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24271. Volume-limited sample of M7-M9.5 dwarfs <20pc
ID:
ivo://CDS.VizieR/J/ApJ/705/1416
Title:
Volume-limited sample of M7-M9.5 dwarfs <20pc
Short Name:
J/ApJ/705/1416
Date:
21 Oct 2021
Publisher:
CDS
Description:
In a volume-limited sample of 63 ultracool dwarfs of spectral type M7-M9.5, we have obtained high-resolution spectroscopy with UVES at the Very Large Telescope and HIRES at Keck Observatory. In this first paper we introduce our volume-complete sample from DENIS and 2MASS targets, and we derive radial velocities and space motion. Kinematics of our sample are consistent with the stars being predominantly members of the young disk. The kinematic age of the sample is 3.1Gyr. We find that six of our targets show strong Li lines implying that they are brown dwarfs younger than several hundred million years. Five of the young brown dwarfs were unrecognized before. Comparing the fraction of Li detections to later spectral types, we see a hint of an unexpected local maximum of this fraction at spectral type M9. It is not yet clear whether this maximum is due to insufficient statistics, or to a combination of physical effects including spectral appearance of young brown dwarfs, Li line formation, and the star formation rate at low masses.
24272. VO-Paris Data Center Naming Authority
ID:
ivo://vopdc
Title:
VO-Paris Data Center Naming Authority
Short Name:
PADC Authority
Date:
10 Jan 2017
Publisher:
Paris Astronomical Data Centre
Description:
This naming authority is the root of the naming of the resources from VO-Paris Data Center and partners
24273. VO-Paris Data Center Publishing Registry
ID:
ivo://vopdc/registry
Title:
VO-Paris Data Center Publishing Registry
Short Name:
PADC Registry
Date:
10 Jan 2017
Publisher:
Paris Astronomical Data Centre
Description:
This registry provides access to resources from VO-Paris Data Center and partners.
24274. VO-Paris Data Discovery Portal
ID:
ivo://vopdc.obspm/portal
Title:
VO-Paris Data Discovery Portal
Short Name:
PADC Portal
Date:
10 Jan 2017
Publisher:
Paris Astronomical Data Centre
Description:
The Paris Astronomical Data Centre Portal provides an easy way to access to all VO data available at Paris Observatory.
24275. VO Paris Southern Atlas
ID:
ivo://vopdc.obspm/gepi/vopsat
Title:
VO Paris Southern Atlas
Short Name:
VOPSAT
Date:
10 Jan 2017
Publisher:
Paris Astronomical Data Centre - GEPI
Description:
VOPSAT is a set of southern sky digital surveys based on ESO-R, SRC-J and POSS1-E atlases. The plates have been digitized with the MAMA microdensitometer with a resolution of 0.7 arc-sec. Pixel resampling will allow mosaicing neighbouring Schmidt fields up to hundreds of square degrees.
24276. VOResource: an XML Encoding Schema for Resource Metadata
ID:
ivo://ivoa.net/std/VOResource
Title:
VOResource: an XML Encoding Schema for Resource Metadata
Short Name:
VOResource
Date:
02 Apr 2013 11:19:48
Publisher:
International Virtual Observatory Alliance
Description:
This document describes an XML encoding standard for IVOA Resource Metadata, referred to as VOResource. This schema is primarily intended to support interoperable registries used for discovering resources; however, any application that needs to describe resources may use this schema. In this document, we define the types and elements that make up the schema as representations of metadata terms defined in the IVOA standard, Resource Metadata for the Virtual Observatory [Hanisch et al. 2004]. We also describe the general model for the schema and explain how it may be extended to add new metadata terms and describe more specific types of resources.
24277. V643 Ori differential light curves
ID:
ivo://CDS.VizieR/J/A+A/624/A88
Title:
V643 Ori differential light curves
Short Name:
J/A+A/624/A88
Date:
21 Oct 2021
Publisher:
CDS
Description:
One of the greatest uncertainties in modelling the mass-exchange phases during the evolution of a binary system is the amount of mass and angular momentum that has been lost from the system. In order to constrain this problem, a favourable, evolved and detached real binary system is valuable as an example of the end result of this process. We study the 52-day post-mass-exchange eclipsing binary V643 Ori from complete uvby light curves and high-resolution spectra. V643 Ori is double-lined and shows total primary eclipses. The orbit is accurately circular and the rotation of both stars synchronised with the orbit, but the photometry from a single year (1993) shows signs of weak spot activity (0.02mag) around the primary eclipse. We determine accurate masses of 3.3 and 1.9M_{sun}_ from the spectroscopic orbit and solve the four light curves to determine radii of 16 and 21R_{sun}_, using the Wilson-Devinney photometric code. The rotational velocities from the cross-correlation profiles agree well with those computed from the known radii and orbital parameters. All observable parameters are thus very precisely determined, but the masses and radii of V643 Ori are incompatible with undisturbed post-main-sequence evolution. We have attempted to simulate the past evolutionary history of V643 Ori under both conservative and non-conservative Case B mass transfer scenarios. In the non-conservative case we varied the amounts of mass and angular momentum loss needed to arrive at the present masses in a circular 52-day orbit, keeping the two stars detached and synchronized as now observed, but without following the evolution of other stellar properties in any detail. Multiple possible solutions were found. Further attempts were made using both the BSE formalism and the binary MESA code in order to track stellar evolution more closely, and make use of the measured radii and temperatures as important additional constraints. Those efforts did not yield satisfactory solutions, possibly due to limitations in handling mass transfer in evolved stars such as these. We remain hopeful that future theoreticians can more fully model the system under realistic conditions.
