2009A&A...507..911R


Query : 2009A&A...507..911R

2009A&A...507..911R - Astronomy and Astrophysics, volume 507, 911-921 (2009/11-4)

Observations and asteroseismological analysis of the rapid subdwarf B pulsator EC 09582-1137.

RANDALL S.K., VAN GROOTEL V., FONTAINE G., CHARPINET S. and BRASSARD P.

Abstract (from CDS):

We made photometric and spectroscopic observations of the rapidly pulsating subdwarf B star EC 09582-1137 with the aim of determining the target's fundamental structural parameters from asteroseismology. This analysis forms part of a long-term programme geared towards distinguishing between different proposed formation scenarios for hot B subdwarfs on the basis of their internal characteristics. So far, secure asteroseismic solutions have been computed for 9 of these pulsators, and first comparisons with results from evolutionary calculations look promising. The new data comprise ∼30h of fast time-series photometry obtained with SUSI2 at the NTT on La Silla, Chile, as well as 1h of low-resolution spectroscopy gathered with EMMI, also mounted on the NTT. From the photometry we detected 5 independent harmonic oscillations in the 135-170s period range with amplitudes up to 0.5% of the mean brightness of the star. In addition, we extracted two periodicities interpreted as components of a rotationally split multiplet that indicate a rotation period of the order of 2-5 days. We also recovered the first harmonic of the dominant pulsation, albeit at an amplitude below the imposed 4σ detection threshold. The spectroscopic observations led to the following estimates of the atmospheric parameters of EC 09582-1137: Teff=34806±233K, logg=5.80±0.04, and logN(He)/N(H)=-1.68±0.06. Using the observed oscillations as input, we searched in model parameter space for unique solutions that present a good fit to the data. Under the assumption that the two dominant observed periodicities correspond to radial or dipole modes, we were able to isolate a well-constrained optimal model that agrees with the atmospheric parameters derived from spectroscopy. The observed oscillations are identified with low-order acoustic modes with degree indices l=0,1,2, and 4 and match the computed periods with a dispersion of 0.57%. Non-adiabatic calculations reveal all theoretical modes in the observed period range to be unstable, an important a posteriori consistency check for the validity of the optimal model. The inferred structural parameters of EC 09582-1137 are Teff=34806K (from spectroscopy), logg=5.788±0.004, M*=0.485±0.011M, log(Menv/M*)=-4.39±0.10, R=0.147±0.002R, and L=28.6±1.7L. We additionally derive the absolute magnitude MV=4.44±0.05 and the distance d=1460±66pc.

Abstract Copyright:

Journal keyword(s): stars: fundamental parameters - stars: individual: EC 09582-1137 - stars: oscillations - subdwarfs - stars: variables: general - stars: interiors

Simbad objects: 10

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Number of rows : 10
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2023
#notes
1 PG 0014+068 HS* 00 16 54.2537878176 +07 04 30.043437816   15.3       sdO 70 1
2 V* DT Lyn HS* 09 14 55.3780066224 +45 23 41.396157600   14.92       sdBO 26 0
3 PG 0958-116 HS* 10 00 41.8235310624 -11 51 34.585561008   15.01 15.26     sdB 20 0
4 V* UY Sex HS* 10 50 02.8265487864 -00 00 36.879009588 12.063 13.184 13.474 13.606 13.769 sdO9VIIHe6 156 0
5 Feige 48 HS* 11 47 14.4978515760 +61 15 31.789400364   13.12 13.28     sdB 114 0
6 PG 1219+534 HS* 12 21 29.0914917288 +53 04 36.796062144   12.41       sdB 81 1
7 PG 1325+102 HS* 13 27 48.5600155368 +09 54 51.049107756   13.73 13.98 14.29   sdBO 54 1
8 V* NY Vir HS* 13 38 48.1466908176 -02 01 49.207286748   13.43 13.66 13.75   sdB1VIIHe1 210 1
9 CD-40 13747 HS* 20 15 04.7880723672 -40 05 44.110361148 11.91 12.09 11.82     sdO 45 0
10 Balloon 90100001 HS* 23 15 21.4810390968 +29 05 01.433373360   11.90 12.30     sdB 85 0

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2023.02.01-19:47:10

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