The SOPHIE search for northern extrasolar planets. V. Follow-up of ELODIE candidates: Jupiter-analogs around Sun-like stars

Abstract

We present radial-velocity measurements obtained in a programs underway to
search for extrasolar planets with the spectrograph SOPHIE at the 1.93-m
telescope of the Haute-Provence Observatory. Targets were selected from
catalogs observed with ELODIE, mounted previously at the telescope, in order to
detect long-period planets with an extended database close to 15 years. Two new
Jupiter-analog candidates are reported to orbit the bright stars HD150706 and
HD222155 in 16.1 and 10.9 yr at 6.7 (+4.0,-1.4) and 5.1(+0.6,-0.7) AU and to
have minimum masses of 2.71 (+1.44,-0.66) and 1.90 (+0.67,-0.53) M_Jup,
respectively. Using the measurements from ELODIE and SOPHIE, we refine the
parameters of the long-period planets HD154345b and HD89307b, and publish the
first reliable orbit for HD24040b. This last companion has a minimum mass of
4.01 +/- 0.49 M_Jup orbiting its star in 10.0 yr at 4.92 +/- 0.38 AU. Moreover,
the data provide evidence of a third bound object in the HD24040 system. With a
surrounding dust debris disk, HD150706 is an active G0 dwarf for which we
partially corrected the effect of the stellar spot on the SOPHIE
radial-velocities. HD222155 is an inactive G2V star. On the basis of the
previous findings of Lovis and collaborators and since no significant
correlation between the radial-velocity variations and the activity index are
found in the SOPHIE data, these variations are not expected to be only due to
stellar magnetic cycles. Finally, we discuss the main properties of this new
population of long-period Jupiter-mass planets, which for the moment, consists
of fewer than 20 candidates. These stars are preferential targets either for
direct-imaging or astrometry follow-up to constrain the system parameters and
for higher precision radial-velocity to search for lower mass planets, aiming
to find a Solar System twin.

Full text

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arXiv:1205.5835v3 [astro-ph.EP] 10 Aug 2012
Astronomy & Astrophysics manuscript no. LonguesP˙Boisse˙v13
August 13, 2012
c ? ESO 2012
The SOPHIE search for northern extrasolar planets⋆,⋆⋆
V. Follow-up of ELODIE candidates: Jupiter-analogs around Sun-like stars
I. Boisse1,2, F. Pepe3, C. Perrier4, D. Queloz3, X. Bonfils4, F. Bouchy2,5, N.C. Santos1,6, L. Arnold5, J.-L. Beuzit4, R.F.
D´ ıaz7, X. Delfosse4, A. Eggenberger4, D. Ehrenreich4, T. Forveille4, G. H´ ebrard2,5, A.-M. Lagrange4, C. Lovis3, M.
Mayor3, C. Moutou7, D. Naef3, A. Santerne7, D. S´ egransan3, J.-P. Sivan7, and S. Udry3
1Centro de Astrof´ ısica, Universidade do Porto, Rua das Estrelas, 4150-762 Porto, Portugal
e-mail: Isabelle.Boisse@astro.up.pt
2Institut d’Astrophysique de Paris, UMR7095 CNRS, Universit´ e Pierre & Marie Curie, 98bis Bd Arago, 75014 Paris, France
3Observatoire de Gen` eve, Universit´ e de Gen` eve, 51 Ch. des Maillettes, 1290 Sauverny, Switzerland
4UJF-Grenoble 1 / CNRS-INSU, Institut de Plantologie et d’Astrophysique de Grenoble (IPAG) UMR 5274, Grenoble, F-38041,
France
5Observatoire de Haute Provence, CNRS/OAMP, 04870 St Michel l’Observatoire, France
6Departamento de F´ ısica e Astronomia, Faculdade de Ciˆ encias, Universidade do Porto, Rua do Campo Alegre, 4169-007 Porto,
Portugal
7Laboratoire d’Astrophysique de Marseille, Universit´ e de Provence & CNRS, 38 rue Fr´ ed´ eric Joliot-Curie, 13388 Marseille cedex
13, France
Received XX; accepted XX
ABSTRACT
We present radial-velocity measurements obtained in one of a number of programs underway to search for extrasolar planets with the
spectrograph SOPHIE at the 1.93-m telescope of the Haute-Provence Observatory. Targets were selected from catalogs observed with
ELODIE, which had been mounted previously at the telescope, in order to detect long-period planets with an extended database close
to 15 years.
Two new Jupiter-analog candidates are reported to orbit the bright stars HD150706 and HD222155 in 16.1 yr and 10.9 yr at 6.7+4.0
and 5.1+0.6
and SOPHIE, we refine the parameters of the long-period planets HD154345b and HD89307b, and publish the first reliable orbit for
HD24040b. This last companion has a minimum mass of 4.01±0.49 MJuporbiting its star in 10.0 yr at 4.92±0.38 AU. Moreover, the
data provide evidence of a third bound object in the HD24040 system.
With a surrounding dust debris disk, HD150706 is an active G0 dwarf for which we partially corrected the effect of the stellar spot
on the SOPHIE radial-velocities. In contrast, HD222155 is an inactive G2V star. In the SOPHIE measurements, an instrumental
effect could be characterized and partly corrected. On the basis of the previous findings of Lovis and collaborators and since no
significant correlation between the radial-velocity variations and the activity index are found in the SOPHIE data, these variations
are not expected to be only due to stellar magnetic cycles. Finally, we discuss the main properties of this new population of long-
period Jupiter-mass planets, which for the moment, consists of fewer than 20 candidates. These stars are preferential targets either for
direct-imaging or astrometry follow-up surveys to constrain the system parameters and for higher-precision radial-velocity searches
for lower mass planets, aiming to find a solar system twin. In the Appendix, we determine the relation that defines the radial-velocity
offset between the ELODIE and SOPHIE spectrographs.
−1.4AU
−0.7AU and to haveminimum masses of 2.71+1.14
−0.66MJupand 1.90+0.67
−0.53MJup, respectively. Using themeasurements from ELODIE
Key words. planetary systems – techniques: radial velocimetry – stars: individual: HD222155, HD150706 ,HD24040, HD154345,
HD89307– magnetic cycle
1. Introduction
One motivation of our search for planetary systems is to put the
solar system into perspectiveand understandits formation.Until
now, most discovered systems have not resembled the planets
of our system. If we were to observe the Sun in radial-velocity
(hereafter RV), the main source of perturbationshould be that of
⋆Based on observations made with the ELODIE and the SOPHIE
spectrographs on the 1.93-m telescope at Observatoire de Haute-
Provence (OHP, CNRS/OAMP), France (program 07A.PNP.CONS)
and on spectral data retrieved from the ELODIE archive at OHP.
⋆⋆Tables A.1 to A.10 are only available in electronic form at the
CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via
http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/
Jupiter with a period of 11.86 yr, an orbital distance of 5.2 UA,
and a RV semi-amplitude of about 12 ms−1. The detection of
long-period Jupiter-like planets are therefore expected to be the
first step in the quest to discover an analog of the solar system.
This step is already achievable, in contrast to the detection of
earth-like planets in the habitable zone of their host stars which
will generally require the next generation of instruments.
The long-term accuracy of several spectrographs and the
timescale of some RV surveys has started to permit the discover-
ies of long-periodplanets. Few planets are known to date within
the orbital distance range of Jupiter with fewer than seventeen
planetshavingbeenfoundtobe orbitingat distancesgreaterthan
4 AU (cf. Table 1). Some of these have been announced with in-
complete orbits. These planets overlap with the few microlens-
1

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I. Boisse et al.: The SOPHIE search for northern extrasolar planets
ing detections at these orbital distances and in the Jupiter-mass
regime, as OGLE235-MOA53b is a 2.6 MJupplanet at 5.1AU
(Bond et al. 2008). We note that the planet-host stars are ex-
pected to be low-mass stars and their giant planets are colder
than Jupiter.
The SOPHIE consortium started a large program to search
for planets in October 2006 (Bouchy et al. 2009) that led to sev-
eral planet discoveries (e.g. H´ ebrard et al. 2010, Boisse et al.