24278. V380 Ori emission line spectrum
ID:
ivo://CDS.VizieR/J/A+AS/136/95
Title:
V380 Ori emission line spectrum
Short Name:
J/A+AS/136/95
Date:
21 Oct 2021
Publisher:
CDS
Description:
Table 3 presents the emission line spectrum of V380 Ori in the optical region observed at OHP in January 1995 with a mean resolution of 10000. For the line blends the wavelength and flux (not reddening corrected) of each contributor are given. For the P-Cygni profiles the equivalent widths of the absorption component are also reported. We estimate an error of less than 10% for the strongest lines, 10% to 40% for the weakest lines.
24279. V1647 Ori long-term optical & NIR observations
ID:
ivo://CDS.VizieR/J/ApJ/778/116
Title:
V1647 Ori long-term optical & NIR observations
Short Name:
J/ApJ/778/116
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a detailed study of McNeil's nebula (V1647 Ori) in its ongoing outburst phase starting from 2008 September to 2013 March. Our 124 nights of photometric observations were carried out in optical V, R, I, and near-infrared J, H, K bands, and 59 nights of medium-resolution spectroscopic observations were done in the 5200-9000{AA} wavelength range. All observations were carried out with the 2m Himalayan Chandra Telescope and 2m IUCAA Girawali Telescope. Our observations show that over the past four and a half years, V1647 Ori and region C near the Herbig-Haro object HH 22A have been undergoing a slow dimming at a rate of ~0.04mag/yr and ~0.05mag/yr, respectively, in R band, which is six times slower than the rate during a similar stage of V1647 Ori in the 2003 outburst. We detected change in flux distribution over the reflection nebula, implying changes in circumstellar matter distribution between the 2003 and 2008 outbursts. Apart from steady wind of velocity ~350km/s, we detected two episodic magnetic reconnection driven winds. Forbidden [OI]{lambda}6300 and [FeII]{lambda}7155 lines were also detected, implying shock regions probably from jets. We tried to explain the outburst timescales of V1647 Ori using the standard models of the FUors kind of outburst and found that pure thermal instability models like Bell and Lin cannot explain the variations in timescales. In the framework of various instability models we conclude that one possible reason for the sudden ending of the 2003 outburst in 2005 November was a low-density region or gap in the inner region (~1AU) of the disk.
24280. V1118 Ori UBVRIJHK outburst light curves
ID:
ivo://CDS.VizieR/J/A+A/511/A63
Title:
V1118 Ori UBVRIJHK outburst light curves
Short Name:
J/A+A/511/A63
Date:
21 Oct 2021
Publisher:
CDS
Description:
The accretion history of low-mass young stars is not smooth but shows spikes of accretion that can last from months and years to decades and centuries. Observations of young stars in outbursts can help us understand the temporal evolution of accreting stars and the interplay between the accretion disk and the stellar magnetosphere. The young late-type star V1118 Orionis was in outburst from 2005 to 2006. We followed the outburst with optical and near-infrared photometry. The X-ray emission was further probed with observations taken with XMM-Newton and Chandra during and after the outburst. In addition, we obtained mid-infrared photometry and spectroscopy with Spitzer at the peak of the outburst and in the post-outburst phase. The spectral energy distribution of V1118 Ori varied significantly over the course of the outburst. The optical flux showed the largest variations, most likely caused by enhanced emission by a hot spot. The hot spot dominated the optical and near-infrared emission at the peak of the outburst, while the disk emission dominated in the mid-infrared. The emission silicate feature in V1118 Ori is flat and does not vary in shape, but was slightly brighter at the peak of the outburst compared to the post-outburst spectrum. The X-ray flux correlated with the optical and infrared fluxes, indicating that accretion affected the magnetically active corona and the stellar magnetosphere. The thermal structure of the corona was variable with some indication of a cooling of the coronal temperature in the early phase of the outburst with a gradual return to normal values. Color-color diagrams in the optical and infrared showed variations during the outburst, with no obvious signature of reddening caused by circumstellar matter. Using Monte-Carlo realizations of star+disk+hotspot models to fit the spectral energy distributions in "quiescence" and at the peak of the outburst, we determined that the mass accretion rate varied from about 2.5x10^-7^M_{sun}_/yr to 1.0x10^-6^M_{sun}_/yr; in addition, the fractional area of the hotspot increased significantly. The multi-wavelength study of the V1118 Ori outburst helped us to understand the variations in spectral energy distributions and demonstrated the interplay between the disk and the stellar magnetosphere in a young, strongly accreting star.

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