J/AJ/149/49 Radial velocities of AW UMa (Rucinski+, 2015)
Time sequence spectroscopy of AW UMa. The 518 nm Mg I triplet region analyzed
with broadening functions.
Rucinski S.M.
<Astron. J., 149, 49 (2015)>
=2015AJ....149...49R 2015AJ....149...49R
ADC_Keywords: Binaries, eclipsing ; Radial velocities
Keywords: binaries: close - binaries: eclipsing - stars: individual: AW UMa
Abstract:
High-resolution spectroscopic observations of AW UMa, obtained on
three consecutive nights with a median time resolution of 2.1minutes,
have been analyzed using the broadening function method in the
spectral window of 22.75nm around the 518nm MgI triplet region.
Doppler images of the system reveal the presence of vigorous mass
motions within the binary system; their presence puts into question
the solid-body rotation assumption of the contact binary model. AW UMa
appears to be a very tight, semi-detached binary; the mass transfer
takes place from the more massive to the less massive component. The
primary, a fast-rotating star with Vsini=181.4±2.5km/s, is covered
with inhomogeneities: very slowly drifting spots and a dense network
of ripples more closely participating in its rotation. The spectral
lines of the primary show an additional broadening component (called
the "pedestal") that originates either in the equatorial regions,
which rotate faster than the rest of the star by about 50km/s, or in
an external disk-like structure. The secondary component appears to be
smaller than predicted by the contact model. The radial velocity field
around the secondary is dominated by accretion of matter transferred
from (and possibly partly returned to) the primary component. The
parameters of the binary are Asini=2.73±0.11R☉ and
M1sin3i=1.29±0.15M☉, M2sin3i=0.128±0.016M☉.
The mass ratio, qsp=M2/M1=0.099±0.003, while still the most
uncertain among the spectroscopic elements, is substantially different
from the previous numerous and mutually consistent photometric
investigations which were based on the contact model. It should be
studied why photometry and spectroscopy give such discrepant results
and whether AW UMa is an unusual object or if only very high-quality
spectroscopy can reveal the true nature of W UMa-type binaries.
Description:
The observations of AW UMa were obtained on the nights of 2011 March
11-13 using the Canada-France-Hawaii Telescope (CFHT) and its Espadons
spectrograph working in the spectro-polarimetric mode. The nominal
spectral resolving power was R∼68000. Four consecutive observations
with different positions of the polarization analyzer can be used to
determine the Stokes circular polarization parameter V. In total, 146
series of polarization measurements were obtained.
Objects:
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RA (ICRS) DE Designation(s) (Period)
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11 30 04.32 +29 57 52.7 V* AW UMa = HIP 56109 (P=0.43872420)
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table3.dat 34 584 Radial velocities of the primary component
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See also:
B/gcvs : General Catalogue of Variable Stars (Samus+ 2007-2013)
J/AJ/146/70 : Spectroscopy of W UMa-type binary stars (Rucinski+, 2013)
Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 6 F6.4 d HJD [1.8/4.2] Heliocentric Julian Date
at mid-exposure (HJD-2455630)
8- 13 F6.4 --- Phase [0.4556/5.6781] Phase φ (1)
15- 20 F6.2 km/s RV45 Radial velocity of the primary star corresponding
to the low cutoff to the rotational profile fit
at 0.45 of broadening function maximum (2)
22- 27 F6.2 km/s RV50 Radial velocity of the primary star corresponding
to the low cutoff to the rotational profile fit
at 0.50 of broadening function maximum (2)
29- 34 F6.2 km/s RV55 Radial velocity of the primary star corresponding
to the low cutoff to the rotational profile fit
at 0.55 of broadening function maximum (2)
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Note (1): The phases are computed with the assumed initial epoch
HJD=2455631.6498 and the period 0.43872420day.
Note (2): Radial velocity measurements for all observations are listed, but only
those within the fractional phase interval 0.25-0.75 were used for the
orbital solutions.
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Sylvain Guehenneux [CDS] 24-Feb-2015