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See detailStructural and core parameters of the hot B subdwarf KPD 0629-0016 from CoRoT g-mode asteroseismology
Van Grootel, Valérie ULg; Charpinet, Stéphane; Fontaine, Gilles et al

in Astronomy and Astrophysics (2010), 524

Context. The asteroseismic exploitation of long period, g-mode hot B subdwarf pulsators (sdBVs), undermined so far by limitations associated with ground-based observations, has now become possible, thanks ... [more ▼]

Context. The asteroseismic exploitation of long period, g-mode hot B subdwarf pulsators (sdBVs), undermined so far by limitations associated with ground-based observations, has now become possible, thanks to high quality data obtained from space such as those recently gathered with the CoRoT (COnvection, ROtation, and planetary Transits) satellite. Aims. We propose a detailed seismic analysis of the sdBVs star KPD 0629-0016, the first compact pulsator monitored with CoRoT, using the g-mode pulsations recently uncovered by that space-borne observatory during short run SRa03. Methods. We use a forward modeling approach on the basis of our latest sdB models, which are now suitable for the accurate com- putation of the g-mode pulsation properties. The simultaneous match of the independent periods observed in KPD 0629-0016 with those of the models leads objectively to the identification of the pulsation modes and, more importantly, to the determination of the structural and core parameters of the star. Results. The optimal model we found closely reproduces the 18 observed periods retained in our analysis at a 0.23% level on av- erage. These are identified as low-degree (l = 1 and 2), intermediate-order (k = −9 through −74) g-modes. The structural and core parameters for KPD 0629-0016 are the following (formal fitting errors only): Teff = 26 290 ± 530 K, log g = 5.450 ± 0.034, M∗ = 0.471 ± 0.002 M⊙, log (Menv/M∗) = −2.42 ± 0.07, log (1 − Mcore/M∗) = −0.27 ± 0.01, and Xcore(C+O) = 0.41 ± 0.01. We addition- ally derive an age of 42.6 ± 1.0 Myr after the zero-age extreme horizontal branch, the radius R = 0.214 ± 0.009 R⊙, the luminosity L = 19.7 ± 3.2 L⊙, the absolute magnitude MV = 4.23 ± 0.13, the reddening index E(B − V) = 0.128 ± 0.023, and the distance d = 1190 ± 115 pc. Conclusions. The advent of high-precision time-series photometry from space with instruments like CoRoT now allows as demon- strated with KPD 0629-0016 the full exploitation of g-modes as deep probes of the internal structure of these stars, in particular for determining the mass of the convective core and its chemical composition. [less ▲]

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See detailEXOTIME: searching for planets around pulsating subdwarf B stars
Schuh, Sonja; Silvotti, Roberto; Lutz, Ronny et al

in Astrophysics & Space Science (2010, October), 329

In 2007, a companion with planetary mass was found around the pulsating subdwarf B star V391 Pegasi with the timing method, indicating that a previously undis- covered population of substellar companions ... [more ▼]

In 2007, a companion with planetary mass was found around the pulsating subdwarf B star V391 Pegasi with the timing method, indicating that a previously undis- covered population of substellar companions to apparently single subdwarf B stars might exist. Following this serendip- itous discovery, the EXOTIME (http://www.na.astro.it/ ~silvotti/exotime/) monitoring program has been set up to follow the pulsations of a number of selected rapidly pul- sating subdwarf B stars on time scales of several years with two immediate observational goals: (1) determine P ̇ of the pulsational periods P (2) search for signatures of substellar companions in O– C residuals due to periodic light travel time variations, which would be tracking the central star’s companion- induced wobble around the centre of mass These sets of data should therefore, at the same time, on the one hand be useful to provide extra constraints for classical asteroseismological exercises from the P ̇ (comparison with “local” evolutionary models), and on the other hand allow one to investigate the preceding evolution of a target in terms of possible “binary” evolution by extending the otherwise unsuccessful search for companions to potentially very low masses. While timing pulsations may be an observationally ex- pensive method to search for companions, it samples a dif- ferent range of orbital parameters, inaccessible through or- bital photometric effects or the radial velocity method: the latter favours massive close-in companions, whereas the timing method becomes increasingly more sensitive toward wider separations. In this paper we report on the status of the on-going ob- servations and coherence analysis for two of the currently five targets, revealing very well-behaved pulsational charac- teristics in HS 0444+0458, while showing HS 0702+6043 to be more complex than previously thought. [less ▲]

