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Blue hook stars in globular clusters

Blue hook stars in globular clusters
Blue hook stars in globular clusters
Blue hook (BHk) stars are a rare class of horizontal branch stars that have so far been found in only very few Galactic globular clusters (GCs). The dominant mechanism for producing these objects is currently still unclear. In order to test if the presence of BHk populations in a given GC is linked to specific physical or structural cluster properties, we have constructed a parent sample of GCs for which existing data are sufficient to establish the presence or absence of BHk populations with confidence. We then compare the properties of those clusters in our parent sample that do contain a BHk population to those that do not. We find that there is only one compelling difference between BHk and non-BHk clusters: all known BHk clusters are unusually massive. However, we also find that the BHk clusters are consistent with being uniformly distributed within the cumulative mass distribution of the parent sample. Thus, while it is attractive to suggest that there is a lower mass cut-off for clusters capable of forming BHk stars, the data do not require this. Instead, the apparent preference for massive clusters could still be a purely statistical effect: intrinsically rare objects can only be found by searching a sufficiently large number of stars
stars: horizontal branch, globular clusters: general
0035-8711
L56-L60
Dieball, A.
5f595453-aa6b-4067-a3e1-026867fb9f7a
Knigge, C.
ac320eec-631a-426e-b2db-717c8bf7857e
Maccarone, T.J.
5d8ee27f-a174-424c-b3b7-a6739bfeea50
Long, K.S.
91417b3d-d408-475a-8907-eec131e17c66
Hannikainen, D.C.
75e8f67a-ed96-44d1-aee8-6ea2ea7889c4
Zurek, D.
55dc9102-d0ed-4b0e-a053-f74fee5a0e6c
Shara, M.
1ff52820-d17b-432e-90f0-777540daea67
Dieball, A.
5f595453-aa6b-4067-a3e1-026867fb9f7a
Knigge, C.
ac320eec-631a-426e-b2db-717c8bf7857e
Maccarone, T.J.
5d8ee27f-a174-424c-b3b7-a6739bfeea50
Long, K.S.
91417b3d-d408-475a-8907-eec131e17c66
Hannikainen, D.C.
75e8f67a-ed96-44d1-aee8-6ea2ea7889c4
Zurek, D.
55dc9102-d0ed-4b0e-a053-f74fee5a0e6c
Shara, M.
1ff52820-d17b-432e-90f0-777540daea67

Dieball, A., Knigge, C., Maccarone, T.J., Long, K.S., Hannikainen, D.C., Zurek, D. and Shara, M. (2009) Blue hook stars in globular clusters. Monthly Notices of the Royal Astronomical Society, 394 (1), L56-L60. (doi:10.1111/j.1745-3933.2008.00609.x).

Record type: Article

Abstract

Blue hook (BHk) stars are a rare class of horizontal branch stars that have so far been found in only very few Galactic globular clusters (GCs). The dominant mechanism for producing these objects is currently still unclear. In order to test if the presence of BHk populations in a given GC is linked to specific physical or structural cluster properties, we have constructed a parent sample of GCs for which existing data are sufficient to establish the presence or absence of BHk populations with confidence. We then compare the properties of those clusters in our parent sample that do contain a BHk population to those that do not. We find that there is only one compelling difference between BHk and non-BHk clusters: all known BHk clusters are unusually massive. However, we also find that the BHk clusters are consistent with being uniformly distributed within the cumulative mass distribution of the parent sample. Thus, while it is attractive to suggest that there is a lower mass cut-off for clusters capable of forming BHk stars, the data do not require this. Instead, the apparent preference for massive clusters could still be a purely statistical effect: intrinsically rare objects can only be found by searching a sufficiently large number of stars

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More information

Published date: March 2009
Keywords: stars: horizontal branch, globular clusters: general

Identifiers

Local EPrints ID: 79543
URI: http://eprints.soton.ac.uk/id/eprint/79543
ISSN: 0035-8711
PURE UUID: b8af90c7-aa49-4d31-9de3-555e8c2370c0

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Date deposited: 17 Mar 2010
Last modified: 08 Nov 2021 18:03

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Contributors

Author: A. Dieball
Author: C. Knigge
Author: T.J. Maccarone
Author: K.S. Long
Author: D.C. Hannikainen
Author: D. Zurek
Author: M. Shara

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