2011A&A...526A...4V


C.D.S. - SIMBAD4 rel 1.7 - 2020.07.10CEST03:11:13

2011A&A...526A...4V - Astronomy and Astrophysics, volume 526A, 4-4 (2011/2-1)

Modelling chromospheric line profiles as diagnostics of velocity fields in ω Centauri red giant stars.

VIEYTES M., MAUAS P., CACCIARI C., ORIGLIA L. and PANCINO E.

Abstract (from CDS):

Mass loss of ∼0.1-0.3M from Population II red giant stars (RGB) is a requirement of stellar evolution theory in order to account for several observational evidences in globular clusters. The aim of this study is to detect the presence of outward velocity fields, which are indicative of mass outflow, in six luminous red giant stars of the stellar cluster ω Cen. We compare synthetic line profiles computed using relevant model chromospheres to observed profiles of the Hα and CaII K lines. The spectra were taken with UVES (R=45000) and the stars were selected so that three of them belong to the metal-rich population and three to the metal-poor population, and sample as far down as 1 to 2.5mag fainter than the respective RGB tips. We do indeed reveal the presence of low-velocity outward motions in four of our six targets, without any apparent correlation with astrophysical parameters. This provides direct evidence that outward velocity fields and mass motions exist in RGB stars as much as 2.5mag fainter than the tip. On the assumption that the mass outflow may eventually lead to mass loss from the star, we estimate mass-loss rates of some 10–9-10–10M/yr that are compatible with the stellar evolution requirements. These rates seem to be correlated with luminosity rather than metallicity.

Abstract Copyright:

Journal keyword(s): line: profiles - globular clusters: individual: ω Cen - stars: atmospheres - stars: mass-loss - stars: Population II - techniques: spectroscopic

Simbad objects: 13

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Number of rows : 13

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2020
#notes
1 NGC 104 GlC 00 24 05.359 -72 04 53.20   5.78 4.09     ~ 3548 0
2 NGC 362 GlC 01 03 14.26 -70 50 55.6     6.58     ~ 938 0
3 IRAS 09110-6439 GlC 09 12 03.10 -64 51 48.6   7.77 5.69     ~ 1245 0
4 2MASS J13251752-4724266 RG* 13 25 17.5227414595 -47 24 26.551906518   13.36 11.98   10.45 ~ 34 0
5 Cl* NGC 5139 LEID 41039 RB? 13 25 53.7675050423 -47 28 12.183731539   13.481 12.251   10.97 ~ 26 0
6 2MASS J13260383-4728327 RG* 13 26 03.8376899994 -47 28 32.726647565   14.950 13.789   12.408 ~ 10 0
7 NGC 5139 GlC 13 26 47.28 -47 28 46.1   6.12 5.33     ~ 2997 0
8 2MASS J13270238-4726059 RG* 13 27 02.3928324072 -47 26 06.015806276   13.593 12.430   11.15 ~ 19 0
9 NGC 5139 523 * 13 27 04.759 -47 31 01.30   14.680 13.320 13.31 11.93 K5: 14 0
10 Cl* NGC 5139 LEID 32149 * 13 27 14.5542480659 -47 23 51.133664313   14.870 13.568 13.46 12.111 ~ 9 0
11 M 13 GlC 16 41 41.634 +36 27 40.75     5.8     ~ 2007 0
12 M 92 GlC 17 17 07.39 +43 08 09.4     6.52     ~ 1905 0
13 M 15 GlC 21 29 58.33 +12 10 01.2   3       ~ 2907 0

    Equat.    Gal    SGal    Ecl

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2020.07.10-03:11:13

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