277 results on '"Cowan, Nicolas B."'
Search Results
252. Inverting Phase Functions to Map Exoplanets
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Cowan, Nicolas B., primary and Agol, Eric, additional
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- 2008
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253. The Environment of Galaxies at Low Redshift
- Author
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Cowan, Nicolas B., primary and Ivezić, Željko, additional
- Published
- 2008
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254. A map of the day–night contrast of the extrasolar planet HD 189733b
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Knutson, Heather A., primary, Charbonneau, David, additional, Allen, Lori E., additional, Fortney, Jonathan J., additional, Agol, Eric, additional, Cowan, Nicolas B., additional, Showman, Adam P., additional, Cooper, Curtis S., additional, and Megeath, S. Thomas, additional
- Published
- 2007
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- View/download PDF
255. Clearing up the clouds on hot gas giants.
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Cowan, Nicolas B. and Rauscher, Emily
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- 2020
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256. Transiting Exoplanet Studies and Community Targets for JWST 's Early Release Science Program
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Stevenson, Kevin B., Lewis, Nikole K., Bean, Jacob L., Beichman, Charles, Fraine, Jonathan, Kilpatrick, Brian M., Krick, J. E., Lothringer, Joshua D., Mandell, Avi M., Valenti, Jeff A., Agol, Eric, Angerhausen, Daniel, Barstow, Joanna K., Birkmann, Stephan M., Burrows, Adam, Charbonneau, David, Cowan, Nicolas B., Crouzet, Nicolas, Cubillos, Patricio E., Curry, S. M., Dalba, Paul A., de Wit, Julien, Deming, Drake, Désert, Jean-Michel, Doyon, René, Dragomir, Diana, Ehrenreich, David, Fortney, Jonathan J., García Muñoz, Antonio, Gibson, Neale P., Gizis, John E., Greene, Thomas P., Harrington, Joseph, Heng, Kevin, Kataria, Tiffany, Kempton, Eliza M.-R., Knutson, Heather, Kreidberg, Laura, Lafrenière, David, Lagage, Pierre-Olivier, Line, Michael R., Lopez-Morales, Mercedes, Madhusudhan, Nikku, Morley, Caroline V., Rocchetto, Marco, Schlawin, Everett, Shkolnik, Evgenya L., Shporer, Avi, Sing, David K., Todorov, Kamen O., Tucker, Gregory S., and Wakeford, Hannah R.
- Abstract
The James Webb Space Telescope (JWST) will likely revolutionize transiting exoplanet atmospheric science due to a combination of its capability for continuous, long duration observations and its larger collecting area, spectral coverage, and spectral resolution compared to existing space-based facilities. However, it is unclear precisely how well JWST will perform and which of its myriad instruments and observing modes will be best suited for transiting exoplanet studies. In this article, we describe a prefatory JWST Early Release Science (ERS) Cycle 1 program that focuses on testing specific observing modes to quickly give the community the data and experience it needs to plan more efficient and successful transiting exoplanet characterization programs in later cycles. We propose a multi-pronged approach wherein one aspect of the program focuses on observing transits of a single target with all of the recommended observing modes to identify and understand potential systematics, compare transmission spectra at overlapping and neighboring wavelength regions, confirm throughputs, and determine overall performances. In our search for transiting exoplanets that are well suited to achieving these goals, we identify 12 objects (dubbed “community targets”) that meet our defined criteria. Currently, the most favorable target is WASP-62b because of its large predicted signal size, relatively bright host star, and location in JWST’s continuous viewing zone. Since most of the community targets do not have well-characterized atmospheres, we recommend initiating preparatory observing programs to determine the presence of obscuring clouds/hazes within their atmospheres. Measurable spectroscopic features are needed to establish the optimal resolution and wavelength regions for exoplanet characterization. Other initiatives from our proposed ERS program include testing the instrument brightness limits and performing phase-curve observations. The latter are a unique challenge compared to transit observations because of their significantly longer durations. Using only a single mode, we propose to observe a full-orbit phase curve of one of the previously characterized, short-orbital-period planets to evaluate the facility-level aspects of long, uninterrupted time-series observations., Astronomy
- Published
- 2016
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- View/download PDF
257. STABILIZING CLOUD FEEDBACK DRAMATICALLY EXPANDS THE HABITABLE ZONE OF TIDALLY LOCKED PLANETS.
- Author
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JUN YANG, COWAN, NICOLAS B., and ABBOT, DORIAN S.
- Published
- 2013
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258. WARM SPITZER PHOTOMETRY OF THREE HOT JUPITERS: HAT-P-3b, HAT-P-4b AND HAT-P-12b.
- Author
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TODOROV, KAMEN O., DEMING, DRAKE, KNUTSON, HEATHER A., BURROWS, ADAM, FORTNEY, JONATHAN J., LEWIS, NIKOLE K., COWAN, NICOLAS B., AGOL, ERIC, DESERT, JEAN-MICHEL, SADA, PEDRO V., CHARBONNEAU, DAVID, LAUGHLIN, GREGORY, LANGTON, JONATHAN, and SHOWMAN, ADAM P.
