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531. A deep survey of galaxies
ID:
ivo://CDS.VizieR/J/AJ/88/1285
Title:
A deep survey of galaxies
Short Name:
J/AJ/88/1285
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a sample of galaxies in six fields, each of area 2 sq deg, located in the North and South galactic polar caps. Photoelectrically calibrated photographic magnitudes and J-F colors have been determined for 512 galaxies brighter than completeness limits which range from F=16.5 to F=17.2 among the fields. Velocities, with typical accuracies of 150km/s have been obtained for 280 of the brighter galaxies. Using these data and previously published work, we determine the general galaxy luminosity function parameters to be M*_F_=-22.7, {alpha}=-1.25, and the mean visual luminosity density of the universe to be {rho}=2.3x10^8^hL_{sun}_/Mpc^3^. Assuming M/L_v_=300h, this implies {OMEGA}~0.26.
532. Adiabatic mass loss in binary stars. II.
ID:
ivo://CDS.VizieR/J/ApJ/812/40
Title:
Adiabatic mass loss in binary stars. II.
Short Name:
J/ApJ/812/40
Date:
21 Oct 2021
Publisher:
CDS
Description:
In the limit of extremely rapid mass transfer, the response of a donor star in an interacting binary becomes asymptotically one of adiabatic expansion. We survey here adiabatic mass loss from Population I stars (Z=0.02) of mass 0.10M_{sun}_-100M_{sun}_ from the zero-age main sequence to the base of the giant branch, or to central hydrogen exhaustion for lower main sequence stars. The logarithmic derivatives of radius with respect to mass along adiabatic mass-loss sequences translate into critical mass ratios for runaway (dynamical timescale) mass transfer, evaluated here under the assumption of conservative mass transfer. For intermediate- and high-mass stars, dynamical mass transfer is preceded by an extended phase of thermal timescale mass transfer as the star is stripped of most of its envelope mass. The critical mass ratio q_ad_ (throughout this paper, we follow the convention of defining the binary mass ratio as q{equiv}M_donor_/M_accretor_) above which this delayed dynamical instability occurs increases with advancing evolutionary age of the donor star, by ever-increasing factors for more massive donors. Most intermediate- or high-mass binaries with nondegenerate accretors probably evolve into contact before manifesting this instability. As they approach the base of the giant branch, however, and begin developing a convective envelope, q_ad_ plummets dramatically among intermediate-mass stars, to values of order unity, and a prompt dynamical instability occurs. Among low-mass stars, the prompt instability prevails throughout main sequence evolution, with q_ad_ declining with decreasing mass, and asymptotically approaching q_ad_=2/3, appropriate to a classical isentropic n=3/2 polytrope. Our calculated q_ad_ values agree well with the behavior of time-dependent models by Chen & Han (2003MNRAS.341..662C) of intermediate-mass stars initiating mass transfer in the Hertzsprung gap. Application of our results to cataclysmic variables, as systems that must be stable against rapid mass transfer, nicely circumscribes the range in q_ad_ as a function of the orbital period in which they are found. These results are intended to advance the verisimilitude of population synthesis models of close binary evolution.
533. Adiabatic Mass Loss in Binary Stars. III.
ID:
ivo://CDS.VizieR/J/ApJ/899/132
Title:
Adiabatic Mass Loss in Binary Stars. III.
Short Name:
J/ApJ/899/132
Date:
14 Mar 2022 07:06:32
Publisher:
CDS
Description:
The distinguishing feature of the evolution of close binary stars is the role played by the mass exchange between the component stars. Whether or not the mass transfer is dynamically stable is one of the essential questions in binary evolution. In the limit of extremely rapid mass transfer, the response of a donor star in an interacting binary becomes asymptotically one of adiabatic expansion. We use the adiabatic mass-loss model to systematically survey the thresholds for dynamical timescale mass transfer over the entire span of possible donor star evolutionary states. We also simulate mass-loss process with isentropic envelopes, the specific entropy of which is fixed to be that at the base of the convective envelope, to artificially mimic the effect of such mass loss in superadiabatic surface convection regions, where the adiabatic approximation fails. We illustrate the general adiabatic response of 3.2M{odot} donor stars at different evolutionary stages. We extend our study to a grid of donor stars with different masses (from 0.1 to 100 M{sun} with Z=0.02) and at different evolutionary stages. We proceed to present our criteria for dynamically unstable mass transfer in both tabular and graphical forms. For red giant branch (RGB) and asymptotic giant branch (AGB) donors in systems with such mass ratios, they may have convective envelopes deep enough to evolve into common envelopes on a thermal timescale, if the donor star overfills its outer Lagrangian radius. Our results show that the RGB and AGB stars tend to be more stable than previously believed, and this may be helpful to explain the abundance of observed post-AGB binary stars with an orbital period of around 1000 days.
