- ID:
- ivo://CDS.VizieR/J/AJ/149/131
- Title:
- Parameters of galactic nearby main-sequence stars
- Short Name:
- J/AJ/149/131
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The mass-luminosity (M-L), mass-radius (M-R), and mass-effective temperature (M-T_eff_) diagrams for a subset of galactic nearby main-sequence stars with masses and radii accurate to {<=}3% and luminosities accurate to {<=}30% (268 stars) has led to a putative discovery. Four distinct mass domains have been identified, which we have tentatively associated with low, intermediate, high, and very high mass main-sequence stars, but which nevertheless are clearly separated by three distinct break points at 1.05, 2.4, and 7M_{sun}_ within the studied mass range of 0.38-32M_{sun}_. Further, a revised mass-luminosity relation (MLR) is found based on linear fits for each of the mass domains identified. The revised, mass-domain based MLRs, which are classical (L{propto}M^{alpha}^), are shown to be preferable to a single linear, quadratic, or cubic equation representing an alternative MLR. Stellar radius evolution within the main sequence for stars with M>1M_{sun}_ is clearly evident on the M-R diagram, but it is not clear on the M-T_eff_ diagram based on published temperatures. Effective temperatures can be calculated directly using the well known Stephan-Boltzmann law by employing the accurately known values of M and R with the newly defined MLRs. With the calculated temperatures, stellar temperature evolution within the main sequence for stars with M>1M_{sun}_ is clearly visible on the M-T_eff_ diagram. Our study asserts that it is now possible to compute the effective temperature of a main-sequence star with an accuracy of ~6%, as long as its observed radius error is adequately small (<1%) and its observed mass error is reasonably small (<6%).
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- ID:
- ivo://CDS.VizieR/J/AJ/154/105
- Title:
- Parameters of 529 Kepler eclipsing binaries
- Short Name:
- J/AJ/154/105
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present precise values of the eccentricity and periastron angle of 529 detached, eccentric, eclipsing stars from the Kepler Eclipsing Binary catalog that were determined by modeling their long cadence data. The temperatures and relative radii of their components as well as their mass ratios were calculated based on approximate values of the empirical relations of MS stars. Around one-third of the secondary components were revealed to be very late dwarfs, some of them possible brown dwarf candidates. Most of our targets fall below the envelope P(1-e^2^)^3/2^=5days. The (e,P) distribution of the known eccentric binaries exhibits a rough trend of increasing eccentricity with the period. The prolonged and continuous Kepler observations allowed us to identify 60 new highly eccentric targets with e>0.5.
- ID:
- ivo://CDS.VizieR/J/AJ/152/6
- Title:
- Parameters of Kepler stars using LAMOST & seismic data
- Short Name:
- J/AJ/152/6
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Asteroseismology is a powerful tool to precisely determine the evolutionary status and fundamental properties of stars. With the unprecedented precision and nearly continuous photometric data acquired by the NASA Kepler mission, parameters of more than 10^4^ stars have been determined nearly consistently. However, most studies still use photometric effective temperatures (Teff) and metallicities ([Fe/H]) as inputs, which are not sufficiently accurate as suggested by previous studies. We adopted the spectroscopic Teff and [Fe/H] values based on the LAMOST low-resolution spectra (R~1,800), and combined them with the global oscillation parameters to derive the physical parameters of a large sample of stars. Clear trends were found between {Delta}logg(LAMOST-seismic) and spectroscopic Teff as well as logg, which may result in an overestimation of up to 0.5dex for the logg of giants in the LAMOST catalog. We established empirical calibration relations for the logg values of dwarfs and giants. These results can be used for determining the precise distances to these stars based on their spectroscopic parameters.
