- ID:
- ivo://nasa.heasarc/rotxraycat
- Title:
- StarswithRotationPeriods&X-RayLuminositiesCatalog
- Short Name:
- ROTXRAYCAT
- Date:
- 27 Sep 2024
- Publisher:
- NASA/GSFC HEASARC
- Description:
- This table contains photometric and derived stellar parameters for a sample of 820 solar and late-type stars (the original table of 824 entries had 4 near-duplicate entries for the stars HD 19668, HD 95188, HD 216803 and HD 285382 which have been removed by the HEASARC) from nearby open clusters and the field, including rotation periods and X-ray luminosities. This sample was used by the authors to study the relationship between rotation and stellar activity and derive a new estimate of the convective turnover time. From an unbiased subset of this sample the power law slope of the unsaturated regime, L<sub>X</sub>/L<sub>bol</sub> ~ R<sub>o</sub><sup>beta</sup>, is fit as beta = -2.70 +/- 0.13. This is inconsistent with the canonical beta = -2 slope to a confidence of 5 sigma, and argues for an additional term in the dynamo number equation. From a simple scaling analysis, this implies Delta(Omega)/Omega ~ Omega<sup>0.7</sup>, i.e. the differential rotation of solar-type stars gradually declines as they spin down. Super-saturation is observed for the fastest rotators in this sample and its parametric dependencies are explored. Significant correlations are found with both the corotation radius and the excess polar updraft, the latter theory providing a stronger dependence and being supported by other observations. The authors estimate mass-dependent empirical thresholds for saturation and super- saturation and map out three regimes of coronal emission. Late F-type stars are shown never to pass through the saturated regime, passing straight from super-saturated to unsaturated X-ray emission. The theoretical threshold for coronal stripping is shown to be significantly different from the empirical saturation threshold (R<sub>o</sub> < 0.13), suggesting it is not responsible. Instead, the authors suggest that a different dynamo configuration is at work in stars with saturated coronal emission. This is supported by a correlation between the empirical saturation threshold and the time when stars transition between convective and interface sequences in rotational spin-down models. This table was created by the HEASARC in March 2012 based on <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/ApJ/743/48">CDS Catalog J/ApJ/743/48</a> file catalog.dat. The original table had 824 entries, including 4 near-duplicate entries for the stars HD 19668, HD 95188, HD 216803 and HD 285382, which have been removed by the HEASARC. This is a service provided by NASA HEASARC .
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Search Results
- ID:
- ivo://vopdc.obspm/usn
- Title:
- Station de Radioastronomie de Nançay
- Short Name:
- USN
- Date:
- 25 Apr 2017 15:00:00
- Publisher:
- Paris Astronomical Data Centre - USN
- Description:
- The main activity at Nançay is the development and application of new radio techniques to fundamental research in astrophysics and astronomy. A number of instruments are operated on behalf of researchers in France and worldwide to conduct scientific programmes of observation of the Universe, including the nearby Earth-Space environment, the study of the Sun and the solar system, and the study of distant stars and galaxies in the Universe.
- ID:
- ivo://CDS.VizieR/J/MNRAS/421/3027
- Title:
- Statisical study of galaxy dust emissions
- Short Name:
- J/MNRAS/421/3027
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use the Herschel-ATLAS survey to conduct the first large-scale statistical study of the submillimetre properties of optically selected galaxies. Using ~80000 r-band selected galaxies from 126deg^2^ of the GAMA survey, we stack into submillimetre imaging at 250, 350 and 500um to gain unprecedented statistics on the dust emission from galaxies at z<0.35. We find that low-redshift galaxies account for 5 per cent of the cosmic 250-um background (4 per cent at 350um; 3 per cent at 500um), of which approximately 60 per cent comes from 'blue' and 20 per cent from 'red' galaxies (rest-frame g-r).
- ID:
- ivo://CDS.VizieR/J/A+A/627/A31
- Title:
- Statistial HATLAS Lensed Objects Selec.
