arXiv:astro-ph/0610459v1 16 Oct 2006 ino onigi obecn teCoRoT (the double–cone a is pointing for of CCDs direc- tion CoRoT selected two The aper- case. with scientific 27–cm each equipped a telescope instrument: unique ture a has mis- The sion cur- 2006. is December plan- for launch extrasolar scheduled The rently for part). exoplanetary asteroseis- search (the (the the ets and interiors part) stellar the mic the twofold: unprece- is of with goal study Its accuracy. high photo- of dented perform observations will metric Transits) ROtation planetary (COnvection, and CoRoT satellite The Introduction 1. 1 1, Vol. S.A.It. Mem. edo Send c At2004 SAIt ff 3 ilosreaot600tresi h ag 11.0 range the in targets 60000 about observe will 1 general 4 2 e words. Key asterose the for undertaken those complement actions These o novdaedsrbd ihapriua mhsso h ob It the the on which e emphasis the in particular on work a fields, preparatory with the described, are of involved parts The equator. the Abstract. rn eussto requests print ff NF–Osraoi srnmc iRm,VaFact 3 I- 33, Frascati Via e-mail: Roma, di Astronomico Osservatorio – INAF NF–Osraoi srnmc iBea i .Baci46, Bianchi E. Via Brera, di e-mail: Astronomico Osservatorio – INAF NF–Osraoi srnmc iCpdmne i Moiare Via Capodimonte, e-mail: di Italy. Astronomico Osservatorio – INAF NF–Osraoi srfiiod aai,VaS oa7,I- 78, Sofia S. Via Catania, di mail: Astrofisico Osservatorio – INAF rtepsiiiyt eetetaoa lnt ymaso t of means by planets extrasolar detect to possibility the er .Poretti E. n lanza,[email protected] [email protected] [email protected] h pc iso oo Cneto,Rtto n planetar and ROtation (COnvection, CoRoT mission space The tr:atvt tr:paeaysses–Tcnqe:ph Techniques: – systems planetary Stars: – activity Stars: ff [email protected] cso tla ciiyadbcgon tr n nteoutr the on and stars background and activity stellar of ects .Poretti E. : 1 ..Lanza A.F. , 2 .Maceroni C. , ys etrdat centered eyes) tla pc gnyAIwtde h o the the withdrew community, ASI Agency national Space the Italian collected in ESA. interest which of wide participation a participation initial a an as After well Belgium, as Austria, Germany Spain, other countries: involves european also mission CoRoT the (80%), fec y s10 is eye each of upr otepoet ept hs ru of group a this, Despite project. the to support o 5 ah(ogrn) o oede- the more visit a instrument For the runs). site of (long description each tailed fields d five 150 observe for uninterruptly will CoRoT i Anticenter tic 3 eie ao rnhparticipation French major a Besides http://smsc.cnes.fr/COROT/ < .Pagano I. , V < 60 oae nfiefilsnear fields five in located 16.0, sooi programme. ismologic etastmto.Tesatellite The method. transit he evtost hrceiethe characterize to servations Memorie / Center), la omnt a been has community alian 04 ot ozo Italy. Porzio, Monte 00040 2 n .Ripepi V. and , 52 aai,Iay e- Italy. Catania, 95123 l 6 -03 Napoli, I-80131 16, llo -30 eae Italy. Merate, I-23807 α o tmti Binaries: – otometric = oaheeisgoals, its achieve To . 6h50m della δ rnis will Transits) y ahactivities. each = / 85m(galac- 18h50m 0 o 4 h radius the ; . ffi cial 2 Poretti et al.: CoRoT and

