2011A&A...535A..59B


Query : 2011A&A...535A..59B

2011A&A...535A..59B - Astronomy and Astrophysics, volume 535A, 59-59 (2011/11-1)

Chromosphere of K giant stars. Geometrical extent and spatial structure detection.

BERIO P., MERLE T., THEVENIN F., BONNEAU D., MOURARD D., CHESNEAU O., DELAA O., LIGI R., NARDETTO N., PERRAUT K., PICHON B., STEE P., TALLON-BOSC I., CLAUSSE J.M., SPANG A., McALISTER H., TEN BRUMMELAAR T., STURMANN J., STURMANN L., TURNER N., FARRINGTON C. and GOLDFINGER P.J.

Abstract (from CDS):

Interferometers provide accurate diameter measurements of stars by analyzing both the continuum and the lines formed in photospheres and chromospheres. Tests of the geometrical extent of the chromospheres are therefore possible by comparing the estimated radius in the continuum of the photosphere and the estimated radii in chromospheric lines. We aim to constrain the geometrical extent of the chromosphere of non-binary K giant stars and detect any spatial structures in the chromosphere. We performed observations with the CHARA interferometer and the VEGA beam combiner at optical wavelengths. We observed seven non-binary K giant stars (β and η Cet, δ Crt, ρ Boo, β Oph, 109 Her, and ι Cep). We measured the ratio of the radii of the photosphere to the chromosphere using the interferometric measurements in the Hα and the CaII infrared triplet line cores. For β Cet, spectro-interferometric observations are compared to a non-local thermal equilibrium (NLTE) semi-empirical model atmosphere including a chromosphere. The NLTE computations provide line intensities and contribution functions that indicate the relative locations where the line cores are formed and can constrain the size of the limb-darkened disk of the stars with chromospheres. We measured the angular diameter of seven K giant stars and deduced their fundamental parameters: effective temperatures, radii, luminosities, and masses. We determined the geometrical extent of the chromosphere for four giant stars (β and η Cet, δ Crt and ρ Boo). The chromosphere extents obtained range between 16% to 47% of the stellar radius. The NLTE computations confirm that the CaII/849 nm line core is deeper in the chromosphere of β Cet than either of the CaII/854 nm and CaII/866 nm line cores. We present a modified version of a semi-empirical model atmosphere derived by fitting the CaII triplet line cores of this star. In four of our targets, we also detect the signature of a differential signal showing the presence of asymmetries in the chromospheres. It is the first time that geometrical extents and structure in the chromospheres of non-binary K giant stars are determined by interferometry. These observations provide strong constrains on stellar atmosphere models.

Abstract Copyright:

Journal keyword(s): techniques: interferometric - stars: chromospheres - stars: fundamental parameters - stars: atmospheres - radiative transfer

Simbad objects: 18

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Number of rows : 18
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 * 2 Cet * 00 03 44.3878420 -17 20 09.571938 4.4 4.483 4.536   4.58 B9IVn 106 0
2 * zet Cas Pu* 00 36 58.2841866 +53 53 48.867311 2.58 3.47 3.66 3.74 3.95 B2IV 429 0
3 * del And SB* 00 39 19.6751809 +30 51 39.678320 6.04 4.56 3.28 2.36 1.70 K3III-IIIbCN0.5 316 0
4 * bet Cet PM* 00 43 35.37090 -17 59 11.7827 3.90 3.02 2.01 1.29 0.78 G9.5IIICH-1 505 0
5 * eta Cet HB* 01 08 35.3914827 -10 10 56.156955 5.80 4.61 3.45 2.61 2.03 K2-IIIb 203 0
6 * zet Aur EB* 05 02 28.6873880 +41 04 33.019985 5.35 4.97 3.75 2.62 1.75 K5II+B7V 441 0
7 * del Crt PM* 11 19 20.4475617 -14 46 42.741307 5.66 4.67 3.56 2.73 2.13 G9IIICH0.5 158 0
8 * tet Crt PM* 11 36 40.9133537 -09 48 08.091238   4.604 4.673     B9.5V 201 0
9 * 16 Com * 12 26 59.2961544883 +26 49 32.527285792   5.045 4.959   4.93 A4V 149 0
10 * rho Boo PM* 14 31 49.7896173 +30 22 17.178087 6.33 4.89 3.59 2.67 2.02 K3-III 249 0
11 * pi. Ser * 16 02 17.6918382424 +22 48 16.020768024   4.887 4.817     A3V 83 0
12 * iot Oph PM* 16 54 00.4715122 +10 09 55.298255 3.98 4.30 4.38     B8V 102 0
13 * bet Oph PM* 17 43 28.3526482 +04 34 02.295484 5.150 3.930 2.750 1.96 1.38 K2IIICN0.5 458 0
14 * 101 Her * 18 08 52.8635204306 +20 02 42.838708227   5.259 5.099     A8III 43 0
15 * 36 Dra PM* 18 13 53.8327884671 +64 23 50.225272101   5.407 4.987 4.8   F5V 185 0
16 * 109 Her ** 18 23 41.8896673559 +21 46 11.085401616 6.18 5.02 3.84 2.99 2.39 K2IIIab 169 0
17 * iot Cep PM* 22 49 40.8169435 +66 12 01.463616 5.50 4.60 3.54 2.69 2.19 K0-III 236 0
18 * ome01 Aqr PM* 23 39 47.0654520800 -14 13 19.737433446   5.221 4.977     A7IV 53 0

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2021.10.19-21:12:10

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