2010b, D´ ıaz et al. 2012). Among the different subprograms,one
focuses on the follow-up of the drifts and long-period signals
detected in the ELODIE sample, in line with the continuity of
the historical program initiated by M. Mayor and D. Queloz in
1994 with the spectrograph ELODIE over more than 12 years
(Mayor& Queloz1995;Naef et al. 2005).These trendsare iden-
tified as incomplete orbits of gravitationally bound companions
and the monitoring aims to determine their periods and masses,
(thus establish either their planetary, brown dwarf, or stellar
nature). The SOPHIE spectrograph has replaced ELODIE at
the 1.93m-telescope at Observatoire de Haute-Provence (OHP)
since October 2006. About 40 targets were selected from the
original ELODIE catalog, which contained about 400 targets.
They are mainly G and K dwarfs, which have been observed
with SOPHIE with the objective of detecting very long-period
planets (>8 yr) and multiple systems.
We report the detection of two Jupiter-analogs around the
Sun-likestars HD150706andHD222155basedon ELODIEand
SOPHIE RV measurements. The observations are presented in
Section 2, and we characterize the planet-host stars in Sect. 3.
In Sect. 4, we analyze the RV measurements and constrain the
planetary parameters. In Sect. 5, we determine the first reliable
orbitforHD24040b(Wrightetal.2007),andrefinetheplanetary
parameters of HD154345b (Wright et al. 2008) and HD89307b
(Fischer et al. 2009). Finally in Sect. 6, we discuss how the ob-
served RV variations should not come from long-term magnetic
cycles, before putting these new planets in the context of the
other discoveries and the perspectives for these systems to be
followed. In the Appendix, we determine the RV shift between
the ELODIE and SOPHIE data.
2. Radial velocity measurements
Measurements were obtained with the cross-dispersed echelle
ELODIE spectrograph mounted on the 1.93-m telescope at the
Observatoire de Haute-Provence observatory (OHP, France) be-
tween late 1993 and mid 2006 (Baranne et al. 1996). The stars
were subsequently monitored by the SOPHIE spectrograph that
replacedELODIEwhichprovidedimprovementsintermsofsta-
bility, limiting magnitude, and resolution. For the two instru-
ments, the stellar spectrum were recorded simultaneously with a
thorium-argoncalibration(thosimult mode,Bouchy et al. 2009),
allowing an estimation of the intrinsic drift of the spectrograph
at the same time as the observation. The optical fibers include a
double scrambler in the path of light to improve the RV stability.
A mean time exposureof 900 s (which variedbetween 600 s and
1200s depending on the weather conditions) helped to minimize
the photon noise and average the acoustic oscillation modes (p-
modes).
ELODIE has a resolving power R=λ/∆λ ≈ 42000 (at
550 nm,see e.g.Perrier et al. 2003for more details). The spectra
are correlated with a G2-spectral type numerical mask. The re-
sulting cross-correlationfunctions(CCF) are fitted by Gaussians
to derive the RV values (Baranne et al. 1996, Pepe et al. 2002).
The SOPHIE observations were performed in high-
resolution mode reaching a resolution power of ∆λ/λ ≈ 75000
(at550nm).TheSOPHIEautomaticdatareductionsoftwarewas
used to derive the RV from the spectra, after a cross-correlation
with a G2-spectral type numerical mask (Baranne et al. 1996;
Pepe et al. 2002) and a fit of a Gaussian to the resulting CCF.
The typical photon-noise uncertainty is around 1.5 ms−1, which
was calculated as described in Boisse et al. 2010b. However, the
main error source in these measurements originates from the in-
strument, namely the seeing effect (Boisse et al. 2010a,b). This
instrumental effect is due to the insufficient scrambling of one
multimode fiber that leads to the non-uniform illumination of
the entrance of the spectrograph. We note that this noise was
removed by a fiber link modification, which includes a piece
of octagonal-section fiber in June 2011 (Perruchot et al. 2011).
An external systematic error of 4 ms−1for instrumental errors
(guiding, centering, and seeing) was then quadratically added
to the SOPHIE mean measurement uncertainty. Seeing error is
not expected in the ELODIE measurements as the instrumen-
tal configuration was different, but the RV uncertainty take into
account the guiding and centering errors. In the following, the
signal-to-noise ratio (SNR) are given per pixel at 550 nm. We
note the sampling per resolution element (full width half max-
imum, FWHM) is 2.2 pixels for ELODIE and 2.7 pixels in the
high-resolution mode for SOPHIE.
The RV data are available at the CDS as tables, which con-
tain in theirs cols. 1-3, the time of the observation (barycentric
Julian date), the RV, and its error, respectively
2.1. HD150706
Over nine years, between July 1997 and June 2006, 50 RV
measurements were done with the ELODIE spectrograph. We
did not take into account two measurements with SNR<10.
SOPHIE obtained 59 observations of HD150706 between May
2007 and April 2011. Five measurements with SNR lower than
100 were removed. One spectrum contaminated by moonlight
was also discarded. The final data set contains 48 ELODIE and
53 SOPHIE measurements with a typical SNR of, respectively,
80 and 172. The data are available at the CDS in Tables A.1
(ELODIE) and A.2 (SOPHIE).
2.2. HD222155
We obtained 44 spectra of HD222155 with the ELODIE spec-
trograph on a timescale of eight years between August 1997 and
November2005. HD222155was observed 71 times by SOPHIE
between July 2007 and January 2011. Three measurements with
SNR lower than 100 were removed. We discarded one observa-
tion, which had been made with the background sky spectrum
recorded simultaneously (objAB mode, Bouchy et al. 2009) in
order to measure the stellar parameters (cf. Sect. 3.2). The fi-
nal data set comprises 44 ELODIE measurements with a typical
SNR of 92 and 67 SOPHIE values with a mean SNR of 173.The
data are available at the CDS in Tables A.3 (ELODIE) and A.4
(SOPHIE).
3. Planet host stars
3.1. HD150706
HD150706 (HIP80902) is a G0V star with an apparent Johnson
V-bandmagnitudeofmV=7.0(Hipparcoscatalogue,ESA 1997).
Assuming an astrometric parallax of π=35.43±0.33mas (van
Leeuwen 2007), we derived a distance of 28.2±0.3 pc, which
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I. Boisse et al.: The SOPHIE search for northern extrasolar planets
Table 2. Stellar parameters for HD150706 and HD222155.
Parameters
Sp. T.
mV
B - V
π [mas]
Teff[K]
log g [cgs]
Fe/H [dex]
vsini⋆[kms−1]
M⋆[M⊙]
R⋆[R⊙]
logR′
Age [Gyr]
Distance [pc]
HD150706
G0V
7.0
0.57
35.43±0.33
5961±27(1)
4.5±0.1(1)
-0.01±0.04(1)
3.7±1.0(3)
1.17±0.12(1)
0.96±0.02
-4.47±0.10(3)
1-5
28.2±0.3
HD222155
G2V
7.1
0.64
20.38±0.62
5765±22(2)
4.10±0.13(2)
-0.11±0.05(2)
3.2±1.0(3)
1.13±0.11
1.67±0.07
-5.06±0.10(3)
8.2±0.7
49.1±1.5
HK[dex]
(1)Parameter derived from the UES spectra (Santos et al. 2003).
(2)Parameter derived from the SOPHIE spectrum (Santos et al. 2004).
(3)Parameter derived from the SOPHIE CCF (Boisse et al. 2010b).
leads to an absolute V-band magnitude of 4.75. A stellar diam-
eter R⋆=0.96±0.02R⊙was estimated by Masana et al. (2006)
from photometric measurements.
A spectroscopic analysis (Santos et al. 2004) was done on
high-resolution spectra obtained with the UES spectrograph on
the 4-m William Herschel telescope (Santos et al. 2003). They
derived an effective temperature Teff=5961±27 K, a surface
gravity log g=4.5±0.1, a metallicity [Fe/H]=-0.01±0.04, and
a stellar mass M⋆=1.17±0.12M⊙.
From the SOPHIE CCF (Boisse et al. 2010b), we estimated
vsini⋆=3.7±1.0 kms−1and a metallicity of [Fe/H]=0.08±0.10
in agreement with the spectroscopic analysis. We assessed the
stellar activity level from the emission in the core of the
CaII H&K bands, which was measured in each SOPHIE spec-
tra of HD150706 with the calibration reported in Boisse et al.