each long run in the 11.0< V <16.0 range. Thus, during the expected 2.5–y satellite life- time, a total of 60000 light curves will be pro- duced at a sampling rate of 8 min. The detec- tion of the extrasolar planets will be perfomed by measuring the weak decrease of the flux due to the transit of a planet in front of the star disk. The first observational evidence of this phenomenonhas been obtained by Henry et al. (1999) on HD 209458. Figure 1 shows un- published observations of another transit of that planet, measured some weeks after its dis- covery with the 50–cm telescope at Merate Observatory. For the brightest stars color in- formation will be available and will help in discriminating single transit events from stel- lar activity or other artefacts. To get these sup- plementary and useful data, a dispersive ele- Fig. 1. V–band light curve of HD 209458 observed ment has been included in the optical path of on the night of November 25, 1999 at Merate the exoplanetary channel. In such a way the Observatory. The transit of the planet originates point spread function of the stellar image is with the dimming in the of the star; the split roughly in three colours. upper line finishes at the time of the first contact, the The main targets of the exoplanetary mis- lower one starts at the time of the second one. The sion are bodies having the size of the Earth. measurements of the check star, which are arbitrar- Some hypotheses have been made to estimate ily shifted, are reported for the purpose of compari- the number of possible transits due to tel- son. luric planets (numbers of young stars with dust discs, radii and distances of the planets from researchers still remained active on various as- the parent stars, ...). With a photometry opti- pects. Poretti (2003) described the Italian con- mised up to V=15.5 (expected precision at the tribution to the asteroseismologic part. Here 0.1 mmag level) the expected number of detec- we report on the contribution to the exoplan- tions is (L´eger et al., 2000): etary part. Four main issues are addressed: the 1. 25 planets having a radius of 1.6 R at characterization of the stellar content of the ex- ⊕ 0.3 AU; oplanetary fields, the disentangling of the plan- 2. 40 planets having a radius of 2.0 R at etary transits from stellar activity, the influence ⊕ 0.3 AU; of background stars in the transit detection, the 3. a few planets of around 2.0 R in the “hab- preparatory tools and outreach activities. ⊕ itable” zone (with the indispensable help of the chromatic information); 2. Stars and planets 4. several hundreds of hot–Jupiters and Uranus–like planets, with detailed light In the asteroseismic channel the long–duration curves. and continuous CoRoT survey will result in high–precision photometry, with an expected The two CoRoT programmes are not in- noise level in the frequency spectrum of dependent: once a specific asteroseismic tar- 0.7 ppm (parts per million) over a 5 d time get has been proposed (primary target), the baseline for a V ∼6.0 star. This means that corresponding exoplanetary field has to match CoRoT will be able to detect solar–like oscilla- the requirements for a fruitful search for tran- tions. In the exoplanetary channel, CoRoT will sits. Moreover, we also need to assure that the monitor simultaneously up to 12000 stars in stars surrounding the primary target are also Poretti et al.: CoRoT and exoplanets 3 interesting for asteroseismology. Therefore, some preliminary investigations of both the asteroseismologic and exoplanetary fields are mandatory. Here we report on two specific and different applications.

2.1. The case study of HD 52265 HD 52265 will be the target of the second CoRoT long run in the Anticenter direction (September 2007–March 2008). It has been proposed for an asteroseismic investigation since it is the only star with an already known planet in the CoRoT eyes (Butler et al., 2000). Fig. 2. (a) The transit of an Earth–like planet of ra- dius R = 2.3R and of 30.0 d super- Transits do not occur since the planet is not ⊕ posed on the total solar irradiance variation; the ir- on our line of sight. However, the asteroseis- radiance values are normalized to the maximum ob- mic investigation of HD 52265 should allow served in the given time interval; (b) The same time us a better understanding of the properties of series after subtracting the best fit model light curve its planetary systems; moreover, considering computed with the model after Lanza et al. (2003). that HD 52265 has a of 1.1 M⊙, at the The transit dips are now clearly visible also dur- same time removing the observational singu- ing the phases with moderate or high solar activity, larity of our Solar System. The approach to whereas they were lost in the irradiance fluctuations study the parent star to investigate its plane- during the same phases in panel (a). tary system could be an important guideline for future space missions and perhaps HD 52265 spectra have been reduced using the ESO could constitute an interesting pathfinder. pipeline, and an automatic procedure is going The characterization of the HD 52265 to be applied to obtain the spectroscopic clas- field resulted in the detection of several pul- sification for all the investigated objects. This, sators: the δ Sct star HD 50870 (Poretti et al., in turn, will allow us to test the spectral types 2005), the hot Be stars HD 50891, HD 51193, previously obtained through photometry only. HD 51242 and the cold Be star HD 51404. The main goal is to separate dwarf from giant Therefore, the field has been validated for the stars in the most reliable way. After such pro- asteroseismic programme and looks very ap- cedure, only the dwarf stars will be selected for pealing. additional photometric monitoring.

