J/MNRAS/457/836 Eclipsing binaries MgI b and Hα EW (Eaton, 2016)
AW Ursae Majoris: a semidetached mass-transferring system indeed?
Eaton J.A.
<Mon. Not. R. Astron. Soc., 457, 836-843 (2016)>
=2016MNRAS.457..836E 2016MNRAS.457..836E (SIMBAD/NED BibCode)
ADC_Keywords: Binaries, eclipsing ; Stars, late-type ; Equivalent widths
Keywords: binaries: close - binaries: eclipsing - stars: individual: AW UMa
Abstract:
I have reinterpreted Rucinski's line profiles (broadening functions)
for the hot A-type W Ursae Majoris binary AW UMa in terms of various
contact models, finding that the detached/semidetached geometry he
postulates does not fit the system's light variation or its line
profiles. The highly overcontact geometry that actually fits the
system's ellipsoidal light variation reproduce the total breadth of
the lines but give profiles too broad to fit their shapes. The best
solution to this dilemma is differential rotation of both stars in
which the mid-latitudes are rotating 20-30 per cent slower than
synchronously. This approach preserves the traditional light-curve
solution and explains the drift of ripples seen in the line profiles.
In addition, there are obviously other flows superimposed on the
rotation which make the profiles asymmetrical. Fitting the line
profiles is complicated by uncertainties in how the equivalent widths
of the lines change with effective temperature and how much they are
limb darkened. The contribution of any point on the stellar surface to
the equivalent width depends only very weakly on local temperature
throughout the range of W UMa binaries. The limb darkening of the
lines is probably small, although the effect remains unexplored. I
also speculate about the nature of hypothetical star-spots in this
system.
Description:
I am using the V light curve of Paczynski (1964AJ.....69..124P 1964AJ.....69..124P) to
define the light variations and the BF of Rucinski (2015, Cat.
J/AJ/149/49) to define the line profiles. Although Rucinski et al.
(2013IBVS.6079....1R 2013IBVS.6079....1R) obtained a ridiculously precise light curve from
the MOST satellite, they declined to publish it because of concerns
about saturation (private communication), so Paczynski's data remain
the best available in the literature. I will also renormalize the BFs
to 1.0 at maximum and refer to the BFs as 'intensities' to
simplify my discussion.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
tablea1.dat 33 120 Strengths at MgI b and Hα
--------------------------------------------------------------------------------
Byte-by-byte Description of file: tablea1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 2 A2 --- --- [HD]
3- 8 I6 --- HD Star HD number
10- 19 A10 --- SpType MK spectral type
20- 23 F4.2 mag B-V B-V colour index
25- 28 F4.2 0.1nm EWMgI Equivalent width in MgI b band at 5166-5188Å
30- 33 F4.2 0.1nm EWHa Equivalent width in Hα band at
6555-6572 Å
--------------------------------------------------------------------------------
History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 18-Nov-2016