The 8 μm phase variation of the hot saturn HD 149026b

Heather A. Knutson, David Charbonneau, Nicolas B. Cowan, Jonathan J. Fortney, Adam Showman, Eric Agol, Gregory W. Henry

Research output: Contribution to journalArticle

92 Citations (Scopus)

Abstract

We monitor the star HD 149026 and its Saturn-mass planet at 8.0 μm over slightly more than half an orbit using the Infrared Array Camera on the Spitzer Space Telescope. We find an increase of 0.0227% 0.0066% (3.4σ significance) in the combined planet-star flux during this interval. The minimum flux from the planet is 45% 19% of the maximum planet flux, corresponding to a difference in brightness temperature of 480 140 K between the two hemispheres. We derive a new secondary eclipse depth of 0.0411% 0.0076% in this band, corresponding to a dayside brightness temperature of 1440 150 K. Our new secondary eclipse depth is half that of a previous measurement (3.0σ difference) in this same bandpass by Harrrington et al. We re-fit the Harrrington et al. data and obtain a comparably good fit with a smaller eclipse depth that is consistent with our new value. In contrast to earlier claims, our new eclipse depth suggests that this planet's dayside emission spectrum is relatively cool, with an 8 μm brightness temperature that is less than the maximum planet-wide equilibrium temperature. We measure the interval between the transit and secondary eclipse and find that that the secondary eclipse occurs 20.9+7.2 -6.5 minutes earlier (2.9σ) than predicted for a circular orbit, a marginally significant result. This corresponds to ecos(ω) = -0.0079+0.0027 -0.0025, where e is the planet's orbital eccentricity and ω is the argument of pericenter.

Original languageEnglish (US)
Pages (from-to)769-784
Number of pages16
JournalAstrophysical Journal
Volume703
Issue number1
DOIs
StatePublished - 2009

Fingerprint

Saturn
eclipses
planets
planet
brightness temperature
intervals
stars
Space Infrared Telescope Facility
circular orbits
transit
hemispheres
eccentricity
emission spectra
cameras
orbits
orbitals

Keywords

  • Eclipses
  • Planetary systems
  • Stars: individual (HD 149026b)
  • Techniques: photometric

ASJC Scopus subject areas

  • Space and Planetary Science
  • Astronomy and Astrophysics

Cite this

Knutson, H. A., Charbonneau, D., Cowan, N. B., Fortney, J. J., Showman, A., Agol, E., & Henry, G. W. (2009). The 8 μm phase variation of the hot saturn HD 149026b. Astrophysical Journal, 703(1), 769-784. https://doi.org/10.1088/0004-637X/703/1/769

The 8 μm phase variation of the hot saturn HD 149026b. / Knutson, Heather A.; Charbonneau, David; Cowan, Nicolas B.; Fortney, Jonathan J.; Showman, Adam; Agol, Eric; Henry, Gregory W.

In: Astrophysical Journal, Vol. 703, No. 1, 2009, p. 769-784.

Research output: Contribution to journalArticle

Knutson, HA, Charbonneau, D, Cowan, NB, Fortney, JJ, Showman, A, Agol, E & Henry, GW 2009, 'The 8 μm phase variation of the hot saturn HD 149026b', Astrophysical Journal, vol. 703, no. 1, pp. 769-784. https://doi.org/10.1088/0004-637X/703/1/769
Knutson HA, Charbonneau D, Cowan NB, Fortney JJ, Showman A, Agol E et al. The 8 μm phase variation of the hot saturn HD 149026b. Astrophysical Journal. 2009;703(1):769-784. https://doi.org/10.1088/0004-637X/703/1/769
Knutson, Heather A. ; Charbonneau, David ; Cowan, Nicolas B. ; Fortney, Jonathan J. ; Showman, Adam ; Agol, Eric ; Henry, Gregory W. / The 8 μm phase variation of the hot saturn HD 149026b. In: Astrophysical Journal. 2009 ; Vol. 703, No. 1. pp. 769-784.
@article{5fd943a12dcc4d7f97ce5719ced3c157,
title = "The 8 μm phase variation of the hot saturn HD 149026b",
abstract = "We monitor the star HD 149026 and its Saturn-mass planet at 8.0 μm over slightly more than half an orbit using the Infrared Array Camera on the Spitzer Space Telescope. We find an increase of 0.0227{\%} 0.0066{\%} (3.4σ significance) in the combined planet-star flux during this interval. The minimum flux from the planet is 45{\%} 19{\%} of the maximum planet flux, corresponding to a difference in brightness temperature of 480 140 K between the two hemispheres. We derive a new secondary eclipse depth of 0.0411{\%} 0.0076{\%} in this band, corresponding to a dayside brightness temperature of 1440 150 K. Our new secondary eclipse depth is half that of a previous measurement (3.0σ difference) in this same bandpass by Harrrington et al. We re-fit the Harrrington et al. data and obtain a comparably good fit with a smaller eclipse depth that is consistent with our new value. In contrast to earlier claims, our new eclipse depth suggests that this planet's dayside emission spectrum is relatively cool, with an 8 μm brightness temperature that is less than the maximum planet-wide equilibrium temperature. We measure the interval between the transit and secondary eclipse and find that that the secondary eclipse occurs 20.9+7.2 -6.5 minutes earlier (2.9σ) than predicted for a circular orbit, a marginally significant result. This corresponds to ecos(ω) = -0.0079+0.0027 -0.0025, where e is the planet's orbital eccentricity and ω is the argument of pericenter.",
keywords = "Eclipses, Planetary systems, Stars: individual (HD 149026b), Techniques: photometric",
author = "Knutson, {Heather A.} and David Charbonneau and Cowan, {Nicolas B.} and Fortney, {Jonathan J.} and Adam Showman and Eric Agol and Henry, {Gregory W.}",
year = "2009",
doi = "10.1088/0004-637X/703/1/769",
language = "English (US)",
volume = "703",
pages = "769--784",
journal = "Astrophysical Journal",
issn = "0004-637X",
publisher = "IOP Publishing Ltd.",
number = "1",

