Stellar encounter driven red-giant star mass loss in globular clusters

Mario Pasquato, Andrea De Luca, Gabriella Raimondo, Roberta Carini, Anthony Moraghan, Chul Chung, Enzo Brocato, Young-Wook Lee

Research output: Contribution to journalArticle

5 Citations (Scopus)

Abstract

Globular cluster (GC) color-magnitude diagrams (CMDs) are reasonably well understood in terms of standard stellar evolution. However, there are still some open issues, such as fully accounting for the horizontal branch (HB) morphology in terms of chemical and dynamical parameters. Mass loss on the red giant branch (RGB) shapes the mass distribution of the HB stars, and the color distribution in turn. The physical mechanisms driving mass loss are still unclear, as direct observations fail to reveal a clear correlation between mass-loss rate and stellar properties. The HB mass distribution is further complicated by helium-enhanced multiple stellar populations due to differences in the evolving mass along the HB. We present a simple analytical mass-loss model based on tidal stripping through Roche-Lobe overflow during stellar encounters. Our model naturally results in a non-Gaussian mass-loss distribution with high skewness and contains only two free parameters. We fit it to the HB mass distribution of four Galactic GCs, as obtained from fitting the CMD with zero age HB models. The best-fit model accurately reproduces the observed mass distribution. If confirmed on a wider sample of GCs, our results would account for the effects of dynamics in RGB mass-loss processes and provide a physically motivated procedure for synthetic CMDs of GCs. Our physical modeling of mass loss may result in the ability to disentangle the effects of dynamics and helium-enhanced multiple populations on the HB morphology and is instrumental in making HB morphology a probe of the dynamical state of GCs, leading to an improved understanding of their evolution.

Original languageEnglish
Article number28
JournalAstrophysical Journal
Volume789
Issue number1
DOIs
Publication statusPublished - 2014 Jul 1

Fingerprint

red giant stars
globular clusters
encounters
mass distribution
color-magnitude diagram
diagram
helium
horizontal branch stars
skewness
loss
stellar evolution
stripping
lobes
color
distribution
probes

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Pasquato, M., De Luca, A., Raimondo, G., Carini, R., Moraghan, A., Chung, C., ... Lee, Y-W. (2014). Stellar encounter driven red-giant star mass loss in globular clusters. Astrophysical Journal, 789(1), [28]. https://doi.org/10.1088/0004-637X/789/1/28
Pasquato, Mario ; De Luca, Andrea ; Raimondo, Gabriella ; Carini, Roberta ; Moraghan, Anthony ; Chung, Chul ; Brocato, Enzo ; Lee, Young-Wook. / Stellar encounter driven red-giant star mass loss in globular clusters. In: Astrophysical Journal. 2014 ; Vol. 789, No. 1.
@article{c7e0d793ae2b40f9a070924835702c44,
title = "Stellar encounter driven red-giant star mass loss in globular clusters",
abstract = "Globular cluster (GC) color-magnitude diagrams (CMDs) are reasonably well understood in terms of standard stellar evolution. However, there are still some open issues, such as fully accounting for the horizontal branch (HB) morphology in terms of chemical and dynamical parameters. Mass loss on the red giant branch (RGB) shapes the mass distribution of the HB stars, and the color distribution in turn. The physical mechanisms driving mass loss are still unclear, as direct observations fail to reveal a clear correlation between mass-loss rate and stellar properties. The HB mass distribution is further complicated by helium-enhanced multiple stellar populations due to differences in the evolving mass along the HB. We present a simple analytical mass-loss model based on tidal stripping through Roche-Lobe overflow during stellar encounters. Our model naturally results in a non-Gaussian mass-loss distribution with high skewness and contains only two free parameters. We fit it to the HB mass distribution of four Galactic GCs, as obtained from fitting the CMD with zero age HB models. The best-fit model accurately reproduces the observed mass distribution. If confirmed on a wider sample of GCs, our results would account for the effects of dynamics in RGB mass-loss processes and provide a physically motivated procedure for synthetic CMDs of GCs. Our physical modeling of mass loss may result in the ability to disentangle the effects of dynamics and helium-enhanced multiple populations on the HB morphology and is instrumental in making HB morphology a probe of the dynamical state of GCs, leading to an improved understanding of their evolution.",
author = "Mario Pasquato and {De Luca}, Andrea and Gabriella Raimondo and Roberta Carini and Anthony Moraghan and Chul Chung and Enzo Brocato and Young-Wook Lee",
year = "2014",
month = "7",
day = "1",
doi = "10.1088/0004-637X/789/1/28",
language = "English",
volume = "789",
journal = "Astrophysical Journal",
issn = "0004-637X",
publisher = "IOP Publishing Ltd.",
number = "1",