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See detailEarly asteroseismic results from Kepler: structural and core parameters of the hot B subdwarf KPD 1943+4058 as inferred from g-mode oscillations
Van Grootel, Valérie ULg; Charpinet, Stéphane; Fontaine, Gilles et al

in Astrophysical Journal Letters (2010), 718

We present a seismic analysis of the pulsating hot B subdwarf KPD 1943+4058 (KIC 005807616) on the basis of the long-period, gravity-mode pulsations recently uncovered by Kepler. This is the first time ... [more ▼]

We present a seismic analysis of the pulsating hot B subdwarf KPD 1943+4058 (KIC 005807616) on the basis of the long-period, gravity-mode pulsations recently uncovered by Kepler. This is the first time that g-mode seismology can be exploited quantitatively for stars on the extreme horizontal branch, all previous successful seismic analyses having been confined so far to short-period, p-mode pulsators. We demonstrate that current models of hot B subdwarfs can quite well explain the observed g-mode periods, while being consistent with independent constraints provided by spectroscopy. We identify the 18 pulsations retained in our analysis as low- degree (l = 1 and 2), intermediate-order (k = −9 through −58) g-modes. The periods (frequencies) are recovered, on average, at the 0.22% level, which is comparable to the best results obtained for p-mode pulsators. We infer the following structural and core parameters for KPD 1943+4058 (formal fitting uncertainties only): Teff = 28,050 ± 470 K, log g = 5.52 ± 0.03, M∗ = 0.496 ± 0.002 M⊙, log (Menv/M∗) = −2.55 ± 0.07, log (1 − Mcore/M∗) = −0.37 ± 0.01, and Xcore (C+O) = 0.261 ± 0.008. We additionally derive the age of the star since the zero-age extended horizontal branch 18.4 ± 1.0 Myr, the radius R = 0.203 ± 0.007 R⊙, the luminosity L = 22.9 ± 3.13 L⊙, the absolute magnitude MV = 4.21 ± 0.11, the reddening index E(B − V ) = 0.094 ± 0.017, and the distance d = 1180 ± 95 pc. [less ▲]

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See detailStructural and core parameters of the hot B subdwarf KPD 1943+4058 as inferred from g-mode oscillations
Van Grootel, Valérie ULg; Charpinet, Stéphane; Fontaine, Gilles et al

Conference (2010, June)

We present a seismic analysis of the pulsating hot B subdwarf KPD 1943+4058 (KIC 005807616) on the basis of the long-period, gravity-mode pulsations recently uncovered by Kepler. This is the first time ... [more ▼]

We present a seismic analysis of the pulsating hot B subdwarf KPD 1943+4058 (KIC 005807616) on the basis of the long-period, gravity-mode pulsations recently uncovered by Kepler. This is the first time that g-mode seismology can be exploited quantitatively for stars on the extreme horizontal branch, all previous successful seismic analyses having been confined so far to short-period, p-mode pulsators. We demonstrate that current models of hot B subdwarfs can explain quite well the observed g-mode periods, while being consistent with independent constraints provided by spectroscopy. We identify the 18 pulsations retained in our analysis as low-degree (l = 1 and 2), intermediate-order (k = −9 through −58) g-modes. The periods (frequencies) are recovered, on the average, at the 0.22% level, which is comparable to the best results obtained for p-mode pulsators. We infer the following structural and core parameters for KPD 1943+4058 : Teff = 28,050 ± 470 K, log g = 5.520 ± 0.029, M∗ = 0.4964 ± 0.0013 M⊙, log (Menv/M∗) = −2.552 ± 0.070, log (1−Mcore/M∗) = −0.366 ± 0.010, and Xcore(C+O) = 0.2612 ± 0.0080. We additionally derive the age of the star since the Zero-Age EHB 18.4 ± 1.0 Myr, the radius R = 0.2026 ± 0.0070 R⊙, the luminosity L = 22.92 ± 3.13 L⊙, the absolute magnitude MV = 4.21 ± 0.11, the reddening index E(B − V ) = 0.094 ± 0.017, and the distance d = 1183 ± 93 pc. [less ▲]

