J/MNRAS/361/1091 U Gem spectroscopy (Naylor+, 2005)
The masses, radii and luminosities of the components of U Geminorum.
Naylor T., Allan A., Long K.S.
<Mon. Not. R. Astron. Soc., 361, 1091-1101 (2005)>
=2005MNRAS.361.1091N 2005MNRAS.361.1091N
ADC_Keywords: Binaries, eclipsing ; Stars, white dwarf ; Radial velocities ;
Spectroscopy
Keywords: binaries: eclipsing - stars: fundamental parameters -
stars: individual: U Gem - stars: late-type -
novae, cataclysmic variables - white dwarfs
Abstract:
We present a phase-resolved spectroscopic study of the secondary star
in the cataclysmic variable (CV) U Gem. We use our data to measure the
radial velocity semi-amplitude, systemic velocity and rotational
velocity of the secondary star. Combining this with literature data
allows us to determine masses and radii for both the secondary star
and white dwarf, which are independent of any assumptions about their
structure. We use these to compare their properties to those of field
stars and find that both components follow field mass-radius
relationships. The secondary star has the mass, radius, luminosity and
photometric temperature of an M2 star, but a spectroscopic temperature
of M4. The latter may well be due to a high metallicity. There is a
troubling inconsistency between the radius of the white dwarf inferred
from its gravitational redshift and inclination and that inferred from
its temperature, flux and astrometric distance.
Description:
Spectra were obtained on the nights beginning 2001 January 4, 5, 6 and
7 and 2000 January 17 using the 2.5-m Isaac Newton Telescope with the
235-mm camera of the Intermediate Dispersion Spectrograph using a
1.5-arcsec slit.
Objects:
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RA (2000) DE Designation(s) (file)
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07 55 05.2 +22 00 04 U Gem = H 0751+22 (table1.dat)
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 47 118 Measured radial velocities from the Na I feature
in the lower resolution spectra of U Gem
table2.dat 78 7 Measured parameters for 7 other stars
sp/* . 125 Individual low resolution spectra
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Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 13 F13.5 d BJD Barycentric Julian Date for the middle
of the exposure
15- 20 F6.4 --- Phase Calculated phase for the exposure
22- 27 I6 --- Image Image number
29- 32 I4 km/s RV Radial velocity
34- 35 I2 km/s e_RV rms uncertainty on RV (1)
37- 47 A11 --- Spectrum Spectrum filename in subdirectory "sp"
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Note (1): Uncertainties are scaled to give a (chinu)2 of 1 for a
circular fit.
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 4 A4 --- SpType MK spectral type
6- 11 A6 --- Name Name
13- 15 I3 km/s gamma Assumed gamma velocity
17- 19 I3 km/s K2(NaI) Observed radial velocity semi-amplitude of
the secondary star, K2, derived from NaI
feature in the lower resolution spectra
21- 23 I3 km/s K2(KI/TiO) Observed radial velocity semi-amplitude of
the secondary star, K2, derived from KI/TiO
feature in the lower resolution spectra
25- 27 I3 km/s v2siniNaI Best-fitting value of the rotational velocity
of the secondary star, v2sini derived from
NaI feature in the lower resolution spectra
29- 31 F3.1 --- Chi2NaI (Chinu)2 associated to v2siniNaI
33- 35 I3 km/s v2siniKI/TiO Best-fitting value of the rotational velocity
of the secondary star, v2sini derived from
NaI feature in the lower resolution spectra
37- 39 F3.1 --- Chi2KI/TiO (Chinu)2 associated to v2siniKI/TiO
41- 43 I3 km/s v2siniNaIh ? Best-fitting value of the rotational
velocity of the secondary star, v2sini,
derived from NaIh feature in the
lower resolution spectra
45- 47 F3.1 --- Chi2NaIh ? (Chinu)2 associated to v2siniNaIh
49- 51 I3 --- fNaI Implied fraction of the light originating
from the secondary star in NaI lower
resolution spectra
53- 55 I3 --- fKI/TiO Implied fraction of the light originating
from the secondary star in KI/TiO lower
resolution spectra
57- 58 I2 --- fNaIh ? Implied fraction of the light originating
from the secondary star in NaI higher
resolution spectra
60- 61 I2 km/s gamma2NaI Derived mean velocity of the secondary star,
gamma2, from NaI feature in the lower
resolution spectra (1)
63- 64 I2 km/s gamma2KI/TiO Derived mean velocity of the secondary star,
gamma2 from KI/TiO feature in the
lower resolution spectra (1)
66- 67 I2 km/s gamma2NaIh ? Derived mean velocity of the secondary
star, gamma2 from NaI feature in the
higher resolution spectra (1)
69- 78 A10 --- Spectrum Spectrum filename in subdirectory "sp"
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Note (1): Mean values for GL109, GJ213, GL51, GL65A:
gamma2NaI = 24±5km/s
gamma2KI/TiO = 34±4km/s
gamma2NaIh = 27±3km/s
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 20-Sep-2005