J/ApJ/772/148 Blue straggler and red giant stars in M30 (Lovisi+, 2013)
Flames and XSHOOTER spectroscopy along the two blue straggler star sequences
of M30.
Lovisi L., Mucciarelli A., Lanzoni B., Ferraro F.R., Dalessandro E.,
Monaco L.
<Astrophys. J., 772, 148 (2013)>
=2013ApJ...772..148L 2013ApJ...772..148L
ADC_Keywords: Clusters, globular ; Abundances ; Radial velocities ; Stars, giant
Keywords: blue stragglers; globular clusters: individual: M30;
stars: abundances; stars: evolution; techniques: spectroscopic
Abstract:
We present spectroscopic observations acquired with FLAMES and
XSHOOTER at the Very Large Telescope for a sample of 15 blue straggler
stars (BSSs) in the globular cluster (GC) M30 (NGC 7099). The targets
have been selected to sample the two BSS sequences discovered, with
seven BSSs along the blue sequence and eight along the red one. No
difference in the kinematical properties of the two groups of BSSs has
been found. In particular, almost all the observed BSSs have projected
rotational velocities lower than ∼30 km/s, with only one (blue) fast
rotating BSS (>90km/s), identified as a W UMa binary. This rotational
velocity distribution is similar to those obtained in 47 Tucanae and
NGC 6397, while M4 remains the only GC studied so far that harbors a
large fraction of fast rotating BSSs. All stars hotter than ∼7800K
(regardless of the parent BSS sequence) show iron abundances larger
than those measured from normal cluster stars, with a clear-cut trend
with the effective temperature. This behavior suggests that particle
transport mechanisms driven by radiative levitation occur in the
photosphere of these stars, as already observed for the BSSs in NGC
6397. Finally, four BSSs belonging to the red sequence (not affected
by radiative levitation) show a strong depletion of [O/Fe], with
respect to the abundance measured in red giant branch and horizontal
branch stars. This O-depletion is compatible with the chemical
signature expected in BSSs formed by mass-transfer processes in binary
systems, in agreement with the mechanism proposed for the formation of
BSSs in the red sequence.
Description:
This work is based on spectroscopic observations collected with the
spectrographs FLAMES and XSHOOTER both mounted at the Unit Telescope 2
at the Very Large Telescope of the European Southern Observatory.
The FLAMES observations have been performed with the multi-object
high-resolution spectrograph FLAMES in the UVES+GIRAFFE combined mode
during the nights 2011 August 7-9. Two different setups have been used
for the spectroscopic observations: HR5A (with spectral coverage
4340-4587Å and spectral resolution R∼18500) and HR18
(7468-7889Å, R=18400).
Observations of three blue straggler stars (BSSs) have been secured
during the nights 2012 June 27 and 28 with XSHOOTER. The three targets
have been observed in stare mode enabling simultaneously the UVB
(∼3300-5500Å) and the VIS (∼5500-10000Å) channels. The slit
width was set at 0.8" (R=6200) and 0.7" (R=11000) for the UVB and the
VIS channels, respectively.