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See detailCoRoT opens a new era in hot B subdwarf asteroseismology. Detection of multiple g-mode oscillations in KPD 0629-0016
Charpinet, Stéphane; Green, Elizabeth M.; Baglin, Annie et al

in Astronomy and Astrophysics (2010), 516

Context. The asteroseismic exploitation of long period, g-mode hot B subdwarf (sdB) pulsators has been a long sought objective undermined, thus far, by the difficulty of obtaining sufficiently precise and ... [more ▼]

Context. The asteroseismic exploitation of long period, g-mode hot B subdwarf (sdB) pulsators has been a long sought objective undermined, thus far, by the difficulty of obtaining sufficiently precise and continuous time series data from the ground. Aims: Fast photometry from space appears to be the only means of gathering the appropriate asteroseismic data for this type of star. We explore this possibility with the CoRoT (COnvection, ROtation, and planetary Transits) satellite. Methods: We obtained ~24 days of high quality, nearly continuous photometric data with CoRoT during a short run (SRa03) dedicated to the long period sdB pulsator KPD 0629-0016. We analysed the frequency (period) content of the CoRoT time series by combining Fourier analysis, nonlinear least squares fitting, and prewhitening techniques. Results: Our study has led to the detection of a large number of g-mode pulsations in KPD 0629-0016, with 17 frequencies clearly identified in addition to 7 possible (although more uncertain) peaks emerging above the mean noise level (estimated at ~57 ppm). This is more than is typically detected for sdB stars from the ground and, more importantly, the frequencies of all uncovered g-modes are, for the first time, reliably measured. This paves the way for a detailed asteroseismic analysis of this star. The oscillations are found in the 90-400 μHz frequency range with a dominant mode at 205.29 μHz (P = 1.353 h) of amplitude 0.246% of the mean brightness, i.e., typical of mid-radial order g-mode pulsations. Conclusions: These photometric observations of KPD 0629-0016 demonstrate that g-mode sdB pulsators have rich oscillation spectra that are accessible to current space-based facilities. CoRoT opens up a new era in asteroseismology of hot B subdwarf stars. [less ▲]

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See detailProgress in Sounding the Interior of Pulsating Hot Subdwarf Stars
Charpinet, Stéphane; Brassard, Pierre; Fontaine, Gilles et al

in AIP Conference Proceedings (2009, September), 1170

Hot subdwarf stars, including helium core burning subdwarf B (sdB) stars and more evolved subdwarf O (sdO) stars, host three classes of nonradial pulsators. Two of them show rapid acoustic mode ... [more ▼]

Hot subdwarf stars, including helium core burning subdwarf B (sdB) stars and more evolved subdwarf O (sdO) stars, host three classes of nonradial pulsators. Two of them show rapid acoustic mode oscillations (with periods in the 60-600 s range), while the third class features slow gravity mode vibrations of period typically 1h. All three classes provide a strong potential for sounding the internal properties of stars in these evolved phases of stellar evolution through asteroseismology. This has so far been exploited mainly for the rapid p-mode sdB pulsators, but the long period g-mode sdB pulsators, with the advent of space observations, carry good promises for sounding even deeper regions inside these stars. In this review paper, we summarize the properties of pulsating hot subdwarf stars and we outline progress that have recently occured in the asteroseismic exploitation of the pulsations observed in sdB stars. [less ▲]

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See detailTesting the forward modeling approach in asteroseismology. II. Structure and internal dynamics of the hot B subdwarf component in the close eclipsing binary system PG 1336-018
Charpinet, Stéphane; Van Grootel, Valérie ULg; Reese, Daniel et al

in Astronomy and Astrophysics (2008), 489

Aims: We present a stringent test on the forward modeling technique in asteroseismology by confronting the predictions of a detailed seismic analysis of the pulsating subdwarf component in the unique ... [more ▼]

