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16831. Vertical structure of edge-on galaxies
ID:
ivo://CDS.VizieR/J/A+A/389/795
Title:
Vertical structure of edge-on galaxies
Short Name:
J/A+A/389/795
Date:
21 Oct 2021
Publisher:
CDS
Description:
To analyze the vertical structure of edge-on galaxies, we have used images of a large uniform sample of flat galaxies that have been taken during the 2MASS all-sky survey. The photometric parameters, such as the radial scale length, the vertical scale height, and the deprojected central surface brightness of galactic disks have been obtained. We find a strong correlation between the central surface brightness and the ratio of the vertical scale height to the vertical scale length: the thinner the galaxy, the lower the central surface brightness of its disk. The vertical scale height does not increase systematically with the distance from the galaxy center in the frames of this sample.
16832. Very cold C-rich circumstellar envelopes
ID:
ivo://CDS.VizieR/J/A+A/267/515
Title:
Very cold C-rich circumstellar envelopes
Short Name:
J/A+A/267/515
Date:
21 Oct 2021
Publisher:
CDS
Description:
The paper develops a method for identification of very cold C-rich circumstellar envelopes (CSEs) in IR regions colder than region VII (i.e., larger value of IRAS flux ratio S25/S12), by reviewing the different criteria and by identifying C-rich CSEs in a sample of 228 bright IRAS sources. By using the results of OH surveys and catalogs together with the results of additional HCN/CO millimeter observations performed on critical classes of objects, a C/O classification is proposed for 94 percent of the sources with a good probability. It is shown that the low-resolution spectra by themselves are a reasonable and easy way to identify C-rich late AGB CSEs. For post-AGB object with cold CSEs, HCN and OH observations or visible/near IR spectroscopy are necessary.
16833. Very Low-Luminosity Objects (VeLLOs) from 1.25-850um
ID:
ivo://CDS.VizieR/J/ApJS/225/26
Title:
Very Low-Luminosity Objects (VeLLOs) from 1.25-850um
Short Name:
J/ApJS/225/26
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the results of a search for Very Low-Luminosity Objects (VeLLOs) in the Gould Belt (GB) clouds using infrared and sub-millimeter (sub-mm) data from 1.25 to 850{mu}m and our N_2_H^+^(J=1-0) observations. We modified the criteria by Dunham et al. (2008, J/ApJS/179/249) to select the VeLLOs in the GB clouds, finding 95 VeLLO candidates, 79 of which are newly identified in this study. Out of 95 sources, 44 were detected in both sub-mm continuum and N_2_H^+^ emission and were classified as Group A (the VeLLOs), and 51 sources detected in either sub-mm emission or N_2_H^+^ emission were classified with Group B as candidate VeLLOs. We find that these VeLLOs and the candidates are forming in environments different from those of the likely VeLLOs. Seventy-eight sources are embedded within their molecular clouds, and thus are likely VeLLOs forming in a dense environment. The remaining 17 sources are located in low-level extinction regions (A_V_<1) connected to the clouds, and can be either background sources or candidate substellar objects forming in an isolated mode. The VeLLOs and the candidates are likely more luminous and their envelopes tend to be more massive in denser environments. The VeLLOs and the candidates are more populous in the clouds where more YSOs form, indicating that they form in a manner similar to that of normal YSOs. The bolometric luminosities and temperatures of the VeLLOs are compared to predictions of episodic accretion models, showing that the low luminosities for most VeLLOs can be well explained by their status in the quiescent phases of a cycle of episodic mass accretion.
16834. Very low-mass binaries with Gaia DR2 data
ID:
ivo://CDS.VizieR/J/ApJ/889/176
Title:
Very low-mass binaries with Gaia DR2 data
Short Name:
J/ApJ/889/176
Date:
21 Oct 2021
Publisher:
CDS
Description:
We report the discovery of WISE 2150-7520AB (W2150AB): a widely separated (~341au) very low-mass L1+T8 co-moving system. The system consists of the previously known L1 primary 2MASS J21501592-7520367 and a newly discovered T8 secondary found at position 21:50:18.99-75:20:54.6 (MJD=57947) using Wide-field Infrared Survey Explorer data via the Backyard Worlds: Planet 9 citizen science project. We present Spitzer ch1 and ch2 photometry (ch1-ch2=1.41+/-0.04mag) of the secondary and Folded-port InfraRed Echellette prism spectra of both components. The sources show no peculiar spectral or photometric signatures, indicating that each component is likely field age. Using all observed data and the Gaia DR2 parallax of 41.3593+/-0.2799mas for W2150A we deduce fundamental parameters of log(L_bol_/L_{sun}_)=-3.69+/-0.01, Teff=2118+/-62K, and an estimated mass=72+/-12M_Jup_ for the L1 and log(L_bol_/L_{sun}_)=-5.64+/-0.02, Teff=719+/-61K, and an estimated mass=34+/-22M_Jup_ for the T8. At a physical separation of ~341au this system has E_bin_=10^41^erg, making it the lowest binding energy system of any pair with M_tot_<0.1M_{sun}_ not associated with a young cluster. It is equivalent in estimated mass ratio, E_bin_, and physical separation to the ~2Myr M7.25+M8.25 binary brown dwarf 2MASS J11011926-7732383AB (2M1101AB) found in the Chameleon star-forming region. W2150AB is the widest companion system yet observed in the field where the primary is an L dwarf or later.
