The peculiar properties of horizontal branch stars in omega Centauri

Abstract

We measured temperatures, gravities, and masses for a large sample of blue horizontal branch stars in omega Centauri, comparing the results with theoretical expectations for canonical and He-enriched stars, and with previous measurements in three other clusters. The measured gravities of omega Cen stars are systematically lower than canonical models, in agreement with expectations for He-enriched stars, and contrary to that observed in the comparison clusters. However, the derived masses are unrealistically too low as well. This cannot be explained by low gravities alone, nor by any of the other parameters entering in the calculation. We find that the same stars are not brighter than their analogs in the other clusters, contrary to the expectations of the He-enrichment scenario. The interpretation of the results is thus not straightforward, but they reveal an intrinsic, physical difference between HB stars in omega Cen and in the three comparison clusters.

Accepted for publication in ApJ Letters

References in corpus (8)

• NGC 6441: another indication for a very high helium content in Globular Cluster stars
• New HST WFC3/UVIS observations augment the stellar-population complexity of omega Centauri
• The hot horizontal-branch stars in omega Centauri
• Constraints on Helium Enhancement in the Globular Cluster M3 (NGC 5272): The Horizontal Branch Test
• Spectroscopy of horizontal branch stars in NGC6752 - Anomalous results on atmospheric parameters and masses
• The subgiant branch of omega Cen seen through high-resolution spectroscopy. I. The first stellar generation in omega Centauri?
• Stratification of the elements in the atmospheres of blue horizontal-branch stars
• Observations of the Hot Horizontal-Branch Stars in the Metal-Rich Bulge Globular Cluster NGC 6388 - Indications of Helium Enrichment and a Lesson in Crowded Field Spectroscopy

Cited by in corpus (12)

• Effects of Helium Enrichment in Globular Clusters I.Theoretical Plane with PGPUC stellar evolution code
• Star Formation Histories of Globular Clusters with Multiple Populations. I. ω Cen, M22, and NGC 1851
• Horizontal-branch morphology and multiple stellar populations in the anomalous globular cluster M22
• SHOTGLAS I: The ultimate spectroscopic census of extreme horizontal branch stars in $\omega$ Centauri
• Spectroscopy of horizontal branch stars in Omega Centauri
• Double Horizontal Branches in NGC 6440 and NGC 6569 unveiled by the VVV Survey
• Origin of a massive hyper-runaway subgiant star LAMOST-HVS1 -- implication from Gaia and follow-up spectroscopy
• Hot horizontal branch stars in NGC 288 - effects of diffusion and stratification on their atmospheric parameters
• SHOTGLAS II. MUSE spectroscopy of blue horizontal branch stars in the core of $\omega$ Centauri and NGC 6752
• Spectroscopy of blue horizontal branch stars in NGC 6656 (M22)
• Globular Cluster UVIT legacy Survey (GlobUleS) III. Omega Centauri in Far-Ultraviolet
• Just how hot are the $\omega$ Centauri extreme horizontal branch pulsators?