D. J. Wright

A new method for the spectroscopic identification of stellar non-radial pulsation modes - II. Mode identification of the delta Scuti star FG Virginis

Aims. We present a mode identification based on new high-resolution time-series spectra of the non-radially pulsating delta Scuti star FG Vir (HD 106384, V = 6.57, A5V). From 2002 February to June a global Delta Scuti Network (DSN) campaign, utilizing high-resolution spectroscopy and simultaneous photometry has been conducted for FG Vir in order to provide a theoretical pulsation model. In this campaign we have acquired 969 Echelle spectra covering 147 h at six observatories. Methods. The mode identification was carried out by analyzing line profile variations by means of the Fourier parameter fit method, where the observational Fourier parameters across the line are fitted with theoretical values. This method is especially well suited for determining the azimuthal order m of non-radial pulsation modes and thus complementary with the method of Daszynska-Daszkiewicz (2002) which does best at identifying the degree l. Results. 15 frequencies between 9.2 and 33.5 d(-1) were detected spectroscopically. We determined the azimuthal order m of 12 modes and constrained their harmonic degree l. Only modes of low degree (l <= 4) were detected, most of them having axisymmetric character mainly due to the relatively low projected rotational velocity of FG Vir. The detected non-axisymmetric modes have azimuthal orders between -2 and 1. We derived an inclination of 19 degrees, which implies an equatorial rotational rate of 66 km s(-1).

Discovery of non-radial pulsations in the spectroscopic binary Herbig Ae star RS Chamaeleontis

Context: To understand the origin of stellar activity in pre-main-sequence Herbig Ae/Be stars and to get a deeper insight into the interior of these enigmatic stars, the pulsational instability strip of Palla and Marconi is investigated. In this article we present a first discovery of non radial pulsations in the Herbig Ae spectroscopic binary star RS Cha. Aims: The goal of the present work is to detect non-radial pulsations in a Herbig Ae star for the first time directly by spectrographic means and to identify the largest amplitude pulsation modes. Methods: The spectroscopic binary Herbig Ae star RS Cha was monitored in quasi-continuous observations during 14 observing nights (Jan. 2006) at the 1 m Mt. John (New Zealand) telescope with the Hercules high-resolution echelle spectrograph. The cumulative exposure time on the star was 44 h, corresponding to 255 individual high-resolution echelle spectra with R = 45 000. Least-square deconvolved spectra (LSD) were obtained for each spectrum, representing the effective photospheric absorption profile modified by pulsations. Difference spectra were calculated by subtracting rotationally broadened artificial profiles, these residual spectra were analysed and non-radial pulsations detected. A subsequent analysis with two complementary methods, namely Fourier Parameter Fit (FPF) and Fourier 2D (F2D) has been performed and first constraints on the pulsation modes derived. Results: For the very first time, we discovered by direct observational means using high-resolution echelle spectroscopy, non-radial oscillations in a Herbig Ae star. In fact, both components of the spectroscopic binary are Herbig Ae stars and both show NRPs. The FPF method identified 2 modes for the primary component with (degree l, azimuthal order m) couples ordered by decreasing probability: f1 = 21.11 d-1 with (l, m) = (11, 11), (11, 9) or (10, 6) and f2 = 30.38 d-1 with (l, m) = ( 10, 6) or (9, 5). The F2D analysis indicates for f1 a degree l = 8-10. For the secondary component, the FPF method identified 3 modes with (l,m) ordered by decreasing probability: f1 = 12.81 d-1 with (l, m) = (2, 1) or (2, 2), f_2b = 19.11 d-1 with (l, m) = (13, 5) or (10, 5) and f3 = 24.56 d-1 with (l, m) = (6, 3) or (6,5). The F2D analysis indicates for f1 a degree l = 2 or 3, but proposes a contradictory identification of f_2b as a radial pulsation (l = 0). Based on observations collected at the 1 m McLellan telescope at Mt John, NZ.

Is HD 147787 a double‐lined binary with two pulsating components? Preliminary results from a spectroscopic multi‐site campaign

The double‐lined binary HD 147787 has been observed from three southern observatories to gather a time series of high‐quality, high‐resolution spectroscopic data. We here report upon the first analysis of the 2008 data obtained with the spectrographs HARPS and HERCULES. An eccentric orbit of 39.880(2) days was obtained. For the primary component. we derived a projected rotational velocity νsin i of 7(2) km s−1 and found that the temporal changes of the line profiles are dominated by 0.6897(8) d−1, which is the main frequency known from photometry. There is evidence for multiperiodicity. For the secondary component, we derived a νsin i of 33(2) km s 1, but there is no firm evidence for pulsations.

Frequency and mode identification of γ Doradus from photometric and spectroscopic observations

The prototype star for the gamma Doradus class of pulsating variables was studied employing photometric and spectroscopic observations to determine the frequencies and modes of pulsation. The four frequencies found are self-consistent between the observation types and almost identical to those found in previous studies (1.3641 d(-1), 1.8783 d(-1), 1.4742 d(-1), and 1.3209 d(-1)). Three of the frequencies are classified as l, m = (1, 1) pulsations and the other is ambiguous between l, m = (2, 0) and (2, -2) modes. Two frequencies are shown to be stable over 20 yr since their first identification. The agreement in ground-based work makes this star an excellent calibrator between high-precision photometry and spectroscopy with the upcoming TESS observations and a potential standard for continued asteroseismic modelling.

Mode identification from spectroscopy of gravity-mode pulsators

The gravity modes present in γ Doradus stars probe the deep stellar interiors and are thus of particular interest in asteroseismology. For the MUSICIAN programme at the University of Canterbury, we obtain extensive high-resolution echelle spectra of γ Dor stars from the Mt John University Observatory in New Zealand. We analyze these to obtain the pulsational frequencies and identify these with the multiple pulsational modes excited in the star. A summary of recent results from our spectroscopic mode-identification programme is given.

Towards asteroseismology of main‐sequence g‐mode pulsators: spectroscopic multi‐site campaigns for slowly pulsating B stars and γ Doradus stars

We introduce the spectroscopic multi‐site campaigns that are organised for a sample of slowly pulsating B and γ Doradus stars to make a big step forward in the asteroseismic studies of these main‐sequence g‐mode pulsators.

Results from Classification Observations and a Multi‐site Campaign on γ Doradus and SPB Type Stars

As part of a observational project aiming to investigate the effects of rotation on main‐sequence g‐mode non‐radial pulsation we have obtained at least one (generally more) high‐resolution spectroscopic observation of more than 50 confirmed or candidate γ Doradus and slowly pulsating B stars and have completed a spectroscopic multi‐site campaign. The campaign was one of those outlined in De Cat et al. (these proceedings) and included five observatories and focused on the γ Doradus, and now planet hosting star HD 218396 (HR 8799) and the SPB stars HD 21071 and HD 25558.