}

Pasquato, M, De Luca, A, Raimondo, G, Carini, R, Moraghan, A, Chung, C, Brocato, E & Lee, Y-W 2014, 'Stellar encounter driven red-giant star mass loss in globular clusters', Astrophysical Journal, vol. 789, no. 1, 28. https://doi.org/10.1088/0004-637X/789/1/28

Stellar encounter driven red-giant star mass loss in globular clusters. / Pasquato, Mario; De Luca, Andrea; Raimondo, Gabriella; Carini, Roberta; Moraghan, Anthony; Chung, Chul; Brocato, Enzo; Lee, Young-Wook.

In: Astrophysical Journal, Vol. 789, No. 1, 28, 01.07.2014.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Stellar encounter driven red-giant star mass loss in globular clusters

AU - Pasquato, Mario

AU - De Luca, Andrea

AU - Raimondo, Gabriella

AU - Carini, Roberta

AU - Moraghan, Anthony

AU - Chung, Chul

AU - Brocato, Enzo

AU - Lee, Young-Wook

PY - 2014/7/1

Y1 - 2014/7/1

N2 - Globular cluster (GC) color-magnitude diagrams (CMDs) are reasonably well understood in terms of standard stellar evolution. However, there are still some open issues, such as fully accounting for the horizontal branch (HB) morphology in terms of chemical and dynamical parameters. Mass loss on the red giant branch (RGB) shapes the mass distribution of the HB stars, and the color distribution in turn. The physical mechanisms driving mass loss are still unclear, as direct observations fail to reveal a clear correlation between mass-loss rate and stellar properties. The HB mass distribution is further complicated by helium-enhanced multiple stellar populations due to differences in the evolving mass along the HB. We present a simple analytical mass-loss model based on tidal stripping through Roche-Lobe overflow during stellar encounters. Our model naturally results in a non-Gaussian mass-loss distribution with high skewness and contains only two free parameters. We fit it to the HB mass distribution of four Galactic GCs, as obtained from fitting the CMD with zero age HB models. The best-fit model accurately reproduces the observed mass distribution. If confirmed on a wider sample of GCs, our results would account for the effects of dynamics in RGB mass-loss processes and provide a physically motivated procedure for synthetic CMDs of GCs. Our physical modeling of mass loss may result in the ability to disentangle the effects of dynamics and helium-enhanced multiple populations on the HB morphology and is instrumental in making HB morphology a probe of the dynamical state of GCs, leading to an improved understanding of their evolution.

AB - Globular cluster (GC) color-magnitude diagrams (CMDs) are reasonably well understood in terms of standard stellar evolution. However, there are still some open issues, such as fully accounting for the horizontal branch (HB) morphology in terms of chemical and dynamical parameters. Mass loss on the red giant branch (RGB) shapes the mass distribution of the HB stars, and the color distribution in turn. The physical mechanisms driving mass loss are still unclear, as direct observations fail to reveal a clear correlation between mass-loss rate and stellar properties. The HB mass distribution is further complicated by helium-enhanced multiple stellar populations due to differences in the evolving mass along the HB. We present a simple analytical mass-loss model based on tidal stripping through Roche-Lobe overflow during stellar encounters. Our model naturally results in a non-Gaussian mass-loss distribution with high skewness and contains only two free parameters. We fit it to the HB mass distribution of four Galactic GCs, as obtained from fitting the CMD with zero age HB models. The best-fit model accurately reproduces the observed mass distribution. If confirmed on a wider sample of GCs, our results would account for the effects of dynamics in RGB mass-loss processes and provide a physically motivated procedure for synthetic CMDs of GCs. Our physical modeling of mass loss may result in the ability to disentangle the effects of dynamics and helium-enhanced multiple populations on the HB morphology and is instrumental in making HB morphology a probe of the dynamical state of GCs, leading to an improved understanding of their evolution.

UR - http://www.scopus.com/inward/record.url?scp=84902595150&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=84902595150&partnerID=8YFLogxK

U2 - 10.1088/0004-637X/789/1/28

DO - 10.1088/0004-637X/789/1/28

M3 - Article

VL - 789

JO - Astrophysical Journal

JF - Astrophysical Journal

SN - 0004-637X

IS - 1

M1 - 28

ER -

Pasquato M, De Luca A, Raimondo G, Carini R, Moraghan A, Chung C et al. Stellar encounter driven red-giant star mass loss in globular clusters. Astrophysical Journal. 2014 Jul 1;789(1). 28. https://doi.org/10.1088/0004-637X/789/1/28