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Astron. Nachr. / AN 999 , No. 88, 789 792 (2006) / DOI please set DOI!

Characteristics of 100+ Kepler Asteroseismic Targets from Ground-Based Observations

J. Molenda- Zakowicz 1 , , M. Jerzykiewicz 1 , A. Frasca 2 , G. Catanzaro 2 , G. Kopacki 1 , and D.W.

Latham3

1 Instytut Astronomiczny Uniwersytetu Wrocawskiego, ul. Kopernika 11, 51-622 Wrocaw, Poland2 INAFOsservatorio Astrosico di Catania, Via Soa 78, 95123 Catania, Italy3 Harvard Smithsonian Center for Astrophysics, Cambridge, Massachusetts, USA

Received 1 April 2010, accepted Published online later

Key words space vehicles: Kepler stars: fundamental parameters stars: variables: general

We present results of our 5-years-long program of ground-based spectroscopic and photometric observations of individualKepler asteroseismic targets and the open clusters NGC 6866 and NGC 6811 from the Kepler eld of view. We determinedthe effective temperature, surface gravity, metallicity, the projected rotational velocity and the radial velocity of 119 Keplerasteroseismic targets for which we acquired high-resolution spectra. For many of these stars the derived atmosphericparameters agree with T eff , log g , and [Fe/H] from the Kepler Input Catalog (KIC) to within their error bars. Only for starshotter than 7000 K we notice signicant differences between the effective temperature derived from spectroscopy and T eff given in the KIC. For 19 stars which we observed photoelectrically, we measured the interstellar reddening and we foundit to be negligible. Finally, our discovery of the Sct and Dor pulsating stars in the open cluster NGC 6866 allowed usto discuss the frequency of the occurrence of Dor stars in the open clusters of different age and metallicity and show thatthere are no correlations between these parameters.

c 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

1 Introduction

Our program of ground-based spectroscopic and photomet-ric observations of stars selected for the asteroseismic tar-

gets for the Kepler space telescope by the Kepler Aster-oseismic Science Consortium KASC 1 was started in 2005at the Osservatorio Astrosico di Catania, OACt, (the M.G.Fracastoro station, Mt. Etna, Italy) and is continued sincethen. Apart from the OACt, we perform spectroscopic andphotometric observations of Kepler asteroseismic targets atthe F. L. Whipple Observatory, FLWO, (Mount Hopkins,Arizona, USA), and the Astrophysical Observatory of theUniversity of Wrocaw in Biak ow (Poland).

At the OACt, we use a 91-cm telescope, at FLWO, a1.5-m telescope, and at the Biak ow Observatory, a 60-cmtelescope. We make use also of the archival data collectedat the 1.5-m telescope at the Oak Ridge Observatory, ORO,(Harvard, Massachusetts, USA) and at the Multiple MirrorTelescope, MMT, before it was converted to the monolithic6.5-m mirror. The data used in this paper have been obtained at the Wrocaw Uni-

versity Observatory in Biak ow, the Osservatorio Astrosico di Catania,the F. L. Whipple Observatory, Mount Hopkins, Arizona, the Oak RidgeObservatory, Harvard, Massachusetts, and the MMT. e-mail: molenda@astro.uni.wroc.pl

1 Kepler Asteroseismic Science Consortium (KASC) is a group of col-laborating scientists and/or institutions established to accomplish the ac-tivities of the Kepler Asteroseismic Investigation (KAI), represented byRonald Gilliland (see http://astro.phys.au.dk/KASC ).

Using the spectroscopic data acquired at OACt, FLWO,ORO, and MMT, we aim at the determination of the at-mospheric parameters of the program stars, i.e., the effec-tive temperature, T eff , surface gravity, log g, and metallic-ity, [Fe/ H], and measuring the projected rotational velocity,v sin i, and the radial velocity, vr , of the stars.

At the Biakow Observatory, we perform photometrictime-series observations of the open clusters NGC 6866 andNGC6811 in the Kepler eld of view, aiming at the dis-covery of new pulsating stars, and the determination of thedegree of the modes of their pulsations.

Both sites, the Biak ow Observatory and the OACt, took part in the international multi-site photometric campaign onNGC 6866 launched in 2009, and will take part in a similarcampaign on NGC 6811 which will be launched in 2010 (forthe details, see Uytterhoeven et al. 2010b.)

2 Radial velocity and the projectedrotational velocity

When analyzing the spectrograms with the aim of derivingthe atmospheric parameters, we measured the projected ro-tational velocity of the program stars and their radial ve-locity. As expected, we found the F, G, and K type starsto be slow rotators having v sin i typically below 5 km s 1 .The early-type stars discussed by Catanzaro et al. (2010)rotate signicantly faster and although several of them havev sin i < 10 km s 1 , this low projected rotational velocity

c 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

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790 J. Molenda- Zakowicz et al.: Characteristics of 100+ Kepler Asteroseismic Targets from Ground-Based Observations

Fig. 1 The Kepler asteroseismic targets observed at theOsservatorio Astrosico di Catania, the F. L. Whipple Ob-servatory, and the Oak Ridge Observatory. Indicated are theborders of the 42 Kepler CCDs and the borders of the con-stellations.

may be due to the orientation of the axis of the rotation of the star in the sky.

From the analysis of the radial velocities of the programstars, we discovered six single-lined, SB1, and four double-lined, SB2, spectroscopic binaries (see Molenda- Zakowiczet al. 2007, 2010; Molenda- Zakowicz, Frasca & Latham2008; Catanzaro et al. 2010; Frasca et al. 2010). For twoof the new SB1 systems and one new SB2 star we calcu-lated the systems mass functions and the orbital solutions,respectively. More spectroscopic and photometric observa-tions are needed to derive the mass functions and orbital so-lutions for the remaining stars, and to check which of thesesystems are eclipsing.

In Table 1, we give the number of the spectrograms ac-quired for each program star at the OACt, FLWO, ORO andMMT.

3 Atmospheric parameters

We measured the effective temperature, T eff , the surfacegravity, log g, and the metallicity, [Fe/ H], of 119 stars se-lected for asteroseismic targets for Kepler. There is one sub-dwarf in this sample, HIP 92775; all the remaining starshave solar metallicity or are slightly metal-decient (seeMolenda- Zakowicz et al. 2007, 2010; Molenda- Zakowicz,Frasca & Latham 2008; Catanzaro et al. 2010; Frasca et al.2010.)

In the top panel of Fig. 2, we plot the program stars inthe T eff log g diagram constructed with the use of the pa-rameters derived from spectroscopy (dots) and those fromthe Kepler Input Catalog 2 KIC (circles) derived from thephotometric observations acquired in the Sloan lters. Thenext panels show the differences between the T eff , logg and

2 http://archive.stsci.edu/

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Fig.2 Top: The T eff log g diagram for the program starsplotted with the use of T eff and logg from the Kepler In-put Catalog KIC (circles) and the values derived from spec-troscopy (dots). The next panels from top to bottom: The dif-ferences between T eff , log g and [Fe/H] derived from spec-troscopy and those given in the KIC.

c 2006 WILEY-VCH Verlag GmbH& Co. KGaA, Weinheim www.an-journal.org

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