2006ApJ...648..637R


Query : 2006ApJ...648..637R

2006ApJ...648..637R - Astrophys. J., 648, 637-651 (2006/September-1)

Further observations and analysis of the rapidly pulsating subdwarf B star EC 20117-4014.

RANDALL S.K., FONTAINE G., CHARPINET S., LYNAS-GRAY A.E., LOPES I.P., O'TOOLE S.J. and BRASSARD P.

Abstract (from CDS):

We present the results of further observations and the subsequent analysis of the rapidly pulsating subdwarf B star EC 20117-4014. Despite our efforts, the only pulsations detected were those already reported by O'Donoghue et al., at 137.3, 142.1, and 157.4 s. We attempted a detailed asteroseismological analysis by thoroughly exploring the four-dimensional parameter space defining our equilibrium stellar structures [Teff, logg, M*, logq(H)] in search of models that could account precisely for the three observed periodicities. We were able to isolate just two potential families of optimal models, one of which is to be preferred on the basis of the period fit achieved and the surface gravity inferred. To proceed, we used external constraints on the effective temperature from published independent optical spectroscopy. Unfortunately, the contamination of the optical spectrum of EC 20117-4014 made it hard to quantify the uncertainties on the estimated spectroscopic temperature of ∼34,800 K, and consequently, we adopted the conservative point of view that the true value would lie somewhere in the rather broad interval 32,800-36,800 K. Despite this limitation, leading to less accurate estimates of structural parameters than has been possible before for isolated pulsating EC 14026 stars, we still find that our asteroseismological exercise has been quite fruitful. Indeed, on the basis of our current models, we find that EC 20117-4014 would have a (logarithmic) surface gravity in the range 5.848-5.864 dex, a total mass in the range 0.50-0.59 M, and a (logarithmic) fractional mass of its H envelope in the interval from -4.10 to -4.25 dex. From these primary parameters, we obtained useful estimates of secondary quantities such as the radius, the luminosity, the absolute visual magnitude, and the distance.

Abstract Copyright:

Journal keyword(s): stars: individual (EC 20117-4014) - Stars: Interiors - Stars: Oscillations - Stars: Subdwarfs

Simbad objects: 9

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Number of rows : 9
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2022
#notes
1 PG 0014+068 HS* 00 16 54.2537878176 +07 04 30.043437816   15.3       sdO 70 1
2 V* UY Sex HS* 10 50 02.8265487864 -00 00 36.879009588 12.063 13.184 13.474 13.606 13.769 sdO9VIIHe6 154 0
3 Feige 48 HS* 11 47 14.4978515760 +61 15 31.789400364   13.12 13.28     sdB 113 0
4 PG 1219+534 HS* 12 21 29.0914917288 +53 04 36.796062144   12.41       sdB 80 1
5 V* V361 Hya ** 14 05 33.00 -27 01 34.1   15.45 15.26 15.16   sdB+ 113 0
6 PG 1605+072 HS* 16 08 03.6872637792 +07 04 28.748468964   12.53 12.83 13.18   sdB0.2VIHe3 125 0
7 KPD 1930+2752 HS* 19 32 14.8088063952 +27 58 35.445679608 12.80 13.75 13.82     sdB 153 0
8 GSC 07952-01358 * 20 15 03.2374494384 -40 05 29.189479200   13.0 12.12     ~ 5 0
9 CD-40 13747 HS* 20 15 04.7880723672 -40 05 44.110361148 11.91 12.09 11.82     sdO 45 0

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2022.09.27-04:12:46

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