- ID:
- ivo://CDS.VizieR/J/AJ/158/73
- Title:
- Parameters of OB stars & their bow shock nebulae
- Short Name:
- J/AJ/158/73
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Second only to initial mass, the rate of wind-driven mass loss determines the final mass of a massive star and the nature of its remnant. Motivated by the need to reconcile observational values and theory, we use a recently vetted technique to analyze the mass-loss rates in a sample of OB stars that generate bow shock nebulae. We measure peculiar velocities from new Gaia parallax and proper motion data and their spectral types from new optical and infrared spectroscopy. For our sample of 70 central stars in morphologically selected bow shock nebulae, 67 are OB stars. The median peculiar velocity is 11 km/s, significantly smaller than classical "runaway star" velocities. Mass-loss rates for these O and early B stars agree with recently lowered theoretical predictions, ranging from ~10^-7^ M_{sun}_/yr for mid-O dwarfs to 10^-9^ M_{sun}_/yr for late O dwarfs - a factor of about 2.7 lower than the often-used Vink et al. (2000A&A...362..295V, 2001A&A...369..574V) formulation. Our results provide the first observational mass-loss rates for B0-B3 dwarfs and giants - 10^-9^ to 10^-8^ M_{sun}_/yr. We find evidence for an increase in the mass-loss rates below a critical effective temperature, consistent with predictions of the bistability phenomenon in the range T_eff_=19000-27000 K. The sample exhibits a correlation between modified wind momentum and luminosity, consistent in slope but lower by 0.43 dex in magnitude compared to canonical wind-luminosity relations. We identify a small subset of objects deviating most significantly from theoretical expectations as probable radiation-driven bow wave nebulae by virtue of their low stellar-to-nebular luminosity ratios. For these, the inferred mass-loss rates must be regarded as upper limits.
- ID:
- ivo://CDS.VizieR/J/MNRAS/462/2295
- Title:
- 25 parsec local white dwarf population
- Short Name:
- J/MNRAS/462/2295
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have extended our detailed survey of the local white dwarf population from 20 to 25pc, effectively doubling the sample volume, which now includes 232 stars. In the process, new stars within 20 pc have been added, a more uniform set of distance estimates as well as improved spectral and binary classifications are available. The present 25pc sample is estimated to be about 68 per cent complete (the corresponding 20pc sample is now 86 per cent complete). The space density of white dwarfs is unchanged at 4.8+/-0.5x10^-3^pc^-3^. This new study includes a white dwarf mass distribution and luminosity function based on the 232 stars in the 25pc sample. We find a significant excess of single stars over systems containing one or more companions (74 per cent versus 26 per cent). This suggests mechanisms that result in the loss of companions during binary system evolution. In addition, this updated sample exhibits a pronounced deficiency of nearby 'Sirius-like' systems. 11 such systems were found within the 20pc volume versus only one additional system found in the volume between 20 and 25pc. An estimate of white dwarf birth rates during the last ~8Gyr is derived from individual remnant cooling ages. A discussion of likely ways new members of the local sample may be found is provided.
- ID:
- ivo://CDS.VizieR/J/ApJ/834/207
- Title:
- Periodicity & magnitude of Kepler LCs variation
- Short Name:
- J/ApJ/834/207
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The variation of a stellar light curve owing to rotational modulation by magnetic features (starspots and faculae) on the star's surface can be used to investigate the magnetic properties of the host star. In this paper, we use the periodicity and magnitude of the light-curve variation as two proxies to study the stellar magnetic properties for a large sample of G-type main sequence Kepler targets, for which the rotation periods were recently determined. By analyzing the correlation between the two magnetic proxies, it is found that: (1) the two proxies are positively correlated for most of the stars in our sample, and the percentages of negative, zero, and positive correlations are 4.27%, 6.81%, and 88.91%, respectively; (2) negative correlation stars cannot have a large magnitude of light-curve variation; and (3) with the increase of rotation period, the relative number of positive correlation stars decreases and the negative correlation one increases. These results indicate that stars with shorter rotation period tend to have positive correlation between the two proxies, and a good portion of the positive correlation stars have a larger magnitude of light-curve variation (and hence more intense magnetic activities) than negative correlation stars.