Aims: We present a stringent test on the forward modeling technique in asteroseismology by confronting the predictions of a detailed seismic analysis of the pulsating subdwarf component in the unique close eclipsing binary system PG 1336-018 with those derived independently from modeling the binary light curve of the system. We also take advantage of the observed rotationally-split rich period spectrum to investigate the internal dynamics of the pulsating component in this system expected to be tidally locked. Methods: We carry out numerical exercises based on the double optimization technique that we developed within the framework of the forward modeling approach in asteroseismology. We use a recently updated version that now incorporates the effects of stellar rotation on the pulsation properties. We thus search in parameter space for the optimal model that objectively leads to the best simultaneous match of the 25 periods (including rotationally-split components) observed in PG 1336-018. For the first time, we also attempt to precisely reconstruct the internal rotation profile of the pulsator from its oscillations. Results: Our principal result is that our seismic model, which closely reproduces the observed periods, is remarkably consistent with one of the best-fitting possible solutions uncovered independently from the binary light curve analysis, in effect pointing to the correct one. The latter indicates a mass of Mast = 0.466±0.006 Msun and a radius of Rast = 0.15±0.01 Rsun for the sdB star. In comparison, our seismic analysis, combined to high-quality time-averaged spectroscopy, leads to the following estimates of the basic structural parameters of the sdB component: Mast = 0.459±0.005 Msun, Rast = 0.151±0.001 Rsun, log g = 5.739±0.002, Teff = 32 740 ± 400 K, and log(Menv/Mast) = -4.54±0.07. We also find strong evidence that the sdB star has reached spin-orbit synchronism and rotates as a solid body down to at least r ~ 0.55 Rast. We further estimate that higher-order perturbation effects due to rotation and tidal deformation of the star are insufficient to alter in a significant way the proposed asteroseismic solution itself (i.e., the derived structural parameters and rotation properties). Future efforts to improve further the accuracy of the seismic models will clearly have to incorporate such effects, however. Conclusions: We conclude that our approach to the asteroseismology of sdB stars has passed a fundamental test with this analysis of PG 1336-018. The structural parameters and inferences about the internal dynamics of this star derived in the present paper through this approach should rest on very solid grounds. More generally, our results underline the power and usefulness of the forward modeling method in asteroseismology, despite historical misgivings about it. [less ▲]

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See detailTesting the forward modeling approach in asteroseismology. I. Seismic solutions for the hot B subdwarf Balloon 090100001 with and without a priori mode identification
Van Grootel, Valérie ULg; Charpinet, Stéphane; Fontaine, Gilles et al

in Astronomy and Astrophysics (2008), 488

Context: Balloon 090100001, the brightest of the known pulsating hot B subdwarfs, exhibits simultaneoulsy both short- and long-period pulsation modes, and shows relatively large amplitudes for its ... [more ▼]

Context: Balloon 090100001, the brightest of the known pulsating hot B subdwarfs, exhibits simultaneoulsy both short- and long-period pulsation modes, and shows relatively large amplitudes for its dominant modes. For these reasons, it has been studied extensively over the past few years, including a successful experiment carried out at the Canada-France-Hawaii Telescope to pin down or constrain the value of the degree index ℓ of several pulsation modes through multicolor photometry. Aims: The primary goal of this paper is to take advantage of such partial mode identification to test the robustness of our standard approach to the asteroseismology of pulsating subdwarf B stars. The latter is based on the forward approach whereby a model that best matches the observed periods is searched for in parameter space with no a priori assumption about mode identification. When successful, this method leads to the determination of the global structural parameters of the pulsator. As a bonus, it also leads, after the fact, to complete mode identification. For the first time, with the availability of partial mode identification for Balloon 090100001, we are able to evaluate the sensitivity of the inferred seismic model to possible uncertainty in mode identification. Methods: We carry out a number of exercises based on the double optimization technique that we developed within the framework of the forward modeling approach in asteroseismology. We use the set of ten periods corresponding to the independent pulsation modes for which values of ℓ have been either formally identified or constrained through multicolor photometry in Balloon 090100001. These exercises differ in that they assume different a priori mode identification. Results: Our primary result is that the asteroseismic solution stands very robust, whether or not external constraints on the values of the degree ℓ are used. Although this may come as a small surprise, the test proves to be conclusive, and small differences in mode identification among the ten modes do not affect in any significant way, at the typical accuracy presently achieved, the final emergent seismic model. This is due to the structure of the p-mode pulsation spectra in sdB stars. In all cases, the inferred structural parameters of Balloon 090100001 remain practically unchanged. They correspond, and this constitutes our second important result, to a star beyond the TAEHB with T_eff = 28 000 ± 1 200 K, log g = 5.383 ± 0.004, M⋆/Msun = 0.432 ± 0.015, and log{M_env/M⋆} = -4.89 ± 0.14. Other structural parameters are also derived. [less ▲]

