J/AJ/157/177 The evolutionary status of GK subgiants (Abt, 2019)
The evolutionary status of GK subgiants.
Abt H.A.
<Astron. J., 157, 177 (2019)>
=2019AJ....157..177A 2019AJ....157..177A (SIMBAD/NED BibCode)
ADC_Keywords: Stars, giant ; Stars, G-type ; Stars, K-type ; Spectral types ;
Binaries, spectroscopic ; Effective temperatures ;
Radial velocities
Keywords: binaries: spectroscopic - stars: evolution - stars: late-type
Abstract:
Snowden & Young (2005ApJS..157..126S 2005ApJS..157..126S) suggested that the reason why there
are GK subgiants is because they are members of binaries, which would bring
them above the main sequence in an Hertzsprung-Russell (HR) diagram. They
studied a sample of 30 G0-K1 IV stars and were disappointed to find only
two to be spectroscopic binaries. With more accurate radial velocities
I found seven binaries in their samples of subgiants and control stars;
orbital elements are given for those seven. Using Hipparcos parallaxes
and SIMBAD data, I found that nearly all of the G0-K1 IV stars fall on
the evolutionary tracks by Girardi et al. (2000, J/A+AS/141/371) for
Population I stars with masses of 0.9-1.9 M☉ and ages of up to
1010 yr, which are normal parameters for nearby field stars. Therefore
there is no problem regarding the existence of GK subgiants.
Description:
The Snowden-Young (2005ApJS..157..126S 2005ApJS..157..126S) sample of GK class IV stars
north of -20° decl. was selected from the Yale Catalog of Bright Stars
(Hoffleit 1964, Cat. V/50). In addition, Snowden & Young observed 14
additional stars as controls. They were GK III standards of radial
velocities and three known spectroscopic binaries: HD 102928
(Massarotti et al. 2008, J/AJ/135/209), HD 150680 (Katoh et al. 2013,
J/AJ/145/41), and HD 170829 (Katoh et al. 2013, J/AJ/145/41).
Most of the new radial velocities of these bright stars were obtained
with the 1.53 m Harvard Tillinghast telescope at the Oak Ridge Station.
The original digital spectrograph, which gave velocity accuracies of
σ~±0.3 km/s, was replaced in 2011 with an echelle spectrograph
(Tillinghast Reflector Echelle Spectrograph) giving α=±0.10 km/s.
The individual velocities can be found at
http://www.cfa.harvard.edu/~latham/snowden/snowden.orb.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 72 30 The Snowden-Young candidate GK subgiants
table2.dat 72 27 The standard velocity stars, class V, class III,
and three binaries
table3.dat 76 2317 The Latham measures for the subgiants and control
stars
table4.dat 118 8 Spectroscopic orbital elements
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See also:
V/50 : Bright Star Catalogue, 5th Revised Ed. (Hoffleit+, 1991)
J/A+AS/141/371 : Low-mass stars evolutionary tracks & isochrones
(Girardi+, 2000)
J/AJ/135/209 : Rotational and radial velocities 761 HIP giants
(Massarotti+, 2008)
J/AJ/145/41 : Radial velocities of 33 spectroscopic binaries (Katoh+, 2013)
http://www.cfa.harvard.edu/~latham/snowden/snowden.orb : onlive version of
the Latham radial velocities
Byte-by-byte Description of file: table1.dat table2.dat
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Bytes Format Units Label Explanations
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1- 8 A8 --- HD HD number
10- 20 A11 --- SpType MK spectral type from Simbad
22- 26 F5.2 mag MMag [-1.32/5.06] Absolute magnitude M derived from
Hipparcos parallaxe
28- 31 F4.2 [K] logTeff [3.66/3.77]? Log effective temperature (only
in Table 1)
33- 36 F4.2 [Lsun] logL [0.04/1.46]? Log luminosity (logL/L☉)
(only in Table 1)
38- 44 F7.2 km/s RVmean [-100.34/58.99]? Mean radial velocity measured
by Latham
46- 50 F5.2 km/s e_RVmean [0.02/11.01]? Uncertainty in RVmean
52- 54 I3 --- Nrv [4/369]? Number of radial velocity measures
56- 61 A6 --- Bin Information about binary (SBO=spectroscopic
binary with orbital elements; VB=visual
binary)
63- 72 F10.4 d Per [9.3449/16925.685]? Orbital period
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 8 A8 --- HD HD number
10- 11 I2 h RAh Hour of Right Ascension (J2000)
13- 14 I2 min RAm Minute of Right Ascension (J2000)
16- 19 F4.1 s RAs Second of Right Ascension (J2000)
21 A1 --- DE- Sign of the Declination (J2000)
22- 23 I2 deg DEd Degree of Declination (J2000)
25- 26 I2 arcmin DEm Arcminute of Declination (J2000)
28- 29 I2 arcsec DEs Arcsecond of Declination (J2000)
31- 46 A16 --- Obs Observation file identifier
48- 57 F10.4 d MJD [40517.6836/56709.871] Modified Julian Date
59- 65 F7.2 km/s RV [-102.69/60.37] Radial velocity
67- 71 F5.1 cm Ap [33/153.7] Telescope aperture (1)
73- 76 F4.2 --- Phase [0.09/1.03] Orbital phase
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Note (1): The 153.3 cm telescope aperture corresponds to the 1.53-meter Harvard
Tillinghast telescope at the Oak Ridge station and the 153.7 cm telescope
aperture corresponds to the 61-inch Wyeth Reflector telescope at the Oak Ridge
station.
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 6 A6 --- HD HD number
8- 16 F9.4 d Per [9.3449/5266.9] Orbital period
18- 24 F7.4 d e_Per [0.0002/58.5] Uncertainty in Per
26- 32 F7.3 km/s gamma [-58.3/22.76] Center-of-mass velocity γ
34- 38 F5.3 km/s e_gamma [0.03/0.2] Uncertainty in gamma
40- 44 F5.2 km/s K [0.49/14.95] Radial velocity semi-amplitude
46- 49 F4.2 km/s e_K [0.1/1.63] Uncertainty in K
51- 55 F5.3 --- e [0.016/0.82] Eccentricity
57- 61 F5.3 --- e_e [0.01/0.18] Uncertainty in e
63- 67 F5.1 deg omega [23.3/314.1] Argument of periastron ω
69- 72 F4.1 deg e_omega [3.6/45.2] Uncertainty in omega
74- 80 F7.1 d T [47414/52167] Periastron time (JD-2400000)
82- 86 F5.1 d e_T [0.2/117] Uncertainty in T
88- 94 F7.3 Gm asini [0.221/190] Projected semi-major axis
96-101 F6.3 Gm e_asini [0.06/75.2] Uncertainty in asini
103-111 E9.5 Msun f(m) [0.00112/320] Mass function
113-118 F6.4 Msun e_f(m) [0.0041/6.8] Uncertainty in f(m)
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History:
From electronic version of the journal
(End) Prepared by [AAS], Tiphaine Pouvreau [CDS] 31-Jul-2019