2.2. The characterization of the 3. Magnetic activity in late–type stars fields and planetary transit detection In order to contribute to the characterization Main–sequence late–type stars have an outer of the exoplanetary field aside HD 49434 and convective envelope that, in combination with HD 49933, the open cluster Dolidze 25 has a sufficiently fast rotation, becomes the site of been observed. In particular, a photometric hydromagnetic dynamo action (Parker, 1979; (RI filters) and spectroscopic investigation has R¨udiger & Hollerbach, 2004). The key param- been carried out by using the VIRMOS@VLT eter measuring the efficiency of the magnetic instrument (Ripepi et al., 2006). Photometry field generation is the Rossby number Ro, i.e., has been used to select targets for spec- the ratio of the rotation period to the convec- troscopy. In total we obtained ∼900 spec- tive turnover time at the base of the convec- tra with medium resolution (2.5 Å/pixel) and tion zone. When Ro is of the order of the unity, ∼600 with higher resolution (0.6 Å/pixel). The the amplification and modulation of magnetic 4 Poretti et al.: CoRoT and exoplanets

Fig. 3. Two subsets of the time series of the total solar irradiance (TSI) and spectral irradiances at 402, 500 and 862 nm (black dots) with their respective best fits (solid lines) are plotted in panels (a), (c), (e) and (g) for the labelled passbands in the left and the right columns, respectively. The best fits are obtained with the -as-a-star model introduced by Lanza et al. (2004). The fits are usually embedded into the data sequence, except when data gaps are present. The residuals are plotted in the corresponding lower panels (b), (d), (f) and (h), respectively. The time is indicated in days from 1st January 1996 on the lower scale and in on the upper scale. The data subsets are close to the maximum of cycle 23 and range from 29 January 2000 to 29 March 2000 in the left panels, and from 29 March 2000 to 28 May 2000 in the right panels, respectively.

fields take place and the star displays the typi- longer than the period produce cal signatures of solar–like activity. The optical the rotational modulation of the stellar flux. flux is modulated by cool spots and bright fac- The observations of the solar disk- ulae in the photosphere which evolve on time integrated irradiance show that the amplitude scales from a few hoursup to tens of days. The of the flux modulation due to the surface active regions with a lifetime comparable to or brightness inhomogeneities is of the order of 2000 − 3000 ppm around the maximum Poretti et al.: CoRoT and exoplanets 5