- Short Name:
- J/A+A/627/A31
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The statistical analysis of large sample of strong lensing events can be a powerful tool to extract astrophysical or cosmological valuable information. Their selection using submillimetre galaxies has been demonstrated to be very effective with more than ~200 proposed candidates in the case of Herschel-ATLAS data and several tens in the case of the South Pole Telescope. However, the number of confirmed events is still relatively low, i.e. a few tens, mostly because of the lengthy observational validation process on individual events. In this work we propose a new methodology with a statistical selection approach to increase by a factor of ~5 the number of such events within the Herschel-ATLAS data set. Although the methodology can be applied to address several selection problems, it has particular benefits in the case of the identification of strongly lensed galaxies: objectivity, minimal initial constrains in the main parameter space, and preservation of statistical properties. The proposed methodology is based on the Bhattacharyya distance as a measure of the similarity between probability distributions of properties of two different cross-matched galaxies. The particular implementation for the aim of this work is called SHALOS and it combines the information of four different properties of the pair of galaxies: angular separation, luminosity percentile, redshift, and the ratio of the optical to the submillimetre flux densities. The SHALOS method provides a ranked list of strongly lensed galaxies. The number of candidates within ~340{deg}^2^ of the Herschel-ATLAS surveyed area for the final associated probability, P_tot_>0.7, is 447 and they have an estimated mean amplification factor of 3.12 for a halo with a typical cluster mass. Additional statistical properties of the SHALOS candidates, as the correlation function or the source number counts, are in agreement with previous results indicating the statistical lensing nature of the selected sample.
- ID:
- ivo://CDS.VizieR/J/ApJ/794/159
- Title:
- Statistical analysis of exoplanet surveys
- Short Name:
- J/ApJ/794/159
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We conduct a statistical analysis of a combined sample of direct imaging data, totalling nearly 250 stars. The stars cover a wide range of ages and spectral types, and include five detections ({kappa} And b, two ~60 M_J_ brown dwarf companions in the Pleiades, PZ Tel B, and CD-35 2722B). For some analyses we add a currently unpublished set of SEEDS observations, including the detections GJ 504b and GJ 758B. We conduct a uniform, Bayesian analysis of all stellar ages using both membership in a kinematic moving group and activity/rotation age indicators. We then present a new statistical method for computing the likelihood of a substellar distribution function. By performing most of the integrals analytically, we achieve an enormous speedup over brute-force Monte Carlo. We use this method to place upper limits on the maximum semimajor axis of the distribution function derived from radial-velocity planets, finding model-dependent values of ~30-100 AU. Finally, we model the entire substellar sample, from massive brown dwarfs to a theoretically motivated cutoff at ~5 M_J_, with a single power-law distribution. We find that p(M,a){prop.to}M^-0.65+/-0.60^a^-0.85+/-0.39^ (1{sigma} errors) provides an adequate fit to our data, with 1.0%-3.1% (68% confidence) of stars hosting 5-70 M_J_ companions between 10 and 100 AU. This suggests that many of the directly imaged exoplanets known, including most (if not all) of the low-mass companions in our sample, formed by fragmentation in a cloud or disk, and represent the low-mass tail of the brown dwarfs.
- ID:
- ivo://CDS.VizieR/J/ApJ/786/19
- Title:
- Statistical analysis of solar active regions
- Short Name:
- J/ApJ/786/19
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The subsurface properties of active regions (ARs) prior to their appearance at the solar surface may shed light on the process of AR formation. Helioseismic holography has been applied to samples taken from two populations of regions on the Sun (pre-emergence and without emergence), each sample having over 100 members, that were selected to minimize systematic bias, as described in Paper I (Leka et al. 2013ApJ...762..130L). Paper II (Birch et al. 2013ApJ...762..131B) showed that there are statistically significant signatures in the average helioseismic properties that precede the formation of an AR. This paper describes a more detailed analysis of the samples of pre-emergence regions and regions without emergence based on discriminant analysis. The property that is best able to distinguish the populations is found to be the surface magnetic field, even a day before the emergence time. However, after accounting for the correlations between the surface field and the quantities derived from helioseismology, there is still evidence of a helioseismic precursor to AR emergence that is present for at least a day prior to emergence, although the analysis presented cannot definitively determine the subsurface properties prior to emergence due to the small sample sizes.
