Fast-rotating Blue Straggler Stars in the Globular Cluster NGC 3201

被引:3
作者
Billi, Alex [1 ,2 ]
Ferraro, Francesco R. [1 ,2 ]
Mucciarelli, Alessio [1 ,2 ]
Lanzoni, Barbara [1 ,2 ]
Cadelano, Mario [1 ,2 ]
Monaco, Lorenzo [3 ]
Mateo, Mario [4 ]
Bailey, John I. [5 ]
Reiter, Megan [6 ]
Olszewski, Edward W. [7 ]
机构
[1] Univ Bologna, Dipartimento Fis & Astron, Via Gobetti 93-2, I-40129 Bologna, Italy
[2] INAF Osservatorio Astrofis & Sci Spazio Bologna, Via Gobetti 93-3, I-40129 Bologna, Italy
[3] Univ Andres Bello, Fac Ciencias Exactas, Inst Astrofis, Sede Concepc, Talcahuano, Chile
[4] Univ Michigan, Dept Astron, 1085 S Univ, Ann Arbor, MI 48109 USA
[5] UCSB, Dept Phys, Santa Barbara, CA 93016 USA
[6] Rice Univ, Dept Phys & Astron, 6100 Main St, Houston, TX 77005 USA
[7] Univ Arizona, Steward Observ, 933 N Cherry Ave, Tucson, AZ 85721 USA
关键词
DWARF SPHEROIDAL GALAXIES; HORIZONTAL-BRANCH STARS; MASS-TRANSFER; STELLAR COLLISIONS; DYNAMICAL CLOCK; KINEMATICAL PROPERTIES; TIDAL SYNCHRONIZATION; POPULATION; CORE; EVOLUTION;
D O I
10.3847/1538-4357/acf372
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
We used high-resolution spectra acquired with the Magellan Telescope to measure radial and rotational velocities of approximately 200 stars in the Galactic globular cluster NGC 3201. The surveyed sample includes blue straggler stars (BSSs) and reference stars in different evolutionary stages (main-sequence turnoff, subgiant, red giant, and asymptotic giant branches). The average radial velocity value (V (r) = 494.5 +/- 0.5 km s(-1)) confirms a large systemic velocity for this cluster and was used to distinguish 33 residual field interlopers. The final sample of member stars has 67 BSSs and 114 reference stars. Similarly to what is found in other clusters, the totality of the reference stars has negligible rotation (< 20 km s(-1)), while the BSS rotational velocity distribution shows a long tail extending up to similar to 200 km s(-1), with 19 BSSs (out of 67) spinning faster than 40 km s(-1). This sets the percentage of fast-rotating BSSs to similar to 28%. Such a percentage is roughly comparable to that measured in other loose systems (omega Centauri, M4, and M55) and significantly larger than that measured in high-density clusters (as 47 Tucanae, NGC 6397, NGC 6752, and M30). This evidence supports a scenario where recent BSS formation (mainly from the evolution of binary systems) is occurring in low-density environments. We also find that the BSS rotational velocity tends to decrease for decreasing luminosity and surface temperature, similarly to what is observed in main-sequence stars. Hence, further investigations are needed to understand the impact of BSS internal structure on the observed rotational velocities.
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页数:10
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