(2010b).Thisyields a valueoflogR
is an active star and we may expect to find a RV jitter caused by
stellar spots of about 15ms−1(Santos et al. 2000). According
to the calibrations of Noyes et al. (1984) and Mamajek &
Hillenbrand (2008), the logR′
rotationperiod of Prot≈5.6 days. From the vsini⋆and stellar ra-
dius values, we inferredthat Prot? 18 days (Bouchyet al. 2005).
Holmberg et al. (2009) estimated an age of 5.1+3.7
which agrees with the Marsakov et al. (1995) value of 4.69 Gyr.
However younger ages were derived from CaII measurements,
namely 1.4 Gyr (Wright et al. 2004) and 1.16 Gyr (Rocha-Pinto
et al. 2004), and by comparing with stellar isochrones, namely
2.3 Gyr (Gonzalez et al. 2010).
Meyer et al. (2004) detected a dust debris disk surrounding
HD150706 using IRAC and MIPS Spitzer data. The authors ar-
gued for the presence of a companion in order to explain their
observation of a large inner hole in the dust distribution of the
disk.
The parameter values for the star are gathered in Table 2.
′
HK=-4.47±0.10.HD150706
HKvalue of HD150706 implies a
−4.5Gyr,
3.2. HD222155
HD222155 (HIP116616) is a G2V bright star with an appar-
entJohnsonV-bandmagnitudeofmV=7.1(Hipparcoscatalogue,
ESA 1997)anda B−V=0.64.Van Leeuwen(2007)derivedfrom
the Hipparcos measurements a parallax of 20.38±0.62mas,
leading us to infer a distance of 49.1±1.5pc with an absolute
V magnitude of 3.65 mag.
The star’s effective temperature Teff=5765±22K, sur-
face gravity logg=4.10±0.13, micro-turbulence velocity
Vt=1.22±0.02 kms−1, and metallicity [Fe/H]=-0.11±0.05
dex, were determined using the spectroscopic analysis method
described in Santos et al. (2004). The analysis was performed
on a spectrum of high SNR measured with SOPHIE without
a simultaneous calibration. When combined with isochrones
(da Silva et al. 2006)1, these parameters yield a stellar mass
M⋆=1.06±0.10M⊙, a stellar radius of R⋆=1.67±0.07R⊙, and
an age 8.2±0.7 Gyr in agreement with the 8.4 Gyr estimated by
Holmberg et al. (2009). The values of the radius and the mass
agree with those derived by Allende-Prieto & Lambert (1999)
of M⋆=1.20±0.11M⊙and R⋆=1.66±0.07R⊙. For the stellar
mass, we chose the mean value M⋆=1.13±0.11M⊙.
Theprojectedrotationalvelocityvsini⋆=3.2±1.0kms−1is
estimated from the SOPHIE CCF (Boisse et al. 2010b). The al-
ternative estimate of the stellar metallicity [Fe/H]=0.02±0.10
from the CCF is consistent with the more accurate determina-
tion based on spectral analysis. The stellar activity index is de-
rived from the stellar spectra calculated in the CaII H&K lines,
logR′
These stars have a lower logR′
2011b) owing to their higher luminosities and/or lower surface
gravities compared to main-sequence stars of the same color.
These stars are expected to have smaller long-term variabilities
thanmain-sequencestars.HD222155isthenalow-activestarfor
which we expect intrinsic variability at a lower level than those
caused by instrumental effects. For logR′
Hillenbrand (2008) noted that the correlation between logR′
and the Rossby number is poor and they were unable to derive a
reliable relation to derive a Prot.
The stellar parameters are given in Table 2.
HK=-5.06±0.10. HD222155 is on its way to be a subgiant.
HK(Wright et al. 2004,Lovis et al.
HK?-5.0, Mamajek &
HK
4. Radial velocity analysis and planetary
parameters
4.1. HD150706b, a Jupiter analog around an active star
A
HD150706b, was announced during the ”Scientific Frontiers
in Research on Extrasolar Planets” conference, Washington,
in June 2002 based on ELODIE RV measurements. However,
later observations led the conclusion that the RV variations
are instead caused by a longer-period planet (S. Udry, private
communication).
Using Eq. A.2 from our Appendix A, we first fixed the
∆(RV)E−S between ELODIE and SOPHIE data and computed
the weighted and the generalized Lomb Scargle periodograms.
For both, the highest peak is detected close to 5000 days with a
false alarm probability (fap)<0.001. The fap was generated us-
ing both Monte Carlo simulations to draw new measurements
according to their error bars, and the random permutation of the
date of the observations, as described in Lovis et al. (2011a).
Eight Keck measurements were published by Moro-Mart´ ın
et al. (2007) which showed that the short period solution was
incorrect. We added these measurements to our RV data. An er-
ror of 5ms−1was quadratically added to their instrumental error
barsinordertotakeintoaccountthestellaractivityjitter.TheRV
data were then fitted with a Keplerian model using a Levenberg-
Marquardt algorithm, after selecting starting values with a ge-
Jupiter-massplanetinan eccentric 265-dayorbit,
1Web interface available on http://stev.oapd.inaf.it/cgi-bin/param.
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I. Boisse et al.: The SOPHIE search for northern extrasolar planets
-0.04-0.0200.020.04 0.06
-0.04
-0.02
0
0.02
0.04
0.06
Fig.1. SOPHIE residuals from the Keplerian fit of HD150706
as a function of the BIS. The best-linear fit is plotted as a black
line. The scale is the same in the x and y axis.
netic algorithm (S´ egransan et al. 2011). The ∆(RV)E−S was al-
lowed to vary and the fitted value,−31.1±13.6ms−1is in agree-
ment with the calibration value of ∆(RV)E−S=-40±23ms−1.
The best-fit solution is consistent with an orbital period of
P=3950 days and a semi-amplitude K=31ms−1. The residuals
of the best-fit Keplerian model are equal to σ(O−C)=19.5ms−1,
which consists of components of 18ms−1for the ELODIE RV,
and 20ms−1for the SOPHIE ones. These values are large com-
pared to the mean error bars. The 6.1ms−1dispersion for the
residuals of the Keck data points may be smaller due to a small
number of points and the free offset between datasets.
HD150706 is an active star and we may expect to measure
some RV jitter as discussed in Sect. 3.1. We note that by exam-
iningat the periodogramof the (O−C)values,a peak close to 10
days is scarcely detected, value in the domain of the Protthat we
derive in Sect.3.1. With a vsini=3.7kms−1, an anti-correlation
between (O − C) and the bisector span (BIS) is expected if RV
variationsare due to stellar activity.The ELODIEmeasurements
have an error bars of about 10ms−1for the RV and 20ms−1for
the BIS. This precision hampers the detection of a correlation
for data with a dispersion of 16ms−1. On the other hand, an anti-
correlation is observed in the SOPHIE data as shown in Fig. 2.
The correlation coefficient is equal to -0.56 with a fap<10−5and
the Spearman coefficient is -0.47. The fap is calculated with ran-
dom permutations of the RV data. As in Melo et al. (2007) and
Boisse et al. (2009), we corrected the SOPHIE RV for this trend
RVcorrected1[kms−1]=RV [kms−1]+1.32× BIS [kms−1].
Moreover, at high SNR, SOPHIE data are polluted by an
instrumental limitation, called the seeing effect (Boisse et al.
2010a,b). This apparent RV shift is related to the illumination
of the spectrograph, which varies mainly owing to the see-
ing. Its current characteristic signature is a linear correlation
between the RV and a seeing estimator
counts for the flux entering into the spectrograph per unit of
time, Σ = SNR2/Texp, where Texpis the time exposure. The
HD150706 SOPHIE (O−C) are plotted in Fig. 2. A linear trend
is detected with correlation and Spearman coefficients of -0.48
with fap<10−4. The SOPHIE RV was corrected for this slope,
RVcorrected2[kms−1]=RVcorrected1[kms−1]+0.00071×Σ. We note
Sigma, which ac-
20 30 405060
-0.04
-0.02
0
0.02
Fig.2. HD150706 SOPHIE residuals from the Keplerian fit of
the RV corrected for the active jitter as a function of the seeing
estimator, illustrating the instrumental effect on RV caused by
seeing variations. The best-least squares linear fit is also plotted.
that swappingthe orderof the correctionsdo notchangethe final
result as the order of magnitudeof the two effects are equivalent.