- ID:
- ivo://CDS.VizieR/J/A+A/398/363
- Title:
- Statistical properties of exoplanets II
- Short Name:
- J/A+A/398/363
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Table2 file is an extended version of table 2 in the paper. It contains the stellar parameters as well as the number of FeI and FeII lines used (and the rms around the mean value) in the analysis, the spectrograph used, and the derived stellar masses for each star. Velocity files contains the U, V, and W space velocities for the planet host stars used in Figs. 9 and 10.
- ID:
- ivo://CDS.VizieR/J/ApJ/851/91
- Title:
- Statistical studies of solar white-light flares
- Short Name:
- J/ApJ/851/91
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Recently, many superflares on solar-type stars have been discovered as white- light flares (WLFs). The statistical study found a correlation between their energies (E) and durations ({tau}): {tau}{propto}E^0.39^, similar to those of solar hard/soft X-ray flares, {tau}{propto}E^0.2-0.33^. This indicates a universal mechanism of energy release on solar and stellar flares, i.e., magnetic reconnection. We here carried out statistical research on 50 solar WLFs observed with Solar Dynamics Observatory/HMI and examined the correlation between the energies and durations. As a result, the E-{tau} relation on solar WLFs ({tau}{propto}E^0.38^) is quite similar to that on stellar superflares ({tau}{propto}E^0.39^). However, the durations of stellar superflares are one order of magnitude shorter than those expected from solar WLFs. We present the following two interpretations for the discrepancy: (1) in solar flares, the cooling timescale of WLFs may be longer than the reconnection one, and the decay time of solar WLFs can be elongated by the cooling effect; (2) the distribution can be understood by applying a scaling law ({tau}{propto}E^1/3^B^-5/3^) derived from the magnetic reconnection theory. In the latter case, the observed superflares are expected to have 2-4 times stronger magnetic field strength than solar flares.
- ID:
- ivo://CDS.VizieR/J/A+A/587/A31
- Title:
- Statistical test on binary stars non-coevality
- Short Name:
- J/A+A/587/A31
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We develop a statistical test on the expected difference in age estimates of two coeval stars in detached double-lined eclipsing binary systems that are only caused by observational uncertainties. We focus on stars in the mass range [0.8; 1.6] Msun, with an initial metallicity [Fe/H] from -0.55 to 0.55dex, and on stars in the main-sequence phase. The ages were obtained by means of the SCEPtER technique, a maximum-likelihood procedure relying on a pre-computed grid of stellar models. The observational constraints used in the recovery procedure are stellar mass, radius, effective temperature, and metallicity [Fe/H]. To check the effect of the uncertainties affecting observations on the (non-)coevality assessment, the chosen observational constraints were subjected to a Gaussian perturbation before applying the SCEPtER code. We defined the statistic W computed as the ratio of the absolute difference of estimated ages for the two stars over the age of the older one. We determined the critical values of this statistics above which coevality can be rejected in dependence on the mass of the two stars, on the initial metallicity [Fe/H], and on the evolutionary stage of the primary star. The median expected difference in the reconstructed age between the coeval stars of a binary system - caused alone by the observational uncertainties - shows a strong dependence on the evolutionary stage. This ranges from about 20% for an evolved primary star to about 75% for a near ZAMS primary. The median difference also shows an increase with the mass of the primary star from 20% for 0.8M_{sun}_ stars to about 50% for 1.6M_{sun}_ stars. The reliability of these results was checked by repeating the process with a grid of stellar models computed by a different evolutionary code; the median difference in the critical values was only 0.01. We show that the W test is much more sensible to age differences in the binary system components than the alternative approach of comparing the confidence interval of the age of the two stars. We also found that the distribution of W is, for almost all the examined cases, well approximated by beta distributions. The proposed method improves upon the techniques that are commonly adopted for judging the coevality of an observed system. It also provides a result founded on reliable statistics that simultaneously accounts for all the observational uncertainties.
20630. STC utype generator
- ID:
- ivo://org.gavo.dc/stctrans/q/utypes
- Title:
- STC utype generator
- Short Name:
- stcs to utype
- Date:
- 15 Aug 2024 15:17:02
- Publisher:
- The GAVO DC team
- Description:
- This services converts the representations of STC objects in XML, utypes, and STC-S into each other.