Extrasolar Planets and Brown Dwarfs Around AF Type Stars. II. a Planet Found with ELODIE Around the F6V Star HD 33564

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HD fapae rudoeo h bet uvydwith surveyed objects the of one around planet a of T pte eut hwta hsifae xesi u oabac 33564 2006). HD a al. around et to disk circumstellar (Bryden due a is to not excess and infrared som galaxy ground this Indeed, system. that the show of results formation Spitzer the circumste dusty of K) remnant (65 disk, cold lar a by could surrounded star star, this Vega-like that a suggested which 1991), Willson & Patten adH 36 (DM 33564 HD ward 6 trH 36.Terda eoiymaueet,ob- measurements, velocity radial The 33564. HD star F6V e ff oi tr:erytp tr:bondaf planetary - dwarfs brown stars: - early-type stars: - copic / nifae xeshsbe eetda 60 at detected been has excess infrared An = H] 1 .Pepe F. , 20K n ufc rvt log gravity surface and K, 6250 = M 01 r ae rmNrsro ta.(2004). al. Nordström et from taken are -0.12 1 = 1 2 . 25 .L Beuzit J.-L. , − + 0 0 . . 04 03 v sin M + 919 ihIA Amn 1985, (Aumann IRAS with 169) 79 ⊙ i ffl g 3 age , = i ta.1991). al. et eit 2k s km 12 1 n .Mayor M. and , M 1 Jup − 1 . o h companion. the for e , 0 g − + = 0 0 ff . . 3 6 . r ae from taken are 4.0 cietemperature ective y,metallicity Gyr, oebr7 2018 7, November 2 e ELODIE s. µ ⋆ m in m ults oc- to- be k- is l- e , 2 F. Galland et al.: Extrasolar planets and brown dwarfs around A-F type stars

Table 1. HD33564 stellar properties. Photometric and Table 2. ELODIE best orbital solution for HD33564. astrometric data are extracted from the HIPPARCOS catalogue (ESA 1997); spectroscopic data are from Nordstr¨om et al. (2004) and Acke & Waelkens (2004). Parameter HD 33564 P [days] 388 ± 3 T [JD-2400000] 52603 ± 8 ± Parameter HD 33564 e 0.34 0.02 γ [km s−1] 0.107 ± 0.006 Spectral Type F6V − ω [deg] 205 ± 4 v sin i [km s 1] 12 K [km s−1] 0.232 ± 0.005 V 5.08 N 15 B-V 0.506 meas − −1 ± σ(O C) [ms ] 6.7 π [mas] 47.66 0.52 −3 a1 sin i [10 AU] 7.8 Distance [pc] 21.0 −7 f(m) [10 M⊙] 4.21 MV 3.47 [Fe/H] − 0.12 M1 [M⊙] 1.25 m2 sin i [MJup] 9.1 Teﬀ [K] 6250 log g 4.0 a [AU] 1.1 +0.03 M1 [M⊙] 1.25−0.04 +0.6 Age [Gyr] 3.0−0.3

2.2. Radial velocity measurements

By April 2005, 15 spectra have been acquired with ELODIE over a time span of 417 days. The wavelength range of the spectra is 3850-6800Å. The typical exposure time was 15 min, leading to S/N equal to ∼ 150. The exposures were performed with the simultaneous-thorium mode to follow and correct for the local astroclimatic drift of the instrument. The radial velocities have been measured using the method described in Chelli (2000) and PaperI. They are displayed in Fig 1. The uncertainty is 11 m s−1 on average. It is consistent with the value of 10ms−1 obtained from simulations in PaperI by applying the relation between the radial velocity uncertainties and v sin i to HD33564, with S/N values equal to 150.

2.3. Orbital parameters The amplitude of the radial velocity variations is much larger than the uncertainties. The orbital parameters derived from the Fig. 1. Top: ELODIE radial velocities and orbital solution for best Keplerian solution (Fig. 1) are given in Table 2. The resid- HD 33564. Bottom: Residuals to the fitted orbital solution. uals dispersion is 7 m s−1. The eccentricity is 0.34. Assuming a primary mass of 1.25M⊙, the companion mass falls in the dial velocity variations obtained with ELODIE have a semi- planetary domain, with a minimum mass of 9.1M . The or- Jup amplitude lower than 250ms−1, not detectable with CORAVEL. bital period is 388days (separation of 1.1AU). Note that the maximum of the radial velocity variations could not be observed. The orbital period is close to one year 3. Ruling out other origins of the variations and a long time will still be necessary to be able to cover the 3.1. A single star whole phase. To quantify the resulting uncertainty on m2 sin i, we tried several fits fixing different values for the eccentricity. HD33564is referencedas a double star, but the high difference We find that residuals are acceptable with values of this ec- between the proper motions of the two components indicates centricity between 0.28 and 0.40. The resulting minimum mass that they are probably not bound. Besides, the separation be- ranges then from 8.7 to 9.6MJup, hence an uncertainty of 6% tween the two components is larger than 6 arcsec, so that the on the minimum mass correspondingto the best solution (given flux from the secondarydoesnot enter into the fiber of the spec- the primary mass). trograph, even in bad seeing conditions. Hence, the spectra are Besides, this star was also observed with the CORAVEL not polluted by the secondary spectra. In both cases, the pres- spectrograph. The obtained radial velocities are constant over ence of the secondary is not responsible for the observed radial 4 years given uncertainties of 500ms−1 on average. The ra- velocity variations of the considered component, HD33564A. F. Galland et al.: Extrasolar planets and brown dwarfs around A-F type stars 3

