J/ApJ/801/67 Grid of binary colors in M30 (NGC7099) (Xin+, 2015)
The binary mass transfer origin of the red blue straggler sequence in M30.
Xin Y., Ferraro F.R., Lu P., Deng L., Lanzoni B., Dalessandro E.,
Beccari G.
<Astrophys. J., 801, 67 (2015)>
=2015ApJ...801...67X 2015ApJ...801...67X
ADC_Keywords: Stars, double and multiple ; Stars, masses ; Clusters, globular ;
Models
Keywords: binaries: close; blue stragglers;
globular clusters: individual: (M30, NGC 7099)
Abstract:
Two separated sequences of blue straggler stars (BSSs) have been
revealed by Ferraro et al. (2009Natur.462.1028F 2009Natur.462.1028F) in the
color-magnitude diagram (CMD) of the Milky Way globular cluster M30.
Their presence has been suggested to be related to the two BSS
formation channels (namely, collisions and mass transfer in close
binaries) operating within the same stellar system. The blue sequence
was indeed found to be well reproduced by collisional BSS models. In
contrast, no specific models for mass-transfer BSSs were available for
an old stellar system like M30. Here we present binary evolution
models, including case-B mass transfer and binary merging,
specifically calculated for this cluster. We discuss in detail the
evolutionary track of a 0.9+0.5M☉ binary, which spends
approximately 4Gyr in the BSS region of the CMD of a 13Gyr old
cluster. We also run Monte Carlo simulations to study the distribution
of mass-transfer BSSs in the CMD and to compare it with the
observational data. Our results show that (1) the color and magnitude
distribution of synthetic mass-transfer BSSs defines a strip in the
CMD that nicely matches the observed red-BSS sequence, thus providing
strong support to the mass-transfer origin for these stars; (2) the
CMD distribution of synthetic BSSs never attains the observed location
of the blue-BSS sequence, thus reinforcing the hypothesis that the
latter formed through a different channel (likely collisions); (3)
most (∼60%) of the synthetic BSSs are produced by mass-transfer
models, while the remaining <40% requires the contribution from merger
models.
Objects:
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RA (ICRS) DE Designation(s)
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21 40 22.12 -23 10 47.5 M30 = NGC 7099
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 33 223 Grid of binary models
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See also:
J/ApJ/772/148 : Blue straggler and red giant stars in M30 (Lovisi+, 2013)
J/ApJ/748/91 : Blue straggler stars in M75 (Contreras+, 2012)
J/ApJ/681/311 : Blue stragglers in NGC 2419 (Dalessandro+, 2008)
J/ApJ/677/1069 : Blue stragglers in NGC 6388 (Dalessandro+, 2008)
J/A+A/483/183 : Catalogue of Blue Stragglers (Moretti+, 2008)
J/A+A/455/247 : Grid of binaries experiencing mass exchange (Tian+, 2006)
J/MNRAS/319/215 : Binary evolution (Han+, 2000)
J/ApJ/522/983 : M80 blue straggler stars (Ferraro+, 1999)
J/MNRAS/298/525 : Stellar evolution models for Z = 0.0001 to 0.03 (Pols+ 1998)
J/AJ/116/1757 : M30 UBV photometry (Guhathakurta+, 1998)
J/A+A/324/915 : Blue stragglers in M3 (Ferraro+ 1997)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 4 F4.1 Gyr Age [13] Current age
7- 9 F3.1 Msun M1g [0.7/1] Initial mass of primary
12- 14 F3.1 Msun M2g [0.3/0.8] Initial mass of secondary
17- 19 F3.1 Rsun ag [1.6/7.3] Initial orbital separation of binary
22- 26 F5.2 mag F555W [0.6/5.3] HST/WFPC2 F555W band magnitudes
at 13Gyr
29- 33 F5.2 mag V-I [-0.05/1] The (F555W-F814W) color index at 13Gyr
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 15-Jul-2015