/A+A/601/A10
Date:
21 Oct 2021
Publisher:
CDS
Description:
S-type stars are late-type giants whose atmospheres are enriched in carbon and s-process elements because of either extrinsic pollution by a binary companion or intrinsic nucleosynthesis and dredge-up on the thermally-pulsing asymptotic giant branch. A grid of MARCS model atmospheres has been computed for S stars, covering the range 2700<=Teff(K)<=4000, 0.50<=C/O<0.99, 0<=logg<=5, [Fe/H]=0., -0.5dex, and [s/Fe]= 0, 1, and 2 dex (where the latter quantity refers to the global overabundance of s-process elements). The MARCS models make use of a new ZrO line list. Synthetic spectra computed from these models are used to derive photometric indices in the Johnson and Geneva systems, as well as TiO and ZrO band strengths. A method is proposed to select the model best matching any given S star, a non-trivial operation since the grid contains more than 3500 models covering a five-dimensional parameter space. The method is based on the comparison between observed and synthetic photometric indices and spectral band strengths, and has been applied on a vast subsample of the Henize sample of S stars. Our results confirm the old claim by Piccirillo (1980MNRAS.190..441P) that ZrO bands in warm S stars (Teff > 3200K) are not caused by the C/O ratio being close to unity, as traditionally believed, but rather by some Zr overabundance. The TiO and ZrO band strengths, combined with V-K and J-K photometric indices, are used to select Teff, C/O, [Fe/H] and [s/Fe]. The Geneva U-B_1 and B_2-V_1 indices (or any equivalent) are good at selecting the gravity. The defining spectral features of dwarf S stars are outlined, but none is found among the Henize S stars. More generally, it is found that, at Teff=3200K, a change of C/O from 0.5 to 0.99 has a strong impact on V-K (2mag). Conversely, a range of 2 mag in V-K corresponds to a 200K shift along the (Teff, V-K) relationship (for a fixed C/O value). Hence, the use of a (Teff, V-K) calibration established for M stars will yield large errors for S stars, so that a specific calibration must be used, as provided in the present paper. Using the atmospheric parameters derived by our method for the sample of Henize S stars, we show that the extrinsic-intrinsic dichotomy among S stars reveals itself very clearly as a bimodal distribution in the effective temperatures. Moreover, the increase of s-process element abundances with increasing C/O ratios and decreasing temperatures is apparent among intrinsic stars, confirming theoretical expectations.
5. AllWISE motion survey
ID:
ivo://CDS.VizieR/J/ApJ/783/122
Title:
AllWISE motion survey
Short Name:
J/ApJ/783/122
Date:
21 Oct 2021
Publisher:
CDS
Description:
The AllWISE processing pipeline has measured motions for all objects detected on Wide-field Infrared Survey Explorer (WISE) images taken between 2010 January and 2011 February. In this paper, we discuss new capabilities made to the software pipeline in order to make motion measurements possible, and we characterize the resulting data products for use by future researchers. Using a stringent set of selection criteria, we find 22445 objects that have significant AllWISE motions, of which 3525 have motions that can be independently confirmed from earlier Two Micron All Sky Survey (2MASS) images, yet lack any published motions in SIMBAD. Another 58 sources lack 2MASS counterparts and are presented as motion candidates only. Limited spectroscopic follow-up of this list has already revealed eight new L subdwarfs. These may provide the first hints of a "subdwarf gap" at mid-L types that would indicate the break between the stellar and substellar populations at low metallicities (i.e., old ages). Another object in the motion list --WISEA J154045.67-510139.3-- is a bright (J~9mag) object of type M6; both the spectrophotometric distance and a crude preliminary parallax place it ~6pc from the Sun. We also compare our list of motion objects to the recently published list of 762 WISE motion objects from Luhman (2014, J/ApJ/781/4). While these first large motion studies with WISE data have been very successful in revealing previously overlooked nearby dwarfs, both studies missed objects that the other found, demonstrating that many other nearby objects likely await discovery in the AllWISE data products.
