Transit timing variation in exoplanet WASP-3b - the full manuscipt of the paper
WASP-3 - the web page of the WASP-3 system at Exoplanet.eu
Press release MNRAS
Presseerklärung der Uni Jena
An additional component to the extrasolar transiting planetary system WASP-3, a 15 Earth mass planet was detected by an international team of astronomers led by Dr. Gracjan Maciejewski of Jena University. This is the first planet detected with the new technique called Transit Timing Variations.
"We detected periodic variations in the transit timing of WASP-3b. We found that the amplitude of these variations can be explained by an additional planet in the system, with a mass of 15 Earth-mass (i.e. one Uranus mass) and period of 3.75 days." - Dr. Maciejewski said, "According to international rules, we call this new planet WASP-3c". This newly discovered planet is among the least massive planets known to-date and also the least massive planet known orbiting a star which is more massive than our Sun. The host star WASP-3 is also younger than our Sun.
This is the first time, that a new extra-solar planet is discovered by this method. This technique is an indirect detection technique, such as the previously successful radial velocity and transit techniques themselves.
This is already a second planet in the system. It is much smaller than the one originally discovered of 2 Jupiter masses (about 630 Earth masses). The discovery of the second, 15 Earth mass planet makes the system very intriguing. The new planet, appears to be trapped in external orbit, twice longer than the orbit of the more massive planet. Such a configuration is probably a result of early evolution of the system.
"There are only some 80 planets, of about 450 extra-solar planets and planet candidates discovered so far around other stars, which orbit their stars in the plane of our line-of-sight, so that we can observe how the stars dim slightly (typically about 1 per cent) when the planet transits in front of the stellar disk. One of those transiting planets is WASP-3b, at a distance about 700 light years, in the constellation Lyra, which is known to host a hot-Jupiter type planet with less than 2 day orbital period." - Prof. Ralph Neuhäuser explains.
"In 2008, we started our observing campaign to search for such Transit Timing Variations in selected transiting exoplanets." - Dr. Maciejewski said. "We observed six new transits of the known planet WASP-3b, three with the 90-cm telescopes of the University Observatory Jena operated by the Astrophysical Institute of the Friedrich Schiller University and three with the 60-cm telescope of the Rozhen National Astronomical Observatory operated by the Institute of Astronomy, Bulgarian Academy of Sciences." On the Jena telescope, a new CCD detector was used, installed partly for this project in the telescope's so-called Schmidt focus (60-cm effective mirror), which was supported by the Thuringian science ministry.
"We are currently observing the new planet also by radial velocities with the 10-meter Hobby-Eberly-Telescope in Texas to get additional evidence for our finding." - Prof. Andrzej Niedzielski said. The new planet should be detectable by both radial velocity as well as own transit observations, which we will try to perform in order to finally confirm the existence of this new planet.
The new technique for discovering additional planets around transiting planets host stars, Transit Timing Variation, was suggested a few years ago. In a single-planet extra-solar transiting system, a planet orbits its host star on a Keplerian orbit and transits occur at equal time intervals, the orbital period. If there is another (not necessarily transiting) planet in the system, it interacts gravitationally with the transiting planet and generates deviations from the strictly Keplerian case. Hence the name of the method. From the period and amplitude of the variations, one can derive the parameters of the perturbing planet by comparing observations with tens of thousands of configurations of various planetary systems calculated with a computer.
The transit timing variation (TTV) method is very attractive, because it is particularly sensitive to small perturbing planets, even down to few Earth masses. E.g., a one Earth-mass planet perturbing a typical hot-Jupiter gas giant is expected to cause deviations in transit timing up to 1 minute. This effect can be detected by 1-meter class telescopes. The search for planets with this technique is one of main topics of German-Polish scientific cooperation funded by DAAD and Polish Ministry of Science and Higher Education; on the Jena side, it is also supported by the European Union through a Marie-Curie project.
The paper describing the discovery has been accepted for publication by the typical peer review system in the international high-standard astrophysical journal called Monthly Notices of the Royal Astronomical Society (London, UK). The research is a cooperation between Astrophysical Institute of the Friedrich Schiller University in Jena, Germany, the Institute of Astronomy of the Bulgarian Academy of Sciences in Sofia, Bulgaria, and the Torun Centre for Astronomy of the Nicolaus Copernicus University in Torun, Poland. The research was led by Jena post-doc Dr. Gracjan Maciejewski, originally from Torun, Poland. The full paper can be found at http://xxx.lanl.gov/abs/1006.1348. The authors of the paper are Gracjan Maciejewski (Jena), Dinko Dimitrov (Rozhen), Ralph Neuhäuser (Jena), Andrzej Niedzielski (Torun), Markus Mugrauer (Jena) as well as several Jena PhD and Diploma students (Stefanie Raetz, Christian Ginski, Christian Adam, Claudia Marka, and Mohammad Moualla).