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See detailAn Asteroseismological Analysis of the Pulsating B Subdwarf Feige 48 Taking into Account Rotation
Van Grootel, Valérie ULg; Charpinet, Stéphane; Fontaine, Gilles et al

in Leaflet - Astronomical Society of the Pacific (2008, January), 392

We present a new analysis of the short period pulsating sdB star Feige 48 using the same observations as done in our previous work, but exploiting, this time, our new period-matching codes that include ... [more ▼]

We present a new analysis of the short period pulsating sdB star Feige 48 using the same observations as done in our previous work, but exploiting, this time, our new period-matching codes that include the rotation of the star. The pulsation spectrum of Feige 48 shows the signature of rotational splitting with a mean frequency spacing of about 28 μHz between the components of three different frequency multiplets. In addition, Feige 48 has been shown to be a member of a close binary system with an invisible (most likely a white dwarf) companion. Assuming various internal rotation laws, we are now able to fit all nine observed frequencies simultaneously, and not only the four m = 0 components that we identified a priori in our previous effort. For solid body rotation, our optimal model shows slightly different structural parameters than those obtained previously on the basis of purely spherical models. Interestingly, that optimal model is also characterized by a rotation period of 9.028 h, which falls exactly on the value of the orbital period found independently from spectroscopy, namely, 9.024 ± 0.072 h. This very strongly implies that Feige 48 is tidally locked, a suggestion quite consistent with theoretical expectations for such a close binary system. In the same vein, our investigations also demonstrate explicitly that the idea of a fast rotating core can be eliminated for Feige 48. [less ▲]

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See detailAn Asteroseismological Study of the Rapidly Pulsating Subdwarf B Star PG 0911+456
Randall, Suzanna K.; Green, Elizabeth M.; Van Grootel, Valérie ULg et al

in Leaflet - Astronomical Society of the Pacific (2008, January), 392

We present the analysis and interpretation of 57 hours of time-series photometry obtained with the new Mont4kccd on Mt. Bigelow, Arizona, for the rapidly pulsating sdB star PG 0911+456. Thanks to the ... [more ▼]

We present the analysis and interpretation of 57 hours of time-series photometry obtained with the new Mont4kccd on Mt. Bigelow, Arizona, for the rapidly pulsating sdB star PG 0911+456. Thanks to the impressively high S/N of the data we were able to extract 7 independent periodicities in the 140-200 s range with amplitudes down to 0.05 % of the mean stellar brightness. On the basis of these we performed an asteroseismological search for the optimal model and derived the star's fundamental parameters. Given that there are now 12 sdB stars for which asteroseismology has been performed, the results are starting to become significant from a statistical point of view and evolutionary trends are slowly emerging. [less ▲]

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See detailAsteroseismic Solutions for the Two Fast Subdwarf B Pulsators Balloon 090100001 and PG 1336-018
Charpinet, Stéphane; Van Grootel, Valérie ULg; Brassard, Pierre et al

in Leaflet - Astronomical Society of the Pacific (2008, January), 392

We present two new asteroseismic studies of the rapid sdB pulsator PG 1336-018 and the hybrid sdB pulsator Balloon (BAL) 090100001. For PG 1336-018, the analysis is based on 25 periods extracted from the ... [more ▼]