6. A sample of 7146 M or K-dwarfs from KIC and Gaia
ID:
ivo://CDS.VizieR/J/AJ/161/203
Title:
A sample of 7146 M or K-dwarfs from KIC and Gaia
Short Name:
J/AJ/161/203
Date:
21 Oct 2021
Publisher:
CDS
Description:
The planet-metallicity correlation serves as a potential link between exoplanet systems as we observe them today and the effects of bulk composition on the planet formation process. Many observers have noted a tendency for Jovian planets to form around stars with higher metallicities; however, there is no consensus on a trend for smaller planets. Here, we investigate the planet-metallicity correlation for rocky planets in single and multi-planet systems around Kepler M-dwarf and late-K-dwarf stars. Due to molecular blanketing and the dim nature of these low-mass stars, it is difficult to make direct elemental abundance measurements via spectroscopy. We instead use a combination of accurate and uniformly measured parallaxes and photometry to obtain relative metallicities and validate this method with a subsample of spectroscopically determined metallicities. We use the Kolmogorov-Smirnov (K-S) test, Mann-Whitney U-test, and Anderson-Darling (AD) test to compare the compact multiple planetary systems with single-transiting planet systems and systems with no detected transiting planets. We find that the compact multiple planetary systems are derived from a statistically more metal-poor population, with a p-value of 0.015 in the K-S test, a p-value of 0.005 in the Mann-Whitney U-test, and a value of 2.574 in the AD test statistic, which exceeds the derived threshold for significance by a factor of 25. We conclude that metallicity plays a significant role in determining the architecture of rocky planet systems. Compact multiples either form more readily, or are more likely to survive on gigayear timescales, around metal-poor stars.
7. A standard stellar library. II.
ID:
ivo://CDS.VizieR/J/A+AS/130/65
Title:
A standard stellar library. II.
Short Name:
J/A+AS/130/65
Date:
21 Oct 2021
Publisher:
CDS
Description:
A standard library of theoretical stellar spectra intended for multiple synthetic photometry applications including spectral evolutionary synthesis is presented. The grid includes M dwarf model spectra, hence complementing the first library version established in Paper I (Lejeune et al., 1997, Cat. <J/A+AS/125/229>). It covers the following wide ranges of fundamental parameters: Teff: 50,000 to 2000K, logg: 5.5 to -1.02, and [Fe/H]: +1.0 to -5.0. A correction procedure is also applied to the theoretical spectra in order to provide color-calibrated flux distributions over a large domain of effective temperatures. Empirical Teff-color calibrations are constructed between 11500K and 2000K, and semi-empirical calibrations for non-solar abundances ([Fe/H]=-3.5 to +1.0) are established. Model colors and bolometric corrections for both the original and the corrected spectra, synthesized in the UBV(RI)c(JHKLL'M) system, are given for the full range of stellar parameters. Synthetic colors: ---------------- Synthetic UBV(RI)c(JHKLM) colors have been computed from both the original and the corrected model flux distributions presented in Paper I (1997A&AS..125..229L; see catalog <J/A+AS/125/229>), as the files lcb98ori.dat and lcb98cor.dat respectively; the results are also presented in individual files lcb98xxx.ori and lcb98xxx.cor, where xxx designates the metallicity (ex: 'm15' --> [Fe/H]=-1.5). For each file, we give synthetic colors computed from energy-weighted and photon-weighted stellar fluxes. Semi-empirical calibrations: --------------------------- Empirical ([Fe/H]=0.0) and semi-empirical (-3.5<=[Fe/H]<=+1.0) Teff-colors (UBVRIJHKLM) calibrations are given in Tables 1 to 10.
