An Analysis of Spitzer Phase Curves for WASP-121b and WASP-77Ab
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| Format: | Preprint |
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2025
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| author | Davenport, Brian Kennedy, Thomas May, E. M. Rauscher, Emily Kempton, Eliza M. -R. Malsky, Isaac Stevenson, Kevin B. Bean, Jacob L. Mansfield, Megan Weiner |
| author_facet | Davenport, Brian Kennedy, Thomas May, E. M. Rauscher, Emily Kempton, Eliza M. -R. Malsky, Isaac Stevenson, Kevin B. Bean, Jacob L. Mansfield, Megan Weiner |
| contents | We present analyses of Spitzer InfraRed Array Camera (IRAC) 3.6 $μ$m and 4.5 $μ$m phase curve observations of hot Jupiters WASP-77Ab and WASP-121b. For WASP-121b, we find amplitudes of 1771 $\pm$ 95 ppm (3.6 $μ$m) and 2048 $\pm$ 109 ppm (4.5 $μ$m), and near-zero offsets of -0.78 $\pm$ 1.87$^{\circ}$ (3.6 $μ$m) and 0.42 $\pm$ 1.74$^{\circ}$ (4.5 $μ$m), consistent within 2.2$σ$ and 1.3$σ$, respectively, with JWST NIRSpec results. For WASP-77Ab, we find amplitudes of 535 $\pm$ 52 ppm (3.6 $μ$m) and 919 $\pm$ 40 ppm (4.5 $μ$m), and offsets of 33.45 $\pm$ 2.79$^{\circ}$ (3.6 $μ$m) and 16.28 $\pm$ 2.52$^{\circ}$ (4.5 $μ$m). We report day- and nightside brightness temperatures: for WASP-121b, 2779 $\pm$ 40 K (3.6 $μ$m) and 2905 $\pm$ 51 K (4.5 $μ$m) (day) and 1259 $\pm$ 67 K (3.6 $μ$m) and 1349 $\pm$ 54 K (4.5 $μ$m) (night), and for WASP-77Ab, 1876 $\pm$ 23 K (3.6 $μ$m) and 1780 $\pm$ 25 K (day) and 1501 $\pm$ 22 K (3.6 $μ$m) and 1234 $\pm$ 20 K (4.5 $μ$m) (night). Comparing WASP-121b data to general circulation models, we find evidence for drag inhibiting day-to-night heat transfer, which our model reproduces using magnetic circulation. Further, comparing both planets' data to Energy Balance Models, we show suppressed circulation in WASP-121b and potential evidence for an unusually high Bond albedo in WASP-77Ab. We add both planets to the Spitzer population study of previously identified trends in offset versus orbital period, finding that a positive trend is weakened, but not eliminated, by including these planets. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2503_12521 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | An Analysis of Spitzer Phase Curves for WASP-121b and WASP-77Ab Davenport, Brian Kennedy, Thomas May, E. M. Rauscher, Emily Kempton, Eliza M. -R. Malsky, Isaac Stevenson, Kevin B. Bean, Jacob L. Mansfield, Megan Weiner Earth and Planetary Astrophysics We present analyses of Spitzer InfraRed Array Camera (IRAC) 3.6 $μ$m and 4.5 $μ$m phase curve observations of hot Jupiters WASP-77Ab and WASP-121b. For WASP-121b, we find amplitudes of 1771 $\pm$ 95 ppm (3.6 $μ$m) and 2048 $\pm$ 109 ppm (4.5 $μ$m), and near-zero offsets of -0.78 $\pm$ 1.87$^{\circ}$ (3.6 $μ$m) and 0.42 $\pm$ 1.74$^{\circ}$ (4.5 $μ$m), consistent within 2.2$σ$ and 1.3$σ$, respectively, with JWST NIRSpec results. For WASP-77Ab, we find amplitudes of 535 $\pm$ 52 ppm (3.6 $μ$m) and 919 $\pm$ 40 ppm (4.5 $μ$m), and offsets of 33.45 $\pm$ 2.79$^{\circ}$ (3.6 $μ$m) and 16.28 $\pm$ 2.52$^{\circ}$ (4.5 $μ$m). We report day- and nightside brightness temperatures: for WASP-121b, 2779 $\pm$ 40 K (3.6 $μ$m) and 2905 $\pm$ 51 K (4.5 $μ$m) (day) and 1259 $\pm$ 67 K (3.6 $μ$m) and 1349 $\pm$ 54 K (4.5 $μ$m) (night), and for WASP-77Ab, 1876 $\pm$ 23 K (3.6 $μ$m) and 1780 $\pm$ 25 K (day) and 1501 $\pm$ 22 K (3.6 $μ$m) and 1234 $\pm$ 20 K (4.5 $μ$m) (night). Comparing WASP-121b data to general circulation models, we find evidence for drag inhibiting day-to-night heat transfer, which our model reproduces using magnetic circulation. Further, comparing both planets' data to Energy Balance Models, we show suppressed circulation in WASP-121b and potential evidence for an unusually high Bond albedo in WASP-77Ab. We add both planets to the Spitzer population study of previously identified trends in offset versus orbital period, finding that a positive trend is weakened, but not eliminated, by including these planets. |
| title | An Analysis of Spitzer Phase Curves for WASP-121b and WASP-77Ab |
| topic | Earth and Planetary Astrophysics |
| url | https://arxiv.org/abs/2503.12521 |