ELODIE − HD33564 − F6V − vsini: 12 km/s

− o − − −o − . − o o − 200 −− −o

− − o 1.5 o − − 0 o o o o o o o o 0 o o − o −−. . oo. −o 1.0 −− o− − − bisector (m/s) o

− normalized flux o − −200 − o − Radial Velocity (m/s) − o −200 − 0.5 5.32 5.34 10+4 0 200 3930 3935 3940 Julian Day − 2400000 Radial Velocity (m/s) wavelength (Angstroms) ELODIE − HD25998 − F7V − vsini: 17 km/s

o − o

100 o . o 1.5 − − 0 − o − o. o o − o − − o −. . o o o. − o− −o − − − − − .− o o.. − o. o. o. − − −o − − o.o. o −o. − . − o 0 − − o. − −− − −100 − − − o o. o o . o o.

o bisector (m/s) . o − −. o − . − 1.0

− o normalized flux − − − o o . o. − − o

Radial Velocity (m/s) −200 −100 o

5.30 5.32 5.34 10+4 −100 0 100 3930 3935 3940 Julian Day − 2400000 Radial Velocity (m/s) wavelength (Angstroms)

Fig. 3. Left: radial velocity measurements of HD33564 (top) and HD25998 (bottom): they are signiﬁcantly variable. Center: the line bisector (see text) is not variable for HD33564, while it is variable for HD25998, in a similar range, and linearly related to the radial velocities. This is typical of the presence of spots, induced by stellar activity (Queloz et al. 2001a). Right: no emission in the Ca K line in the case of HD33564,emission in the case of HD 25998.

3.2. A similar star constant in radial velocity (F7V, v sin i = 17kms−1), for comparison. It is flat i.e. there is no correlation between the radial velocities and the shape of the To rule out any possibility of artifact linked with the Earth or- lines for HD33564. On the other hand, it varies linearly with bital motion, we show in Fig. 2 the radial velocities of a similar the radial velocity in the case of HD25998 (the slope value is star, close to HD 33564, but constant within the present levelof -1.4), which is typical of spots induced by stellar activity (see −1 uncertainties: HD17948 is an F4V star with v sin i = 11kms . Queloz et al. 2001a for further details). It also belongs to our ELODIE survey. By April 2005, 5 spectra have been gathered for this star, with S/N equal to 136 on average. The typical uncertainty is 10ms−1 comparable to the one obtained for HD33564. The observed radial velocity disper- Moreover, no emission in the core of the CaII lines is ob- sion of 8.4 ms−1 shows that star is constant over the 150 days served (see Fig3 for the case of the CaIIK line). The chromo- of the measurement span. spheric flux in the CaII K and H lines of HD33564 has been measuredby e.g. Gray et al. (2003),who givesan activity index ′ − 3.3. An activity-quiet star log(RHK) = 4.95, leading to the classification of HD33564 as ′ − an inactive star. For comparison, the value of log(RHK) is 4.47 We show here that activity is not responsible for the radial ve- in the case of the active star HD25998. Hence, contrary to locity variations of HD33564. First, the bisector shape of the HD25998, activity is not responsible for the radial velocity lines is estimated on the cross-correlation function (inverse bi- variations observed for HD33564. This is also confirmed by sector slope) in the same way as in Queloz et al. (2001a). It is the fact that the period of the radial velocity variations is much displayed in Fig 3, together with the one of a known active star larger than the rotational period of HD33564 (less than 7 days (Gray et al. 2003) included in our ELODIE survey, HD 25998 given its value of v sin i). 4 F. Galland et al.: Extrasolar planets and brown dwarfs around A-F type stars

ELODIE − HD17948 − F4V − vsini: 11 km/s minimum mass of 9.1MJup and a period of 388 days, hence a separation of 1.1AU.

