2011A&A...533A.107D


C.D.S. - SIMBAD4 rel 1.7 - 2021.05.07CEST10:11:40

2011A&A...533A.107D - Astronomy and Astrophysics, volume 533A, 107-107 (2011/9-1)

Structure of the outer layers of cool standard stars.

DEHAES S., BAUWENS E., DECIN L., ERIKSSON K., RASKIN G., BUTLER B., DOWELL C.D., ALI B. and BLOMMAERT J.A.D.L.

Abstract (from CDS):

Among late-type red giants, an interesting change occurs in the structure of the outer atmospheric layers as one moves to later spectral types in the Hertzsprung-Russell diagram: a chromosphere is always present, but the coronal emission diminishes and a cool massive wind steps in. Where most studies have focussed on short-wavelength observations, this article explores the influence of the chromosphere and the wind on long-wavelength photometric measurements. The goal of this study is to assess wether a set of standard near-infrared calibration sources are fiducial calibrators in the far-infrared, beyond 50µm. The observational spectral energy distributions were compared with the theoretical model predictions for a sample of nine K- and M-giants. The discrepancies found are explained using basic models for flux emission originating in a chromosphere or an ionised wind. For seven out of nine sample stars, a clear flux excess is detected at (sub)millimetre and/or centimetre wavelengths, while only observational upper limits are obtained for the other two. The precise start of the excess depends upon the star under consideration. For six sources the flux excess starts beyond 210µm and they can be considered as fiducial calibrators for Herschel/PACS (60-210µm). Out of this sample, four sources show no flux excess in the Herschel/SPIRE wavelength range (200-670µm) and are good calibration sources for this instrument as well. The flux at wavelengths shorter than ∼1mm is most likely dominated by an optically thick chromosphere, where an optically thick ionised wind is the main flux contributor at longer wavelengths. Although the optical to mid-infrared spectrum of the studied K- and M-type infrared standard stars is represented well by a radiative equilibrium atmospheric model, a chromosphere and/or ionised stellar wind at higher altitudes dominates the spectrum in the (sub)millimetre and centimetre wavelength ranges. The presence of a flux excess has implications on the role of the stars as fiducial spectrophotometric calibrators in these wavelength ranges.

Abstract Copyright:

Journal keyword(s): stars: chromospheres - stars: late-type - stars: winds, outflows - radio continuum: stars

VizieR on-line data: <Available at CDS (J/A+A/533/A107): stars.dat mod/* fit/*>

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 * bet And PM* 01 09 43.92388 +35 37 14.0075 5.58 3.62 2.05 0.81 -0.19 M0+IIIa 538 0
2 * alf Cet LP? 03 02 16.77307 +04 05 23.0596 6.10 4.17 2.53 1.18 0.02 M1.5IIIa 442 0
3 V* HL Tau Or* 04 31 38.471952 +18 13 58.08504   15.89 14.49 14.39   K5 1254 0
4 IRAS 04287+1807 mul 04 31 38.8 +18 13 57           ~ 796 0
5 * alf Tau LP? 04 35 55.23907 +16 30 33.4885 4.32 2.40 0.86 -0.37 -1.31 K5+III 1195 1
6 RAFGL 618 pA* 04 42 53.6245215366 +36 06 53.397219192   16.32   12.59   C-rich 966 0
7 * iot Aur V* 04 56 59.6210887 +33 09 57.958479 6.00 4.22 2.69 1.63 0.81 K3II-III 266 0
8 * alf CMa SB* 06 45 08.91728 -16 42 58.0171 -1.51 -1.46 -1.46 -1.46 -1.43 A0mA1Va 1426 0
9 3C 286 Sy1 13 31 08.2885060664 +30 30 32.960825107   17.51 17.25     ~ 3864 2
10 ICRF J135704.4+191907 Sy1 13 57 04.43665381 +19 19 07.3724675   16.33 16.03 15.3   ~ 418 2
11 * alf Boo RG* 14 15 39.67207 +19 10 56.6730 2.46 1.18 -0.05 -1.03 -1.68 K1.5IIIFe-0.5 2170 0
12 * bet UMi V* 14 50 42.32580 +74 09 19.8142 5.32 3.55 2.08 0.97 0.21 K4-III 309 0
13 * sig Lib LP* 15 04 04.2160765 -25 16 55.060636 6.86 4.91 3.21 1.60 0.33 M2.5III 176 0
14 IC 4553 SyG 15 34 57.22396 +23 30 11.6084   14.76 13.88     ~ 2742 4
15 * gam Dra * 17 56 36.36988 +51 29 20.0242 5.630 3.760 2.230 1.08 0.23 K5III 523 0
16 * alf Lyr dS* 18 36 56.33635 +38 47 01.2802 0.03 0.03 0.03 0.07 0.10 A0Va 2544 0
17 V* V1610 Cyg pA* 21 02 18.27 +36 41 37.0           F5Iae 839 1
18 * bet Peg LP* 23 03 46.45746 +28 04 58.0336 6.05 4.09 2.42 0.92 -0.40 M2.5II-III 581 0

    Equat.    Gal    SGal    Ecl

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2021.05.07-10:11:40

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