- Subjects
ASTRONOMICAL photometry ,JUPITER (Planet) ,PLANETARY orbits ,ECLIPSES ,PHOTOMETRY - Abstract
We present Warm Spitzer/IRAC secondary eclipse time series photometry of three short-period transiting exoplanets, HAT-P-3b, HAT-P-4b and HAT-P-12b, in both the available 3.6 and 4.5μm bands. HAT-P-3b and HAT-P-4b are Jupiter-mass objects orbiting an early K and an early G dwarf star, respectively. For HAT-P-3b we find eclipse depths of 0.112%
-0.030% +0.015% (3.6μm) and 0.094%-0.009% +0.016% (4.5μm). The HAT-P-4b values are 0.142%-0.016% +0.014% (3.6μm) and 0.122%-0.014% +0.012% (4.5μm). The two planets' photometry is consistent with inefficient heat redistribution from their day to night sides (and low albedos), but it is inconclusive about possible temperature inversions in their atmospheres. HAT-P-12b is a Saturn-mass planet and is one of the coolest planets ever observed during secondary eclipse, along with the hot Neptune GJ 436b and the hot Saturn WASP-29b. We are able to place 3σ upper limits on the secondary eclipse depth of HAT-P-12b in both wavelengths: <0.042% (3.6μm) and <0.085% (4.5μm).We discuss these results in the context of the Spitzer secondary eclipse measurements of GJ 436b and WASP-29b. It is possible that we do not detect the eclipses of HAT-P-12b due to high eccentricity, but find that weak planetary emission in these wavelengths is a more likely explanation. We place 3σ upper limits on the ∣e cos ω∣ quantity (where e is eccentricity and ω is the argument of periapsis) for HAT-P-3b (<0.0081) and HAT-P-4b (<0.0042), based on the secondary eclipse timings. [ABSTRACT FROM AUTHOR]- Published
- 2013
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259. Measures of galaxy environment - I. What is 'environment'?
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Muldrew, Stuart I., Croton, Darren J., Skibba, Ramin A., Pearce, Frazer R., Ann, Hong Bae, Baldry, Ivan K., Brough, Sarah, Choi, Yun-Young, Conselice, Christopher J., Cowan, Nicolas B., Gallazzi, Anna, Gray, Meghan E., Grützbauch, Ruth, Li, I-Hui, Park, Changbom, Pilipenko, Sergey V., Podgorzec, Bret J., Robotham, Aaron S. G., Wilman, David J., and Yang, Xiaohu
- Subjects
STAR catalogs ,GALAXIES ,LITERATURE reviews ,NEAREST neighbor analysis (Statistics) ,STATISTICAL correlation ,CONSTRAINTS (Physics) ,ASTRONOMICAL photometry - Abstract
ABSTRACT The influence of a galaxy's environment on its evolution has been studied and compared extensively in the literature, although differing techniques are often used to define environment. Most methods fall into two broad groups: those that use nearest neighbours to probe the underlying density field and those that use fixed apertures. The differences between the two inhibit a clean comparison between analyses and leave open the possibility that, even with the same data, different properties are actually being measured. In this work, we apply 20 published environment definitions to a common mock galaxy catalogue constrained to look like the local Universe. We find that nearest-neighbour-based measures best probe the internal densities of high-mass haloes, while at low masses the interhalo separation dominates and acts to smooth out local density variations. The resulting correlation also shows that nearest-neighbour galaxy environment is largely independent of dark matter halo mass. Conversely, aperture-based methods that probe superhalo scales accurately identify high-density regions corresponding to high-mass haloes. Both methods show how galaxies in dense environments tend to be redder, with the exception of the largest apertures, but these are the strongest at recovering the background dark matter environment. We also warn against using photometric redshifts to define environment in all but the densest regions. When considering environment, there are two regimes: the 'local environment' internal to a halo best measured with nearest neighbour and 'large-scale environment' external to a halo best measured with apertures. This leads to the conclusion that there is no universal environment measure and the most suitable method depends on the scale being probed. [ABSTRACT FROM AUTHOR]
- Published
- 2012
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260. A SPITZER TRANSMISSION SPECTRUM FOR THE EXOPLANET GJ 436b, EVIDENCE FOR STELLAR VARIABILITY, AND CONSTRAINTS ON DAYSIDE FLUX VARIATIONS.
