J/AJ/154/4 Times of transits and occultations of WASP-12b (Patra+, 2017)
The apparently decaying orbit of WASP-12b.
Patra K.C., Winn J.N., Holman M.J., Yu L., Deming D., Dai F.
<Astron. J., 154, 4-4 (2017)>
=2017AJ....154....4P 2017AJ....154....4P (SIMBAD/NED BibCode)
ADC_Keywords: Planets ; Stars, double and multiple
Keywords: planetastar interactions -
planets and satellites: individual WASP-12 b
Abstract:
We present new transit and occultation times for the hot Jupiter
WASP-12b. The data are compatible with a constant period derivative:
P.=-29±3ms/yr and P/P.=3.2Myr. However, it is difficult to tell
whether we have observed orbital decay or a portion of a 14-year
apsidal precession cycle. If interpreted as decay, the star's tidal
quality parameter Qstar is about 2*105. If interpreted as
precession, the planet's Love number is 0.44±0.10. Orbital decay
appears to be the more parsimonious model: it is favored by
Δχ2^_=5.5 despite having two fewer free parameters than
the precession model. The decay model implies that WASP-12 was
discovered within the final ∼0.2% of its existence, which is an
unlikely coincidence but harmonizes with independent evidence that the
planet is nearing disruption. Precession does not invoke any temporal
coincidence, but it does require some mechanism to maintain an
eccentricity of ~0.002 in the face of rapid tidal
circularization. To distinguish unequivocally between decay and
precession will probably require a few more years of monitoring.
Particularly helpful will be occultation timing in 2019 and
thereafter.
Description:
Between 2016 October and 2017 February, we observed seven transits of
WASP-12 with the 1.2m telescope at the Fred Lawrence Whipple
Observatory on Mt. Hopkins, Arizona. Images were obtained with the
KeplerCam detector through a Sloan r'-band filter. The typical
exposure time was 15s, chosen to give a signal-to-noise ratio of about
200 for WASP-12. The field of view of this camera is 23.1' on a side.
We used 2*2 binning, giving a pixel scale of 0.68''.
We measured two new occultation times based on hitherto unpublished
Spitzer observations in 2013 December (program 90186, P.I. Todorov).
Two different transits were observed, one at 3.6µm and one at
4.5µm. The data take the form of a time series of 32*32-pixel
subarray images, with an exposure time of 2.0s per image. The data
were acquired over a wide range of orbital phases, but for our
purpose, we analyzed only the ∼14000 images within 4hr of each
occultation.
Objects:
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RA (ICRS) DE Designation(s) (Period)
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06 30 32.79 +29 40 20.3 WASP-12 = TYC 1891-1178-1 (P=1.091420025)
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 79 113 Transit and occultation times
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See also:
J/A+A/588/L6 : WASP-12 transit light curves (Maciejewski+ 2016)
J/ApJ/785/126 : HIRES radial velocity measurements (Knutson+, 2014)
J/A+A/551/A108 : Multi-site obs. of WASP-12 b transit (Maciejewski+, 2013)
J/ApJ/757/161 : Spectroscopy of 56 exoplanet host stars (Torres+, 2012)
J/ApJ/757/18 : Radial velocities for hot Jupiter host stars (Albrecht+, 2012)
J/ApJ/727/125 : Two secondary eclipses of WASP-12b with Spitzer (Campo+, 2011)
J/AJ/141/179 : Transits of TrES-4b, HAT-P-3b and WASP-12b (Chan+, 2011)
J/ApJ/720/872 : A spectropolarimetric analysis of WASP-12 (Fossati+, 2010)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 3 A3 --- Event Event (occ=occultation, tra=transit)
5- 17 F13.5 d BJD Barycentric Julian Date (BJD) of midtransit time
(BJDTDB)
19- 25 F7.5 d e_BJD [0.0001/0.0022] Uncertainty in BJD
27- 31 I5 --- E [-1640/1370] Epoch number
33 A1 --- f_Ref [ab] Flag on Reference (a or b) (1)
35- 79 A45 --- Ref Reference
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Note (1): Flag is defined as follows:
a = Refers to the light curve obtained by Hebb et al. (2009ApJ...693.1920H 2009ApJ...693.1920H)
with the 2m Liverpool telescope, as analyzed by Maciejewski et al. 2013
(Cat. J/A+A/551/A108);
b = Re-analyzed in this work.
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History:
From electronic version of the journal
(End) Sylvain Guehenneux [CDS] 09-Aug-2017