- ID:
- ivo://CDS.VizieR/J/ApJS/179/1
- Title:
- The OPTX project: CLANS, CLASXS and CDF-N
- Short Name:
- J/ApJS/179/1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the redshift catalogs for the X-ray sources detected in the Chandra Deep Field-North (CDF-N), the Chandra Large Area Synoptic X-ray Survey (CLASXS), and the Chandra Lockman Area North Survey (CLANS). The catalogs for the CDF-N and CLASXS fields include redshifts from previous work, while the redshifts for the CLANS field are all new. For fluxes above 10^-14^ergs/cm^2^/s (2-8keV) we have redshifts for 76% of the sources. We extend the redshift information for the full sample using photometric redshifts. The goal of the OPTX Project is to use these three surveys, which are among the most spectroscopically complete surveys to date, to analyze the effect of spectral type on the shape and evolution of the X-ray luminosity functions and to compare the optical spectral types with the X-ray spectral properties. We also present the CLANS X-ray catalog. The nine ACIS-I fields cover a solid angle of ~0.6deg^2^ and reach fluxes of 7x10^-16^ergs/cm^2^/s (0.5-2keV) and 3.5x10^-15^ergs/cm^2^/s (2-8keV). We find a total of 761 X-ray point sources. In addition, we present the optical and infrared photometric catalog for the CLANS X-ray sources, as well as updated optical and infrared photometric catalogs for the X-ray sources in the CLASXS and CDF-N fields.
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21922. The OPTX project. III.
- ID:
- ivo://CDS.VizieR/J/ApJ/703/2160
- Title:
- The OPTX project. III.
- Short Name:
- J/ApJ/703/2160
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We compare the optical spectral types with the X-ray spectral properties for a uniformly selected (sources with fluxes greater than the 3{sigma} level and above a flux limit of f(2-8keV)>3.5x10^-15^erg/cm^2^/s), highly spectroscopically complete (>80% for f(2-8keV)>10^-14^erg/cm^2^/s and >60% below) 2-8keV X-ray sample observed in three Chandra fields (CLANS, CLASXS, and the CDF-N) that cover ~1.2deg^2^. For our sample of 645 spectroscopically observed sources, we confirm that there is significant overlap of the X-ray spectral properties, as determined by the effective photon indices, {Gamma}_eff_, obtained from the ratios of the 0.5-2keV to 2-8keV counts, for the different optical spectral types. Thus, one cannot use the X-ray spectral classifications and the optical spectral classifications equivalently. Since it is not understood how X-ray and optical classifications relate to the obscuration of the central engine, we strongly advise against a mixed classification scheme, as it can only complicate the interpretation of X-ray AGN samples.
- ID:
- ivo://CDS.VizieR/J/ApJ/707/L114
- Title:
- The orbit of S2 star around Sgr A*
- Short Name:
- J/ApJ/707/L114
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Two recent papers (Ghez et al. 2008ApJ...689.1044G; Gillessen et al. 2009ApJ...692.1075G) have estimated the mass of and the distance to the massive black hole (MBH) in the center of the Milky Way using stellar orbits. The two astrometric data sets are independent and yielded consistent results, even though the measured positions do not match when simply overplotting the two sets. In this Letter, we show that the two sets can be brought to excellent agreement with each other when we allow for a small offset in the definition of the reference frame of the two data sets. The required offsets in the coordinates and velocities of the origin of the reference frames are consistent with the uncertainties given in Ghez et al. The so-combined data set allows for a moderate improvement of the statistical errors of the mass of and the distance to Sgr A*, but the overall accuracies of these numbers are dominated by systematic errors and the long-term calibration of the reference frame.
- ID:
- ivo://CDS.VizieR/J/AJ/153/147
- Title:
- The orbits of Jupiter's irregular satellites
- Short Name:
- J/AJ/153/147
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report on the improved ephemerides for the irregular Jovian satellites. We used a combination of numerically integrated equations of motion and a weighted least-squares algorithm to fit the astrometric measurements. The orbital fits for 59 satellites are summarized in terms of state vectors, post-fit residuals, and mean orbital elements. The current data set appears to be sensitive to the mass of Himalia, which is constrained to the range of GM=0.13-0.28 km^3^/s^2^. Here, GM is the product of the Newtonian constant of gravitation, G and the body's mass, M. Our analysis of the orbital uncertainties indicates that 11 out of 59 satellites are lost owing to short data arcs. The lost satellites hold provisional International Astronomical Union (IAU) designations and will likely need to be rediscovered.
- ID:
- ivo://CDS.VizieR/J/ApJ/852/7
- Title:
- Theoretical charge exchange X-ray cross sections
- Short Name:
- J/ApJ/852/7
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The fundamental collisional process of charge exchange (CX) has been established as a primary source of X-ray emission from the heliosphere, planetary exospheres, and supernova remnants. In this process, X-ray emission results from the capture of an electron by a highly charged ion from a neutral atom or molecule, to form a highly excited, high-charge state ion. As the captured electron cascades down to the lowest energy level, photons are emitted, including X-rays. To provide reliable CX-induced X-ray spectral models to realistically simulate these environments, line ratios and spectra are computed using theoretical CX cross sections obtained with the multi-channel Landau-Zener (MCLZ), atomic-orbital close-coupling (AOCC), molecular-orbital close-coupling (MOCC), and classical trajectory Monte Carlo methods for various collisional velocities relevant to astrophysics. X-ray spectra were computed for collisions of bare and H-like C to Al ions with H, He, and H_2_ with results compared to available experimental data. Using these line ratios, XSPEC models of CX emission in the northeast rim of the Cygnus Loop supernova remnant and the heliosphere are shown as examples with ion velocity dependence.