Finally, we fitted using a Keplerian model the ELODIE and
Keck measurements together with the corrected SOPHIE ones.
The final orbital elements are listed in Table 3. They were com-
puted using 4.8 106Monte Carlo simulations with a prior on
the ∆(RV)E−S equals to the calibrated value and its uncertainty.
The uncertainties in the final parameters correspond to their
0.95 confidence intervals. The best-fit solution is consistent with
a non-significant eccentric orbit, e=0.38+0.28
of P=5894+5584
Takingintoaccounttheerrorbarin the stellar mass, HD150706b
is a planet with a minimum mass mpsini=2.71+1.14
ing its star with a semi-major axis of 6.7+4.0
best-fit Keplerianmodel is superimposedon the ELODIE, Keck,
and SOPHIE velocities. We also add plots in Fig.4 to illustrate
the dependence of the K, P, and e parameters on ∆(RV)E−S.
We did not find any indication of a second planet in the sys-
tem with the currentdataset. Fromoursolution,whichhas a dis-
persionof15ms−1,theRV residualsexcludeaninnerplanetwith
mpsini > 1.3MJup. On the other hand, owing to the time span of
13.3 yr covered by our observations, we should not have missed
an external planet that induces a drift larger than 1.1ms−1yr−1.
−0.32that has a period
−1498days and a semi-amplitude K=31.1+6.3
−4.8ms−1.
−0.66MJuporbit-
−1.4AU. In Fig. 3, the
4.2. HD222155b, a Jupiter analog around a quiet star
We usedthesamemethodologyasforHD150706.First, wefixed
the ∆(RV)E−Sderived by the calibration (Appendix A) and used
a Lomb Scargle periodogram to estimate the significance level
of the detection of a long-period planet. With a fap<0.001, the
highest peak corresponds to a period close to 4000 days.
The ELODIE and SOPHIE RV data were then fitted with a
Keplerian model. The eccentricity as well as the RV offset be-
tween the data sets were set as free parameters. The fitted off-
set -49±8ms−1agrees with the calibrated one within the error
bars, -70±23ms−1. The orbit has an insignificant eccentricity of
e=0.26±0.24,a semi-amplitudeof K=20.1ms−1, and a periodof
3259 days. The residuals to the fit σ(O−C)=19.9ms−1are large
compared to the mean error bar.
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I. Boisse et al.: The SOPHIE search for northern extrasolar planets
Fig.4. Covariance between the semi-amplitude K (left panels), the eccentricity e (middle panels), the period P (right panels), and
the ∆(RV)E−S for the HD150706 (top panels), HD222155 (middle panels) and HD24040 systems (bottom panels). The red, blue,
and purple contour lines represent, respectively, the one, two, and three-σ confidence intervals.
The star is inactive and we do not expect any jitter as an
astrophysical noise. On the other hand, the seeing effect is char-
acterized in the SOPHIE data. In Fig. 5, SOPHIE residuals are
plotted as a function of the seeing estimator Σ. The correlation
coefficient is equal to -0.51 and the Spearman coefficient to -0.5
with fap<10−5, justifyinga linear least squaresfit to the data. We
corrected the SOPHIE RV for this trend RVcorrected[kms−1]=RV
[kms−1]+0.00068×Σ.
We then fitted a Keplerian model to the corrected SOPHIE
RV and the ELODIE measurements. The final orbital elements
were computed based on 4.8 106Monte Carlo simulations
with a prior on the ∆(RV)E−S equals to the calibrated value
and its uncertainty (and accounting for the correction on the
SOPHIE RV). The uncertainties correspond to the 0.95 confi-
dence interval. They are listed in Table 3. The best-fit solution
is an insignificant eccentric orbit (e=0.16+0.27
3999+469
spondingplanet has a minimum mass of mpsini=1.90+0.67
and orbits HD222155 with a semi-major axis of 5.1+0.6
ing into account the error bar in the stellar mass. In Fig. 6, the
best-fit Keplerian model is superimposed to the ELODIE and
−0.22) with a period P=
−4.8ms−1.Thecorre-
−541daysandasemi-amplitude K=24.2+6.4
−0.53MJup
−0.7AU, tak-
SOPHIE velocities. Plots in Fig. 4 show the covarianceof the K,
P, and e parameters with ∆(RV)E−S.
NoperiodicityisdetectedintheRV residuals.Thedispersion
of the residuals, σ(O−C)∼11ms−1, excludes an inner planet with
mpsini > 0.9MJupand an external planet should not induce a
drift larger than 0.8ms−1yr−1.
5. Refine the orbital parameters of previously
announced long-period planets
The following targets were measured for the same subpro-
gram and observed with the same strategy as that adopted for
HD150706 and HD222155, which was detailed in Sect. 2.
5.1. HD24040b
Wright et al. (2007) presented the RV variability of HD24040b
measured for this inactive G0V star using Keck data. At that
time, the authors announced a companion with a period of be-
tween 10 yr and 100 yr and a minimum mass in the range be-
tween 5MJupand 20MJup. The stellar parameters can be found
in Table 2 of Wright et al. (2007).
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I. Boisse et al.: The SOPHIE search for northern extrasolar planets
Table 3. Keplerian solution and inferred planetary parameters
for HD150706b and HD222155b (see text for details).
Parameters
RVmeanelodie [kms−1]
RVmeansophie [kms−1]
RVmeankeck [kms−1]
P [days]
K [ms−1]
e
ω [deg]
T0[JD]
mpsini [MJup]
a [AU]
σ(O−C)elodie [ms−1]
σ(O−C)sophie [ms−1]
σ(O−C)keck [ms−1]
HD150706b
-17.2094+0.0145
-17.1271+0.0127
0.0322+0.0074
5894+5584
31.1+6.3
0.38+0.28
132+37
58179+4396
2.71+1.14
−0.66
6.7+4.0
−1.4
15.3
14.2
6.2
HD222155b
-43.9923+0.0042
-43.9007+0.0129
−0.0064
−0.0052
−0.0118
−0.0114
−0.0075
−1498
3999+469
24.2+6.4
0.16+0.27
137+240
56319+664
1.90+0.67
−0.53
5.1+0.6
−0.7
11.5
9.9
−541
−4.8
−4.8
−0.32
−0.22
−33
−52
−1586
−498
⋆
∗
⋆
∗
⋆Assuming M⋆=1.17±0.12M⊙
∗Assuming M⋆=1.13±0.11M⊙
Fig.3. ELODIE (red), Keck (green), and SOPHIE (blue) RV
data points and their residuals from the best-fit Keplerian model
for HD150706as a function of barycentricJulian date. The best-
fit Keplerian model is represented by the black curve with a re-
duced χ2equal to 2.6. The period is 16.1 yr with a slight eccen-
tricity e=0.38+0.28
−0.32and the planet minimum mass is 2.71 MJup.
Our observations of HD24040, which were obtained dur-
ing, for ELODIE September 1997 and December 2005, and
for SOPHIE February 2008 and December 2010, have provided
respectively 47 ELODIE and 21 SOPHIE measurements. The
SOPHIE data with SNR<100 were removed (four observations)
and we discarded three measurements for which there were ab-
normal flux level in the thorium-argoncalibration lamp.
We combined both the ELODIE and SOPHIE datasets with
the published Keck ones. We found that the best Keplerian fit
converges with a RV offset between ELODIE and SOPHIE of
∆(RV)E−S=-120±12ms−1, which is significantly larger than the
calibrated value of -74±23ms−1for this star with a B−V =0.64.
Moreover,the RV diagram shows a clear trend, as seen in Fig. 8.
We then fit the RV measurements with a Keplerian and a linear
2040 60
-0.04
-0.02
0
0.02
Fig.5. SOPHIEresidualsfromtheKeplerianfit ofHD222155as
a function of the seeing estimator. The best least squares linear
fit is also plotted.