Fig. 4. Top panel: A sample of the synthetized light variations in the four CoRoT passbands for a main– −2 sequence star with Teff = 6000 K, log g = 4.5 (cm s ), a rotation period of 3 days and with spots dominating the light variations. Different linestyles refer to different passbands: solid – white channel; dotted – red channel; dashed – green channel; dash-dotted – blue channel. The mean values of the red, green and blue passband fluxes have been shifted up in order to plot them on the same scale. Lower panel: The short–term relative variations in the white channel that were superposed on the rotationally modulated variations to obtain the light curve in the upper panel. The short–term variations in the other passbands were obtained from those in the white channel by scaling the red, green and blue channels, by factors of 0.923, 1.095, 1.199, respectively (Lanza et al., 2006). of the 11–yr cycle (Fr¨ohlich & Lean, 2004). Such a model allows us to fit the solar varia- The detection of Earth–like planetary transits tion giving residuals of the order of 100–200 requires the observation of flux dips with ppm for the total irradiance which may signifi- amplitudes of the order of 100 ppm. This cantly improve the detection of planetary tran- implies that solar–like activity introduces a sit (Figs. 2 and 3). Moreover, the model can be severe limitation for the detection of Earth– applied to scale the solar variability to the case like transits across the disks of stars similar of younger, more active stars to produce simu- to the Sun or with a higher level of activity lated light curves (Fig. 4) which will be used (Aigrain & Irwin, 2004). for testing different detection algorithms for In the framework of the preparatory work the CoRoT mission, i.e., the so-called CoRoT for the CoRoT mission, we built models of the Exoplanet Blind Tests 1 and 2, described by variability of the Sun as a star. They are based Moutou et al. (2005); Lanza et al. (2006) and on a discrete distribution of active regions plus Moutou et al. (in preparation). a uniformly distributed background whose area The model described above as well as and coordinates vary with a time scale of 14 d those applied to stars with a high level in order to reproduce the modulation of the to- of magnetic activity (Messina et al., 1999; tal as well as spectral solar irradiances at 402, Lanza et al., 2002) allow us to derive informa- 500 and 862 nm (Lanzaet al., 2003, 2004). tion also on the stellar rotation period, the level 6 Poretti et al.: CoRoT and exoplanets of activity and the kind of hydromagnetic dy- similar amplitude (Bebs, binaries with grazing namo operating in a given star. The level of eclipses, other variables); such a sample was activity determines the average UV and X– used in a first blind test (BT1) to estimate the ray stellar fluxes (Messina et al., 2003) which detection threshold of CoRoT (Moutou et al., are important to model the chemistry of exo- 2005), i.e. the minimum detectable planet ra- planet atmospheres. On the other hand, close– dius depending on the period and parent star. It by Jupiter–sized exoplanets may affect stellar served as well to test the efficiency of the var- rotation and magnetic activity through tidal as ious detrending/detection methods developed well as magnetospheric interaction (Saar et al., by the different teams who will work on the 2004; McIvor et al., 2006). real data. Modelling the light curves obtained by CoRoT will allow us to obtain information on the area variation and surface distribution The results of BT1 allowed to derive of stellar active regions which will disclose an empirical “detection curve”, expressing a lower limit of transit depth for detection as the dependence of magnetic activity on funda- −3 −1/2 mental stellar parameters, that is presently not d ≃ 10 n , where d is the depth and n known for stars with an activity level compara- the number of transits during the run. For in- ble to that of the Sun. stance a planet orbiting a G0V star should be detected if Rpl ≥ 2 − 4R⊕ (for Porb = 3 − 50 d). Besides, it was directly confirmed that Bebs 4. Planet detection and background will be in practice the only source of false binaries alarms: the only cases of misidentification by all teams, and therefore not method–related, Another very serious problem for planetary are from eclipsing binaries. transit detection will arise from the contamina- tion by background eclipsing binaries (Bebs). The CoRoT exoplanet program essentially per- A more refined blind test (BT2) is now forms aperture photometry on a crowded stel- in progress with the purpose of analyzing the lar field. In spite of the masks, conceived to problem of Bebs and of estimating the type and optimize photometry and to limit contamina- amount of necessary follow–up observations. tion from nearby stars, a contribution of faint Many cases could be discriminated just by de- backgroundobjects to the light curve of the tar- tailed analysis of the folded lightcurve (on the get is unavoidable (Maceroni & Ribas, 2006). basis of color behavior of the transit and by The high frequency of false alarms from Bebs detection of a secondary minimum). The BT2 was already experienced in the OGLE plane- light curves were produced using the same tary transit search: only five true planets out complex simulator used in BT1, but pollut- of 177 alarms were confirmed by follow–up ing events, whose statistics has been estimated observations (Udalski et al., 2004), a result in using the Corotlux tool (Guillot et al., 2006), agreement with the theoretical estimation of have been included. To provide lightcurves Brown (2003). in the three color “bandpasses” of CoRoT, We need to test the ability of detrend- Corotlux uses the Besanc¸on galactic model ing the lightcurves from instrumental and en- (Robin et al., 2003), real observations of the vironmental biases and of eventually detect- CoRoT fields (to estimate the number of stars ing planets in the specific context of CoRoT. of different type in each field) and the expected Therefore, a complex simulator has been re- binary frequency and distribution of orbital el- alized (Auvergne & al., 2003) to reproduce in- ements (Moutou et al., in preparation). A first strumental noises and to produce the first light result is that in one long run in the CoRoT curves for the exoplanet channel. The simu- Anticenter field a mean number of ∼ 80 can- lator was used to generate a sample output didate planets is expected, with about 80% of of 1000 lightcurves, hiding 20 transiting plan- alarms cleared by follow up photometry and ets and 20 other types of variable objects of 10% by follow–up spectroscopy (Pont, 2006). Poretti et al.: CoRoT and exoplanets 7