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KNUTSON, HEATHER A., MADHUSUDHAN, NIKKU, COWAN, NICOLAS B., CHRISTIANSEN, JESSIE L., AGOL, ERIC, DEMING, DRAKE, DÉSERT, JEAN-MICHEL, CHARBONNEAU, DAVID, HENRY, GREGORY W., HOMEIER, DEREK, LANGTON, JONATHAN, LAUGHLIN, GREGORY, and SEAGER, SARA
- Subjects
SOLAR eclipses ,EXTRASOLAR planets ,SPACE telescopes ,BANDPASS filters ,STANDARD deviations ,STELLAR atmospheres - Abstract
In this paper, we describe a uniform analysis of eight transits and eleven secondary eclipses of the extrasolar planet GJ 436b obtained in the 3.6, 4.5, and 8.0 μm bands using the IRAC instrument on the Spitzer Space Telescope between UT 2007 June 29 and UT 2009 February 4. We find that the best-fit transit depths for visits in the same bandpass can vary by as much as 8% of the total (4.7σ significance) from one epoch to the next. Although we cannot entirely rule out residual detector effects or a time-varying, high-altitude cloud layer in the planet's atmosphere as the cause of these variations, we consider the occultation of active regions on the star in a subset of the transit observations to be the most likely explanation. We find that for the deepest 3.6 μm transit the in-transit data have a higher standard deviation than the out-of-transit data, as would be expected if the planet occulted a star spot. We also compare all published transit observations for this object and find that transits observed in the infrared typically have smaller timing offsets than those observed in visible light. In this case, the three deepest Spitzer transits are all measured within a period of five days, consistent with a single epoch of increased stellar activity. We reconcile the presence of magnetically active regions with the lack of significant visible or infrared flux variations from the star by proposing that the star's spin axis is tilted with respect to our line of sight and that the planet's orbit is therefore likely to be misaligned. In contrast to the results reported by Beaulieu et al., we find no convincing evidence for methane absorption in the planet's transmission spectrum. If we exclude the transits that we believe to be most affected by stellar activity, we find that we prefer models with enhanced CO and reduced methane, consistent with GJ 436b's dayside composition from Stevenson et al. It is also possible that all transits are significantly affected by this activity, in which case it may not be feasible to characterize the planet's transmission spectrum using broadband photometry obtained over multiple epochs. These observations serve to illustrate the challenges associated with transmission spectroscopy of planets orbiting late-type stars; we expect that other systems, such as GJ 1214, may display comparably variable transit depths. We compare the limb-darkening coefficients predicted by PHOENIX and ATLAS stellar atmosphere models and discuss the effect that these coefficients have on the measured planet-star radius ratios given GJ 436b's near-grazing transit geometry. Our measured 8 μm secondary eclipse depths are consistent with a constant value, and we place a 1σ upper limit of 17% on changes in the planet's dayside flux in this band. These results are consistent with predictions from general circulation models for this planet, which find that the planet's dayside flux varies by a few percent or less in the 8 μm band. Averaging over the eleven visits gives us an improved estimate of 0.0452% ± 0.0027% for the secondary eclipse depth; we also examine residuals from the eclipse ingress and egress and place an upper limit on deviations caused by a non-uniform surface brightness for GJ 436b. We combine timing information from our observations with previously published data to produce a refined orbital ephemeris and determine that the best-fit transit and eclipse times are consistent with a constant orbital period. We find that the secondary eclipse occurs at a phase of 0.58672 ± 0.00017, corresponding to e cos(ω) = 0.13754 ± 0.00027, where e is the planet's orbital eccentricity and ω is the longitude of pericenter. We also present improved estimates for other system parameters, including the orbital inclination, a/R
⋆ , and the planet-star radius ratio. [ABSTRACT FROM AUTHOR]- Published
- 2011
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- View/download PDF
261. ROTATIONAL VARIABILITY OF EARTH'S POLAR REGIONS: IMPLICATIONS FOR DETECTING SNOWBALL PLANETS.
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Cowan, Nicolas B., Robinson, Tyler, Livengood, Timothy A., Deming, Drake, Agol, Eric, A'Hearn, Michael F., Charbonneau, David, Lisse, Carey M., Meadows, Victoria S., Seager, Sara, Shields, Aomawa L., and Wellnitz, Dennis D.
- Published
- 2011
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- View/download PDF
262. The 4.5 µm full-orbit phase curve of the hot Jupiter HD 209458B
- Author
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Zellem, Robert T., Lewis, Nikole K., Knutson, Heather A., Griffith, Caitlin A., Showman, Adam P., Fortney, Jonathan J., Cowan, Nicolas B., Agol, Eric, Burrows, Adam, Charbonneau, David, Deming, Drake, Laughlin, Gregory, and Langton, Jonathan
- Subjects
atmospheric effects ,methods: numerical ,planets and satellites: general ,planets and satellites: individual (HD 209458b) ,techniques: photometric - Abstract
The hot Jupiter HD 209458b is particularly amenable to detailed study as it is among the brightest transiting exoplanet systems currently known (V-mag = 7.65; K-mag = 6.308) and has a large planet-to-star contrast ratio. HD 209458b is predicted to be in synchronous rotation about its host star with a hot spot that is shifted eastward of the substellar point by superrotating equatorial winds. Here we present the first full-orbit observations of HD 209458b, in which its 4.5 μm emission was recorded with Spitzer/IRAC. Our study revises the previous 4.5 μm measurement of HD 209458b's secondary eclipse emission downward by ~35% to $0.1391\%^{+0.0072\%}_{-0.0069\%}$, changing our interpretation of the properties of its dayside atmosphere. We find that the hot spot on the planet's dayside is shifted eastward of the substellar point by 40fdg9 ± 6fdg0, in agreement with circulation models predicting equatorial superrotation. HD 209458b's dayside (T bright = 1499 ± 15 K) and nightside (T bright = 972 ± 44 K) emission indicate a day-to-night brightness temperature contrast smaller than that observed for more highly irradiated exoplanets, suggesting that the day-to-night temperature contrast may be partially a function of the incident stellar radiation. The observed phase curve shape deviates modestly from global circulation model predictions potentially due to disequilibrium chemistry or deficiencies in the current hot CH4 line lists used in these models. Observations of the phase curve at additional wavelengths are needed in order to determine the possible presence and spatial extent of a dayside temperature inversion, as well as to improve our overall understanding of this planet's atmospheric circulation., Astronomy
- Published
- 2014
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263. THE 8 ?m PHASE VARIATION OF THE HOT SATURN HD 149026b
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Knutson, Heather A., Charbonneau, David, Cowan, Nicolas B., Fortney, Jonathan J., Showman, Adam P., Agol, Eric, and Henry, Gregory W.
