Refining The Asteroseismic Model For The Young Delta Scuti Star HD 144277 Using HARPS Spectroscopy




Zwintz, K.
Ryabchikova, T.
Lenz, P.
Pamyatnykh, A. A.
Fossati, L.
Sitnova, T.
Breger, M.
Poretti, E.
Rainer, M.
Hareter, M.

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Context. HD 144277 was previously discovered by Microvariability and Oscillations of Stars (MOST) space photometry to be a young and hot delta Scuti star showing regular groups of pulsation frequencies. The first asteroseismic models required lower than solar metallicity to fit the observed frequency range based on a purely photometric analysis. Aims. The aim of the present paper is to determine, by means of high-resolution spectroscopy, fundamental stellar parameters required for the asteroseismic model of HD 144277, and subsequently, to refine it. Methods. High-resolution, high signal-to-noise spectroscopic data obtained with the HARPS spectrograph were used to determine the fundamental parameters and chemical abundances of HD 144277. These values were put into context alongside the results from asteroseismic models. Results. The effective temperature, T-eff, of HD 144277 was determined as 8640(-100)(+300) K, log g is 4.14 +/- 0.15 and the projected rotational velocity, v sin i, is 62.0 +/- 2.0 km s(-1). As the v sin i value is significantly larger than previously assumed, we refined the first asteroseimic model accordingly. The overall metallicity Z was determined to be 0.011 where the light elements He, C, O, Na, and S show solar chemical composition, but the heavier elements are significantly underabundant. In addition, the radius of HD 144277 was determined to be 1.55 +/- 0.65 R-circle dot from spectral energy distribution fitting, based on photometric data taken from the literature. Conclusions. From the spectroscopic observations, we could confirm our previous assumption from asteroseismic models that HD 144277 has less than solar metallicity. The fundamental parameters derived from asteroseismology, T-eff, log g, L/L-circle dot and R/R-circle dot agree within one sigma to the values found from spectroscopic analysis. As the v sin i value is significantly higher than assumed in the first analysis, near-degeneracies and rotational mode coupling were taken into account in the new models. These suggest that HD 144277 has an equatorial rotational velocity of about 80 km s(-1) and is seen equator-on. The observed frequencies are identified as prograde modes.



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Zwintz, Konstanze, Tatiana Ryabchikova, Patrick Lenz, A. A. Pamyatnykh, Luca Fossati, T. Sitnova, Michel Breger et al. >Refining the asteroseismic model for the young δ Scuti star HD 144277 using HARPS spectroscopy.> Astronomy & Astrophysics Vol. 567 (Jul., 2014): A4.