Institute for Astrophysics and Space Sciences | University of Porto | 2015 Dec 02
[img3="This artist’s view shows the hot Jupiter exoplanet 51 Pegasi b, orbits a star about 50 light-years from Earth in the constellation of Pegasus (The Winged Horse). This was the first exoplanet around a normal star to be found in 1995. Twenty years later this object was also the first exoplanet to be be directly detected spectroscopically in visible light. (Credit: ESO/M. Kornmesser/Nick Risinger (skysurvey.org))"]http://www.iastro.pt/img/news/2015Dez02_1.jpg[/img3][hr][/hr]An international team led by Alexandre Santerne from Instituto de Astrofísica e Ciências do Espaço (IA) made a 5-year radial velocity campaign of Kepler’s giant exoplanet candidates, using the SOPHIE spectrograph (Observatory of Haute-Provence, France), and found that 52.3% were actually eclipsing binaries, while 2.3% were brown dwarfs [6].
Santerne (IA & University of Porto), first author of this paper, commented: “It was thought that the reliability of the Kepler exoplanets detection was very good -- between 10 and 20% of them were not planets. Our extensive spectroscopic survey, of the largest exoplanets discovered by Kepler, shows that this percentage is much higher, even above 50%. This has strong implications in our understanding of the exoplanet population in the Kepler field.”
One of the team members, Vardan Adibekyan (IA & University of Porto), added: “Detecting and characterizing planets is usually a very subtle and difficult task. In this work, we showed that even big, easy to detect planets are also difficult to deal with. In particular, it was shown that less than half of the detected big transiting planet candidates are actually there. The rest are false positives, due to different kind of astrophysical sources of light or noise.”
Giant transiting exoplanets are easily mimicked by false positives, so spectroscopic follow-up observations are needed to establish the planetary nature of the transit detections, and easily reveal blended multiple stellar systems. ...
The research, which ran between July 2010 and July 2015, started with all 8826 objects on the list of Kepler objects of interest (KOI). The sample number was progressively reduced to 129 KOIs on 125 target stars, by removing already known false positives, stars too faint to be observed by SOPHIE, and candidates with orbits of more than 400 days, to insure that at least 3 transits could be observed. ...
SOPHIE velocimetry of Kepler transit candidates XVII. The physical
properties of giant exoplanets within 400 days of period - A. Santerne et al
- arXiv.org > astro-ph > arXiv:1511.00643 > 02 Nov 2015