Fig. 5. Starting menu of the ”Dal cuore delle stelle ... ai pianeti abitabili” multimedia flash project.

5. Outreach activities 3. the observational technique; 4. the CoRoT sky; We are taking care of outreach activities related 5. the science project; to the CoRoT mission and to the research on 6. the history of the project; extrasolar planets. 7. the involved people and institutions 8. a section with background information, 5.1. CoRoT mission from basic definition to the physics of os- cillations and . A multimedia product (Macromedia Flash) illustrating the CoRoT mission and its sci- Each of the above subjects is a starting point to ence objectives was developed in French at the exploration of several sub–subjects, as well the Observatoire de Paris. We have edited as it is possible to access to pop–up insights and translated the project in Italian and by clicking on highlighted words. Our aim is published it on the web site of Catania to put this multimedia product on CD–ROM Observatory (http://www.ct.astro.it/gass/CD- support and distribute it to schools and to the CoRoT/corot.swf). The multimedia project, general public during education and outreach titled “Dal cuore delle stelle ... ai pianeti activities regurarly carried out in the INAF abitabili” 1, allows the user to explore the Observatories involved in the CoRoT projects. following subjects (Fig. 5): 5.2. The extrasolar planets 1. the space mission; encyclopaedia 2. the instrument; The extrasolar planets encyclopaedia 1 From the stellar core ... to habitable planets (http://exoplanet.eu) is a working tool 8 Poretti et al.: CoRoT and exoplanets

Fig. 6. Top panel: Homepage of the extrasolar planets encyclopaedia (http://exoplanet.eu). Bottom panel: Distribution of extrasolar planet . This is an example of the histograms and correlation diagrams that can be build from the interactive catalog of the extrasolar planets encyclopaedia.

providing all the latest detections and data (Figure 6, top panel) it is possible to access announced by professional astronomers, an interactive catalog of all known extrasolar useful to facilitate progress in exoplanetology. planets, and to update information on bibliog- It has been established and mantained by Jean raphy, meetings, ongoing research programs Schneider of the CNRS – Paris Observatory and future projects. Finally, links to related since February 1995. From the homepage sites are provided. Poretti et al.: CoRoT and exoplanets 9