Fig.6. ELODIE (red) and SOPHIE (blue) RV and residuals
from the best-fit Keplerian model for HD222155 as a function
of barycentric Julian date. The best-fit Keplerian model is rep-
resented by the black curve with a reduced χ2equal to 2.2. The
planet has a period of 10.9 yr in a non-significant eccentric orbit
(e=0.16+0.27
−0.22), and a minimum mass of 1.90 MJup.
trend. We search for the seeing effect in the residuals of the fit.
The SOPHIE (O − C) data are plotted as a function of the see-
ing estimator in Fig. 7. The correlation coefficient, which equals
−0.30,is not significantwith a 30% probabilitythat the two vari-
ables are uncorrelated.We removedfrom the study the measure-
ment with the highest seeing estimator value, which is certainly
biased by the seeing effect. The final ELODIE and SOPHIE
datasets are available electronically in Tables A.5 and A.6.
Were-adjustedthedatawithasimultaneousfitofaKeplerian
and a linear trend. The RV offset is equal to -67±13ms−1, in
agreement within the error bars with the calibrated value. The
final orbital elements are computed from 4.8 106Monte Carlo
simulations with a prior on the ∆(RV)E−S equals to the cali-
brated value and its uncertainty. Fig. 8 shows the velocities as
6

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I. Boisse et al.: The SOPHIE search for northern extrasolar planets
152025 30 35
-0.02
-0.01
0
0.01
Fig.7. HD24040 SOPHIE residuals from the Keplerian fit as a
functionofthe seeingestimator.The lineartrendis insignificant.
Fig.8. ELODIE (red), Keck (green) SOPHIE (blue) RV and
residuals to the best-fit Keplerian model (black curve) for
HD24040 as a function of barycentric Julian date. It shows a
4.01 MJupcompanion with an orbital period of 10.0 yr. A linear
trend is fitted simultaneouslypointingout the presence of a third
body in the system.
a functionof time, as well as the fitted Keplerian orbit with a pe-
riod of 3668 days and the linear trend of 3.85+1.43
underlying linear drift easily explains why Wright et al. (2007)
overestimated the period and the mass of HD24040b when fit-
ting over a fraction of the orbital period. The solution is circu-
lar, e=0.04+0.07
inferred minimum mass of the companion, accounting for the
uncertainty in the stellar mass, is 4.01±0.49 MJupwith a semi-
majoraxis of 4.92±0.38AU (Table5). Therelations betweenthe
K, P, and e parameters and ∆(RV)E−Sare plotted in Fig. 4.
The residuals has a dispersion of 7.5ms−1and do not show
any evidence of shorter period companions, and an inner planet
with mpsini>0.62MJupis excluded.
−1.29ms−1yr−1. The
−0.06, with a semi-amplitude of K=47.4+2.7
−2.6ms−1. The
Table 5. Keplerian solution and inferred planetary parameters
for HD24040b with the combined measurements of ELODIE,
SOPHIE, and the Keck RV data published by Wright et al.
(2007).
Parameters
RVmeanelodie [kms−1]
RVmeansophie [kms−1]
RVmeankeck [kms−1]
RVlinear[ms−1yr−1]
P [days]
K [ms−1]
e
ω [deg]
T0[JD]
mpsini [MJup]
a [AU]
σ(O−C)elodie [ms−1]
σ(O−C)sophie [ms−1]
σ(O−C)keck [ms−1]
HD24040b
-9.4003 ±0.0040
-9.3118+0.0150
0.0311+0.0039
3.85+1.43
3668+169
47.4+2.7
0.04+0.07
154+84
54308+859
4.01±0.491
4.92±0.381
14.9
7.3
7.2
−0.0156
−0.0036
−1.29
−171
−2.6
−0.06
−54
−839
1Assuming M⋆=1.18±0.10M⊙
5.2. HD89307b
On the basis of observations acquired at the Lick Observatory
since 1998, Fischer et al. (2009) published evidence of a
companion of mpsini=1.78±0.13MJup with a period of
2157±63daysandan eccentricityof0.24 ± 0.07inorbitaround
HD89307, which is a bright inactive G0 dwarf. We refer the
reader to the Fischer et al. (2009) stellar parameters (cf. their
Table 1). We note that their stellar values agree with those de-
rived by Sousa et al. (2006) based on a SARG observation at
TNG.
We performed 46 ELODIE and 11 SOPHIE observations,
respectively, between December 1997 and April 2006, and be-
tween December 2006 and February 2011. Our corresponding
RV data are available electronically in Tables A.7 and A.8.
We combined our measurements with the Lick RV. Figure 9
shows the Keplerian orbit and the residuals around the solu-
tion. The RV shift between ELODIE and SOPHIE, ∆(RV)E−S=-
66±12ms−1, agrees with the calibrated one, -49±23ms−1. No
instrumental effect is observed in the SOPHIE data. The plan-
etary parameters agree with those of Fischer et al. (2009).
The fitted parameters for the companion and their uncertainties
corresponding to the 0.95 confidence interval computed from
5000 permutation simulations are listed in Table 9. Assuming
a stellar mass of M⋆=1.03 M⊙ and taking into account its
uncertainty (±0.10M⊙), we computed a planetary minimum
mass of mpsini=2.0±0.4MJupfor the HD89307 companion,
which is slightly higher than the previous published value. The
planet has a little longer period of 2199±61days and orbits at
3.34±0.17AU. We confirm the probable eccentricity of the orbit
with e=0.25 ± 0.09.
The residuals do not show periodicity. With a dispersion of
8ms−1, the residuals excludethe presence of an inner planet with
a minimum mass mpsini>0.5MJup.
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I. Boisse et al.: The SOPHIE search for northern extrasolar planets
Fig.9. ELODIE (blue), Lick (green), and SOPHIE (red) RV and
residuals from the best-fit Keplerian model (black curve) for
HD89307 as a function of time. The fitted orbit corresponds to a
planet with a minimum mass of 2.0 MJup, a period of 6.0 yr, and
a slightly eccentricity orbit e=0.25±0.09.
5.3. HD154345b
Wright et al. (2008)reportedthe detectionof HD154345bwith a
minimum mass of mpsini = 0.94 ± 0.09MJup, an orbital period
P=3539±66d, and an insignificant eccentricity of e = 0.044 ±
0.046. The host star is a bright quiet G8V (mV=6.7) star with
an estimated mass M⋆=0.88±0.09M⊙. The stellar parameters
can be found in Table 1 of Wright et al. (2008).
The star was also observed by ELODIE and SOPHIE with,
respectively, 49 and 15 measurements spanning 12.2 yr and
3.2 yr. Three measurements were removed from the SOPHIE
sample owing to the abnormal flux levels of the thorium-argon
calibration lamp during observations and one because it was of
too low SNR. We combined these measurements with the Keck
RV and fit them with a Keplerian model. The best-fit solution
converges with a RV offset between ELODIE and SOPHIE of
∆(RV)E−S=107±6ms−1, in agreement with the calibrated one
of 108±23ms−1for this star with a B − V=0.73 (see App. A).
We searched for any seeing effect in the SOPHIE data. As in
HD24040, we found that only one measurements was signifi-
cantly affected by the instrumental effect. We removed this data
point from the sample and fit the three data sets with a Keplerian
model. The final ELODIE and SOPHIE datasets are available
electronically in Tables A.9 and A.10. We found that the best-
fit solution has an equivalent mass and period to Wright et
al. (2008) values and an insignificant eccentricity e=0.26±0.15.
The fitted parameters for the companions and their uncertainties
computed from 5000 permutations simulations and their 0.95
confidence intervals are listed in Table 9. The final RV offset is
equal to ∆(RV)E−S=112±10ms−1. We inferred a minimum mass
of 1.0±0.3 MJup, and semi-major axis of 4.3±0.4 AU. The error
bars take into account the uncertainty in the stellar mass. The
best-fit solution is plotted in Fig. 10. No significant variability
is found in the residuals, and for a total dispersion of 4ms−1, an
inner planet with mpsini>0.3MJupis not allowed.
