2007A&A...476.1317R

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 Query : 2007A&A...476.1317R

2007A&A...476.1317R - Astronomy and Astrophysics, volume 476, 1317-1329 (2007/12-4)

Observations and asteroseismic analysis of the rapidly pulsating hot B subdwarf PG 0911+456.

RANDALL S.K., GREEN E.M., VAN GROOTEL V., FONTAINE G., CHARPINET S., LESSER M., BRASSARD P., SUGIMOTO T., CHAYER P., FAY A., WROBLEWSKI P., DANIEL M., STORY S. and FITZGERALD T.

Abstract (from CDS):

The principal aim of this project is to determine the structural parameters of the rapidly pulsating subdwarf B star PG 0911+456 from asteroseismology. Our work forms part of an ongoing programme to constrain the internal characteristics of hot B subdwarfs with the long-term goal of differentiating between the various formation scenarios proposed for these objects. So far, a detailed asteroseismic interpretation has been carried out for 6 such pulsators, with apparent success. First comparisons with evolutionary theory look promising, however it is clear that more targets are needed for meaningful statistics to be derived. The observational pulsation periods of PG 0911+456 were extracted from rapid time-series photometry using standard Fourier analysis techniques. Supplemented by spectroscopic estimates of the star's mean atmospheric parameters, they were used as a basis for the forward modelling'' approach in asteroseismology. The latter culminates in the identification of one or more optimal'' models that can accurately reproduce the observed period spectrum. This naturally leads to an identification of the oscillations detected in terms of degree l and radial order k, and infers the structural parameters of the target. The high S/N low- and medium resolution spectroscopy obtained led to a refinement of the atmospheric parameters for PG 0911+456, the derived values being Teff=31940±220K, logg=5.767±0.029, and logHe/H=-2.548±0.058. From the photometry it was possible to extract 7 independent pulsation periods in the 150-200 s range with amplitudes between 0.05 and 0.8% of the star's mean brightness. There was no indication of fine frequency splitting over the ∼68-day time baseline, suggesting a very slow rotation rate. An asteroseismic search of parameter space identified several models that matched the observed properties of PG 0911+456 well, one of which was isolated as the optimal'' model on the basis of spectroscopic and mode identification considerations. All the observed pulsations 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 only ∼0.26%, typical of the asteroseismological studies carried out to date for this type of star. The inferred structural parameters of PG 0911+456 are Teff=31940±220K (from spectroscopy), logg=5.777±0.002, M*/M=0.39±0.01, logMenv/M*=-4.69±0.07, R/R=0.133±0.001 and L/L=16.4±0.8. We also derive the absolute magnitude MV=4.82±0.04 and a distance d=930.3±27.4pc.

Journal keyword(s): stars: individual: PG 0911+456 - stars: interiors - stars: horizontal-branch - stars: oscillations

Full paper

 Number of rows : 11
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 HS 0039+4302 HS* 00 42 42.3970259304 +43 19 00.846907716   15.1       sdB 25 0
3 V* DT Lyn HS* 09 14 55.3780066224 +45 23 41.396157600   14.92       sdBO 26 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 157 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 KPD 1930+2752 HS* 19 32 14.8088063952 +27 58 35.445679608 12.80 13.75 13.82     sdB 154 0
9 CD-40 13747 HS* 20 15 04.7880723672 -40 05 44.110361148 11.91 12.09 11.82     sdO 46 0
10 KPD 2109+4401 HS* 21 11 47.6445824136 +44 13 50.620755936 12.14 13.11 13.30 13.64   sdB 64 0
11 Balloon 90100001 HS* 23 15 21.4810390968 +29 05 01.433373360   11.90 12.30     sdB 87 0

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2023.03.21-11:21:08