scholarly journals High-precision Dynamical Masses of Pre-main-sequence Stars with ALMA and Gaia

2019 ◽  
Vol 874 (2) ◽  
pp. 136 ◽  
Author(s):  
Patrick D. Sheehan ◽  
Ya-Lin Wu ◽  
Josh A. Eisner ◽  
John J. Tobin
Keyword(s):  
High Precision ◽  
Main Sequence ◽  
Main Sequence Stars ◽  
Dynamical Masses

High-precision abundances of elements in stars with asteroseismic ages

2017 ◽  
Vol 13 (S334) ◽  
pp. 166-169
Author(s):  
P. E. Nissen ◽  
V. Silva Aguirre ◽  
J. Christensen-Dalsgaard ◽  
R. Collet ◽  
F. Grundahl ◽  
...  
Keyword(s):  
High Precision ◽  
Main Sequence ◽  
Potential Problem ◽  
Galactic Evolution ◽  
The Other ◽  
Main Sequence Stars ◽  
Refractory Elements ◽  
Other Hand ◽  
New Information ◽  
Oscillation Frequencies

AbstractHigh-precision abundances of elements have been derived from HARPS-N spectra of F and G main-sequence stars having ages determined from oscillation frequencies delivered by the Kepler mission. The tight relations between abundance ratios of refractory elements, e.g., [Mg/Fe] and [Y/Mg], and stellar age previously found for solar twin stars are confirmed. These relations provide new information on nucleosynthesis and Galactic evolution. Abundance ratios between volatile and refractory elements, e.g., [C/Fe] and [O/Fe], show on the other hand a significant scatter at a given age, which may be related to planet-star interactions. This is a potential problem for chemical tagging studies.

scholarly journals Dynamical Masses for Pre–Main‐Sequence Stars: A Preliminary Physical Orbit for V773 Tau A

2007 ◽  
Vol 670 (2) ◽  
pp. 1214-1224 ◽  
Author(s):  
Andrew F. Boden ◽  
Guillermo Torres ◽  
Anneila I. Sargent ◽  
Rachel L. Akeson ◽  
John M. Carpenter ◽  
...  
Keyword(s):  
Main Sequence ◽  
Main Sequence Stars ◽  
Dynamical Masses

scholarly journals Anomalous Spectral Types and Intrinsic Colors of Young Stars

2015 ◽  
Vol 10 (S314) ◽  
pp. 85-90 ◽  
Author(s):  
Mark J. Pecaut
Keyword(s):  
Infrared Spectra ◽  
Spectral Type ◽  
Main Sequence ◽  
Near Infrared ◽  
Systematic Errors ◽  
Optical Spectra ◽  
Young Stars ◽  
Main Sequence Stars ◽  
Near Infrared Spectra ◽  
Dynamical Masses

AbstractWe highlight differences in spectral types and intrinsic colors observed in pre-main sequence (pre-MS) stars. Spectral types of pre-MS stars are wavelength-dependent, with near-infrared spectra being 3-5 spectral sub-classes later than the spectral types determined from optical spectra. In addition, the intrinsic colors of young stars differ from that of main-sequence stars at a given spectral type. We caution observers to adopt optical spectral types over near-infrared types, since Hertzsprung-Russell (H-R) diagram positions derived from optical spectral types provide consistency between dynamical masses and theoretical evolutionary tracks. We also urge observers to deredden pre-MS stars with tabulations of intrinsic colors specifically constructed for young stars, since their unreddened colors differ from that of main sequence dwarfs. Otherwise, V-band extinctions as much as ~0.6 mag erroneously higher than the true extinction may result, which would introduce systematic errors in the H-R diagram positions and thus bias the inferred ages.

scholarly journals Astrometric study of Gaia DR2 stars for interstellar communication

2020 ◽  
Vol 19 (4) ◽  
pp. 308-313
Author(s):  
Naoki Seto ◽  
Kazumi Kashiyama
Keyword(s):  
High Precision ◽  
Main Sequence ◽  
Opening Angle ◽  
Main Sequence Stars ◽  
Extraterrestrial Intelligence ◽  
Data Release ◽  
Interstellar Communication ◽  
Host Stars ◽  
Gaia Dr2 ◽  
Better Than

AbstractWe discuss the prospects of high precision pointing of our transmitter to habitable planets around Galactic main sequence stars. For an efficient signal delivery, the future sky positions of the host stars should be appropriately extrapolated with accuracy better than the beam opening angle Θ of the transmitter. Using the latest data release (DR2) of Gaia, we estimate the accuracy of the extrapolations individually for 4.7 × 107 FGK stars, and find that the total number of targets could be ~107 for the accuracy goal better than 1″. Considering the pairwise nature of communication, our study would be instructive also for SETI (Search for Extraterrestrial Intelligence), not only for sending signals outward.

scholarly journals uvby photometry with a CCD

1986 ◽  
Vol 118 ◽  
pp. 267-268
Author(s):  
Barbara J. Anthony-Twarog
Keyword(s):  
High Precision ◽  
Main Sequence ◽  
Open Cluster ◽  
Main Sequence Stars ◽  
Apparent Absence ◽  
Ccd Detector ◽  
Sufficient Precision

