J/AJ/148/62 Spectroscopy of HD 5980 (Koenigsberger+, 2014)
The HD 5980 multiple system: masses and evolutionary status.
Koenigsberger G., Morrell N., Hillier D.J., Gamen R., Schneider F.R.N.,
Gonzalez-Jimenez N., Langer N., Barba R.
<Astron. J., 148, 62 (2014)>
=2014AJ....148...62K 2014AJ....148...62K
ADC_Keywords: Stars, Wolf-Rayet ; Stars, luminous ; Binaries, eclipsing ;
Radial velocities
Keywords: binaries: eclipsing - stars: evolution - stars: individual: HD 5980 -
stars: massive - stars: Wolf-Rayet
Abstract:
New spectroscopic observations of the LBV/WR multiple system HD 5980
in the Small Magellanic Cloud are used to address the question of the
masses and evolutionary status of the two very luminous stars in the
19.3 day eclipsing binary system. Two distinct components of the
NV4944Å line are detected in emission and their radial velocity
variations are used to derive masses of 61 and 66M☉, under the
assumption that binary interaction effects on this atomic transition
are negligible. We propose that this binary system is the product of
quasi-chemically homogeneous evolution with little or no mass
transfer. Thus, both of these binary stars may be candidates for
gamma-ray burst progenitors or even pair instability supernovae.
Analysis of the photospheric absorption lines belonging to the
third-light object in the system confirm that it consists of an O-type
star in a 96.56day eccentric orbit (e=0.82) around an unseen
companion. The 5:1 period ratio and high eccentricities of the two
binaries suggest that they may constitute a hierarchical quadruple
system.
Description:
Our observations of HD 5980 were obtained at Las Campanas Observatory
(LCO) and consist of seven low dispersion spectra obtained with the
6.5m Magellan telescopes in 2009 and 2010; 25 echelle spectra obtained
with the du Pont telescope between 2006 and 2013; and six spectra
obtained on the 6.5 Clay Magellan telescope between 2007 and 2012.
Tables 1 and 2 list the year the spectrum was obtained, the telescope
and instruments used, and Heliocentric Julian Date of observation.
The Baade 6.5m (Magellan-I) low dispersion spectra were obtained with
IMACS with spectral coverage from roughly 3700 to 6800Å at a
spectral resolution of 1.4-1.5Å (R∼4000). The Clay 6.5m
(Magellan-II) low dispersion spectra were obtained with the Magellan
Echellette (MagE) using the 1'' slit providing a spectral resolution
of 1Å. Thirteen echelle orders were extracted covering the
wavelength region from 3130Å to 9400Å. The high resolution du
Pont telescope spectra were obtained with the echelle spectrograph and
a 1'' slit. The spectral resolution of these data ranges from 0.15 to
0.22Å (R∼25000) and the wavelength coverage goes from 3500 to
8800Å. The high resolution Clay (Magellan-II) spectra were obtained
with the MIKE spectrograph (spectral resolution of ∼34000). In
addition to the new spectra described above, we used data obtained in
1998, 1999, 2005, and 2006 with FEROS on the 2.2m MPI telescope at La
Silla Observatory, previously described in Kaufer et al.
(2002ASPC..260..489K 2002ASPC..260..489K), Schweickhardt (2000ASPC..204..113S 2000ASPC..204..113S), and
Foellmi et al. (2008RMxAA..44....3F 2008RMxAA..44....3F).
Objects:
----------------------------------------------------------
RA (ICRS) DE Designation(s) (Period)
----------------------------------------------------------
00 59 26.57 -72 09 53.9 HD 5980 = AzV 229 (P=19.2654)
----------------------------------------------------------
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 39 7 Low dispersion Las Campanas Observatory (LCO) spectra
table2.dat 39 32 High dispersion Las Campanas Observatory (LCO) spectra
table3.dat 23 47 Radial velocity measurements of NV 4944
table4.dat 39 32 Las Campanas Observatory (LCO) radial velocity
measurements for star C
table5.dat 39 42 *FEROS radial velocity measurements for star C
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Note on table5.dat: FEROS on the 2.2m MPI telescope at La Silla Observatory.
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See also:
J/ApJ/745/173 : UV absorption sight lines of LMC and SMC (Welty+, 2012)
J/AJ/143/28 : Analysis of B6-A9 stars from INES UV spectra (Freire+, 2012)
J/ApJS/187/149 : StarCAT: STIS UV echelle spectra of stars (Ayres, 2010)
J/PASP/121/634 : FUSE observations in Magellanic Clouds (Blair+, 2009)
J/ApJS/144/21 : Galaxy and Magellanic Clouds OB and WR stars (Robert+, 2003)
J/A+A/366/508 : S Dor variables (van Genderen+, 2001)
Byte-by-byte Description of file: table[12].dat
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Bytes Format Units Label Explanations
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1- 4 I4 yr Year [2006/2013] Year of observation
6- 16 A11 --- Tel Telescope (Baade Mag 1, Clay Mag 2, DuPont) (1)
18- 24 A7 --- Inst Instrument (IMACS, MagE=Magellan Echellette)
26- 33 F8.3 d HJD Heliocentric Julian Date (HJD-2450000)
35- 39 F5.3 --- Phase [0/1] Orbital phase (computed with P=19.26d)
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Note (1): Telescope defined as below:
Baade Mag 1 = The Baade 6.5m (Magellan-I);
Clay Mag 2 = The Clay 6.5m (Magellan-II);
DuPont = du Pont telescope.
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 8 F8.3 d HJD Heliocentric Julian Date (HJD-2450000)
10- 14 F5.3 --- Phase [0/1] Orbital phase (computed with P=19.2654d)
16- 18 I3 km/s RVA [-98/399]? Primary radial velocity (1)
20- 23 I4 km/s RVB [-142/344]? Secondary radial velocity (1)
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Note (1): Include the heliocentric correction.
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Byte-by-byte Description of file: table[45].dat
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Bytes Format Units Label Explanations
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1- 8 F8.3 d HJD Heliocentric Julian Date (HJD-2450000)
10- 14 F5.3 --- Phase1 [0/1] Orbital phase computed with P=19.2654d
16- 20 F5.3 --- Phase2 [0/1] Orbital phase computed with P=96.56d
22- 24 I3 km/s RV5592 [68/251]? Radial velocity obtained by fitting
Gaussians to the core of the
OIIIλ5592Å absorption line
25 A1 --- u_RV5592 [:] Uncertainty flag on RV5592
27- 29 I3 km/s RV4471 [69/268]? Radial velocity obtained by fitting
Gaussians to the core of the
HeIλ4471Å absorption line
30 A1 --- u_RV4471 [:] Uncertainty flag on RV4471
32- 34 I3 km/s RV5875 [44/296]? Radial velocity obtained by fitting
Gaussians to the core of the
HeIλ5875Å absorption line
36- 38 I3 km/s RV5696 [-14/256]? Radial velocity obtained by fitting
Gaussians to the core of the
CIIIλ5696Å emission line
39 A1 --- u_RV5696 [:] Uncertainty flag on RV5696
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History:
From electronic version of the journal
(End) Sylvain Guehenneux [CDS] 26-Nov-2014