- ID:
- ivo://CDS.VizieR/J/ApJ/571/512
- Title:
- Distances of white dwarf stars
- Short Name:
- J/ApJ/571/512
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The most recent version of the Catalog of Spectroscopically Identified White Dwarfs lists 2249 white dwarf stars. Among these stars are 109 white dwarfs that have either reliable trigonometric parallaxes or color-based distance moduli that place them at a distance within 20pc of the Sun. Most of these nearby white dwarfs are isolated stars, but 28 (25% of the sample) are in binary systems, including such well-known systems as Sirius A/B and Procyon A/B. There are also three double degenerate systems in this sample of the local white dwarf population. The sample of local white dwarfs is largely complete out to 13pc, and the local density of white dwarf stars is found to be 5.0+/-0.7x10^-3^pc^-3^, with a corresponding mass density of 3.4+/-0.5x10^-3^M{sun}_/pc^3^
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Search Results
- ID:
- ivo://CDS.VizieR/J/other/NewA/47.81
- Title:
- Distances of X-ray binaries
- Short Name:
- J/other/NewA/47.
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The X-ray luminosity functions of galaxies have become a useful tool for population studies of X-ray binaries in them. The availability of long term light-curves of X-ray binaries with the All Sky X-ray Monitors opens up the possibility of constructing X-ray luminosity functions, by also including the intensity variation effects of the galactic X-ray binaries. We have constructed multiple realizations of the X-ray luminosity functions (XLFs) of Milky Way, using the long term light-curves of sources obtained in the 2-10keV energy band with the RXTE-ASM. The observed spread seen in the value of slope of both HMXB and LMXB XLFs are due to inclusion of variable luminosities of X-ray binaries in construction of these XLFs as well as finite sample effects. XLFs constructed for galactic HMXBs in the luminosity range 10^36^-10^39^erg/s is described by a power-law model with a mean power-law index of -0.48 and a spread due to variability of HMXBs as 0.19. XLFs constructed for galactic LMXBs in the luminosity range 10^36^-10^39^erg/s has a shape of cut-off power-law with mean power-law index of -0.31 and a spread due to variability of LMXBs as 0.07.
- ID:
- ivo://CDS.VizieR/I/347
- Title:
- Distances to 1.33 billion stars in Gaia DR2
- Short Name:
- I/347
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- For the majority of stars in the second Gaia data release, reliable distances cannot be obtained by inverting the parallax. A correct inference procedure must instead be used to account for the nonlinearity of the transformation and the asymmetry of the resulting probability distribution. Here we infer distances to almost all 1.33 billion stars with parallaxes published in the second Gaia data release. This is done using a weak distance prior that varies smoothly as a function of Galactic longitude and latitude according to a Galaxy model. The irreducible uncertainty in the distance estimate is characterized by the lower and upper bounds of an asymmetric confidence interval. Although more precise distances can be estimated for a subset of the stars using additional data (such as photometry), our goal is to provide purely geometric distance estimates, independent of assumptions about the physical properties of, or interstellar extinction towards, individual stars. We analyze the characteristics of the catalog and validate it using clusters.
- ID:
- ivo://CDS.VizieR/I/352
- Title:
- Distances to 1.47 billion stars in Gaia EDR3
- Short Name:
- I/352
- Date:
- 05 Jan 2022
- Publisher:
- CDS
- Description:
- Stellar distances constitute a foundational pillar of astrophysics. The publication of 1.47 billion stellar parallaxes from Gaia is a major contribution to this. Yet despite Gaia's precision, the majority of these stars are so distant or faint that their fractional parallax uncertainties are large, thereby precluding a simple inversion of parallax to provide a distance. Here we take a probabilistic approach to estimating stellar distances that uses a prior constructed from a three-dimensional model of our Galaxy. This model includes interstellar extinction and Gaia's variable magnitude limit. We infer two types of distance. The rst, geometric, uses the parallax together with a direction-dependent prior on distance. The second, photogeometric, additionally uses the colour and apparent magnitude of a star, by exploiting the fact that stars of a given colour have a restricted range of probable absolute magnitudes (plus extinction). Tests on simulated data and external validations show that the photogeometric estimates generally have higher accuracy and precision for stars with poor parallaxes. We provide a catalogue of 1.47 billion geometric and 1.35 billion photogeometric distances together with asymmetric uncertainty measures. Our estimates are quantiles of a posterior probability distribution, so they transform invariably and can therefore also be used directly in the distance modulus (5log10r-5). The catalogue may be downloaded or queried using ADQL at various sites (see http://www.mpia.de/~calj/gedr3 distances.html) where it can also be cross-matched with the Gaia catalogue.
- ID:
- ivo://CDS.VizieR/J/A+A/633/A51
- Title:
- Distances to molecular clouds in SFR
- Short Name:
- J/A+A/633/A51
- Date:
- 14 Jan 2022 08:01:32
- Publisher:
- CDS
- Description:
- Accurate distances to local molecular clouds are critical for understanding the star and planet formation process, yet distance measurements are often obtained inhomogeneously on a cloud-by-cloud basis. We have recently developed a method which combines stellar photometric data with Gaia DR2 parallax measurements in a Bayesian framework to infer the distances of nearby dust clouds to a typical accuracy of ~5%. After refining the technique to target lower latitudes and incorporating deep optical data from DECam in the southern Galactic plane, we have derived a catalog of distances to molecular clouds in Reipurth (2008, Star Formation Handbook, vols I and II) which contains a large fraction of the molecular material in the solar neighborhood. Comparison with distances derived from maser parallax measurements towards the same clouds shows our method produces consistent distances with <10% scatter for clouds across our entire distance spectrum (150pc-2.5kpc). We hope this catalog of homogeneous distances will serve as a baseline for future work.
