- ID:
- ivo://CDS.VizieR/J/AJ/127/2856
- Title:
- Brown dwarfs in the 2MASS Survey
- Short Name:
- J/AJ/127/2856
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the discovery of seven new T dwarfs identified in the Two Micron All Sky Survey (Cat. <II/246>). Low-resolution (R~150) 0.8-2.5{mu}m spectroscopy obtained with the Infrared Telescope Facility (IRTF) SpeX instrument reveals the characteristic H_2_O and CH_4_ bands in the spectra of these brown dwarfs. Comparison with spectral standards observed with the same instrument enables us to derive classifications of T3 to T7 for the objects in this sample. Moderate-resolution (R~1200) near-infrared spectroscopy for a subset of these discoveries reveal K I line strengths consistent with previously observed trends with spectral type. Follow-up imaging observations provide proper-motion measurements for these sources, ranging from less than 0.1" to 1.55"/yr. One object, 2MASS 0034+0523, has a spectrophotometric distance placing it within 10pc of the Sun. This source also exhibits a depressed K-band peak reminiscent of the peculiar T dwarf 2MASS 0937+2931 and may be a metal-poor or old, high-mass brown dwarf. We also present low-resolution SpeX data for a set of M- and L-type dwarf, subdwarf, and giant comparison stars used to classify 59 additional candidates identified as background stars. These are primarily M5-M8.5 dwarfs, many exhibiting H I Pa^{gamma}^, but include three candidate ultracool M subdwarfs and one possible early-type L subdwarf.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/385/884
- Title:
- BVRIJHK photometry of 27 post-AGB candidates
- Short Name:
- J/A+A/385/884
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- BVRIJHK photometric observations are presented for 27 post-AGB candidates. Almost all objects show a double peaked spatial energy distribution (SED) curve in the optical to far-infrared wavelengths. Seventeen objects were classified as post-AGB stars on the basis of their spectral type, location in the IRAS color-color diagram and SED. The physical parameters of the observed post-AGB stars, the inner radius of the detached shell, the mass of the shell and the distance were derived using the simple dust shell model. We compared our observational sequence of post-AGB objects to the theoretical evolutionary sequence (Schoenberner, 1983ApJ...272..708S; Bloecker, 1995, Cat. <J/A+A/299/755>) in the stellar temperatures versus age diagram. We found that two post-AGB stars, IRAS 05040+4820 and 08187-1905, have low stellar temperature with a large dynamical age of the dust shell. They appear to provide the first observational evidence that some low-mass stars bypass the planetary nebulae stage because of their slow increase in stellar temperature.
- ID:
- ivo://CDS.VizieR/J/AJ/136/1039
- Title:
- CaII index of SMC red giant branch stars
- Short Name:
- J/AJ/136/1039
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present stellar metallicities derived from Ca II triplet spectroscopy in over 350 red giant branch stars in 13 fields distributed in different positions in the Small Magellanic Cloud, ranging from ~1{deg} to ~4{deg} from its center. In the innermost fields, the average metallicity is [Fe/H]~-1. This value decreases when we move away toward outermost regions. This is the first detection of a spectroscopic metallicity gradient in this galaxy. We show that the metallicity gradient is related to an age gradient, in the sense that more metal-rich stars, which are also younger, are concentrated in the central regions of the galaxy.
- ID:
- ivo://CDS.VizieR/J/AJ/135/836
- Title:
- Calcium triplet index in LMC stars
- Short Name:
- J/AJ/135/836
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Infrared CaII triplet (CaT) spectroscopy has been used to derive stellar metallicities for individual stars in four Large Magellanic Cloud fields situated at galactocentric distances of 3{deg}, 5{deg}, 6{deg}, and 8{deg} to the north of the bar. The combination of spectroscopy with deep CCD photometry has allowed us to break the RGB age-metallicity degeneracy and compute the ages for the objects observed spectroscopically. The obtained age-metallicity relationships (AMRs) for our four fields are statistically indistinguishable. We conclude that the lower mean metallicity in the outermost field is a consequence of it having a lower fraction of intermediate-age stars, which are more metal-rich than the older stars. The disk AMR is similar to that for clusters. However, the lack of objects with ages between 3 and 10Gyr is not observed in the field population. Finally, we used data from the literature to derive consistently the AMR of the bar. Simple chemical evolution models have been used to reproduce the observed AMRs with the purpose of investigating which mechanism has participated in the evolution of the disk and bar.
- ID:
- ivo://CDS.VizieR/J/PASP/120/1128
- Title:
- Calibrated griz magnitudes of Tycho stars
- Short Name:
- J/PASP/120/1128
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Photometric calibration at an accuracy of ~5% in an arbitrary celestial location is frequently needed. However, existing all-sky astronomical catalogue do not reach this accuracy, and time consuming photometric calibration procedures are required. I fitted the Hipparcos B_T_, and V_T_ magnitudes, along with the 2MASS J, H, and K magnitudes of Tycho-2 catalog-stars with stellar spectral templates. From the best fit spectral template derived for each star, I calculated its synthetic SDSS griz magnitudes, and constructed an all-sky catalog of griz magnitudes of bright stars (V<12). Testing this method on SDSS photometric telescope observations, I find that the photometric accuracy, for a single star, is usually about 0.12, 0.12, 0.10 and 0.08 mag (1sigma), for the g, r, i, and z-bands, respectively. However, by using ~10 such stars, the typical errors per calibrated field (systematic + statistical) can be reduced to about 0.04, 0.03, 0.02, and 0.02 mag, in the g, r, i, and z-bands, respectively. Therefore, in cases for which several calibration stars can be observed in the field of view of an instrument, it is possible to photometrically calibrate the image.