8. Astrometric monitoring of ultracool dwarf binaries
ID:
ivo://CDS.VizieR/J/ApJS/231/15
Title:
Astrometric monitoring of ultracool dwarf binaries
Short Name:
J/ApJS/231/15
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the full results of our decade-long astrometric monitoring programs targeting 31 ultracool binaries with component spectral types M7-T5. Joint analysis of resolved imaging from Keck Observatory and Hubble Space Telescope and unresolved astrometry from CFHT/WIRCam yields parallactic distances for all systems, robust orbit determinations for 23 systems, and photocenter orbits for 19 systems. As a result, we measure 38 precise individual masses spanning 30-115M_Jup_. We determine a model-independent substellar boundary that is ~70M_Jup_ in mass (~L4 in spectral type), and we validate Baraffe et al. evolutionary model predictions for the lithium-depletion boundary (60M_Jup_ at field ages). Assuming each binary is coeval, we test models of the substellar mass-luminosity relation and find that in the L/T transition, only the Saumon & Marley (2008ApJ...689.1327S) "hybrid" models accounting for cloud clearing match our data. We derive a precise, mass-calibrated spectral type-effective temperature relation covering 1100-2800K. Our masses enable a novel direct determination of the age distribution of field brown dwarfs spanning L4-T5 and 30-70M_Jup_. We determine a median age of 1.3Gyr, and our population synthesis modeling indicates our sample is consistent with a constant star formation history modulated by dynamical heating in the Galactic disk. We discover two triple-brown-dwarf systems, the first with directly measured masses and eccentricities. We examine the eccentricity distribution, carefully considering biases and completeness, and find that low-eccentricity orbits are significantly more common among ultracool binaries than solar-type binaries, possibly indicating the early influence of long-lived dissipative gas disks. Overall, this work represents a major advance in the empirical view of very low-mass stars and brown dwarfs.
9. Astrometry&photometry for late-type dwarfs&subdwarfs
ID:
ivo://CDS.VizieR/J/AJ/154/147
Title:
Astrometry&photometry for late-type dwarfs&subdwarfs
Short Name:
J/AJ/154/147
Date:
21 Oct 2021
Publisher:
CDS
Description:
New, updated, and/or revised CCD parallaxes determined with the Strand Astrometric Reflector at the Naval Observatory Flagstaff Station are presented. Included are results for 309 late-type dwarf and subdwarf stars observed over the 30+ years that the program operated. For 124 of the stars, parallax determinations from other investigators have already appeared in the literature and we compare the different results. Also included here are new or updated VI photometry on the Johnson-Kron-Cousins system for all but a few of the faintest targets. Together with 2MASS JHK_s_ near-infrared photometry, a sample of absolute magnitude versus color and color versus color diagrams are constructed. Because large proper motion was a prime criterion for targeting the stars, the majority turn out to be either M-type subdwarfs or late M-type dwarfs. The sample also includes 50 dwarf or subdwarf L-type stars, and four T dwarfs. Possible halo subdwarfs are identified in the sample based on tangential velocity, subluminosity, and spectral type. Residuals from the solutions for parallax and proper motion for several stars show evidence of astrometric perturbations.
10. BANYAN All-Sky Survey (BASS) catalog. V. Nearby YMGs
ID:
ivo://CDS.VizieR/J/ApJ/798/73
Title:
BANYAN All-Sky Survey (BASS) catalog. V. Nearby YMGs
Short Name:
J/ApJ/798/73
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the BANYAN All-Sky Survey (BASS) catalog, consisting of 228 new late-type (M4-L6) candidate members of nearby young moving groups (YMGs) with an expected false-positive rate of ~13%. This sample includes 79 new candidate young brown dwarfs and 22 planetary-mass objects. These candidates were identified through the first systematic all-sky survey for late-type low-mass stars and brown dwarfs in YMGs. We cross-matched the Two Micron All Sky Survey and AllWISE catalogs outside of the galactic plane to build a sample of 98970 potential >=M5 dwarfs in the solar neighborhood and calculated their proper motions with typical precisions of 5-15mas/yr. We selected highly probable candidate members of several YMGs from this sample using the Bayesian Analysis for Nearby Young AssociatioNs II tool (BANYAN II, see Gagne+, 2014, J/ApJ/783/121). We used the most probable statistical distances inferred from BANYAN II to estimate the spectral type and mass of these candidate YMG members. We used this unique sample to show tentative signs of mass segregation in the AB Doradus moving group and the Tucana-Horologium and Columba associations. The BASS sample has already been successful in identifying several new young brown dwarfs in earlier publications, and will be of great interest in studying the initial mass function of YMGs and for the search of exoplanets by direct imaging; the input sample of potential close-by >=M5 dwarfs will be useful to study the kinematics of low-mass stars and brown dwarfs and search for new proper motion pairs.

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