- ID:
- ivo://CDS.VizieR/J/ApJ/838/107
- Title:
- Distances to RRab stars from WISE and Gaia
- Short Name:
- J/ApJ/838/107
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Pulsating stars, such as Cepheids, Miras, and RR Lyrae stars, are important distance indicators and calibrators of the "cosmic distance ladder," and yet their period-luminosity-metallicity (PLZ) relations are still constrained using simple statistical methods that cannot take full advantage of available data. To enable optimal usage of data provided by the Gaia mission, we present a probabilistic approach that simultaneously constrains parameters of PLZ relations and uncertainties in Gaia parallax measurements. We demonstrate this approach by constraining PLZ relations of type ab RR Lyrae stars in near-infrared W1 and W2 bands, using Tycho-Gaia Astrometric Solution (TGAS) parallax measurements for a sample of ~100 type ab RR Lyrae stars located within 2.5kpc of the Sun. The fitted PLZ relations are consistent with previous studies, and in combination with other data, deliver distances precise to 6% (once various sources of uncertainty are taken into account). To a precision of 0.05mas (1{sigma}), we do not find a statistically significant offset in TGAS parallaxes for this sample of distant RR Lyrae stars (median parallax of 0.8mas and distance of 1.4kpc). With only minor modifications, our probabilistic approach can be used to constrain PLZ relations of other pulsating stars, and we intend to apply it to Cepheid and Mira stars in the near future.
- ID:
- ivo://CDS.VizieR/J/A+A/486/191
- Title:
- Distances towards 6.7GHz methanol masers
- Short Name:
- J/A+A/486/191
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Distances to most star forming regions are determined using kinematics, through the assumption that the observed radial velocity arises from the motion of the source with respect to the Sun resulting from the differential rotation of Galaxy. The primary challenge associated with the application of this technique in the inner Galaxy is the kinematic distance ambiguity. In this work, we aim to resolve the kinematic distance ambiguity towards a sample of 6.7GHz methanol masers, which are signposts of the early stages of massive star formation. We measured 21cm HI absorption spectra using the Very Large Array in C and CnB configurations. A comparison of the maximum velocity of HI absorption with the source velocity and tangent point velocity was used to resolve the kinematic distance ambiguity.
- ID:
- ivo://CDS.VizieR/J/ApJ/747/50
- Title:
- Distance to Cepheids using the Wesenheit function
- Short Name:
- J/ApJ/747/50
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper, we explore the possibility of using the Wesenheit function to derive individual distances to Galactic Cepheids, as the dispersion of the reddening-free Wesenheit function is smaller than the optical period-luminosity (P-L) relation. When compared to the distances from various methods, the averaged differences between our results and published distances range from -0.061 to 0.009, suggesting that the Wesenheit function can be used to derive individual Cepheid distances. We have also constructed Galactic P-L relations and selected Wesenheit functions based on the derived distances. A by-product from this work is the derivation of Large Magellanic Cloud distance modulus when calibrating the Wesenheit function. It is found to be 18.531+/-0.043 mag.
- ID:
- ivo://CDS.VizieR/J/A+A/610/A64
- Title:
- Distance to the clouds in Chamaeleon complex
- Short Name:
- J/A+A/610/A64
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The determination of the distance to dark star-forming clouds is a key parameter to derive the properties of the cloud itself, and of its stellar content. This parameter is still loosely constrained even in nearby star- forming regions. We want to determine the distances to the clouds in the Chamaeleon-Musca complex and to explore the connection between these clouds and the large scale cloud structures in the galaxy. We use the newly estimated distances obtained from the parallaxes measured by the Gaia satellite and included in the Tycho-Gaia Astrometric Solution catalog. When known members of a region are included in this catalog we use their parallaxes to infer the distance to the cloud. Otherwise, we analyze the dependence of the color excess on the distance of the stars and look for a turn-on of this excess, which is a proxy of the position of the front-edge of the star-forming cloud. We are able to measure the distance to the three Chamaeleon clouds. The distance to Chamaeleon I is 179^+11+11^_-10-10_pc, where the quoted uncertainties are statistical and systematic uncertainties, respectively, 20 pc further away than previously assumed. The Chamaeleon II cloud is located at the distance of 181^+6+11^_-5-10_pc, which agrees with previous estimates. We are able to measure for the first time a distance to the Chamaeleon III cloud of 199^+8+12^_-7-11_pc. Finally, the distance of the Musca cloud is smaller than 603^+91+133^_-70-92_pc. These estimates do not allow us to distinguish between the possibility that the Chamaeleon clouds are part of a sheet of clouds parallel to the galactic plane, or perpendicular to it. We have measured a larger distance to the Chamaeleon I cloud than assumed in the past, confirmed the distance to the Chamaeleon II region, and measured for the first time the distance to the Chamaleon III cloud. These values are consistent with the scenario where the three clouds are part of a single large scale structure. Gaia Data Release 2 will allow us to put more stringent constraints on the distances to these clouds by giving us access to parallax measurements for a larger number of members of these regions.
- ID:
- ivo://CDS.VizieR/J/PASP/105/1465
- Title:
- Distant OB Stars in the Galaxy
- Short Name:
- J/PASP/105/1465
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Distances and reddenings have been computed from UBVbeta photometry for 1044 stars in the Stephenson and Sanduleak (1971) "Catalog of Luminous Stars in the Southern Milky Way".
