Pulsations in beta Pictoris

Abstract

We report on the discovery of at least 18 pulsation modes in β Pictoris from 697 high‐dispersion spectra obtained over a two‐week period. These are seen as absorption subfeatures moving across the spectral line profiles, indicating that they are of relatively high spherical harmonic order. They do not resemble the features seen in the Ca H and K lines generally attributed to infalling bodies. We use the correlation function between an unbroadened synthetic spectrum and the observed spectrum to obtain what is essentially a high signal‐to‐noise ratio representation of the mean line profile. From the correlation intensity as a function of time, we calculated periodograms for every point across the correlation function. In this way, we are able to determine accurate periods for each mode. By phasing the correlation function with the period belonging to a given mode, we can isolate the line profile variations for the mode and deduce the approximate value of the azimuthal order, m. Two of the modes are retrograde, the remainder are prograde and most of them lie in the range 4 ≤|m|≤ 10. Comparison with non‐adiabatic models shows that the periods are in the range expected for unstable modes in a star with the mass and temperature appropriate to β Pic. Some constraints can be placed on the effective temperature. We also report on photometric observations of β Pic obtained during the same run. From our 14 318 photometric observations combined with the discovery data from Koen (2003), we find two definite pulsation modes with frequencies of 47.4 and 38.1 cycle d−1. A third frequency at 47.3 cycle d−1 may also be present. The amplitudes are all smaller than 1.5 mmag.

Extrasolar planets and brown dwarfs around A–F type stars

“…2, top). The square root of the value of the pics in the periodogram stands for the radial velocity semi-amplitude of the corresponding radial velocity periodic variations: These results agree with those obtained by Koen et al (2003) from dedicated photometry and spectroscopy. These authors indeed report detecting of at least 18 pulsation modes in β Pictoris, with a large number of spectra spread over 2 weeks, and detecting 2 low amplitude (≤1.5 mmag) pulsation modes in photometry, with frequencies equal to 47.44 cycle d −1 and 39.05 cycle d −1 , namely the same as we develop here.…”

TheδScuti pulsations ofβPictoris as observed by ASTEP from Antarctica

“…Crifo et al 1997 found that the star is very close to the zero age main sequence (ZAMS), which is a finding confirmed by studies of the age of the β Pictoris moving group, 23±3 Myr (Mamajek & Bell 2014). ⋆ E-mail: mekarnia@oca.eu Very low-amplitude periodic variations in brightness, radial velocity, and line profile have been reported and studied (Koen 2003;Koen et al 2003;Galland et al 2006). These observations showed that β Pictoris is one of the brightest known δ Scuti stars.…”

A photometric survey of stars with circumstellar material

“…β Pictoris presents δ Scuti type stellar variations over periods of about 30 min (Koen et al 2003) which are likely to be unrelated to the circumstellar material. But long-term photometric measurements have revealed that β Pictoris presented slow brightness variations from 1975 to 1981 and rapid and "large" amplitude ( > ∼ 0.04 mag) variations in November 1981.…”