J/MNRAS/435/707 Hα velocity curves of IM Eri (Armstrong+, 2013)
Orbital, superhump and superorbital periods in the cataclysmic variables
AQ Mensae and IM Eridani.
Armstrong E., Patterson J., Michelsen E., Thorstensen J., Uthas H.,
Vanmunster T., Hambsch F.-J., Roberts G., Dvorak S.
<Mon. Not. R. Astron. Soc., 435, 707-717 (2013)>
=2013MNRAS.435..707A 2013MNRAS.435..707A
ADC_Keywords: Binaries, cataclysmic ; Radial velocities
Keywords: accretion, accretion discs - binaries: close -
stars: individual: AQ Mensae - stars: individual: IM Eri -
novae, cataclysmic variables - white dwarfs
Abstract:
We report photometric detections of orbital and superorbital signals,
and negative orbital sidebands, in the light curves of the nova-like
cataclysmic variables AQ Mensae and IM Eridani. The frequencies of the
orbital, superorbital and sideband signals are 7.0686 (3), 0.263 (3)
and 7.332 (3) cycles/d (c/d) in AQ Mensae, and 6.870 (1), 0.354 (7)
and 7.226 (1) c/d in IM Eridani. We also find a spectroscopic orbital
frequency in IM Eridani of 6.86649 (2) c/d. These observations can be
reproduced by invoking an accretion disc that is tilted with respect
to the orbital plane. This model works well for X-ray binaries, in
which irradiation by a primary neutron star can account for the disc's
tilt. A likely tilt mechanism has yet to be identified in CVs, yet the
growing collection of observational evidence indicates that the
phenomenon of tilt is indeed at work in this class of object. The
results presented in this paper bring the number of CVs known to
display signals associated with retrograde disc precession to 12. We
also find AQ Men to be an eclipsing system. The eclipse depths are
highly variable, which suggests that the eclipses are grazing. This
finding raises the possibility of probing variations in disc tilt by
studying systematic variations in the eclipse profile.
Description:
All data reported here were obtained by the globally distributed small
telescopes of the Center for Backyard Astrophysics [see Skillman &
Patterson (1993ApJ...417..298S 1993ApJ...417..298S) for details of the CBA instrumentation
and observing procedure]. We obtained differential photometry of the
CV with respect to a comparison star on the same field, and spliced
overlapping data from different longitudes by adding small constants
to establish a consistent instrumental scale. With an excellent span
of longitudes, we essentially eliminated the possibility of daily
aliasing of frequencies in the power spectra. In order to reach good
signal-to-noise ratio with good time resolution, we generally observe
in unfiltered light. This practice, however, eliminates the
possibility of transforming to a standard magnitude.
Objects:
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RA (2000) DE Designation(s)
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04 24 41.06 -20 07 11.5 IM Eri = V* IM Eri
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table3.dat 33 37 Spectroscopy of IM Eridani
table4.dat 18 170 IM Eri: H-alpha radial velocities
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 11 A11 "date" ObsDate Observation date
13- 14 I2 --- Nframe Number of frames per evening
16- 21 A6 "h:m" HAStart Hour angle of starting observation
23- 28 A6 "h:m" HAEnd Hour angle of ending observation
30- 32 F3.1 m Tel [1.3/2.4] Telescope size
33 A1 --- --- [m]
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 10 F10.4 d BJD Barycentric Julian date (BJD-2400000)
13- 15 I3 km/s RV Hα radial velocity
17- 18 I2 km/s e_RV Hα velocity dispersion
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 13-Jan-2015