J/ApJ/710/L30 On the multiplicity of the O star Herschel 36 (Arias+, 2010)
On the multiplicity of the zero-age main-sequence O star Herschel 36.
Arias J.I., Barba R.H., Gamen R.C., Morrell N.I., Apellaniz J.M.,
Alfaro E.J., Sota A., Walborn N.R., Bidin C.M.
<Astrophys. J., 710, L30-L34 (2010)>
=2010ApJ...710L..30A 2010ApJ...710L..30A
ADC_Keywords: Stars, O ; Stars, double and multiple ; Spectroscopy ;
Radial velocities
Keywords: binaries: close - stars: early-type - stars: individual (Herschel 36)
Abstract:
We present the analysis of high-resolution optical spectroscopic
observations of the zero-age main-sequence O star Herschel 36 spanning
six years. This star is definitely a multiple system, with at least
three components detected in its spectrum. Based on our
radial-velocity (RV) study, we propose a picture of a close massive
binary and a more distant companion, most probably in wide orbit about
each other. The orbital solution for the binary, whose components we
identify as O9V and B0.5V, is characterized by a period of
1.5415±0.0006 days. With a spectral type O7.5V, the third body is
the most luminous component of the system and also presents RV
variations with a period close to 498 days. Some possible hypotheses
to explain the variability are briefly addressed and further
observations are suggested.
Description:
A long-term spectroscopic monitoring of Galactic O and Wolf-Rayet of
the Nitrogen sequence (WN) stars is being carried out (Gamen et al.
2008RMxAC..33...54G 2008RMxAC..33...54G), with the main aim of establishing the
multiplicity status of these objects. As part of this observational
campaign, Her 36 has been systematically observed. Table 1 presents
the journal of the observations used in this work. Most of them came
from the monitoring campaign of Galactic O and WN stars and were
obtained between 2005 April and 2009 May at the observatories of Las
Campanas (LCO) and La Silla, in Chile. A total of 33 high-resolution
spectra were obtained at LCO. Twenty-six more spectra were acquired
with FEROS at ESO La Silla. Four additional spectra were taken at the
Complejo Astronomico El Leoncito (CASLEO), Argentina, in observing
runs prior to 2005, using the REOSC SEL Cassegrain spectrograph.
Objects:
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RA (2000) DE Designation(s) (Period)
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18 03 40.33 -24 22 42.7 ** HER 36 = NAME Herschel 36 (P=1.5415)
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 68 63 Radial-velocity measurements of the stellar
components observed in the spectra of Herschel 36
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See also:
V/116 : Galactic O star catalog (Maiz-Apellaniz+, 2004)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 2 I2 --- Seq Spectrum number
4- 15 F12.4 d HJD Heliocentric Julian Date
17- 21 F5.1 km/s HeIIRVA ? Component A HeII 4686 radial velocity (1)
23- 28 F6.1 km/s HeIIRVB1 ? Component B1 HeII 4686 radial velocity (1)
30- 34 F5.1 km/s HeIRVA ? Component A HeI 5876 radial velocity (1)
36- 41 F6.1 km/s HeIRVB1 ? Component B1 HeI 5876 radial velocity (1)
43- 48 F6.1 km/s HeIRVB2 ? Component B2 HeI 5876 radial velocity (1)
50- 60 A11 --- Obs Observatory/Telescope (Casleo-2.15, ESO-2p2,
LCO-Clay or LCO-DP)
62- 68 A7 --- Spec Spectrograph (Echelle, FEROS, MIKE or REOSC)
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Note (1): Rest wavelengths used in the determination of the radial velocities
are 4685.65 and 5875.65 Angstroms.
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 29-Mar-2012