J/ApJ/727/125 Two secondary eclipses of WASP-12b with Spitzer (Campo+, 2011)
On the orbit of exoplanet WASP-12b.
Campo C.J., Harrington J., Hardy R.A., Stevenson K.B., Nymeyer S.,
Ragozzine D., Lust N.B., Anderson D.R., Collier-Cameron A., Blecic J.,
Britt C.B.T., Bowman W.C., Wheatley P.J., Loredo T.J., Deming D., Hebb L.,
Hellier C., Maxted P.F.L., Pollaco D., West R.G.
<Astrophys. J., 727, 125 (2011)>
=2011ApJ...727..125C 2011ApJ...727..125C
ADC_Keywords: Planets ; Photometry, infrared ; Stars, double and multiple
Keywords: planetary systems - stars: individual (WASP-12) -
techniques: photometric
Abstract:
We observed two secondary eclipses of the exoplanet WASP-12b using the
Infrared Array Camera on the Spitzer Space Telescope. The close
proximity of WASP-12b to its G-type star results in extreme tidal
forces capable of inducing apsidal precession with a period as short
as a few decades. This precession would be measurable if the orbit had
a significant eccentricity, leading to an estimate of the tidal Love
number and an assessment of the degree of central concentration in the
planetary interior. An initial ground-based secondary-eclipse phase
reported by Lopez-Morales et al. (0.510±0.002; 2010ApJ...716L..36L 2010ApJ...716L..36L)
implied eccentricity at the 4.5σ level. The spectroscopic orbit
of Hebb et al. (2009ApJ...693.1920H 2009ApJ...693.1920H) has eccentricity 0.049±0.015, a
3σ result, implying an eclipse phase of 0.509±0.007. However,
there is a well-documented tendency of spectroscopic data to
overestimate small eccentricities. Our eclipse phases are
0.5010±0.0006 (3.6 and 5.8um) and 0.5006±0.0007 (4.5 and 8.0um).
An unlikely orbital precession scenario invoking an alignment of the
orbit during the Spitzer observations could have explained this
apparent discrepancy, but the final eclipse phase of Lopez-Morales et
al. (0.510+0.007-0.006) is consistent with a circular orbit at
better than 2σ. An orbit fit to all the available transit,
eclipse, and radial-velocity data indicates precession at <1σ; a
non-precessing solution fits better. We also comment on analysis and
reporting for Spitzer exoplanet data in light of recent re-analyses.
Description:
We observed two secondary eclipses of WASP-12b with the Spitzer
Infrared Array Camera (IRAC) in full-array mode. Observations on 2008
October 29 at 4.5 and 8.0um (IRAC channels 2 and 4, respectively)
lasted 338 minutes (Program ID 50759); those on 2008 November 3 at 3.6
and 5.8um (channels 1 and 3, respectively) lasted 368 minutes (Program
ID 50517).
Objects:
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RA (2000) DE Designation(s) (Sideral period)
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06 30 32.79 +29 40 20.3 WASP-12b = WASP-12b (Ps=1.0914315)
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
fits.dat 96 4 List of FITS file
fits/* . 4 Light curves parameters of WASP12b, in FITS format,
in Spitzer/IRAC 3.6um, 4.5um, 5.8um and 8um
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See also:
J/A+A/551/A108 : Multi-site obs. of WASP-12 b transit (Maciejewski+, 2013)
J/A+A/528/A65 : WASP-12b transits (Maciejewski+, 2011)
J/AJ/141/179 : Transits of TrES-4b, HAT-P-3b and WASP-12b (Chan+, 2011)
J/MNRAS/414/1278 : Eccentricities of transiting planets (Pont+, 2011)
J/ApJ/709/168 : Eccentric orbits in exoplanets (Anglada-Escude+, 2010)
J/ApJ/720/872 : A spectropolarimetric analysis of WASP-12 (Fossati+, 2010)
Byte-by-byte Description of file: fits.dat
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Bytes Format Units Label Explanations
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1- 9 F9.5 deg RAdeg Right Ascension of center (J2000)
10- 18 F9.5 deg DEdeg Declination of center (J2000)
20- 32 F13.7 d MJD MJD date of observation at DCE start
(JD-2400000.5)
34- 36 F3.1 um lambda Wavelength of filter (3.6, 4.5, 5.8, 8.0)
39- 96 A58 --- FileName Name of FITS file in subdirectory fits
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 25-Oct-2012