We present two new asteroseismic studies of the rapid sdB pulsator PG 1336-018 and the hybrid sdB pulsator Balloon (BAL) 090100001. For PG 1336-018, the analysis is based on 25 periods extracted from the white-light photometry of the Xcov17 Whole Earth Telescope campaign (Kilkenny et al. 2003). For BAL 090100001, we use 10 periods of high amplitudes for which constraints on the ℓ-index have been derived from high S/N multicolour photometry. From asteroseismology, we estimate important structural parameters for these two stars, including the stellar mass and the H-rich envelope thickness. The analyses presented here are of particular interest since the asteroseismic results can be tested using independent constraints, which confirm the robustness of the solutions in both cases. [less ▲]

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See detailConstraints on Seismic Models of Balloon 090100001 through High-Sensitivity Multicolour Photometry
Charpinet, Stéphane; Fontaine, Gilles; Brassard, Pierre et al

in Leaflet - Astronomical Society of the Pacific (2008, January), 392

We report on an analysis of high S/N ratio UBV multicolour photometry of the bright pulsating sdB star Balloon 090100001 gathered at the Canada-France-Hawaii Telescope with the help of the Montreal 3 ... [more ▼]

We report on an analysis of high S/N ratio UBV multicolour photometry of the bright pulsating sdB star Balloon 090100001 gathered at the Canada-France-Hawaii Telescope with the help of the Montreal 3-channel photometer LAPOUNE. Through an application of the color-amplitude method described in Randall et al. (2005), we were able to identify the degree index ℓ of several individual pulsation modes. These identifications provide extremely useful constraints on possible seismic models for Balloon 090100001. [less ▲]

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See detailAchievements and Challenges in the Field of sdB Asteroseismology
Fontaine, Gilles; Charpinet, Stéphane; Green, Elizabeth M. et al

in Leaflet - Astronomical Society of the Pacific (2008, January), 392

We review briefly the status of sdB star asteroseismology. We concentrate on the main achievements that have been obtained so far, and we discuss the current challenges that we now face in the field.

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See detailObservations and asteroseismic analysis of the rapidly pulsating hot B subdwarf PG 0911+456
Randall, Suzanna K.; Green, Elizabeth M.; Van Grootel, Valérie ULg et al

in Astronomy and Astrophysics (2007), 476

Aims: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 ... [more ▼]

Aims: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. Methods: 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. Results: 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 T_eff = 31 940 ± 220 K, log g = 5.767 ± 0.029, and log He/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 T_eff = 31 940 ± 220 K (from spectroscopy), log {g} = 5.777 ± 0.002, Mast/Msun = 0.39 ± 0.01, log{M_env/Mast} = -4.69 ± 0.07, R/Rsun = 0.133 ± 0.001 and L/Lsun = 16.4 ± 0.8. We also derive the absolute magnitude MV = 4.82 ± 0.04 and a distance d = 930.3 ± 27.4 pc. [less ▲]

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See detailThe asteroseismic analysis of the pulsating sdB Feige 48 revisited
Van Grootel, Valérie ULg; Charpinet, Stéphane; Fontaine, Gilles et al

Conference (2007, July)

We present a new detailed analysis of the short period pulsating sdB star Feige 48, based on the same observations than in our previous work (Charpinet et al., 2005, A&A 443, 251) but with our new codes ... [more ▼]

We present a new detailed analysis of the short period pulsating sdB star Feige 48, based on the same observations than in our previous work (Charpinet et al., 2005, A&A 443, 251) but with our new codes including the rotation of the star. Feige 48 is supposed to be a relatively fast rotator, showing a fine structure in its pulsation spectrum about 28 µHz on three groups in the 9 frequencies. On the other side, Feige 48 belongs to a close binary system (likely with a white dwarf) where the orbital period is 9.02 +/- 0.03h (S. O'Toole 2004). With our new codes including the rotation (for a given rotation law, we calculate associated multiplets for each frequency with the perturbative approach on the first order), avoiding us to make assumptions about the m=0 modes, we were able to fit all the 9 periods together, leading to sligthly different estimations for the structural parameters of Feige 48 than in our previous work. Moreover, the rotation of the star is found to be solid with a period of 32,540s <=> 9.038h, very close to the orbital period of the system determined by spectroscopy, confirming the reasonable assumption that the system is tidally locked. In this context, it was possible to exclude that Feige 48 has a fast rotating core in term of much poorer merit functions. [less ▲]

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