The spectroscopic targets have been selected from a photometric
catalog obtained by combining WFPC2@HST data for the central cluster
region and MegaCam (at the Canada-France-Hawaii telescope) data for
the outer region (see Ferraro et al. 2009Natur.462.1028F 2009Natur.462.1028F for details).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 132 15 The blue straggler star (BSS) sample
table2.dat 114 52 The red giant branch (RGB) sample
table3.dat 126 49 The horizontal branch (HB) sample
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See also:
VI/113 : Evolutionary models of Population II stars (Cariulo+, 2004)
VII/202 : Globular Clusters in the Milky Way (Harris, 1997)
J/ApJ/754/91 : Abundances and velocities of NGC 6397 stars (Lovisi+, 2012)
J/MNRAS/412/81 : Lithium abundance in M4 red giants (Mucciarelli+, 2011)
J/A+A/523/A71 : A and F stars abundances in the Hyades (Gebran+, 2010)
J/ApJ/705/328 : Abundance measurements in Sculptor dSph (Kirby+, 2009)
J/ApJ/704/750 : Rotational behavior of metal-poor stars (Cortes+, 2009)
J/A+A/505/139 : Abundances of red giants in 17 GCs (Carretta+, 2009)
J/A+A/505/117 : Abundances of red giants in 15 GCs (Carretta+, 2009)
J/A+A/483/183 : Catalogue of Blue Stragglers (Moretti+, 2008)
J/A+A/462/L9 : Radial velocities in NGC 7099 (Scarpa+, 2007)
J/AJ/130/2140 : Abundances & velocities in globular clusters (Pritzl+, 2005)
J/MNRAS/351/1204 : IR Phot. of 10 Galactic Globular Clusters (Valenti+, 2004)
J/ApJ/518/262 : CCD VIc Photometry of M30 Stars (Sandquist+, 1999)
J/AJ/116/1757 : M30 UBV photometry (Guhathakurta+, 1998)
J/AJ/109/218 : Catalogue of globular cluster profiles (Trager+ 1995)
Byte-by-byte Description of file: table[123].dat
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Bytes Format Units Label Explanations
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1- 9 I9 --- [LML2013] [10201736/924000008] Source identifier
10 A1 --- f_[LML2013] [RB] Read of Blue sequence (1)
12- 22 F11.7 deg RAdeg Right Ascension in decimal degrees (J2000)
24- 34 F11.7 deg DEdeg Declination in decimal degrees (J2000)
36- 40 F5.2 mag Vmag [14.3/18.3] V band magnitude
42- 46 F5.2 mag Imag [13.3/17.9] I band magnitude
48- 52 I5 K Teff [4943/11000] Effective temperature
54- 56 F3.1 [cm/s2] logg [1.9/4.4] Log of the surface gravity
58- 60 F3.1 km/s Vt ? Microturbulent velocity
62- 67 F6.1 km/s RVel [-193/-174]? Radial velocity
69- 71 F3.1 km/s e_RVel [0.2/3.3]? Uncertainty in RVel
73 A1 --- l_vsin(i) Limit flag on vsin(i)
74- 75 I2 km/s vsin(i) [0/90] Rotational velocity
77 I1 km/s e_vsin(i) [1/4]? Uncertainty in vsin(i)
79 A1 --- l_[Fe/H] Limit flag on [Fe/H]
80- 84 F5.2 [Sun] [Fe/H] [-2.5/-0.6]? Metallicity
86- 90 F5.2 [Sun] e_[Fe/H] [0.02/0.25]? Uncertainty in [Fe/H]
91 A1 --- n_[Fe/H] [*] No FeII line detected (2)
93 A1 --- l_[Mg/H] Limit flag on [Mg/H]
94- 98 F5.2 [Sun] [Mg/H] [-2.5/-1.2]? The [Mg/H] abundance
100-103 F4.2 [Sun] e_[Mg/H] [0.05/0.2]? Uncertainty in [Mg/H]
105-109 F5.2 [Sun] [Ti/H] [-2.3/-1.1]? The [Ti/H] abundance
111-114 F4.2 [Sun] e_[Ti/H] [0.04/0.2]? Uncertainty in [Ti/H]
116 A1 --- l_[O/H] Limit flag on [O/H]
117-121 F5.2 [Sun] [O/H] [-2.9/-1.4]? The [O/H] abundance
123-126 F4.2 [Sun] e_[O/H] ? Uncertainty in [O/H]
128-132 A5 --- Notes Note (3)
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Note (1): R and B indicate blue straggler stars (BSSs) in the red and blue
sequences, respectively.
Note (2):
* = For BSS 11000416, no FeII lines have been detected, thus we attributed
to this star the [Fe/H] inferred from the RGB stars.
Note (3): "XSH" labels BSSs observed with XSHOOTER.
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 05-Feb-2015