J/A+A/506/1469 theta Cyg radial velocity variations (Desort+, 2009)
Extrasolar planets and brown dwarfs around A-F type stars.
VII. theta Cygni radial velocity variations: planets or stellar phenomenon?
Desort M., Lagrange A.-M., Galland F., Udry S., Montagnier G., Beust H.,
Boisse I., Bonfils X., Bouchy F., Delfosse X., Eggenberger A.,
Ehrenreich D., Forveille T., Hebrard G., Loeillet B., Lovis C., Mayor M.,
Meunier N ., Moutou C., Pepe F., Perrier C., Pont F., Queloz D.,
Santos N.C., Segransan D., Vidal-Madjar A.
<Astron. Astrophys. 506, 1469 (2009)>
=2009A&A...506.1469D 2009A&A...506.1469D
ADC_Keywords: Stars, double and multiple ; Planets ; Radial velocities
Keywords: techniques: radial velocities - stars: early-type -
stars: planetary systems - stars: individual: theta Cygni
Abstract:
In the frame of the search for extrasolar planets and brown dwarfs
around early-type main-sequence stars, we present the results obtained
on the early F-type star theta Cygni.
ELODIE and SOPHIE at Observatoire de Haute-Provence (OHP) were used to
obtain 91 and 162 spectra, respectively. Our dedicated radial-velocity
measurement method was used to monitor the star's radial velocities
over five years. We also use complementary, high angular resolution
and high-contrast images taken with PUEO at CFHT.
We show that theta Cygni radial velocities are quasi-periodically
variable, with a ∼150-day period. These variations are not due to the
∼0.35M☉ stellar companion that we detected in imaging at more than
46AU from the star.
The absence of correlation between the bisector velocity span variations and
the radial velocity variations for this 7km/s vsini star, as well as
other criteria indicate that the observed radial velocity variations
are not due to stellar spots. The observed amplitude of the bisector
velocity span variations also seems to rule out stellar pulsations.
However, we observe a peak in the bisector velocity span periodogram
at the same period as the one found in the radial velocity
periodogram, which indicates a probable link between these radial
velocity variations and the low amplitude lineshape variations which
are of stellar origin. Long-period variations are not expected from
this type of star to our knowledge. If a stellar origin (hence of new
type) was to be confirmed for these long-period radial velocity
variations, this would have several consequences on the search for
planets around main-sequence stars, both in terms of observational
strategy and data analysis.
An alternative explanation for these variable radial velocities is the
presence of at least one planet of a few Jupiter masses orbiting at
less than 1AU; however this planet alone does not explain all
observed features, and the theta Cygni system is obviously more
complex than a planetary system with 1 or 2 planets.
The available data do not allow to distinguish between these two
possible origins. A vigourous follow-up in spectroscopy and photometry
is needed to get a comprehensive view of the star intrinsic
variability and/or its surrounding planetary system.
Objects:
----------------------------------------------
RA (2000) DE Designation(s)
----------------------------------------------
19 36 26.5 +50 13 16 theta Cyg = HR 7469
----------------------------------------------
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
elodie.dat 33 91 Relative radial velocity measured with ELODIE
sophie.dat 33 162 Relative radial velocity measured with SOPHIE
--------------------------------------------------------------------------------
See also:
J/A+A/491/883 : Radial velocities of HD 60532 (Desort+, 2008)
Byte-by-byte Description of file: elodie.dat sophie.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 14 F14.6 d JD Julian Date
16- 24 F9.6 km/s RV Relative Radial velocity
26- 33 F8.6 km/s e_RV rms uncertainty on RV
--------------------------------------------------------------------------------
Acknowledgements:
Morgan Desort, mdesort(at)obs.ujf-grenoble.fr
References:
Galland et al., Paper I 2005A&A...443..337G 2005A&A...443..337G
Galland et al., Paper II 2005A&A...444L..21G 2005A&A...444L..21G
Galland et al., Paper III 2006A&A...447..355G 2006A&A...447..355G
Galland et al., Paper IV 2006A&A...452..709G 2006A&A...452..709G
Desort et al., Paper V 2008A&A...491..883D 2008A&A...491..883D, Cat. J/A+A/491/883
Lagrange et al., Paper VI 2009A&A...495..335L 2009A&A...495..335L
(End) Morgan Desort [LAOG, France], Patricia Vannier [CDS] 01-Sep-2009