2010A&A...524A..88D


Query : 2010A&A...524A..88D

2010A&A...524A..88D - Astronomy and Astrophysics, volume 524, A88-88 (2010/12-1)

Acoustic oscillations in stars near the tip of the red giant branch.

DZIEMBOWSKI W.A. and SOSZYNSKI I.

Abstract (from CDS):

Small amplitude oscillations are observed in red giant branch (RGB) stars. Data on such oscillations are a source of information about the objects, notably about properties of convection in their envelopes and about the systems these objects inhabit. The OGLE-III catalog contains data for about 80 thousand small amplitude variable red giants (OSARGs) in the Large Magellanic Cloud. We want to explain variability oin OSARGs as the solar-like oscillation and to associate the peaks in power spectra with frequencies of acoustic modes. We use data on reddening-free magnitudes of the objects and interpret them in terms of stellar physical parameters using tabulated isochrones calculated for ages and composition parameters corresponding to the upper RGB of the LMC. Massive data on the peak frequencies and amplitudes are compared with expectations for stochastically excited oscillations. The frequencies are also compared with those calculated for radial modes in envelope models with parameters taken from the isochrones. In stars close to the tip of the RGB, the peaks in power spectra are found in the 0.1-1.0µHz range, which is consistent with extrapolation of the frequency-luminosity relation for the solar-like oscillation. The dominant peaks occur close to the first two radial overtones. The increase in amplitude with luminosity is slower than linear. The exponent s≃0.9 is similar to what is found from recent analysis of CoRoT data on less luminous red giants. Frequency separations between dominant peaks are found to be smaller by about 20% than calculated separations between these modes. After examining various possibilities, we left this discrepancy unexplained. The small amplitude variability of stars at the RGB tip is likely to be caused by a stochastic excitation of acoustic oscillations but interpreting of individual peaks in power spectra presents a problem.

Abstract Copyright:

Journal keyword(s): asteroseismology - stars: evolution - stars: late-type - stars: oscillations - Magellanic Clouds

Simbad objects: 16

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Number of rows : 16
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2022
#notes
1 NAME SMC G 00 52 38.0 -72 48 01   2.79 2.2     ~ 10311 1
2 NAME Magellanic Clouds GrG 03 00 -71.0           ~ 6371 1
3 2MASS J05000601-6910388 LP* 05 00 06.0240945720 -69 10 38.911544436     16.301 13.624 13.475 ~ 3 0
4 2MASS J05043847-6931545 LP* 05 04 38.5039162560 -69 31 54.477329700     16.284   14.025 ~ 2 0
5 BMB-BW 308 AB* 05 08 53.2300103784 -69 11 42.387982116         14.85 M2.0 4 0
6 OGLE LMC-LPV-29151 V* 05 13 25.6694655432 -69 26 42.488792052     16.57 15.75   ~ 3 0
7 2MASS J05202397-7041228 LP* 05 20 23.9710466496 -70 41 22.882535916     16.58 15.62   ~ 3 0
8 OGLE LMC-LPV-43355 V* 05 20 34.04 -70 01 03.2           ~ 2 0
9 2MASS J05225046-6927126 LP* 05 22 50.460 -69 27 12.62     16.77 15.85 15.006 ~ 3 0
10 NAME LMC G 05 23 34.6 -69 45 22     0.4     ~ 16150 1
11 OGLE LMC-LPV-65773 LP* 05 31 32.23 -69 57 29.7       14.814   ~ 3 0
12 OGLE LMC-LPV-70093 V* 05 34 03.829 -70 15 45.90     16.66 15.78   ~ 3 0
13 2MASS J05351751-7010154 LP* 05 35 17.5352319072 -70 10 15.461381028     16.409 14.019 13.886 ~ 3 0
14 2MASS J05363351-7033156 LP* 05 36 33.5161298952 -70 33 15.670480356     16.48 15.54 14.697 ~ 3 0
15 2MASS J05390705-6957234 LP* 05 39 07.056 -69 57 23.44     16.52 14.536 14.481 ~ 4 0
16 NAME Galactic Bulge reg ~ ~           ~ 3895 0

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2022.08.09-00:44:11

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