A CORRELATION BETWEEN STELLAR ACTIVITY AND HOT JUPITER EMISSION SPECTRA

By H. Knutson, Andrew W. Howard, H. Isaacson. 2010

232 citations recorded by the source corpus.

We present evidence for a correlation between the observed properties of hot Jupiter emission spectra and the activity levels of the host stars measured using Ca ii H & K emission lines. We find that planets with dayside emission spectra that are well-described by standard one-dimensional atmosphere models with water in absorption (HD 189733, TrES-1, TrES-3, WASP-4) orbit chromospherically active stars, while planets with emission spectra that are consistent with the presence of a strong high-altitude temperature inversion and water in emission orbit quieter stars. We estimate that active G and K stars have Lyman α fluxes that are typically a factor of 4–7 times higher than quiet stars with analogous spectral types and propose that the increased UV flux received by planets orbiting active stars destroys the compounds responsible for the formation of the observed temperature inversions. In this paper, we also derive a model-independent method for differentiating between these two atmosphere types using the secondary eclipse depths measured in the 3.6 and 4.5 μm bands on the Spitzer Space Telescope and argue that the observed correlation is independent of the inverted/non-inverted paradigm for classifying hot Jupiter atmospheres.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/2917facd2247771d789e07f738a3270a0727aace

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In Astronomy and Astrophysics

1. N. Madhusudhan
2. Jon Fortney
3. A. Showman
4. D. Deming
5. D. Sing
6. D. Charbonneau
7. H. Knutson
8. M. Line

In Instrumentation

1. Jon Fortney
2. N. Madhusudhan
3. A. Showman
4. D. Charbonneau
5. D. Sing
6. H. Knutson
7. M. Line
8. D. Deming

Citations in the corpus

• Hubble Space Telescope hot Jupiter transmission spectral survey: a detection of Na and strong optical absorption in HAT-P-1b (2013, background): “2 with Ca II H&K chromospheric line emission index of logR′H&K = −4.984, Knutson et al. (2010)) for variability of HAT-P-1 above ±0.5% (a scatter of 2 mmag consistent with the photometric noise), which is also compatible with the low chromospheric activity concluded in Bakos et al. (2007) and the…”
• ORBITAL PHASE VARIATIONS OF THE ECCENTRIC GIANT PLANET HAT-P-2b (2013, background): “Measurements of the Ca II H & K lines of HAT-P-2 by Knutson et al. (2010) do not detect any significant emission in the line cores, which would suggest a chromospherically quiet stellar host for HAT-P-2b.”
• THE STATISTICS OF ALBEDO AND HEAT RECIRCULATION ON HOT EXOPLANETS (2009, background): “The cyan asterisks in Figure 7 show the four hot Jupiters without temperature inversions, while most of the remaining planets have inversions (Knutson et al. 2010).”
• H− Opacity and Water Dissociation in the Dayside Atmosphere of the Very Hot Gas Giant WASP-18b (2018, background): “Indeed, the primary diagnostic of these thermal inversions is a flux excess at 4.5 µm (Knutson et al. 2010).”
• The prevalence of dust on the exoplanet HD 189733b from Hubble and Spitzer observations (2012, background): “Knutson et al. (2010) has noted a strong correlation between activity in the host star and apparent temperature inversion inferred from the emission spectrum, which could correlate the temperature inversion with the UV flux of the star instead.”
• HST hot-Jupiter transmission spectral survey: evidence for aerosols and lack of TiO in the atmosphere of WASP-12b (2013, background): “The late F spectral type of WASP-12 and its relatively low measured vsini (Knutson et al. 2010), also makes it unlikely to have significant star spots, which is confirmed by our photometric monitoring.”
• NO THERMAL INVERSION AND A SOLAR WATER ABUNDANCE FOR THE HOT JUPITER HD 209458B FROM HST/WFC3 SPECTROSCOPY (2016, background): “An alternative hypothesis for the apparent lack of inversions, brought forth by Knutson et al. (2010), suggests that high incident UV flux could potentially photolize high altitude absorbers.”
• 3.6 AND 4.5 μm PHASE CURVES AND EVIDENCE FOR NON-EQUILIBRIUM CHEMISTRY IN THE ATMOSPHERE OF EXTRASOLAR PLANET HD 189733b (2012, background): “Stellar Variability HD 189733b is an active K0 star with a Ca II H & K emission line strength of log(R′HK)= −4.5 (Bouchy et al. 2005; Knutson et al. 2010), which has been observed to vary by as much as ±1.5% at visible wavelengths with a rotation period of 11.95 days (Henry & Winn 2008; Knutson et…”
• Carbon monoxide and water vapor in the atmosphere of the non-transiting exoplanet HD 179949 b (2014, background): “However, stellar activity could also influence the onset of thermal inversion layers, because of the UV stellar flux potentially destroying the above-mentioned absorbers (Knutson et al. 2010).”
• FRIENDS OF HOT JUPITERS. I. A RADIAL VELOCITY SEARCH FOR MASSIVE, LONG-PERIOD COMPANIONS TO CLOSE-IN GAS GIANT PLANETS (2013, background): “This is not surprising, as this is one of the most active stars in our sample with a log(R′HK) value of −4.57 (Knutson et al. 2010).”
• A SYSTEMATIC RETRIEVAL ANALYSIS OF SECONDARY ECLIPSE SPECTRA. I. A COMPARISON OF ATMOSPHERIC RETRIEVAL TECHNIQUES (2013, methodology): “At the moment, these observations come in two types, broadband photometry mainly from the Spitzer Space Telescope (see e.g., Knutson et al. 2010) and ground-based instruments (Croll et al. 2010; Anderson et al. 2010; Gibson et al. 2010; Deming et al. 2012; Gillon et al. 2012 ), as well as higher…”
• DISEQUILIBRIUM CARBON, OXYGEN, AND NITROGEN CHEMISTRY IN THE ATMOSPHERES OF HD 189733b AND HD 209458b (2011, background): “…remaining in gas phase on warmer, more highly irradiated hot Jupiters (Hubeny et al. 2003; Burrows et al. 2008; Fortney et al. 2008a); however, Knutson et al. (2010) argue that the lack of a convincing correlation between the incident flux and the presence of an inferred thermal inversion —…”
• C/O RATIO AS A DIMENSION FOR CHARACTERIZING EXOPLANETARY ATMOSPHERES (2012, background): “However, Anderson et al. (2012) note that the planet orbits a chromospherically active star, in which case, according to the hypothesis of Knutson et al. (2010) the high UV flux incident on the planetary atmosphere could potentially dissociate the inversion causing molecules.”
• An HST optical-to-near-IR transmission spectrum of the hot Jupiter WASP-19b: detection of atmospheric water and likely absence of TiO (2013, methodology): “An alternative explanation for a lack of TiO features could be that stellar UV radiation breaks down the molecule as proposed by Knutson et al. (2010).”
• SPECTROSCOPIC EVIDENCE FOR A TEMPERATURE INVERSION IN THE DAYSIDE ATMOSPHERE OF HOT JUPITER WASP-33b (2015, background): “Furthermore, Knutson et al. (2010) explored the possibility that the absorbing molecular species may be destroyed by photodissociation and may, hence, be affected by the activity of the host star.”