The catalog gives access to interactive tools Henry G.W., Marcy G.W., Butler R.P., Vogt to perform statistical analysis, such as the S.S., 1999, IAUC 7307 possibility to build histograms (Fig. 6, bot- Lanza, A. F., Catalano, S., Rodon`o, M., et al. tom panel), and to correlate couples of dif- 2002, A&A 386, 583 ferent parameters. The site can be viewed in Lanza, A. F., Messina, S., Pagano, I., Rodon`o several languages: English, French, Spanish, M. 2006, AN, 327, 21 Portuguese, German, Polish and Italian, al- Lanza, A. F., Rodon`o, M., Pagano, I. 2004, lowing the general public and amateur as- A&A 425, 707 tronomers to easily access high level scientific Lanza, A. F., Rodon`o, M., Pagano, I., Barge, information in the field. We have provided the P., Llebaria, A. 2003, A&A 403, 1135 Italian translation and collaborate to the con- L´eger, A., Baglin, A., Barge, P., Bord´e, tinuous update of the Italian version of the site P., Defay, C., Deleuil, M., Rouan, D., (http://exoplanet.eu/index.it.php). Schneider, J., Vuillemin, A., 2000, IAU Symp. 202, Manchester, eds A.J. Penny et al. 6. Conclusions Maceroni, C., Ribas, I., 2006, IAU Symposium We showed how the Italian contribution to the no. 240, P139 Eds W.I Hartkopf, E.F. CoRoT space mission has allowed a quantita- Guinan & P. Harmanec, Cambridge tive evaluation of instrumental and stellar ef- University Press, in press fects in the planetary transit detection and a McIvor, T., Jardine, M., Holzwarth, V. 2006, more careful evaluation of the stellar content MNRAS, 367, L1 of some specific stellar fields. Also considering Messina, S., Guinan, E. F., Lanza, A. F., the full spectroscopic characterisation of the Ambruster, C., 1999, A&A, 347, 249 targets and the precise photometric evaluation Messina, S., Pizzolato, N., Guinan, E. F., of the stellar variability in the CoRoT fields Rodon`o, M. 2003, A&A, 410, 671 (Poretti, 2003), the Italian researchers provided Moutou, C., Pont, F., Barge, P., et al. 2005, original and useful inputs to the scientific pro- A&A, 437, 355 file to the mission. Parker, E. N. 1979, Cosmical Magnetic Fields, Clarendon Press, Oxford Acknowledgements. The authors wish to thank all Pont, F. 2006, Corot Week 10, the Italian researchers and students (post–doc, PhD, http://www.obs-nice.fr undergraduate) who are participating to the CoRoT Poretti, E., 2003, Mem. SAIt vol. 75, p. 69 activities; they bear witness of the large interest of Poretti, E., et al., 2005, AJ, 129, 2461 our community into this exciting and pioneering space mission. Thanks are also due to Pierre Barge, Ripepi, V., Marconi, M., Palla, F., Bernabei, S., Jean Schneider and Katrien Uytterhoeven for com- Ruoppo, A., Cusano, F., Alcal´a, J. M., 2006, ments on a first draft of the manuscript. Mem. Sait vol. 77, p. 317 Robin, A. C., Reyl´e, C., Derri`ere, S., & Picaud, S. 2003, A&A, 409, 523 References R¨udiger G., Hollerbach, R., 2004, The Aigrain S., Irwin, M. 2004, MNRAS, 350, 331 magnetic Universe, Wiley-VCH Verlag, Auvergne, M., Boisnard, L. & Buey, J-T., Weinheim 2003, SPIE 4853, 170 Saar, S. H., Cuntz, M., Shkolnik, E. 2004, Brown, T. M. 2003, ApJ, 593, L125 in IAU Symp. 219, A. K. Dupree and A. Butler, R. P., Vogt, S. S., Marcy, G. W., Fischer, O. Benz, Eds., Astron. Soc. of Pacific, San D. A., Henry, G. W., Apps, K., 2000, ApJ, Francisco, p. 355 545, 504 Udalski, A., Szymanski, M. K., Kubiak, M., Fr¨ohlich, C., Lean, J. 2004, A&ARv, 12, 273 Pietrzynski, G., Soszynski, I., Zebrun, K., Guillot, T., Garnier, A., Pont, F., Aigrain, S., Szewczyk, O., & Wyrzykowski, L. 2004, Vannier, M., Marmier, M., Fressin, F., 2006, Acta Astronomica, 54, 313 www.obs-nice.fr/guillot/corotlux/