- Abstract
We monitor the star HD 149026 and its Saturn-mass planet at 8.0 mm 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% (3.4s 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 (3.0s 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 mm 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 (2.9s) than predicted for a circular orbit, a marginally significant result. This corresponds to ecos(o) = -0.0079+0.0027 -0.0025, where e is the planet's orbital eccentricity and o is the argument of pericenter.
- Published
- 2009
264. ALIEN MAPS OF AN OCEAN-BEARING WORLD
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Cowan, Nicolas B., Agol, Eric, Meadows, Victoria S., Robinson, Tyler, Livengood, Timothy A., Deming, Drake, Lisse, Carey M., A, Michael F., Wellnitz, Dennis D., Seager, Sara, Charbonneau, David, and EPOXI, the
- Abstract
When Earth-mass extrasolar planets first become detectable, one challenge will be to determine which of these worlds harbor liquid water, a widely used criterion for habitability. Some of the first observations of these planets will consist of disc-averaged, time-resolved broadband photometry. To simulate such data, the Deep Impact spacecraft obtained light curves of Earth at seven wavebands spanning 300-1000 nm as part of the EPOXI mission of opportunity. In this paper, we analyze disc-integrated light curves, treating Earth as if it were an exoplanet, to determine if we can detect the presence of oceans and continents. We present two observations each spanning 1 day, taken at gibbous phases of 57deg and 77deg, respectively. As expected, the time-averaged spectrum of Earth is blue at short wavelengths due to Rayleigh scattering, and gray redward of 600 nm due to reflective clouds. The rotation of the planet leads to diurnal albedo variations of 15%-30%, with the largest relative changes occurring at the reddest wavelengths. To characterize these variations in an unbiased manner, we carry out a principal component analysis of the multi-band light curves; this analysis reveals that 98% of the diurnal color changes of Earth are due to only two dominant eigencolors. We use the time variations of these two eigencolors to construct longitudinal maps of the Earth, treating it as a non-uniform Lambert sphere. We find that the spectral and spatial distributions of the eigencolors correspond to cloud-free continents and oceans despite the fact that our observations were taken on days with typical cloud cover. We also find that the near-infrared wavebands are particularly useful in distinguishing between land and water. Based on this experiment, we conclude that it should be possible to infer the existence of water oceans on exoplanets with time-resolved broadband observations taken by a large space-based coronagraphic telescope.
- Published
- 2009
265. MULTIWAVELENGTH CONSTRAINTS ON THE DAY-NIGHT CIRCULATION PATTERNS OF HD 189733b
- Author
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Knutson, Heather A., Charbonneau, David, Cowan, Nicolas B., Fortney, Jonathan J., Showman, Adam P., Agol, Eric, Henry, Gregory W., Everett, Mark E., and Allen, Lori E.
- Abstract
We present new Spitzer observations of the phase variation of the hot Jupiter HD 189733b in the MIPS 24 mm bandpass, spanning the same part of the planet's orbit as our previous observations in the IRAC 8 mm bandpass (Knutson et al. 2007). We find that the minimum hemisphere-averaged flux from the planet in this bandpass is 76% +- 3% of the maximum flux; this corresponds to minimum and maximum hemisphere-averaged brightness temperatures of 984 +- 48 K and 1220 +- 47 K, respectively. The planet reaches its maximum flux at an orbital phase of 0.396 +- 0.022, corresponding to a hot region shifted 20deg-30deg east of the substellar point. Because tidally locked hot Jupiters would have enormous day-night temperature differences in the absence of winds, the small amplitude of the observed phase variation indicates that the planet's atmosphere efficiently transports thermal energy from the day side to the night side at the 24 mm photosphere, leading to modest day-night temperature differences. The similarities between the 8 and 24 mm phase curves for HD 189733b lead us to conclude that the circulation on this planet behaves in a fundamentally similar fashion across the range of pressures sensed by these two wavelengths. One-dimensional radiative transfer models indicate that the 8 mm band should probe pressures 2-3 times greater than at 24 mm, although the uncertain methane abundance complicates the interpretation. If these two bandpasses do probe different pressures, it would indicate that the temperature varies only weakly between the two sensed depths, and hence that the atmosphere is not convective at these altitudes. We also present an analysis of the possible contribution of star spots to the time series at both 8 and 24 mm based on near-simultaneous ground-based observations and additional Spitzer observations. Accounting for the effects of these spots results in a slightly warmer night-side temperature for the planet in both bandpasses, but does not otherwise affect our conclusions.