Fig.10. ELODIE (red), Keck (green), and SOPHIE (blue) RV
and residuals of the best-fit Keplerian model (black curve) for
HD154345 as a function of barycentric Julian date. The com-
panion has a period of 9.7 yr, and a minimum mass of 1.0 MJup.
Table 9. Keplerian solution and inferred planetary parameters
for HD154345b and HD89307b with the combined measure-
ments of ELODIE, SOPHIE, and the already published RV data.
Parameters
RVmeanelodie [kms−1]
RVmeansophie [kms−1]
RVmeanoriginal RV [kms−1]
P [days]
K [ms−1]
e
ω [deg]
T0[JD]
mpsini [MJup]
a [AU]
σ(O−C)elodie [ms−1]
σ(O−C)sophie [ms−1]
σ(O−C)original RV [ms−1]
HD154345b
-46.954 ± 0.005
-46.842 ± 0.005
-0.004 ± 0.005A
3538±300
17.0 ± 3.7
0.26 ±0.15
-14±160
54701 ± 1000
1.0 ±0.31
4.3±0.41
12.9
6.6
2.9A
HD89307b
23.067 ±0.005
23.133 ±0.007
0.007 ±0.005B
2199±61
32.4±4.5
0.25±0.09
14 ± 33
54549±190
2.0±0.42
3.34±0.172
19.5
4.1
8.4B
AKeck RV (Wright et al. 2008)
BLick RV (Fischer et al. 2009)
1Assuming M⋆=0.88±0.09M⊙
2Assuming M⋆=1.03±0.10M⊙
6. Are we observing magnetic cycles ?
It is only recently that the discoveries of planets with orbital pe-
riods reachingthe rangewhere stellar magneticcycles have been
observed (from 2.5 to 25 years, Baliunas et al. 1995), have been
achievable. A magnetic cycle could induce RV variations with
the periodic modification of the number of spots and plages on
the stellar photosphere (as observed on the Sun on a 11-year pe-
riod), related to changes in the convection pattern and/or other
mechanisms such as meridional flows (Beckers 2007, Makarov
2010), owing to the magnetic field created by dynamo. The
logR’HKindex computed from the CaII H&K lines is sensitive
to the presence of plages in the stellar chromosphere and is a
reliable means of monitoring the magnetic cycle.
Dedicated RV observations of stars with known magnetic
cycles (Santos et al. 2010a, Gomes da Silva et al. 2012)
have measured weak correlations between active lines indices
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I. Boisse et al.: The SOPHIE search for northern extrasolar planets
(CaII H&K, Hα, NaI) and RV, as well as in the parameters of
the CCF. However, these studies have been limited by a nar-
row range of spectral types, respectively, early-K and early-M
dwarfs.
On the other hand, high-precision stabilized fiber-fed spec-
trographs that observe in the visible such as HARPS or SOPHIE
can accurately measure the flux in the CaII H&K lines. They
can monitor with high precision the variation with time in the
logR’HK index (Lovis et al. 2011b). While searching for plan-
ets, HARPS RV measurements have revealed stellar magnetic
cycles (Moutou et al. 2011, S´ egransan et al. 2011, Dumusque et
al. 2011). Lovis et al. (2011b) used the HARPS sample to iden-
tify activity cycles and deriverelations between the RV and CCF
parameter variations as a function of the R′
relations depend on the stellar effective temperature and could
be used to estimate the RV jitter produced by a magnetic cycle.
The FWHM or contrast of the CCF are insufficiently accu-
rateintheELODIEorSOPHIEmeasurementstopermitustoex-
amine their variations. In addition, the accuracy of the ELODIE
BIS is too low to be sensitive to the effect of a magnetic cycle.
Moreover, the use of the thorium-argon lamp during the obser-
vations leads to polluted light on the CCD detector that prevents
the measurement of the flux inside the active lines for ELODIE
spectra. Only SOPHIE measurements of active lines can be used
on a shorter timescale (∼3 years) to check for stellar variability.
Our observations alone cannot provide any conclusions about
the existence of magnetic cycles on the reported stars. Pursuing
further observations is therefore needed.
Nevertheless, we measured the Pearson and Spearman cor-
relation coefficients between the logR’HKand the RV values ex-
tracted from the SOPHIE data. For the only active star of the
sample, HD150706, we averaged the measurements into bins of
30 days to remove the effect of the rotational period. We tested
the significance of these coefficients with 100,000 Monte Carlo
simulations of shuffled data. We did not find any correlation that
could place in doubt the planetary hypothesis.
We can assessed the planetary hypothesis using the results
of Lovis et al. (2011b). We observed that in their Fig. 19 the
maximal RV amplitude induced by a magnetic cycle is 12ms−1.
The detected RV semi-amplitudes reported in our paper are
all greater than 17ms−1, the smallest one being measured for
HD154345. Using Eq. 9 of Lovis et al. (2011b) and the cal-
cium index variations published by Wright et al. (2008), we cal-
culated that the expected RV semi-amplitude due to an active
cycle for HD154345 is 3.65±0.41ms−1, which is far below the
observed one. We also found that the logR’HKsemi-amplitude
needed to induce the RV variation measured in HD89307 is two
times higher than the highest modulation observed by Lovis et
al. (2011b) owing to magnetic cycle (cf. their Fig. 10). We con-
cluded that the most likely explanation of the observed RV vari-
ations for our stars is the planetary hypothesis.
HKvariability. These
7. Concluding remarks
We have presented the detection of two new Jupiter-like
planet candidates around HD150706 and HD222155 with
combined measurements from the ELODIE and the SOPHIE
spectrographs, which were mounted successively on the 1.93-m
telescope at the OHP. Orbiting farther than 5 AU from their
parent stars, the planets have minimum masses of 2.71 MJupand
1.90 MJup, respectively. We have also published the first reliable
orbit for HD24040b, which is another gaseous long-period
planet. We determined a minimum mass of 4.01 MJupfor this
planet in a 10.0 yr orbit at 4.92 AU. We have presented evi-
dence of a third companion in this system. Moreover, we have
refined the planetary parameters of two others Jupiter-analogs,
HD154345b and HD89307b, by combining our RV data with,
respectively,the Keck and the Lick observatoriesmeasurements.
We obtain parameter values in agreement with those of Wright
et al. (2008) and Fischer et al. (2009).
HD150706 is an active star and the signature of its effect
was detected in the BIS of the CCF. We corrected the SOPHIE
measurements for the jitter effect. The four other stars are quiet
with logR′
measurements are affected by instrumental uncertainties caused
by seeing variations, which we partly corrected.
The amplitudes of the RV variations are greater in the case
of all stars than for all the reported active cycles in the literature
(Baliunas et al. 1995, Lovis et al. 2011b). We did not find any
long-term correlations between the RV and the activity index in
the SOPHIE measurements. We concluded that the most likely
explanation of the observed RV variations is the presence of a
planet.
HKvalues lower than −4.9. In contrast, the SOPHIE
In IRAC and MIPS data acquired by Spitzer, Meyer et al.
(2004) detected for HD150706, an infrared excess at 70 µm,
an upper limit at 160 µm, and no evidence of an excess at
λ<35 µm. They interpreted their observations as evidence of a
dust disk surrounding the star with a hole devoid of dust that
has an inner radius of at least 20 AU. The authors proposed
that the presence of an exoplanet could explain the inner edge
of the outer dust disk. The SOPHIE and ELODIE RV data sets
show evidence of a large companion at less than 20 AU around
HD150706. With a minimum mass of 2.71 MJup, HD150706b
orbitingat6.7+4.0
−1.4AU maykeepcleartheinnerregionofthedisk.
Examining the current distribution of the exoplanet candi-
date periodicities discovered by RV (Fig. 11), we observe a drop
after ≈ 4 AU. These long-period planets are part of a new pa-
rameter space, which have been achieved thanks to the exten-
sion of the timelines of RV surveys to longer than 15 years. The
current paper increases to nineteen the number of planets fur-
ther than 4 AU characterizedby the RV measurements(Table 1).
With partial observations (i.e. where the orbital period was not
completely covered) and a small number of objects, it has been
difficult to establish significant statistical trends.