534. A diagnostic diagram for Seyfert 2 Galaxies
ID:
ivo://CDS.VizieR/J/ApJS/121/473
Title:
A diagnostic diagram for Seyfert 2 Galaxies
Short Name:
J/ApJS/121/473
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present and discuss a three-dimensional diagnostic diagram for Seyfert 2 galaxies obtained using X-ray and [O III] data on a large sample of objects (reported in the Appendix). The diagram shows the K{alpha} iron line equivalent width as a function of both the column density derived from the photoelectric cutoff and the 2-10 keV flux normalized to the [O III] optical-line flux (the latter corrected for extinction and assumed to be a true indicator of the source intrinsic luminosity). We find that the hard X-ray properties of type 2 objects depend on a single parameter, the absorbing column density along the line of sight, in accordance with the unified model. The diagram can be used to identify Compton-thick sources and to isolate and study peculiar objects. From this analysis we have obtained a column density distribution of Seyfert 2 galaxies that is thought to be a good approximation of the real distribution. A large population of heavily absorbed objects is discovered, including many Compton-thick candidates. Our results indicate that the mean log N_H_cm^-2^ in type 2 Seyfert galaxies is 23.5 and that as many as 23%-30% of sources have N_H_=>10^24^cm^-2^.
535. AD Leo high resolution spectra
ID:
ivo://CDS.VizieR/J/A+A/637/A13
Title:
AD Leo high resolution spectra
Short Name:
J/A+A/637/A13
Date:
21 Oct 2021
Publisher:
CDS
Description:
Flares and coronal mass ejections (CMEs) are important for the evolution of the atmospheres of planets and their potential habitability, particularly for planets orbiting M stars at a distance <0.4AU. Detections of CMEs on these stars have been sparse, and previous studies have therefore modelled their occurrence frequency by scaling up solar relations. However, because the topology and strength of the magnetic fields on M stars is different from that of the Sun, it is not obvious that this approach works well. We used a large number of high-resolution spectra to study flares, CMEs, and their dynamics of the active M dwarf star AD Leo. The results can then be used as reference for other M dwarfs. We obtained more than 2000 high-resolution spectra (R~35000) of the highly active M dwarf AD Leo, which is viewed nearly pole on. Using these data, we studied the behaviour of the spectral lines H{alpha}, H{beta}, and HeI 5876 in detail and investigated asymmetric features that might be Doppler signatures of CMEs. We detected numerous flares. The largest flare emitted 8.32x10^31^erg in H{beta} and 2.12x10^32^erg in H{alpha}. Although the spectral lines in this and other events showed a significant blue asymmetry, the velocities associated with it are far below the escape velocity. Although AD Leo shows a high level of flare activity, the number of CMEs is relatively low. It is thus not appropriate to use the same flare-to-CME relation for M dwarfs as for the Sun.
536. Adopting the UAT as an IVOA vocabulary
ID:
ivo://ivoa.net/std/uat-as-upstream
Title:
Adopting the UAT as an IVOA vocabulary
Short Name:
uat-as-upstream
Date:
25 Jul 2022 13:00:00
Publisher:
IVOA
Description:
The Unified Astronomy Thesaurus (UAT) provides a comprehensive, interlinked set of concepts relevant for astronomy and astrophysics using SKOS. It is taken up in the Virtual Observatory at least for registry subject keywords. For various reasons, it is desirable to have the UAT available subject to the constraints laid down in the IVOA Vocabularies in the VO 2 specification. This Note describes the rationale and the details of the UAT adoption by the IVOA.
537. ADQL Query
ID:
ivo://org.gavo.dc/__system__/adql/query
Title:
ADQL Query
Short Name:
gavoadql
Date:
15 Aug 2024 15:17:03
Publisher:
The GAVO DC team
Description:
An endpoint for submitting ADQL queries to the data center and retrieving the result in various forms.
538. ADQL Query
ID:
ivo://padc.obspm.maser/__system__/adql/query
Title:
ADQL Query
Short Name:
gavoadql
Date:
16 Jul 2024 14:07:24
Publisher:
Paris Astronomical Data Centre
Description:
An endpoint for submitting ADQL queries to the data center and retrieving the result in various forms.
539. ADQL Query
ID:
ivo://xaovo/adql/adql/query
Title:
ADQL Query
Short Name:
gavoadql
Date:
25 Jun 2024 10:32:04
Publisher:
Xinjiang Astronomical Observatory,CAS
Description:
An endpoint for submitting ADQL queries to the data center and retrieving the result in various forms.
540. ADQL Query
ID:
ivo://pds-ppi/__system__/adql/query
Title:
ADQL Query
Short Name:
gavoadql
Date:
21 Aug 2024 19:41:55
Publisher:
NASA Planetary Data System
Description:
An endpoint for submitting ADQL queries to the data center and retrieving the result in various forms.

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