- ID:
- ivo://CDS.VizieR/J/BaltA/16/327
- Title:
- Camelopardalis dust and molecular clouds
- Short Name:
- J/BaltA/16/327
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using infrared photometric data extracted from the 2MASS, IRAS and MSX databases, 142 suspected young stellar objects (YSOs) are selected from about 2 million stars in the Camelopardalis segment of the Milky Way limited by Galactic coordinates, b=132-158{deg},+/-12{deg}.
- ID:
- ivo://CDS.VizieR/J/ApJS/234/31
- Title:
- Carbon stars from LAMOST using machine learning
- Short Name:
- J/ApJS/234/31
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this work, we present a catalog of 2651 carbon stars from the fourth Data Release (DR4) of the Large Sky Area Multi-Object Fiber Spectroscopy Telescope (LAMOST). Using an efficient machine-learning algorithm, we find these stars from more than 7 million spectra. As a by-product, 17 carbon-enhanced metal- poor turnoff star candidates are also reported in this paper, and they are preliminarily identified by their atmospheric parameters. Except for 176 stars that could not be given spectral types, we classify the other 2475 carbon stars into five subtypes: 864 C-H, 226 C-R, 400 C-J, 266 C-N, and 719 barium stars based on a series of spectral features. Furthermore, we divide the C-J stars into three subtypes, C-J(H), C-J(R), and C-J(N), and about 90% of them are cool N-type stars as expected from previous literature. Besides spectroscopic classification, we also match these carbon stars to multiple broadband photometries. Using ultraviolet photometry data, we find that 25 carbon stars have FUV detections and that they are likely to be in binary systems with compact white dwarf companions.
- ID:
- ivo://CDS.VizieR/J/ApJ/627/621
- Title:
- Catalog of Extremely Red Objects
- Short Name:
- J/ApJ/627/621
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use a serendipitously discovered overdensity of extremely red objects (EROs) to study the morphologies and cumulative surface number density of EROs in a dense environment. Our extremely deep imaging allows us to select very faint EROs, reaching K_S_=21, or ~2mag fainter than the L* of passively evolving ellipticals at z=1.5.
- ID:
- ivo://CDS.VizieR/J/A+A/639/A28
- Title:
- Catalog of super star clusters in IRAS 17138-1017
- Short Name:
- J/A+A/639/A28
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Currently, the global characteristics and evolution of super star clusters (SSCs) are not well understood, due to the large distances to their host galaxies. We aim to study the population of SSCs in IRAS 17138-1017, a luminous infrared galaxy (LIRG), in terms of age, extinction, mass, and luminosity distribution. We analyzed imaging data in the near-infrared from the GeMS/GSAOI instrument on the Gemini telescope and generated simulations with the radiative transfer code MontAGN. The extraction of SSCs from the images and their photometry in J, H, and Ks allowed us to derive color-color and color-magnitude diagrams. Comparison with a theoretical stellar evolutionary track gives a first hint into the extinction towards each SSC, as well as their ages, despite some degeneracy between those two quantities. Spectra given by our radiative transfer code MontAGN, which includes dust emission, also provide insightful predictions and comparisons. We detect with a fair degree of confidence 54 SSCs of m_Ks between 16 mag and 21 mag with a median instrumental uncertainty of 0.05 mag. When plotted on a color-color diagram and a color-magnitude diagram, it appears that most of the sources are very much extinct with respect to an intrinsic theoretical evolutionary track. Once de-reddened, the colors point unambiguously to two distinct and very recent starburst episodes at 2.8 and 4.5Myr. While the SSCs in the 4.5Myr starburst are distributed along the spiral arms, the 2.8Myr SSCs are concentrated in the central region. The luminosity and mass functions present a classical power-law behavior, although with shallower slopes than generally observed in LIRGs. Comparison with radiative transfer simulations shows that, especially for the youngest SSCs, the thermal emission by dust is not negligible and could explain the few very red SSCs that could not be de-reddened safely. This effect could lead to a misevaluation of the age of the starburst by at most 1 or 2Myr.
- ID:
- ivo://CDS.VizieR/II/53
- Title:
- Catalogue of 10-micron Celestial Objects
- Short Name:
- II/53
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The published report was prepared by R.T. Hall (1974) for the Space and Missile systems Organization, Air Force System Command. The machine version includes a 10-micrometer catalog number, object name, right ascension and declination (B1950), galactic coordinates, proper motions, spectral types, magnitudes in the V(0.55um), I(0.84um), K(2.2um) and N(10um) bands, flux measurements at 10um, and cross identifications to the numbering systems of the Durchmusterung catalogs, the SAO catalog, the Bright Star Catalogue, The Henry Draper Catalogue and the GC, and CalTech Two-Micron Sky Survey (Neugebauer and Leighton, Cat. II/2) where such identifications exist.