- Published
- 2009
266. Transiting Exoplanet Studies and Community Targets for JWST 's Early Release Science Program
- Author
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Barstow, Joanna K., Morley, Caroline V., Kempton, Eliza M.-R., Shkolnik, Evgenya L., Gizis, John E., Désert, Jean-Michel, Mandell, Avi M., Fortney, Jonathan J., Dalba, Paul A., Lopez-Morales, Mercedes, Angerhausen, Daniel, García Muñoz, Antonio, Harrington, Joseph, Todorov, Kamen O., Beichman, Charles, Heng, Kevin, Cubillos, Patricio E., Rocchetto, Marco, De Wit, Julien, Cowan, Nicolas B., Birkmann, Stephan M., Lothringer, Joshua D., Dragomir, Diana, Shporer, Avi, Stevenson, Kevin B., Doyon, René, Schlawin, Everett, Kataria, Tiffany, Lafrenière, David, Ehrenreich, David, Gibson, Neale P., Bean, Jacob L., Curry, S. M., Agol, Eric, Burrows, Adam, Deming, Drake, Lewis, Nikole K., Wakeford, Hannah R., Kreidberg, Laura, Kilpatrick, Brian M., Fraine, Jonathan, Krick, J. E., Line, Michael R., Greene, Thomas P., Valenti, Jeff A., Knutson, Heather, Crouzet, Nicolas, Charbonneau, David, Lagage, Pierre-Olivier, Tucker, Gregory S., Sing, David K., and Madhusudhan, Nikku
- Subjects
13. Climate action ,530 Physics ,520 Astronomy ,Astrophysics::Instrumentation and Methods for Astrophysics ,Astrophysics::Earth and Planetary Astrophysics ,500 Science ,3. Good health - Abstract
The James Webb Space Telescope will revolutionize transiting exoplanet atmospheric science due to its capability for continuous, long-duration observations and its larger collecting area, spectral coverage, and spectral resolution compared to existing space-based facilities. However, it is unclear precisely how well JWST will perform and which of its myriad instruments and observing modes will be best suited for transiting exoplanet studies. In this article, we describe a prefatory JWST Early Release Science (ERS) program that focuses on testing specific observing modes to quickly give the community the data and experience it needs to plan more efficient and successful future transiting exoplanet characterization programs. We propose a multi-pronged approach wherein one aspect of the program focuses on observing transits of a single target with all of the recommended observing modes to identify and understand potential systematics, compare transmission spectra at overlapping and neighboring wavelength regions, confirm throughputs, and determine overall performances. In our search for transiting exoplanets that are well suited to achieving these goals, we identify 12 objects (dubbed "community targets") that meet our defined criteria. Currently, the most favorable target is WASP-62b because of its large predicted signal size, relatively bright host star, and location in JWST's continuous viewing zone. Since most of the community targets do not have well-characterized atmospheres, we recommend initiating preparatory observing programs to determine the presence of obscuring clouds/hazes within their atmospheres. Measurable spectroscopic features are needed to establish the optimal resolution and wavelength regions for exoplanet characterization. Other initiatives from our proposed ERS program include testing the instrument brightness limits and performing phase-curve observations.
267. Transiting Exoplanet Studies and Community Targets for JWST's Early Release Science Program
- Author
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Stevenson, Kevin B., Lewis, Nikole K., Bean, Jacob L., Beichman, Charles, Fraine, Jonathan, Kilpatrick, Brian M., Krick, J. E., Lothringer, Joshua D., Mandell, Avi M., Valenti, Jeff A., Agol, Eric, Angerhausen, Daniel, Barstow, Joanna K., Birkmann, Stephan M., Burrows, Adam, Cowan, Nicolas B., Crouzet, Nicolas, Cubillos, Patricio E., Curry, S. M., Dalba, Paul A., Wit, Julien, Deming, Drake, Desert, Jean-Michel, Doyon, Rene, Dragomir, Diana, David Sing, Fortney, Jonathan J., Garcia Munoz, Antonio, Gibson, Neale P., Gizis, John E., Greene, Thomas P., Harrington, Joseph, Heng, Kevin, Kataria, Tiffany, Kempton, Eliza M. -R, Knutson, Heather, Kreidberg, Laura, Lafreniere, David, Lagage, Pierre-Olivier, Line, Michael R., Lopez-Morales, Mercedes, Madhusudhan, Nikku, Morley, Caroline V., Rocchetto, Marco, Schlawin, Everett, Shkolnik, Evgenya L., Shporer, Avi, Sing, David K., Todorov, Kamen O., Tucker, Gregory S., and Wakeford, Hannah R.
268. Near-infrared transmission spectroscopy of HAT-P-18 b with NIRISS: Disentangling planetary and stellar features in the era of JWST.