}

TY - JOUR

T1 - The 8 μm phase variation of the hot saturn HD 149026b

AU - Knutson, Heather A.

AU - Charbonneau, David

AU - Cowan, Nicolas B.

AU - Fortney, Jonathan J.

AU - Showman, Adam

AU - Agol, Eric

AU - Henry, Gregory W.

PY - 2009

Y1 - 2009

N2 - We monitor the star HD 149026 and its Saturn-mass planet at 8.0 μm over slightly more than half an orbit using the Infrared Array Camera on the Spitzer Space Telescope. We find an increase of 0.0227% 0.0066% (3.4σ significance) in the combined planet-star flux during this interval. The minimum flux from the planet is 45% 19% of the maximum planet flux, corresponding to a difference in brightness temperature of 480 140 K between the two hemispheres. We derive a new secondary eclipse depth of 0.0411% 0.0076% in this band, corresponding to a dayside brightness temperature of 1440 150 K. Our new secondary eclipse depth is half that of a previous measurement (3.0σ difference) in this same bandpass by Harrrington et al. We re-fit the Harrrington et al. data and obtain a comparably good fit with a smaller eclipse depth that is consistent with our new value. In contrast to earlier claims, our new eclipse depth suggests that this planet's dayside emission spectrum is relatively cool, with an 8 μm brightness temperature that is less than the maximum planet-wide equilibrium temperature. We measure the interval between the transit and secondary eclipse and find that that the secondary eclipse occurs 20.9+7.2 -6.5 minutes earlier (2.9σ) than predicted for a circular orbit, a marginally significant result. This corresponds to ecos(ω) = -0.0079+0.0027 -0.0025, where e is the planet's orbital eccentricity and ω is the argument of pericenter.

AB - We monitor the star HD 149026 and its Saturn-mass planet at 8.0 μm over slightly more than half an orbit using the Infrared Array Camera on the Spitzer Space Telescope. We find an increase of 0.0227% 0.0066% (3.4σ significance) in the combined planet-star flux during this interval. The minimum flux from the planet is 45% 19% of the maximum planet flux, corresponding to a difference in brightness temperature of 480 140 K between the two hemispheres. We derive a new secondary eclipse depth of 0.0411% 0.0076% in this band, corresponding to a dayside brightness temperature of 1440 150 K. Our new secondary eclipse depth is half that of a previous measurement (3.0σ difference) in this same bandpass by Harrrington et al. We re-fit the Harrrington et al. data and obtain a comparably good fit with a smaller eclipse depth that is consistent with our new value. In contrast to earlier claims, our new eclipse depth suggests that this planet's dayside emission spectrum is relatively cool, with an 8 μm brightness temperature that is less than the maximum planet-wide equilibrium temperature. We measure the interval between the transit and secondary eclipse and find that that the secondary eclipse occurs 20.9+7.2 -6.5 minutes earlier (2.9σ) than predicted for a circular orbit, a marginally significant result. This corresponds to ecos(ω) = -0.0079+0.0027 -0.0025, where e is the planet's orbital eccentricity and ω is the argument of pericenter.

KW - Eclipses

KW - Planetary systems

KW - Stars: individual (HD 149026b)

KW - Techniques: photometric

UR - http://www.scopus.com/inward/record.url?scp=70450220898&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=70450220898&partnerID=8YFLogxK

U2 - 10.1088/0004-637X/703/1/769

DO - 10.1088/0004-637X/703/1/769

M3 - Article

AN - SCOPUS:70450220898

VL - 703

SP - 769

EP - 784

JO - Astrophysical Journal

JF - Astrophysical Journal

SN - 0004-637X

IS - 1

ER -