J/A+A/586/A158 Binary properties of CH and CEMP stars (Jorissen+, 2016)
Binary properties of CH and Carbon-Enhanced Metal-Poor stars.
Jorissen A., Van Eck S., Van Winckel H., Merle T., Boffin H.M.J.,
Andersen J., Nordstroem B., Udry S., Masseron T., Lenaerts L., Waelkens C.
<Astron. Astrophys. 586, A158 (2016)>
=2016A&A...586A.158J 2016A&A...586A.158J (SIMBAD/NED BibCode)
ADC_Keywords: Stars, carbon ; Stars, metal-deficient ; Binaries, orbits
Keywords: binaries: general - stars: carbon
Abstract:
The HERMES spectrograph installed on the 1.2-m Mercator telescope has
been used to monitor the radial velocity of 13 low-metallicity carbon
stars, among which seven carbon-enhanced metal-poor (CEMP) stars and
six CH stars. All stars but one show clear evidence for binarity. New
orbits are obtained for eight systems. The sample covers an extended
range in orbital periods, extending from 3.4d (for the dwarf carbon
star HE 0024-2523) to about 54yr (for the CH star HD 26, the longest
known among barium, CH, and extrinsic S stars). The period -
eccentricity diagram for the 40 low-metallicity carbon stars with
orbits now available shows no difference between CH and CEMP-s stars
(the latter corresponding to those CEMP stars enriched in s-process
elements, as are CH stars). We suggest that they must be considered as
one and the same family and that their different names only stem from
historical reasons. Indeed, these two families have as well very
similar mass-function distributions, corresponding to companions with
masses in the range 0.5-0.7M☉, indicative of white-dwarf
companions, adopting 0.8-0.9M☉ for the primary component. This
result confirms that CH and CEMP-s stars obey the same mass-transfer
scenario as their higher-metallicity analogues, barium stars. The P-e
diagrams of barium, CH, and CEMP-s stars are indeed very similar. They
reveal two different groups of systems: one with short orbital periods
(P<1000d) and mostly circular or almost circular orbits, and another
with longer period and eccentric (e>0.1) orbits. These two groups
either trace different evolutionary channels during the mass-transfer
episode responsible for the chemical peculiarities of the Ba/CH/CEMP-s
stars, or result from the operation of tidal circularisation in a more
recent past, when the current giant star was ascending the first giant
branch.
Description:
Radial velocities for 13 carbon-enhanced metal-poor and CH stars are
listed. They were obtained mostly with the HERMES/Mercator
spectrograph. These velocities made it possible to derive orbits for 8
systems.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 78 13 Properties of the stellar sample
rv.dat 34 612 Radial velocities
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See also:
J/AJ/142/188 : Metal-poor stars from HES using CH G-band (Placco+, 2011)
J/MNRAS/440/1095 : Chemical analysis of CH stars (Karinkuzhi+, 2014)
J/A+A/574/A129 : The First CEMP star in Sculptor dSph (Skuladottir+, 2015)
J/A+A/579/A28 : Abundances of 3 CEMP stars (Bonifacio+, 2015)
J/A+A/581/A22 : 67 CEMP-s stars model analysis (Abate+, 2015)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 12 A12 --- Name Star name
14- 22 A9 --- SpType Spectral type
24- 31 A8 --- Ref References (1)
33- 36 F4.1 [-] [Fe/H] ?=- Metallicity
38- 40 I3 --- Nobs Number of radial-velocity observations
(including older measurements from
McClure & Woodsworth, 1990ApJ...352..709M 1990ApJ...352..709M)
42- 46 I5 d Dt Time span
48- 54 F7.2 km/s Average velocity
56- 59 F4.2 km/s sigma Velocity dispersion (standard deviation)
61- 65 F5.1 --- sigma/e_V Ratio between the standard deviation and
measurement error (estimated to be 55m/s)
68- 78 A11 --- SB/ORB Systems with close to 1yr variations
superimposed on the long-term orbit are
flagged with the label "jitter?"
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Note (1): References as follows:
1 = Goswami (2005MNRAS.359..531G 2005MNRAS.359..531G)
2 = Masseron et al. (2010, Cat. J/A+A/509/A93)
3 = Bidelman (1956VA......2.1428B 1956VA......2.1428B)
4 = Goswami et al. (2010, Cat. J/MNRAS/404/253)
5 = Kennedy et al. (2011AJ....141..102K 2011AJ....141..102K)
6 = Hartwick & Cowley (1985AJ.....90.2244H 1985AJ.....90.2244H)
7 = Zamora et al. (2009A&A...508..909Z 2009A&A...508..909Z)
8 = Barnbaum et al. (1996, Cat. J/ApJS/105/419)
9 = Kipper & Jorgensen (1994A&A...290..148K 1994A&A...290..148K)
10 = This work
11 = Van Eck et al. (2003A&A...404..291V 2003A&A...404..291V)
12 = Sperauskas et al. (2015, ApJ, submitted)
13 = Jorissen et al. (2015A&A...586A.159J 2015A&A...586A.159J)
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Byte-by-byte Description of file: rv.dat
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Bytes Format Units Label Explanations
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1- 12 A12 --- Name Star name
14- 24 F11.3 --- JD Julian Date
26- 32 F7.2 km/s RV Radial velocity
34 I1 --- Inst [1/4] Spectrograph (1)
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Note (1): Numbers refer to the following spectrographs:
1 = CORAVEL (Baranne et al., 1979VA.....23..279B 1979VA.....23..279B,
A new tool for radial velocity measurements)
2 = Coude Echelle Spectrometer (Van Eck et al., 2003A&A...404..291V 2003A&A...404..291V,
More lead stars)
3 = HERMES/Mercator (Raskin et al., 2011A&A...526A..69R 2011A&A...526A..69R,
HERMES: a high-resolution fibre-fed spectrograph)
4 = FIES/NOT (Hansen et al. 2016, A&A in press,
DOI: 10.1051/0004-6361/201527409 (arXiv:1509.05344),
The role of binaries in the enrichment of the early Galactic halo.
I. r-process-enhanced metal-poor stars)
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Acknowledgements:
Alain Jorissen, ajorisse(at)ulb.ac.be
(End) Alain Jorissen [ULB, Belgium], Patricia Vannier [CDS] 18-Nov-2015