- Author
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Fournier-Tondreau, Marylou, MacDonald, Ryan J, Radica, Michael, Lafrenière, David, Welbanks, Luis, Piaulet, Caroline, Coulombe, Louis-Philippe, Allart, Romain, Morel, Kim, Artigau, Étienne, Albert, Loïc, Lim, Olivia, Doyon, René, Benneke, Björn, Rowe, Jason F, Darveau-Bernier, Antoine, Cowan, Nicolas B, Lewis, Nikole K, Cook, Neil J, and Flagg, Laura
- Subjects
- *
NEAR infrared spectroscopy , *LIGHT sources , *STELLAR atmospheres , *NATURAL satellite atmospheres , *NATURAL satellites , *LIGHT curves - Abstract
The JWST Early Release Observations (ERO) included a NIRISS/SOSS (0.6–2.8 μ m) transit of the ∼ 850 K Saturn-mass exoplanet HAT-P-18 b. Initial analysis of these data reported detections of water, escaping helium and haze. However, active K dwarfs like HAT-P-18 possess surface heterogeneities – star-spots and faculae – that can complicate the interpretation of transmission spectra, and indeed, a spot-crossing event is present in HAT-P-18 b's NIRISS/SOSS light curves. Here, we present an extensive reanalysis and interpretation of the JWST ERO transmission spectrum of HAT-P-18 b, as well as HST /WFC3 and Spitzer /IRAC transit observations. We detect H2O (12.5σ), CO2 (7.3σ), a cloud deck (7.4σ), and unocculted star-spots (5.8σ), alongside hints of Na (2.7σ). We do not detect the previously reported CH4 (log CH4 < −6 to 2σ). We obtain excellent agreement between three independent retrieval codes, which find a sub-solar H2O abundance (log H2O ≈ −4.4 ± 0.3). However, the inferred CO2 abundance (log CO2 ≈ −4.8 ± 0.4) is significantly super-solar and requires further investigation into its origin. We also introduce new stellar heterogeneity considerations by fitting for the active regions' surface gravities – a proxy for the effects of magnetic pressure. Finally, we compare our JWST inferences to those from HST /WFC3 and Spitzer /IRAC. Our results highlight the exceptional promise of simultaneous planetary atmosphere and stellar heterogeneity constraints in the era of JWST and demonstrate that JWST transmission spectra may warrant more complex treatments of the transit light source effect. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
269. Constraining Exoplanet Metallicities and Aerosols with the Contribution to ARIEL Spectroscopy of Exoplanets (CASE)
- Author
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Zellem, Robert T., Swain, Mark R., Cowan, Nicolas B., Bryden, Geoffrey, Komacek, Thaddeus D., Colavita, Mark, Ardila, David, Roudier, Gael M., Fortney, Jonathan J., Bean, Jacob, Line, Michael R., Griffith, Caitlin A., Shkolnik, Evgenya L., Kreidberg, Laura, Moses, Julianne I., Showman, Adam P., Stevenson, Kevin B., Wong, Andre, Chapman, John W., Ciardi, David R., Howard, Andrew W., Kataria, Tiffany, Kempton, Eliza M.-R., Latham, David, Mahadevan, Suvrath, Meléndez, Jorge, and Parmentier, Vivien
- Abstract
Launching in 2028, ESA's 0.64 m2Atmospheric Remote-sensing Exoplanet Large-survey (ARIEL) survey of ?1000 transiting exoplanets will build on the legacies of NASA's Keplerand Transiting Exoplanet Survey Satellite(TESS), and complement theJames Webb Space Telescope (JWST) by placing its high-precision exoplanet observations into a large, statistically significant planetary population context. With continuous 0.5-7.8 ?m coverage from both FGS (0.5-0.6, 0.6-0.81, and 0.81-1.1 ?m photometry; 1.1-1.95 ?m spectroscopy) and AIRS (1.95-7.80 ?m spectroscopy), ARIEL will determine atmospheric compositions and probe planetary formation histories during its 3.5 yr mission. NASA's proposed Contribution to ARIEL Spectroscopy of Exoplanets (CASE) would be a subsystem of ARIEL's Fine Guidance Sensor (FGS) instrument consisting of two visible-to-infrared detectors, associated readout electronics, and thermal control hardware. FGS, to be built by the Polish Academy of Sciences Space Research Centre, will provide both fine guiding and visible to near-infrared photometry and spectroscopy, providing powerful diagnostics of atmospheric aerosol contribution and planetary albedo, which play a crucial role in establishing planetary energy balance. The CASE team presents here an independent study of the capabilities of ARIEL to measure exoplanetary metallicities, which probe the conditions of planet formation, and FGS to measure scattering spectral slopes, which indicate if an exoplanet has atmospheric aerosols (clouds and hazes), and geometric albedos, which help establish planetary climate. Our simulations assume that ARIEL's performance will be 1.3× the photon-noise limit. This value is motivated by current transiting exoplanet observations: Spitzer/IRAC and Hubble/WFC3 have empirically achieved 1.15× the photon-noise limit. One could expect similar performance from ARIEL, JWST, and other proposed future missions such as HabEx, LUVOIR, and Origins. Our design reference mission simulations show that ARIEL could measure the mass-metallicity relationship of its 1000-planet single-visit sample to >7.5?and that FGS could distinguish between clear, cloudy, and hazy skies and constrain an exoplanet's atmospheric aerosol composition to ?5?for hundreds of targets, providing statistically transformative science for exoplanet atmospheres.