200 This result is a ﬁrst step toward the extension of the study of planet and brown-dwarf formation processes to stars ear- lier than F7. This is fundamental for a global understanding of the most interesting planetary formation mechanisms involved.

− For example, one of the question to be addressed is whether − . − −.. o 0 o oo −. − − −− o the planetary masses depend on the primary stellar masses: the − more massive the star, the more massive the planets hosted ?

Acknowledgements. We acknowledge support from the French CNRS. We are grateful to the Observatoire de Haute-Provence (OHP) Radial Velocity (m/s) −200 and to the Programme National de Plan´etologie (PNP, INSU) for the time allocation, and to their technical staﬀ. 5.33 5.34 10+4 These results have made use of the SIMBAD database, operated Julian Day − 2400000 at CDS, Strasbourg, France.

Fig. 2. ELODIE radial velocity data for HD17948, a star con- References stant in radial velocity (dispersion of 8.4 m s−1), similar and close to HD33564. The vertical scale is identical to the one Acke, B., Waelkens, C., 2004, A&A, 427, 1009 in Fig. 1. Aumann, H.H., 1985, PASP, 97, 885 Baranne, A., Queloz, D., Mayor, M., et al. 1996, A&A 119, 373 Chelli, A., 2000, A&A 358, L59 4. Status of the HD 33564 system Galland, F., Lagrange, A.M., Udry, S., et al. 2005a, A&A, accepted. Gray, R.O., Corbally, C.J., Garrison, R.F., et al. 2003, AJ 126, 2048 So far 16 stars with spectral type between F7 and F9 have Glebocki et al., 2000, Rotational Velocities of Stars been reported as hosting possible planets detected through ra- ESA 1997, The Hipparcos and Tycho Cat, ESA SP-1200 dial velocities. HD33564 is, to our knowledge, the earliest Hoﬄeit, D., Warren Jr, W.H., 1991, Bright Star Catalogue (5th Revised Ed.), NSSDC/ADC spectral type star around which a companion with m2 sin i in the planetary domain has been announced. The reported Lagrange, A.M., Backman, D.E. and Artymowicz, P., 2000, in m sin i ’s range between 0.4 and 11M . Four objects, namely Protostars and Planets IV (Book - Tucson: University of Arizona 2 Jup Press; eds Mannings, V., Boss, A.P., Russell, S. S.), p. 639 HD23596, HD89744, HD114762 and HD136118, are found Lagrange, A.M., Augereau, J.C., 2004, in Planetary systems and plan- ≥ with m2 sin i 5MJup i.e. 8.0, 7.2, 11.0 and 11.9MJup, re- ets in systems, ISSI workshop spectively. The corresponding estimated planet-star separations Ida, S., Lin, D.N.C, 2005, ApJ, 626, 1045I are 2.7, 0.88, 0.37 and 2.3AU, respectively. HD33564, with Mayor, M., Queloz, D., 1995, Nature, 378, 355 m2 sin i = 9.1MJup and a = 1.1 AU, falls in a similar (mass, sep- Nordtrom B., Mayor, M., Andersen J., et al., 2004, A&A 418, 989 aration) domain. Knowing the inclination of these systems Patten, B.M., Willson, L.A., 1991, AJ, 102, 123 would be very important for constraining planet formation Pepe, F., Mayor, M., Rupprecht, G., et al. 2002, The ESO Messenger, models. If their true masses are found to be planetary, one 110, 9 may wonder how such massive planets could form and stand Queloz, D., Henry, G. W., Sivan, J. P., et al. 2001, A&A, 379, 279 so close to their parent stars. Whether migration has occurred Udry, S., Mayor, M., Queloz, D., 2003, in Scientiﬁc Frontiers in or whether the planets have been formed by gravitational col- Research on Extrasolar Planets, ASP Conf. Ser., in press Udry, S., Mayor, M., Santos, N.C., 2003, A&A, 407, 369 lapse rather than by a scenario including accretion onto a solid Walker, H.J., Wolstencroft, R.D., PASP, 1988, 100, 1509 core are possibilities that need to be investigated. The proposed idea that “the more massive the star, the more massive the planets hosted” is also very interesting. Studies on lower mass stars (Lin & Ida 2005) show such a trend, does it exist for A-F type stars? Besides, we may emphasize the low value of the metallicity for HD33564, which is not common among stars hosting planets. There is however no metallicity trend for the early-type stars with massive planets mentioned above.

5. Conclusions We have presented here the ﬁrst detection of a planet around one of the objects surveyedin our ELODIE program, HD33564, an F6V star with v sin i = 12km s−1. The best Keplerian solution derived from the radial velocity measurements leads to a