- ID:
- ivo://CDS.VizieR/J/ApJ/841/84
- Title:
- Theoretical framework for RR Lyrae. II. MIR data
- Short Name:
- J/ApJ/841/84
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new theoretical period-luminosity-metallicity (PLZ) relations for RR Lyrae stars (RRLs) at Spitzer and WISE wavelengths. The PLZ relations were derived using nonlinear, time-dependent convective hydrodynamical models for a broad range of metal abundances (Z=0.0001-0.0198). In deriving the light curves, we tested two sets of atmospheric models and found no significant difference between the resulting mean magnitudes. We also compare our theoretical relations to empirical relations derived from RRLs in both the field and in the globular cluster M4. Our theoretical PLZ relations were combined with multi-wavelength observations to simultaneously fit the distance modulus, {mu}0, and extinction, A_V_, of both the individual Galactic RRL and of the cluster M4. The results for the Galactic RRL are consistent with trigonometric parallax measurements from Gaia's first data release. For M4, we find a distance modulus of {mu}0=11.257+/-0.035mag with A_V_=1.45+/-0.12mag, which is consistent with measurements from other distance indicators. This analysis has shown that, when considering a sample covering a range of iron abundances, the metallicity spread introduces a dispersion in the PL relation on the order of 0.13mag. However, if this metallicity component is accounted for in a PLZ relation, the dispersion is reduced to ~0.02mag at mid-infrared wavelengths.
21927. Theoretical isochrones
- ID:
- ivo://CDS.VizieR/J/A+AS/106/275
- Title:
- Theoretical isochrones
- Short Name:
- J/A+AS/106/275
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper we present large grids of theoretical isochrones for the initial chemical compositions [Z=0.0004, Y=0.23], [Z=0.004, Y=0.24], [Z=0.008, Y=0.25], [Z=0.02, Y=0.28], and [Z= 0.05, Y=0.352] and ages in the range 4Myr to 16Gyr. These isochrones are derived from stellar models computed with the most recent radiative opacities by Iglesias et al. (1992). In addition to this we present another set with chemical composition [Z=0.001, Y=0.23] based on models calculated with the radiative opacities by Huebner et al. (1977). All the stellar models are followed from the zero age main sequence (ZAMS) to the central carbon ignition for massive stars or to the beginning of the thermally pulsing regime of the asymptotic giant branch phase (TP-AGB) for low and intermediate mass stars. For each isochrone, we give the current mass, effective temperatures, bolometric and visual magnitudes, (U-B), (B-V), (V-R), (V-I), (V-J), (V-H), and (V-K) colors, and the luminosity function for the case of the Salpeter law. In addition to this, integrated magnitudes and colors at several characteristic points are also presented together with the mass of the remnant star when appropriate. The main characteristic that makes this set of isochrones very valuable is based on their extension in mass and chemical composition, besides the calculation of late stages of evolution, beyond the red giant tip till the white dwarf stage after the planetary nebula phase.
- ID:
- ivo://CDS.VizieR/VI/125
- Title:
- Theoretical spectra of red giants and supergiants
- Short Name:
- VI/125
- Date:
- 10 Mar 2022
- Publisher:
- CDS
- Description:
- It remains difficult to interpret the near-IR emission of young stellar populations. One main reason is our incomplete understanding of the spectra of luminous red stars. This work provides a grid of theoretical spectra of red giant (RG) and red supergiant (RSG) stars, that extends through optical and near-IR wavelengths. For the first time, models are also provided with modified surface abundances of C, N and O, as a step towards accounting for the changes that occur due to convective dredge-up in red supergiants or may occur at earlier evolutionary stages in the case of rotation. The aims are (i) to assess how well current models reproduce observed spectra, in particular in the near-IR; (ii) to quantify the effects of the abundance changes on the spectra; and (iii) to determine how these changes affect estimates of fundamental stellar parameters.
- ID:
- ivo://CDS.VizieR/J/A+A/324/366
- Title:
- Theory of motion & ephemerides of Hyperion
- Short Name:
- J/A+A/324/366
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper, we present a new theory of motion for Hyperion, defined like in TASS1.6 for the other Saturn's satellites (Vienne & Duriez, 1995A&A...297..588V), by the osculating saturnicentric orbital elements referred to the equatorial plane of Saturn and to the node of this plane in the mean ecliptic for J2000.0. These elements are expressed as semi-numerical trigonometric series in which the argument of each term is given as an integer combination of 7 natural fundamental arguments (Table 3). These series (Tables 4 to 7) collect all the perturbations caused by Titan on the orbital elements of Hyperion, whose amplitudes are larger than 1km in the long-period terms and than 5km in the short-period ones. Taking also account of the perturbations from other satellites and Sun (Table 8), these series have been fitted to 8136 Earth-based observations of Hyperion in the interval [1874-1985]. The resulting series allows to produce new ephemerides for Hyperion, which have been compared to those previously given by Taylor (1992A&A...265..825T): Using the same set of observations and the same way to weight them, the root mean square (o-c) residual of the present theory is 0.156-arcseconds while the ephemerides of Taylor gives 0.203-arcseconds.
- ID:
- ivo://org.gavo.dc/theossa/q/ssa
- Title:
- TheoSSA - Theoretical Stellar Spectra Access
- Short Name:
- theossa
- Date:
- 27 Dec 2024 08:31:03
- Publisher:
- The GAVO DC team
- Description:
- TheoSSA provides spectral energy distributions based on model atmosphere calculations. Currently, we serve results obtained using the Tübingen NLTE Model Atmosphere Package (TMAP) for hot compact stars.