- Published
- 2019
- Full Text
- View/download PDF
270. A Framework for Prioritizing the TESSPlanetary Candidates Most Amenable to Atmospheric Characterization
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Kempton, Eliza M.-R., Bean, Jacob L., Louie, Dana R., Deming, Drake, Koll, Daniel D. B., Mansfield, Megan, Christiansen, Jessie L., López-Morales, Mercedes, Swain, Mark R., Zellem, Robert T., Ballard, Sarah, Barclay, Thomas, Barstow, Joanna K., Batalha, Natasha E., Beatty, Thomas G., Berta-Thompson, Zach, Birkby, Jayne, Buchhave, Lars A., Charbonneau, David, Cowan, Nicolas B., Crossfield, Ian, Val-Borro, Miguel de, Doyon, René, Dragomir, Diana, Gaidos, Eric, Heng, Kevin, Hu, Renyu, Kane, Stephen R., Kreidberg, Laura, Mallonn, Matthias, Morley, Caroline V., Narita, Norio, Nascimbeni, Valerio, Pallé, Enric, Quintana, Elisa V., Rauscher, Emily, Seager, Sara, Shkolnik, Evgenya L., Sing, David K., Sozzetti, Alessandro, Stassun, Keivan G., Valenti, Jeff A., and Essen, Carolina von
- Abstract
A key legacy of the recently launched the Transiting Exoplanet Survey Satellite(TESS) mission will be to provide the astronomical community with many of the best transiting exoplanet targets for atmospheric characterization. However, time is of the essence to take full advantage of this opportunity. The James Webb Space Telescope(JWST), although delayed, will still complete its nominal five year mission on a timeline that motivates rapid identification, confirmation, and mass measurement of the top atmospheric characterization targets from TESS. Beyond JWST, future dedicated missions for atmospheric studies such as the Atmospheric Remote-sensing Infrared Exoplanet Large-survey(ARIEL) require the discovery and confirmation of several hundred additional sub-Jovian size planets (Rp< 10 R?) orbiting bright stars, beyond those known today, to ensure a successful statistical census of exoplanet atmospheres. Ground-based extremely large telescopes (ELTs) will also contribute to surveying the atmospheres of the transiting planets discovered by TESS. Here we present a set of two straightforward analytic metrics, quantifying the expected signal-to-noise in transmission and thermal emission spectroscopy for a given planet, that will allow the top atmospheric characterization targets to be readily identified among the TESSplanet candidates. Targets that meet our proposed threshold values for these metrics would be encouraged for rapid follow-up and confirmation via radial velocity mass measurements. Based on the catalog of simulated TESSdetections by Sullivan et al., we determine appropriate cutoff values of the metrics, such that the TESSmission will ultimately yield a sample of ?300 high-quality atmospheric characterization targets across a range of planet size bins, extending down to Earth-size, potentially habitable worlds.
- Published
- 2018
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271. Chasing rainbows and ocean glints: Inner working angle constraints for the Habitable Worlds Observatory.
- Author
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Vaughan, Sophia R, Gebhard, Timothy D, Bott, Kimberly, Casewell, Sarah L, Cowan, Nicolas B, Doelman, David S, Kenworthy, Matthew, Mazoyer, Johan, Millar-Blanchaer, Maxwell A, Trees, Victor J H, Stam, Daphne M, Absil, Olivier, Altinier, Lisa, Baudoz, Pierre, Belikov, Ruslan, Bidot, Alexis, Birkby, Jayne L, Bonse, Markus J, Brandl, Bernhard, and Carlotti, Alexis
- Subjects
- *
EARTH (Planet) , *RAINBOWS , *OBSERVATORIES , *RAYLEIGH scattering , *HABITABLE planets - Abstract
NASA is engaged in planning for a Habitable Worlds Observatory (HabWorlds ), a coronagraphic space mission to detect rocky planets in habitable zones and establish their habitability. Surface liquid water is central to the definition of planetary habitability. Photometric and polarimetric phase curves of starlight reflected by an exoplanet can reveal ocean glint, rainbows, and other phenomena caused by scattering by clouds or atmospheric gas. Direct imaging missions are optimized for planets near quadrature, but HabWorlds ' coronagraph may obscure the phase angles where such optical features are strongest. The range of accessible phase angles for a given exoplanet will depend on the planet's orbital inclination and/or the coronagraph's inner working angle (IWA). We use a recently created catalog relevant to HabWorlds of 164 stars to estimate the number of exo-Earths that could be searched for ocean glint, rainbows, and polarization effects due to Rayleigh scattering. We find that the polarimetric Rayleigh scattering peak is accessible in most of the exo-Earth planetary systems. The rainbow due to water clouds at phase angles of ∼20○ − 60○ would be accessible with HabWorlds for a planet with an Earth equivalent instellation in ∼46 systems, while the ocean glint signature at phase angles of ∼130○ − 170○ would be accessible in ∼16 systems, assuming an IWA = 62 mas (3λ/ D). Improving the IWA = 41 mas (2λ/ D) increases accessibility to rainbows and glints by factors of approximately 2 and 3, respectively. By observing these scattering features, HabWorlds could detect a surface ocean and water cycle, key indicators of habitability. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
