J/ApJ/707/671 IM Vir BVRI photometry and radial velocities (Morales+, 2009)
Absolute dimensions of the G7+K7 eclipsing binary star IM Virginis:
discrepancies with stellar evolution models.
Morales J.C., Torres G., Marschall L.A., Brehm W.
<Astrophys. J., 707, 671-685 (2009)>
=2009ApJ...707..671M 2009ApJ...707..671M
ADC_Keywords: Binaries, eclipsing ; Radial velocities ; Photometry, UBVRI
Keywords: binaries: eclipsing - binaries: spectroscopic - stars: late-type -
stars: fundamental parameters - stars: individual (IM Vir)
Abstract:
We report extensive spectroscopic and differential photometric BVRI
observations of the active, detached, 1.309-day double-lined eclipsing
binary IM Vir, composed of a G7-type primary and a K7 secondary. With
these observations, we derive accurate absolute masses and radii of
M1=0.981±0.012M☉, M2=0.6644±0.0048M☉,
R1=1.061±0.016R☉, and R2=0.681±0.013R☉ for the primary
and secondary, with relative errors under 2%. The effective
temperatures are 5570±100K and 4250±130K, respectively. The
significant difference in mass makes this a favorable case for
comparison with stellar evolution theory. We find that both stars are
larger than the models predict, by 3.7% for the primary and 7.5% for
the secondary, as well as cooler than expected, by 100K and 150K,
respectively. These discrepancies are in line with previously reported
differences in low-mass stars, and are believed to be caused by
chromospheric activity, which is not accounted for in current models.
The effect is not confined to low-mass stars: the rapidly rotating
primary of IM Vir joins the growing list of objects of near-solar mass
(but still with convective envelopes) that show similar anomalies. The
comparison with the models suggests an age of 2.4Gyr for the system,
and a metallicity of [Fe/H]~-0.3 that is consistent with other
indications, but requires confirmation.
Description:
IM Vir was observed at the Harvard-Smithsonian Center for Astrophysics
(CfA) with three nearly identical echelle spectrographs on the 1.5-m
Tillinghast reflector at the F. L. Whipple Observatory (Mount Hopkins,
AZ), the 1.5-m Wyeth reflector at the Oak Ridge Observatory (Harvard,
MA), and the 4.5-m equivalent Multiple Mirror Telescope (also on Mount
Hopkins, AZ) prior to its conversion to a 6.5-m monolithic telescope.
The first observation was taken in 1984 January 1, and monitoring
continued until 2009 May 10.
Differential photometric observations of IM Vir were conducted in 2006
April and May using the 0.4-m Ealing Cassegrain reflector of the
Gettysburg College Observatory (GCO, Gettysburg, PA).
Objects:
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RA (2000) DE Designation(s)
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12 49 38.7 -06 04 45 V* IM Vir = HD 111487
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 59 138 Radial velocity measurements of IM Vir
table3.dat 32 595 Differential B-band photometry of IM Vir
table4.dat 32 672 Differential V-band photometry of IM Vir
table5.dat 32 630 Differential R-band photometry of IM Vir
table6.dat 32 631 Differential I-band photometry of IM Vir
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See also:
V/128 : Chromospherically Active Binaries. Third version (Eker+, 2008)
V/136 : Teff and metallicities for Tycho-2 stars (Ammons+, 2006)
J/MNRAS/416/2477 : STEREO observations of variable stars (Wraight+, 2011)
J/PASP/120/1128 : Calibrated griz magnitudes of Tycho star (Ofek, 2008)
J/A+A/446/785 : Catalogue of eclipsing variables (Malkov+, 2006)
J/MNRAS/349/1069 : Chromospherically active binaries (Karatas+, 2004)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 12 F12.4 d HJD Heliocentric Julian Date
14- 20 F7.2 km/s RV1 Primary radial velocity
22- 28 F7.2 km/s RV2 Secondary radial velocity
30- 33 F4.2 km/s e_RV1 The 1σ error in RV1
35- 39 F5.2 km/s e_RV2 The 1σ error in RV2
41- 45 F5.2 km/s (O-C)1 Primary (O-C) value
47- 52 F6.2 km/s (O-C)2 Secondary (O-C) value
54- 59 F6.4 --- Phase Orbital phase
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Byte-by-byte Description of file: table[3456].dat
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Bytes Format Units Label Explanations
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1- 13 F13.5 d HJD Heliocentric Julian Date
15- 20 F6.4 --- Phase Orbital phase
22- 26 F5.3 mag C-V Comparison star minus IM Vir differential magnitude
28- 32 F5.3 mag C-Ch Comparison minus check star differential magnitude
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 04-Jan-2012