J/ApJ/703/L99 Outlandish orbit of HAT-P-7b (Winn+, 2009)
HAT-P-7: a retrograde or polar orbit, and a third body.
Winn J.N., Johnson J.A., Albrecht S., Howard A.W., Marcy G.W.,
Crossfield I.J., Holman M.J.
<Astrophys. J., 703, L99-L103 (2009)>
=2009ApJ...703L..99W 2009ApJ...703L..99W
ADC_Keywords: Radial velocities ; Stars, double and multiple ; Planets
Keywords: planetary systems - planetary systems: formation -
stars: individual (HAT-P-7) - stars: rotation
Abstract:
We show that the exoplanet HAT-P-7b has an extremely tilted orbit,
with a true angle of at least 86° with respect to its parent
star's equatorial plane, and a strong possibility of retrograde
motion. We also report evidence for an additional planet or companion
star. The evidence for the unparalleled orbit and the third body is
based on precise observations of the star's apparent radial velocity
(RV). The anomalous RV due to rotation (the Rossiter-McLaughlin
effect) was found to be a blueshift during the first half of the
transit and a redshift during the second half, an inversion of the
usual pattern, implying that the angle between the sky-projected
orbital and stellar angular momentum vectors is 182.5°±9.4°.
The third body is implicated by excess RV variation of the host star
over 2yr. Some possible explanations for the tilted orbit of HAT-P-7b
are a close encounter with another planet, the Kozai effect, and
resonant capture by an inward-migrating outer planet.
Description:
We observed HAT-P-7 with the High Resolution Spectrograph (HIRES) on
the Keck I 10m telescope, and the High Dispersion Spectrograph (HDS)
on the Subaru 8m telescope. The planet's discoverers (Pal et al.
2008ApJ...680.1450P 2008ApJ...680.1450P) obtained eight HIRES spectra in 2007, to which we
add nine spectra from 2009. All but one of the HIRES spectra were
acquired outside of transits. Of the 49 HDS spectra, 9 were obtained
on 2009 June 17 and 40 were obtained on 2009 July 1. The second of
these nights spanned a transit.
Objects:
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RA (2000) DE Designation(s)
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19 28 59.4 +47 58 10 HAT-P-7 = BD+47 2846
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 29 86 Relative radial velocity measurements of HAT-P-7
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See also:
J/A+A/527/L11 : HAT-P-6 radial velocity curve (Hebrard+, 2011)
J/ApJ/693/794 : Transit of exoplanet HD 17156b (Winn+, 2009)
J/ApJ/675/1531 : Transits of super-Neptune HD 149026b (Winn+, 2008)
J/ApJ/683/1076 : Transits of exoplanet XO-3b (Winn+, 2008)
J/AJ/134/1707 : Six transits of exoplanet HAT-P-1b (Winn+, 2007)
J/ApJ/657/1098 : Transit of TrES-1 (Winn+, 2007)
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 HJD Heliocentric Julian Date
15- 21 F7.2 m/s RV Radial velocity (1)
23- 27 F5.2 m/s e_RV Error in RV (2)
29 I1 --- Inst [1/2] Spectrograph identification:
1=Keck/HIRES; 2=Subaru/HDS.
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Note (1): The radial velocity was measured relative to an arbitrary
template spectrum specific to each spectrograph; only the differences
among the radial velocities from a single spectrograph are significant.
Note (2): The uncertainty is the internal error only and does not account
for any possible "stellar jitter".
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 04-Nov-2011