16835. Very low mass objects in ONC
ID:
ivo://CDS.VizieR/J/A+A/515/A13
Title:
Very low mass objects in ONC
Short Name:
J/A+A/515/A13
Date:
21 Oct 2021
Publisher:
CDS
Description:
Angular momentum (J) loss requires magnetic interaction between the forming star and both the circumstellar disk and the magnetically driven outflows. In order to test these predictions many authors have investigated a rotation-disk connection in pre-main sequence objects with masses larger than about 0.4M_{sun}_. For brown dwarfs (BDs) this connection was not investigated as yet because there are very few samples available. We aim to extend this investigation well down into the substellar regime for our large sample of ~~80 BDs in the Orion Nebula Cluster, for which we have recently measured rotational periods.
16836. Very low mass proper motion members in Pleiades
ID:
ivo://CDS.VizieR/J/A+AS/100/607
Title:
Very low mass proper motion members in Pleiades
Short Name:
J/A+AS/100/607
Date:
21 Oct 2021
Publisher:
CDS
Description:
A proper motion membership list is presented for the lower mass stars in the Pleiades open cluster based on a survey of about a 5x5{deg} area around the cluster center. Finder charts prepared from an R passband Schmidt plate are given. Photographic R and I photometry is given for all stars; where possible a V magnitude is also listed. The photometry is accurate to about 0.1mag.
16837. Very low mass stars in Praesepe
ID:
ivo://CDS.VizieR/J/A+AS/109/29
Title:
Very low mass stars in Praesepe
Short Name:
J/A+AS/109/29
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the results of a deep proper motion survey of a 19 square degree area of the Galactic open cluster Praesepe. Details of the astrometric and photometric reductions are given, along with the selection process for members. A list of these probable members, along with cross identifications from previous less sensitive surveys, is presented and finder charts given in an Appendix.
16838. Very low mass stars in Praesepe
ID:
ivo://CDS.VizieR/J/A+A/510/A27
Title:
Very low mass stars in Praesepe
Short Name:
J/A+A/510/A27
Date:
21 Oct 2021
Publisher:
CDS
Description:
Determination of the mass functions of open clusters of different ages allows us to infer the efficiency with which brown dwarfs are evaporated from clusters to populate the field. In this paper we present the results of a photometric survey to identify low mass and brown dwarf members of the old open cluster Praesepe (age 590^+150^_-120_Myr, distance 190^+6.0^_-5.8_pc) from which we estimate its mass function and compare this with that of other clusters. We performed an optical (Ic-band) and near-infrared (J and Ks-band) photometric survey of Praesepe covering 3.1{deg}^2^. With 5sigma detection limits of Ic=23.4 and J=20.0, our survey is predicted to be sensitive to objects with masses from 0.6 to 0.05M_{sun}.
16839. 10 very-low-mass stars photometry
ID:
ivo://CDS.VizieR/J/A+A/625/A150
Title:
10 very-low-mass stars photometry
Short Name:
J/A+A/625/A150
Date:
21 Oct 2021
Publisher:
CDS
Description:
Measurements of the physical properties of stars at the lower end of the main sequence are scarce. In this context we report masses, radii and surface gravities of ten very-low-mass stars in eclipsing binary systems, with orbital periods of the order of several days. The objects probe the stellar mass-radius relation in the fully convective regime, M*<0.35M_{sun}_, down to the hydrogen burning mass-limit, M_HB_~0.07M_{sun}_. The stars were detected by the WASP survey for transiting extra-solar planets, as low-mass, eclipsing companions orbiting more massive, F- and G-type host stars. We use eclipse observations of the host stars, performed with the TRAPPIST, Leonhard Euler and SPECULOOS telescopes, and radial velocities of the host stars obtained with the CORALIE spectrograph, to determine the physical properties of the low-mass companions. Surface gravities of the low-mass companions are derived from the eclipse and orbital parameters of each system. Spectroscopic measurements of the host star effective temperature and metallicity are used to infer the host star mass and age from stellar evolution models for solar-type stars. Masses and radii of the low-mass companions are then derived from the eclipse and orbital parameters of the binary systems. The objects are compared to stellar evolution models for low-mass stars, to test for an effect of the stellar metallicity and orbital period on the radius of low-mass stars in close binary systems. Measurements are found to be in good agreement with stellar evolution models; a systematic inflation of the radius of low-mass stars with respect to model predictions is limited to 1.6+/-1.2%, in the fully convective low-mass regime. The sample of ten objects indicates a scaling of the radius of low-mass stars with the host star metallicity. No correlation between stellar radii and the orbital periods of the binary systems is determined. A combined analysis with thirteen comparable objects from the literature is consistent with this result.
16840. Very low mass stars radial velocities
ID:
ivo://CDS.VizieR/J/A+A/364/665
Title:
Very low mass stars radial velocities
Short Name:
J/A+A/364/665
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have obtained adaptive optics images and accurate radial velocities for 7 very low mass objects, In the course of a long term effort to determine accurate masses for very low mass stars (M<0.6 M{sun}). We use the new data, together with measurements from the literature for some stars, to determine new or improved orbits for these 7 systems. They provide masses for 16 very low mass stars with accuracies that range between 0.2% and 5%, and in some cases a very accurate distance as well. This information is used in a companion paper to discuss the Mass-Luminosity relation for the V, J, H and K photometric bands.

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