Exocomets: A spectroscopic survey
Journal article, 2020
Context. While exoplanets are now routinely detected, the detection of small bodies in extrasolar systems remains challenging. Since the discovery of sporadic events, which are interpreted to be exocomets (falling evaporating bodies) around β Pic in the early 1980s, only ∼20 stars have been reported to host exocomet-like events. Aims. We aim to expand the sample of known exocomet-host stars, as well as to monitor the hot-gas environment around stars with previously known exocometary activity. Methods. We have obtained high-resolution optical spectra of a heterogeneous sample of 117 main-sequence stars in the spectral type range from B8 to G8. The data were collected in 14 observing campaigns over the course of two years from both hemispheres. We analysed the Ca » II K&H and Na » I D lines in order to search for non-photospheric absorptions that originated in the circumstellar environment and for variable events that could be caused by the outgassing of exocomet-like bodies. Results. We detected non-photospheric absorptions towards 50% of the sample, thus attributing a circumstellar origin to half of the detections (i.e. 26% of the sample). Hot circumstellar gas was detected in the metallic lines inspected via narrow stable absorptions and/or variable blue- and red-shifted absorption events. Such variable events were found in 18 stars in the Ca » II and/or Na » I lines; six of them are reported in the context of this work for the first time. In some cases, the variations we report in the Ca » II K line are similar to those observed in β Pic. While we do not find a significant trend in the age or location of the stars, we do find that the probability of finding CS gas in stars with larger v sin i is higher. We also find a weak trend with the presence of near-infrared excess and with anomalous (λ Boo-like) abundances, but this would require confirmation by expanding the sample.
ISM: clouds
Comets: general
Kuiper belt: general
Stars: general
Author
I. Rebollido
Universidad Autonoma de Madrid (UAM)
C. Eiroa
Calar Alto Astronomical Observatory
Universidad Autonoma de Madrid (UAM)
B. Montesinos
European Space Agency (ESA)
J. Maldonado
Istituto nazionale di astrofisica (INAF)
E. Villaver
Universidad Autonoma de Madrid (UAM)
O. Absil
University of Liège
A. Bayo
University of Valparaíso
H. Canovas
European Space Agency (ESA)
A. Carmona
Paul Sabatier University
C. H. Chen
Space Telescope Science Institute (STScI)
S. Ertel
University of Arizona
T. Henning
Max Planck Society
D. P. Iglesias
University of Valparaíso
R. Launhardt
Max Planck Society
René Liseau
Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics
G. Meeus
Universidad Autonoma de Madrid (UAM)
A. Moór
Hungarian Academy of Sciences
Eötvös Loránd University (ELTE)
A. Mora
European Space Agency (ESA)
J. Olofsson
University of Valparaíso
G. Rauw
University of Liège
P. Riviere-Marichalar
Spanish National Observatory (OAN)
Astronomy and Astrophysics
0004-6361 (ISSN) 1432-0746 (eISSN)
Vol. 639 A11Subject Categories (SSIF 2011)
Astronomy, Astrophysics and Cosmology
Atom and Molecular Physics and Optics
Geology
DOI
10.1051/0004-6361/201936071