- ID:
- ivo://CDS.VizieR/J/ApJS/236/51
- Title:
- PGCCs in lambda Orionis complex. II. Cores at 850um
- Short Name:
- J/ApJS/236/51
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Based on the 850{mu}m dust continuum data from SCUBA-2 at James Clerk Maxwell Telescope (JCMT), we compare overall properties of Planck Galactic Cold Clumps (PGCCs) in the {lambda} Orionis cloud to those of PGCCs in the Orion A and B clouds. The Orion A and B clouds are well-known active star-forming regions, while the {lambda} Orionis cloud has a different environment as a consequence of the interaction with a prominent OB association and a giant HII region. PGCCs in the {lambda} Orionis cloud have higher dust temperatures (T_d_=16.13+/-0.15K) and lower values of dust emissivity spectral index ({beta}=1.65+/-0.02) than PGCCs in the Orion A (T_d_=13.79+/-0.21K, {beta}=2.07+/-0.03) and Orion B (T_d_=13.82+/-0.19K, {beta}=1.96+/-0.02) clouds. We find 119 substructures within the 40 detected PGCCs and identify them as cores. Out of a total of 119 cores, 15 cores are discovered in the {lambda} Orionis cloud, while 74 and 30 cores are found in the Orion A and B clouds, respectively. The cores in the {lambda} Orionis cloud show much lower mean values of size R=0.08pc, column density N(H_2_)=(9.5+/-1.2)x10^22^cm^-2^, number density n(H_2_)=(2.9+/-0.4)x10^5^cm^-3^, and mass M_core_=1.0+/-0.3M_{sun}_ compared to the cores in the Orion A [R=0.11pc, N(H_2_)=(2.3+/-0.3)x10^23^cm^-2^, n(H_2_)=(3.8+/-0.5)x10^5^cm^-3^, and M_core_=2.4+/-0.3M_{sun}_] and Orion B [R=0.16pc, N(H_2_)=(3.8+/-0.4)x10^23^cm^-2^, n(H_2_)=(15.6+/-1.8)x10^5^cm^-3^, and M_core_=2.7+/-0.3M_{sun}_] clouds. These core properties in the {lambda} Orionis cloud can be attributed to the photodissociation and external heating by the nearby H II region, which may prevent the PGCCs from forming gravitationally bound structures and eventually disperse them. These results support the idea of negative stellar feedback on core formation.
- ID:
- ivo://CDS.VizieR/J/ApJ/762/123
- Title:
- PHAT. IV. Initial Mass Function
- Short Name:
- J/ApJ/762/123
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a probabilistic approach for inferring the parameters of the present-day power-law stellar mass function (MF) of a resolved young star cluster. This technique (1) fully exploits the information content of a given data set; (2) can account for observational uncertainties in a straightforward way; (3) assigns meaningful uncertainties to the inferred parameters; (4) avoids the pitfalls associated with binning data; and (5) can be applied to virtually any resolved young cluster, laying the groundwork for a systematic study of the high-mass stellar MF (M>~1M_{sun}_). Using simulated clusters and Markov Chain Monte Carlo sampling of the probability distribution functions, we show that estimates of the MF slope, {alpha}, are unbiased and that the uncertainty, {Delta}{alpha}, depends primarily on the number of observed stars and on the range of stellar masses they span, assuming that the uncertainties on individual masses and the completeness are both well characterized. Using idealized mock data, we compute the theoretical precision, i.e., lower limits, on {alpha}, and provide an analytic approximation for {Delta}{alpha} as a function of the observed number of stars and mass range. Comparison with literature studies shows that ~3/4 of quoted uncertainties are smaller than the theoretical lower limit. By correcting these uncertainties to the theoretical lower limits, we find that the literature studies yield <{alpha}>=2.46, with a 1{sigma} dispersion of 0.35dex. The precision on MF slope recovery in this paper are lower limits, as we do not explicitly consider all possible sources of uncertainty, including dynamical effects (e.g., mass segregation), unresolved binaries, and non-coeval populations.
- ID:
- ivo://CDS.VizieR/J/AJ/108/2338
- Title:
- Photographic astrometry. VIII.
- Short Name:
- J/AJ/108/2338
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- 300 trigonometric parallaxes, 15 revised binary-star orbits, and 24 mass ratios are listed and annotated.
- ID:
- ivo://CDS.VizieR/J/AZh/91/130
- Title:
- Photographic catalog of wide visual double stars
- Short Name:
- J/AZh/91/130
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of the long-term uniform observations of visual double and multiple stars by 26-inch refractor. Set of observations (all plates) is measured with one measuring device for each star. For 259 pairs of visual double stars which were included in 194 systems, relative positions are calculated. For 127 pairs relative motions are also calculated. For 48 stars with well certain parallaxes from the Gipparkos catalog also the bottom limits for the total masses of systems are received under condition of the elliptic orbit is possible (dynamic mass). Comparison of accuracy of three measuring devices, which were applied to measurement of photographic plates, is executed. It is shown that differences in distances between the components, measured on the different measuring devices can reach 0.2" that proves advantage of uniform observations.