Initial observations using uvby filters with a CCD detector were completed in June of 1985, using the Cerro Tololo 4m PFCCD system. It has been possible to derive all Strömgren indices (b-y, m1 and c1) for V<18 from frames with acceptable integration times. For fields in the open cluster IC 4651, averages of 2 to 3 frames with exposure times of 15, 20, 40, and 500 seconds for the y, b, v, and u filters, yielded high precision magnitudes and indices for V<15. Exposure times up to 5 times longer were required for the v and u filters in order to derive c1 indices of sufficient precision for stars with V between 15 and 16. One result of our survey is the apparent absence of main sequence stars below V = 15.

scholarly journals HIGH-PRECISION RADIO AND INFRARED ASTROMETRY OF LSPM J1314+1320AB. II. TESTING PRE-MAIN-SEQUENCE MODELS AT THE LITHIUM DEPLETION BOUNDARY WITH DYNAMICAL MASSES

2016 ◽  
Vol 827 (1) ◽  
pp. 23 ◽  
Author(s):  
Trent J. Dupuy ◽  
Jan Forbrich ◽  
Aaron Rizzuto ◽  
Andrew W. Mann ◽  
Kimberly Aller ◽  
...  
Keyword(s):  
High Precision ◽  
Main Sequence ◽  
Lithium Depletion ◽  
Dynamical Masses

scholarly journals The position of confirmed pre-main sequence pulsators in the H-R diagram and an overview of their properties

2013 ◽  
Vol 9 (S301) ◽  
pp. 149-152
Author(s):  
Konstanze Zwintz ◽  
Mike Casey ◽  
David Guenther
Keyword(s):  
Time Series ◽  
High Resolution ◽  
High Precision ◽  
Parameter Space ◽  
Main Sequence ◽  
Evolutionary Stage ◽  
Main Sequence Stars ◽  
Pms Stars ◽  
Space Data ◽  
Established Group

AbstractPre-main sequence (PMS) stars can become vibrationally unstable during their evolution to the zero-age main sequence (ZAMS). As they gain their energy from gravitational contraction and have not started nuclear fusion in their cores yet, their inner structures are significantly different to those of (post-) main sequence stars and can be probed by asteroseismology.Using photometric time series from ground and from space (MOST, CoRoT & Spitzer) the number of confirmed pulsating pre-main sequence stars has increased significantly within the last years and allowed to find members of new classes of PMS pulsators. Apart from the well-established group of δ Scuti type PMS stars, members of the groups of PMS γ Doradus, PMS δ Scuti – γ Doradus hybrid and PMS slowly pulsating B (SPB) stars have been discovered. For five PMS δ Scuti candidates, space photometry has revealed that they only show irregular variability, but no pulsations.The unique high-precision space data were combined with dedicated high-resolution spectra to probe the parameter space in the H-R diagram and study the properties of PMS pulsators in comparison to their evolutionary stage.

scholarly journals Dynamical Masses for Low‐Mass Pre–Main‐Sequence Stars: A Preliminary Physical Orbit for HD 98800 B

2005 ◽  
Vol 635 (1) ◽  
pp. 442-451 ◽  
Author(s):  
Andrew F. Boden ◽  
Anneila I. Sargent ◽  
Rachel L. Akeson ◽  
John M. Carpenter ◽  
Guillermo Torres ◽  
...  
Keyword(s):  
Main Sequence ◽  
Main Sequence Stars ◽  
Low Mass ◽  
Dynamical Masses

Chromospheric activity as a function of age in main-sequence stars

1966 ◽  
Vol 24 ◽  
pp. 40-43
Author(s):  
O. C. Wilson ◽  
A. Skumanich
Keyword(s):  
Main Sequence ◽  
The Sun ◽  
Main Sequence Stars ◽  
Tentative Conclusion ◽  
Chromospheric Activity ◽  
General Field ◽  
Large Clusters

Evidence previously presented by one of the authors (1) suggests strongly that chromospheric activity decreases with age in main sequence stars. This tentative conclusion rests principally upon a comparison of the members of large clusters (Hyades, Praesepe, Pleiades) with non-cluster objects in the general field, including the Sun. It is at least conceivable, however, that cluster and non-cluster stars might differ in some fundamental fashion which could influence the degree of chromospheric activity, and that the observed differences in chromospheric activity would then be attributable to the circumstances of stellar origin rather than to age.

On The Radii of Ap Stars

1976 ◽  
Vol 32 ◽  
pp. 49-55 ◽  
Author(s):  
F.A. Catalano ◽  
G. Strazzulla
Keyword(s):  
Observational Data ◽  
Line Width ◽  
Main Sequence ◽  
Main Sequence Stars ◽  
Ap Stars

SummaryFrom the analysis of the observational data of about 100 Ap stars, the radii have been computed under the assumption that Ap are main sequence stars. Radii range from 1.4 to 4.9 solar units. These values are all compatible with the Deutsch's period versus line-width relation.

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