Bibcode
Mathur, Savita; García, Rafael A.; Bugnet, Lisa; Santos, Ângela R. G.; Santiago, Netsha; Beck, Paul G.
Bibliographical reference
Frontiers in Astronomy and Space Sciences, Volume 6, id.46 (2019)
Advertised on:
7
2019
Citations
41
Refereed citations
38
Description
Over 2,000 stars were observed for one month with a high enough cadence
in order to look for acoustic modes during the survey phase of the
Kepler mission. Solar-like oscillations have been detected in about 540
stars. The question of why no oscillations were detected in the
remaining stars is still open. Previous works explained the
non-detection of modes with the high level of magnetic activity of the
stars. However, the sample of stars studied contained some classical
pulsators and red giants that could have biased the results. In this
work, we revisit this analysis on a cleaner sample of main-sequence
solar-like stars that consists of 1,014 stars. First we compute the
predicted amplitude of the modes of that sample and for the stars with
detected oscillation and compare it to the noise at high frequency in
the power spectrum. We find that the stars with detected modes have an
amplitude to noise ratio larger than 0.94. We measure reliable rotation
periods and the associated photometric magnetic index for 684 stars out
of the full sample and in particular for 323 stars where the amplitude
of the modes is predicted to be high enough to be detected. We find
that among these 323 stars 32% of them have a level of magnetic activity
larger than the Sun during its maximum activity, explaining the
non-detection of acoustic modes. Interestingly, magnetic activity cannot
be the primary reason responsible for the absence of detectable modes in
the remaining 68
of the stars without acoustic modes detected and with reliable rotation
periods. We investigate metallicity, inclination angle of the rotation
axis, and binarity as possible causes of low mode amplitudes. Using
spectroscopic observations for a subsample, we find that a low
metallicity could be the reason for suppressed modes. No clear
correlation with binarity nor inclination is found. We also derive the
lower limit for our photometric activity index (of 20-30 ppm) below
which rotation and magnetic activity are not detected. Finally, with our
analysis we conclude that stars with a photometric activity index larger
than 2,000ppm have 98.3
probability of not having oscillations detected.
Related projects
Helio and Astero-Seismology and Exoplanets Search
The principal objectives of this project are: 1) to study the structure and dynamics of the solar interior, 2) to extend this study to other stars, 3) to search for extrasolar planets using photometric methods (primarily by transits of their host stars) and their characterization (using radial velocity information) and 4) the study of the planetary
Savita
Mathur