2012A&A...543A.146F


C.D.S. - SIMBAD4 rel 1.7 - 2020.11.28CET22:26:12

2012A&A...543A.146F - Astronomy and Astrophysics, volume 543A, 146-146 (2012/7-1)

Magnetic activity and differential rotation in the young sun-like stars KIC 7985370 and KIC 7765135.

FROEHLICH H.-E., FRASCA A., CATANZARO G., BONANNO A., CORSARO E., MOLENDA-ZAKOWICZ J., KLUTSCH A. and MONTES D.

Abstract (from CDS):

We present a detailed study of the two Sun-like stars KIC7985370 and KIC7765135, to determine their activity level, spot distribution, and differential rotation. Both stars were previously discovered by us to be young stars and were observed by the NASA Kepler mission. The fundamental stellar parameters (vsini, spectral type, Teff, logg, and [Fe/H]) were derived from optical spectroscopy by comparison with both standard-star and synthetic spectra. The spectra of the targets allowed us to study the chromospheric activity based on the emission in the core of hydrogen Hα and CaII infrared triplet (IRT) lines, which was revealed by the subtraction of inactive templates. The high-precision Kepler photometric data spanning over 229 days were then fitted with a robust spot model. Model selection and parameter estimation were performed in a Bayesian manner, using a Markov chain Monte Carlo method. We find that both stars are Sun-like (of G1.5V spectral type) and have an age of about 100-200Myr, based on their lithium content and kinematics. Their youth is confirmed by their high level of chromospheric activity, which is comparable to that displayed by the early G-type stars in the Pleiades cluster. The Balmer decrement and flux ratio of their CaII-IRT lines suggest that the formation of the core of these lines occurs mainly in optically thick regions that are analogous to solar plages. The spot model applied to the Kepler photometry requires at least seven persistent spots in the case of KIC7985370 and nine spots in the case of KIC7765135 to provide a satisfactory fit to the data. The assumption of the longevity of the star spots, whose area is allowed to evolve with time, is at the heart of our spot-modelling approach. On both stars, the surface differential rotation is Sun-like, with the high-latitude spots rotating slower than the low-latitude ones. We found, for both stars, a rather high value of the equator-to-pole differential rotation (dΩ≃0.18rad/d), which disagrees with the predictions of some mean-field models of differential rotation for rapidly rotating stars. Our results agree instead with previous works on solar-type stars and other models that predict a higher latitudinal shear, increasing with equatorial angular velocity, that can vary during the magnetic cycle.

Abstract Copyright:

Journal keyword(s): stars: activity - starspots - stars: rotation - stars: chromospheres - stars: individual: KIC7985370 - stars: individual: KIC7765135

Simbad objects: 28

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Number of rows : 28

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2021
#notes
1 HD 10307 SB* 01 41 47.1431421954 +42 36 48.443521767 5.69 5.58 4.96 4.43 4.10 G1V 469 0
2 * tau Cet PM* 01 44 04.0834226 -15 56 14.926552 4.43 4.22 3.50 2.88 2.41 G8V 1106 1
3 * alf Per V* 03 24 19.3700924 +49 51 40.245455 2.64 2.27 1.79     F5Ib 804 1
4 * eps Eri BY* 03 32 55.8449634 -09 27 29.731165 5.19 4.61 3.73 3.00 2.54 K2V 1721 1
5 Cl Melotte 22 OpC 03 47 00 +24 07.0           ~ 3037 0
6 V* AB Dor TT* 05 28 44.8916324761 -65 26 55.289846904 8.259 7.856 6.999 6.496 5.993 K0V 939 0
7 IC 2391 OpC 08 40 32 -53 02.0           ~ 725 0
8 V* LQ Hya BY* 09 32 25.5684079124 -11 11 04.687410738 9.316 8.761 7.891 7.288 6.815 K1Vp 405 0
9 IC 2602 OpC 10 42 58 -64 24.0           ~ 561 0
10 HD 106506 V* 12 15 18.5535918618 -63 25 30.328597629   9.06 8.46     G1V 54 0
11 NAME Ursa Major Moving Group MGr 12 32 +57.0           ~ 388 2
12 V* NZ Lup BY* 15 53 27.2914974411 -42 16 00.711812290   8.48 7.975   7.213 G2 76 0
13 * w Her PM* 17 20 39.5675395123 +32 28 03.877348066 6.08 6.01 5.39 4.89 4.56 G0V 424 0
14 V* V889 Her BY* 18 34 20.1030244573 +18 41 24.234582456   8.00 7.449   6.720 G2V 120 0
15 * b Aql PM* 19 24 58.2002406780 +11 56 39.882312617 6.35 5.93   4.7   G7IVHdel1 457 0
16 RX J1925.0+4429 Ro* 19 25 02.0048126 +44 29 50.757778   10.83 9.93 9.595   K1V 34 0
17 TYC 3148-2163-1 Ro* 19 42 50.5787960349 +43 24 48.662472426     11.736 11.51 10.986 G2V 17 0
18 V* CI Cyg Al* 19 50 11.8344401438 +35 41 03.000692799   11.97 9.90     Bep+M5III 407 0
19 * omi Aql PM* 19 51 01.6437560393 +10 24 56.595177367   5.66   4.8   F8V 425 0
20 HD 189210 Ro* 19 56 59.7430162616 +43 45 08.300363883   10.58 9.98   9.240 G1.5V 24 0
21 NAME BL Lac BLL 22 02 43.2913773726 +42 16 39.978417860   15.66 14.72     ~ 2025 1
22 HD 224085 RS* 23 55 04.0516465022 +28 38 01.248194500 8.88 8.20   6.9   K2+IVeFe-1 686 0
23 NGC 7790 OpC 23 58 24 +61 12.5   9.18 8.5     ~ 246 0
24 NAME Castor Moving Group As* ~ ~           ~ 117 1
25 NAME Sirius Moving Group MGr ~ ~           ~ 78 0
26 NAME Pleiades Moving Group MGr ~ ~           ~ 241 1
27 NAME Hyades Moving Group MGr ~ ~           ~ 240 0
28 NAME IC 2391 Moving Group MGr ~ ~           ~ 22 0

    Equat.    Gal    SGal    Ecl

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2020.11.28-22:26:12

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