Nevertheless, in Fig. 12, we focused on the planets dis-
covered beyond 4 AU. We remark that no very massive planet
(>8MJup) was found beyond 4 AU, in spite of a RV bias de-
tection toward high-mass objects. We emphasize that the only
one, HD106270b, is a particular object reported by Johnson et
al. (2011)as a verymassive planet (mpsini=11MJup) orbitinga
subgiant. The occurrence rate of planets with minimum masses
higher than 8 MJupis 1/19 for semi-major axes a>4 AU com-
pared to 27/196 (≈ 1/7) for smaller orbits with 1 < a < 4AU2.
Assuming a binomial distribution, this implies that 13.8±2.5%
of the planets with semi-major axes in the range 1 < a < 4AU
and 5.3±22.3% for those with semi-major axes a>4 AU have
minimummasses higherthan8MJup.Thelast errorbarillustrates
theeffects ofsmall numberstatistics. It is unlikelythatthese host
stars would have been discarded from planet surveys as single-
lined spectroscopic binaries: for instance, a 8MJuporbiting in
4000days a one solar-mass star induces a RV semi-amplitude of
102ms−1fora circularorbit,whichleadsto a typicallinearslope
2Statisticswere derived from the catalog of the website exoplanet.eu
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I. Boisse et al.: The SOPHIE search for northern extrasolar planets
of ∼37ms−1yr−1. If this result is not caused by an observational
selection effect, and if we assume that these objects are formed
by core-accretion, an explanation could be that these planets did
notmigratea lot,preventinga largeaccumulationofmaterial.Or
else, the disk coulddissipate whenthese planets formedprevent-
ing them from migrating and growing in mass. We remark that
Mordasini et al. (2012) highlighted that a decrease in frequency
of giant planets at larger distance (>∼5AU) is a solid predic-
tion of the core accretion theory. If this absence of very massive
planets beyond 4-5 AU becomes statistically significant, it is an
important result for formation theory.
If we consider only the planets published with a complete
coverage of their orbits, they are mostly non-eccentric (e<0.25).
In contrast, those with incomplete coverages are almost en-
tirely eccentric(e>0.25),reflectingthat eccentricorbitsare more
easily detected for periods longer that the observation times
(Cumming2004).However,the eccentricitydistributionof these
planets agrees with the current observation of a significant dis-
persion in eccentricities. But we emphasize that a slight eccen-
tricity may hide a longer period planet.
We observe that these planets are found instead in mul-
tiplanetary systems (10 of 19 candidates). This could be due
to an observational bias as systems with planets are preferen-
tially followed-up. The multiple systems (including HD24040)
are plotted in Fig. 13. We remark that the sample includes two
of the most populated systems known, µ Ara (HD160691) and
55 Cnc (HD75732) with respectively, four and five planets. For
these systems, the longer period planet is the most massive one.
HD134987 and HD183263 have similar configurations that our
Jupiter-Saturn system with a lower mass planet outside. Two
stars, HD187123 and HD217107, also host a short-period giant
planet.
Most of the host stars are G-type dwarf stars. This is clearly
an observational bias, as G-type stars were the first spectral type
to be targeted by RV surveys. Fig. 14 shows the distribution of
the host star metallicity. These detections come from different
surveys and samples, and it is not easy to compare the occur-
rence rates. Nevertheless, a first observation would be that giant
gaseous planets appear to occur significantly around stars that
are more metal-rich than average (Santos et al. 2004, Fischer &
Valenti 2005).
These giants planets are supposed to be formed beyond the
”snow line”. According to the models of planet formation and
orbital evolution, giant planets migrate inward on a timescale
comparable with the lifetime of the protoplanetary disk. These
giants planets with long-orbital periods should have neither
migrated or they have followed a scenario that brings them to
this location. They may have formed at the same time as the
disk dissipated preventing them from migrating. They also may
have interacted with other planets in the system causing them
to migrate outwards or hamper their migration. For example,
inward migration could be avoided by resonance trapping if
the mass of the outer planet is a fraction of the mass of the
inner planet, as in the Jupiter-Saturn case (Masset & Snellgrove,
2001, Morbidelli & Crida, 2007).
Our targets are both bright (6.7<mV<7.6) and nearby (be-
tween 18 and 49 pc), hence ideal for follow-up surveys. The
extension of the RV measurements for these targets will allow
to refine the planetary parameters, to search for other planets in
the systems, and to explore the magnetic activity of these stars.
For orbital distances greater than 5 AU, imaging provide critical
observational constraints on the system such as its inclination
and enable to search for outer bodies or provide spectral infor-
0246
0
5
10
15
20
Fig.11. Minimum mass as a function of the semi-major axis for
all planets detected by RV and transit surveys. Empty squared
symbols (filled triangles) represent planets with eccentricities
lower (higher) than 0.25. Crosses indicate fixed eccentricities at
e=0. Jupiter is on the plot. Red points are the Jupiter-like plan-
ets characterized in this paper: HD150706b, HD222155b, and
HD24040b.
46810
0
2
4
6
8
10
12
Fig.12. Minimum mass as a function of the semi-major axis for
planets detected by RV with a >4 AU. Emptymarkers shows the
incomplete orbits, while filled ones represent complete orbits.
Squares and triangles represent, respectively, for low (e<0.25)
and high (e>0.25) eccentricity orbits. The markers surrounded
by blue show multiple systems. The green points indicate the
higher mass planets announced by Marmier et al. (in prep., pri-
vate communication).
mation about the planet. The candidate planets would display
astrometric signatures of hundreds of µas, for example, 550 µas
on HD150706 and 175 µas on HD222155. Despite a duration
mission of timescale shorter than the orbital period, part of these
orbits should be easily detected by Gaia. Moreover, these sys-
tems with long-periodlow-eccentricity Jupiter-type planets may
be similar to the solar system and contain lower mass planets
10

Page 11

I. Boisse et al.: The SOPHIE search for northern extrasolar planets
0.01 0.1110
Fig.13. Multiple systems with semi-major axis greater than
4AU.Thesizeofthedotsshowstheminimummassoftheplanet
on a log scale.
-0.4 -0.20 0.20.4
0
2
4
6
Fig.14. Histogram of host star metallicities [Fe/H] for the plan-
ets with semi-major axis greaterthan 4 AU (all are giant gaseous
planets). In green, the histogram include the six candidates from
Marmier et al. (in prep., private communication)
in shorter orbits such as the µ Ara (HD160691) and 55 Cnc
(HD75732) systems. New fiber scramblers were installed on
SOPHIE in June 2011 (Perruchot et al. 2011), and preliminary
tests showed that they provide a significant improvement in the
stability of the spectrograph illumination, hence the RV accu-
racy. These stars will be followed-up with SOPHIE in order to
search for multiplicity in these systems.
Hence, the transit probabilities for these candidates are very
low at 0.07% and 0.16% for HD150706b and HD222155b, re-
spectively. However, as they may host shorter-period low-mass
planets with higher transit probabilities, they are good targets
to search for Earth-like planets in transit around bright stars in
order to identify a solar system twin.
Acknowledgements. The authors thank all the staff of Haute-Provence
Observatory for their contribution to the success of the ELODIE and SOPHIE
projects and their support at the 1.93-m telescope. We thank the referee
for his/her careful reading and judicious comments. We wish to thank the
“Programme National de Plan´ etologie” (PNP) of CNRS/INSU, the Swiss
National Science Foundation, and the French National Research Agency
(ANR-08-JCJC-0102-01 and ANR-NT05-4-44463) for their continuous sup-
port of our planet-search programs. AE is supported by a fellowship for
advanced researchers from the Swiss National Science Foundation (grant
PA00P2 126150/1). IB and NCS would like to gratefully acknowledge the
support of the European Research Council/European Community under the
FP7 through a Starting Grant, as well from Fundac ¸˜ ao para a Ciˆ encia e
a Tecnologia (FCT), Portugal, through a Ciˆ encia 2007 contract funded by
FCT/MCTES (Portugal) and POPH/FSE (EC), and in the form of grants
reference PTDC/CTE-AST/098528/2008, PTDC/CTE-AST/098604/2008, and
SFRH/BPD/81084/2011. DE and RFD are supported by CNES. This research
has made use of the SIMBAD database and the VizieR catalog access tool oper-
ated at CDS, France.
