Документ взят из кэша поисковой машины. Адрес оригинального документа : http://www.mrao.cam.ac.uk/wp-content/uploads/2014/04/MNeveu.pdf Дата изменения: Thu Apr 17 14:04:57 2014 Дата индексирования: Sun Apr 10 13:26:20 2016 Кодировка: Поисковые слова: massive stars

Searching for additional companions to WASP planets
1O

bservatoire Astronomique de l'UniversitИ de GenХve, 2BaHcock Centre for Experimental Astrophysics, Cavendish Laboratory, 3Kavli InsTtute for Astrophysics & Space Research, MassachuseHs InsTtute of Technology Context:


Marion Neveu-
VanMalle1,2, Didier Queloz2,1, Amaury Triaud3 and Damien SИgransan

1

The discoveries of hot Jupiters shed a new light on the planet formaTon processes with a parTcular emphasis on migraTon mechanisms.


ObservaTons of obliquiTes of hot Jupiters, using Rossiter-
McLaughlin effect, demonstrated that misaligned systems are common. Only dynamical interacTons involving the influence of a third body are currently able to explain such distribuTons. They are divided into two kinds of mechanisms: mulTple-
planet scaHering (e.g. Nagasawa et al. 2008), and eccentric Kozai-
Lidov mechanism in a stellar binary (e.g. Fabrycky & Tremaine 2007 and Wu et al. 2007). It is then reasonable to expect to find hot Jupiters in mulTple systems.


Since 2007 an intensive follow up program is ongoing with the high resoluTon Иchelle spectrograph CORALIE, mounted on the 1.2m Euler Swiss Telescope at La Silla (Chile), to observe WASP transiTng candidates. A special effort is being carried out to search for addiTonal long-
term radial velocity trends, suggesTng the presence of extra stellar or planetary companions. Our sample is now composed of more than 3000 radial velocity data points with a Tme-
span per target up to 7 years.

Surveyed Southern Wasp planets. The X axis is the hot Jupiter's period. The Y axis is the host star's temperature. Blue dots are systems that do not show any significant trend. Purple and red dots are systems with respecTvely a 2 and 3 detecTon of a companion. Hot Jupiters orbiTng young stars hoHer than 6350K (upper doHed line) are usually misaligned, and hot Jupiters orbiTng evolved stars cooler than 6150K (lower doHed line) are mostly aligned (Winn et al. 2010, Triaud 2011).

Simula.on of binaries


.

In order to determine if hot Jupiters are found preferenTally in stellar binaries, we compare our detecTons with the known binary distribuTons (Duquennoy & Mayor 1991, Raghavan et al. 2010). For each WASP system, we simulate the RV signal caused by the known planet added to the signal caused by a stellar companion. The dates of the measurements and the error-
bars are taken from the original data set. 1000 different stellar companions per system are randomly generated from the binaries distribuTons. We run the exact same code to detect trends on those simulated data. Each plot represents the distribuTon of the simulated binaries in period, mass raTo, eccentricity and inclinaTon. The cyan co rresp o n d s to th e wh o l e distribuTon, the purple are the detected objects and the blue are the undetected obje c ts. The pe r iod is the c r iTc al par am e t e r , t he w ide binar ie s ar e undetectable.
. Wasp53
500

Given that only 50% of the stars are in mulTple systems, we esTmate that we should detect 23.4% of these stellar companions. We find that only 13% of our targets show a >3 variaTon. Besides, half of them are most likely giant planets (e.g. Wasp-
53, see figure) and the others are compaTble with planetary masses. Only one is definitely more massive but could be lying in the brown dwarf regime (Triaud et al. in prep).

Conclusions:


0

-500

-1000

100

O-C [m/s]

50 0 -50 -100 5500 5600 5700 5800 5900 6000 6100 6200 6300 6400 6500 6600 6700

Our lack of detecTons suggests that hot Ju p i ters m a y b e f o u n d p r e d o m i n a n t l y around single stars (unlikely) or in wide binaries. That conclusion would be in agreement with dynamical simulaTons (e.g. Naoz et al. 2012) showing that eccentric Kozai-
Lidov mechanism is more likely to produce hot Jupiters in wide binaries.


RV [m/s]

.

BJD - 2450000.0 [days]

.

However we need to be cauTous with this result as our sample is biased, considering that we may have rejected close-
in binaries.