Appendix A: Constraining the RV offset between
ELODIE and SOPHIE
When a star is observed by several instruments, the RV offsets
between the differentdatasets are fitted as a free parameterin the
Keplerian solution. A sample of about 200 stars, that had been
selected as stable from ELODIE measurements, were also ob-
served with SOPHIE to search for low-mass planets (Bouchy et
al. 2009). This sample can be used to constrain the RV offset be-
tween the two spectrographsas these stars have a constant RV at
the level of precision of ELODIE (∼10ms−1) on a timescale of
several years. The ∆(RV) is expected to depend on the color of
thestar(B−V)andtosecondorder(thatwe neglect)onits metal-
licity. Owing to its mean value of 0.003 given by Hipparcos, we
neglect the error in the B − V.
For both instruments, we compute the mean RV for
each star, RVELODIE and RVSOPHIE. The error bars corre-
spond to the quadratic sum of the standard deviations in the
ELODIE and SOPHIE RV data. We then plot the difference
∆(RV)E−S=RVELODIE−RVSOPHIEas a function of the B − V in
Fig. A.1. The RVELODIE are shifted into the blue compared to
RVSOPHIE. We consider separately the RV measurements de-
rived from the G2 (black squares) and the K5 (blue circles)
cross-correlation mask.
With the K5 mask, a linear fit (black dashed line) cannot be
well-constrained and we choose a constant as an offset (green
dashed line)
∆(RV)E−S(K5) = −166ms−1,
(A.1)
where the residuals have a dispersion of 20ms−1, which is con-
sidered to be our error in the RV offset.
In the case of the G2 mask, stars with a B − V > 0.75 may
have different properties from the others and should have been
correlated with the K5 mask. This may be due to a bad spectral
classification of these stars. We then fit a linear relation consid-
ering only the stars with B − V < 0.75 (green line)
∆(RV)E−S(G2) = −425.6(B− V) + 202.4ms−1.
(A.2)
The residuals dispersion around the fit is 23 ms−1, which we
assume to be our offset calibration error.
In Fig. A.2, three stable stars observed over a period of more
than13yrareshown,illustratingthereliabilityofthecalibration.
11

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I. Boisse et al.: The SOPHIE search for northern extrasolar planets
0.60.81
-0.2
-0.1
0
Fig.A.1. Difference between the mean RV from ELODIE and
from SOPHIE, ∆(RV)E−Sas a function of B − V for a sample
of stable stars. The error bars correspond to the quadratic sum
of the standard deviation in the ELODIE and SOPHIE RV data.
Thegreensolidlineisthebestlinearfitforstars correlatedwitha
G2 mask (black squares). Those with B − V>0.75 are discarded
(red triangles). The black dashed line is the best linear fit for
stars correlated with a K5 mask (blue circles). The detection of
the slope is insignificant and a constant value is chosen (green
dashed line).
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I. Boisse et al.: The SOPHIE search for northern extrasolar planets
Table 1. Known exoplanets discovered by RV with orbital distances greater than 4 AU.
Semi-major axis[AU]
4.5-36
6.7+4.0
−1.4
5.8
5.76
5.5
5.4
5.27
5.24
5.15
5.1+0.6
−0.7
4.96±0.30
4.92±0.38△
4.94±0.2
4.89±0.53
4.74±0.08
4.35±0.28
4.3±0.4
4.3±0.4△△
4.2
Period [day]
5-90[yr]
5894+5584
5000±400
5218±230
4885±1600
4970±744
4270±220
4206±759
4218±388
3999+469
4046±370
3668+169
3725±463
3810±420
3658±32
3070±110
2890±390
3538±300
3008±202
Mass [MJup]
3-15
2.71+1.14
−0.66
0.82±0.03
3.84±0.08
3.1
0.36±0.06
2.60±0.15
1.8
1.88±0.15
1.90+0.67
−0.53
2.0±0.5
4.01±0.49△
1.45±0.3
1.99±0.25
3.15±0.14
3.57± 0.55
11±1
1.0±0.3△△
7.2
EccOrbit⋆
incomp.
incomp.
incomp.
comp.
incomp.
comp.
incomp.
comp.
comp.
comp.
comp.
comp.
incomp.
comp.
comp.
incomp.
incomp.
comp.
incomp.
Multiplicity†
1
1
2
5
1
2
2
4
1
1
2
1(+1?∗)
1
2
1
2
1
1
3‡
ref.
HIP70849b
HD150706b
HD134987c
55Cncd
HD190984b
HD99492c
HD217107c
µ Arae
HD13931b
HD222155b
HD7449c
HD24040b
HD220773b
HD187123c
HD72659b
HD183263c
HD106270b
HD154345b
HD125612d
0.47-0.96
0.38+0.28
0.12±0.02
0.03±0.03
0.57±0.10
0.1±0.2
0.517±0.033
0.10±0.06
0.02±0.05
0.16+0.27
0.53±0.08
0.04+0.07
0.51±0.1
0.252±0.033
0.22±0.03
0.239±0.064
0.40±0.05
0.26±0.15
0.28±0.12
S´ egransan et al. (2011)
this paper
Jones et al. (2010)
Fischer et al. (2008)
Santos et al. (2010b)
Meschiari et al. (2010)
Wright et al. (2009)
Pepe et al. (2007)
Howard et al. (2010)
this paper
Dumusque et al. (2011)
this paper
Robertson et al. (2012)
Wright et al. (2009)
Moutou et al. (2011)
Wright et al. (2009)
Johnson et al. (2011)
this paper
Lo Curto et al. (2010)
⋆⋆
−1498
⋆⋆
−0.32
∗∗
−541
∗∗
−0.22
−171
−0.06
⋆comp.: if the RV measurements cover the orbit; incomp.: if the RV measurements did not cover the orbit.
†Give the number of planets pl. in the system. All planets, except HD125612b, orbit single stars.
∗A linear trend is fit to the RV of this system.
‡HD125612A has a stellar companion
⋆⋆Assuming M⋆=1.17±0.12M⊙
∗∗Assuming M⋆=1.13±0.11M⊙
△Assuming M⋆=1.18±0.10M⊙
△△Assuming M⋆=0.88±0.09M⊙
14

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I. Boisse et al.: The SOPHIE search for northern extrasolar planets, Online Material p 1
Table A.1. Radial velocities of HD150706 measured with ELODIE.
BJD RV
±1σ
(kms−1)
0.009
0.014
0.012
0.011
0.010
0.010
0.012
0.008
0.009
0.010
0.008
0.009
0.008
0.009
0.013
0.012
0.012
0.011
0.013
0.011
0.009
0.011
0.012
0.009
0.010
0.009
0.009
0.009
0.008
0.015
0.018
0.011
0.008
0.009
0.009
0.012
0.009
0.009
0.010
0.010
0.009
0.009
0.010
0.012
0.011
0.009
0.009
0.013
-2400000
50649.4745
50942.5543
50970.5200
50970.5325
50972.5962
50973.4466
50973.4591
51269.6057
51723.4471
51728.4541
51757.4065
52081.4290
52113.4120
52137.3848
52160.3491
52163.3009
52360.6618
52361.6448
52384.6408
52388.6133
52414.5642
52451.4536
52451.4667
52482.3970
52508.3361
52747.6042
52748.5678
52751.5813
52752.5889
52773.5429
52774.5403
52776.5571
52778.5717
52797.4581
52800.5201
52801.4400
52803.4532
52806.4494
52809.4272
52812.4224
52813.4814
53160.4959
53164.4548
53223.3977
53486.6043
53490.5529
53517.5451
53900.4554
(kms−1)
-17.194
-17.174
-17.196
-17.196
-17.197
-17.183
-17.178
-17.211
-17.189
-17.172
-17.189
-17.224
-17.255
-17.230
-17.198
-17.203
-17.243
-17.235
-17.227
-17.228
-17.250
-17.258
-17.244
-17.263
-17.243
-17.254
-17.247
-17.221
-17.224
-17.216
-17.228
-17.264
-17.245
-17.253
-17.238
-17.240
-17.253
-17.251
-17.243
-17.261
-17.262
-17.231
-17.236
-17.216
-17.214
-17.238
-17.237
-17.188