272. Awesome SOSS: transmission spectroscopy of WASP-96b with NIRISS/SOSS.
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Radica, Michael, Welbanks, Luis, Espinoza, Néstor, Taylor, Jake, Coulombe, Louis-Philippe, Feinstein, Adina D, Goyal, Jayesh, Scarsdale, Nicholas, Albert, Loïc, Baghel, Priyanka, Bean, Jacob L, Blecic, Jasmina, Lafrenière, David, MacDonald, Ryan J, Zamyatina, Maria, Allart1, Romain, Artigau, Étienne, Batalha, Natasha E, Cook, Neil James, and Cowan, Nicolas B
- Subjects
- *
SPECTROMETRY , *RAYLEIGH scattering , *ATMOSPHERIC models , *NATURAL satellite atmospheres , *DATA reduction , *NATURAL satellites - Abstract
The future is now – after its long-awaited launch in 2021 December, JWST began science operations in 2022 July and is already revolutionizing exoplanet astronomy. The Early Release Observations (ERO) programme was designed to provide the first images and spectra from JWST , covering a multitude of science cases and using multiple modes of each on-board instrument. Here, we present transmission spectroscopy observations of the hot-Saturn WASP-96 b with the Single Object Slitless Spectroscopy (SOSS) mode of the Near Infrared Imager and Slitless Spectrograph, observed as part of the ERO programme. As the SOSS mode presents some unique data reduction challenges, we provide an in-depth walk-through of the major steps necessary for the reduction of SOSS data: including background subtraction, correction of 1/ f noise, and treatment of the trace order overlap. We furthermore offer potential routes to correct for field star contamination, which can occur due to the SOSS mode's slitless nature. By comparing our extracted transmission spectrum with grids of atmosphere models, we find an atmosphere metallicity between 1× and 5× solar, and a solar carbon-to-oxygen ratio. Moreover, our models indicate that no grey cloud deck is required to fit WASP-96 b's transmission spectrum, but find evidence for a slope shortward of 0.9 μm, which could either be caused by enhanced Rayleigh scattering or the red wing of a pressure-broadened Na feature. Our work demonstrates the unique capabilities of the SOSS mode for exoplanet transmission spectroscopy and presents a step-by-step reduction guide for this new and exciting instrument. [ABSTRACT FROM AUTHOR]
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- 2023
- Full Text
- View/download PDF
273. Transiting Exoplanet Studies and Community Targets for JWST's Early Release Science Program
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Stevenson, Kevin B., Lewis, Nikole K., Bean, Jacob L., Beichman, Charles, Fraine, Jonathan, Kilpatrick, Brian M., Krick, J. E., Lothringer, Joshua D., Mandell, Avi M., Valenti, Jeff A., Agol, Eric, Angerhausen, Daniel, Barstow, Joanna K., Birkmann, Stephan M., Burrows, Adam, Charbonneau, David, Cowan, Nicolas B., Crouzet, Nicolas, Cubillos, Patricio E., Curry, S. M., Dalba, Paul A., de Wit, Julien, Deming, Drake, Désert, Jean-Michel, Doyon, René, Dragomir, Diana, Ehrenreich, David, Fortney, Jonathan J., García Muñoz, Antonio, Gibson, Neale P., Gizis, John E., Greene, Thomas P., Harrington, Joseph, Heng, Kevin, Kataria, Tiffany, Kempton, Eliza M.-R., Knutson, Heather, Kreidberg, Laura, Lafrenière, David, Lagage, Pierre-Olivier, Line, Michael R., Lopez-Morales, Mercedes, Madhusudhan, Nikku, Morley, Caroline V., Rocchetto, Marco, Schlawin, Everett, Shkolnik, Evgenya L., Shporer, Avi, Sing, David K., Todorov, Kamen O., Tucker, Gregory S., and Wakeford, Hannah R.
- Abstract
The James Webb Space Telescope (JWST)will likely revolutionize transiting exoplanet atmospheric science, due to a combination of its capability for continuous, long duration observations and its larger collecting area, spectral coverage, and spectral resolution compared to existing space-based facilities. However, it is unclear precisely how well JWSTwill perform and which of its myriad instruments and observing modes will be best suited for transiting exoplanet studies. In this article, we describe a prefatory JWSTEarly Release Science (ERS) Cycle 1 program that focuses on testing specific observing modes to quickly give the community the data and experience it needs to plan more efficient and successful transiting exoplanet characterization programs in later cycles. We propose a multi-pronged approach wherein one aspect of the program focuses on observing transits of a single target with all of the recommended observing modes to identify and understand potential systematics, compare transmission spectra at overlapping and neighboring wavelength regions, confirm throughputs, and determine overall performances. In our search for transiting exoplanets that are well suited to achieving these goals, we identify 12 objects (dubbed "community targets") that meet our defined criteria. Currently, the most favorable target is WASP-62b because of its large predicted signal size, relatively bright host star, and location in JWST's continuous viewing zone. Since most of the community targets do not have well-characterized atmospheres, we recommend initiating preparatory observing programs to determine the presence of obscuring clouds/hazes within their atmospheres. Measurable spectroscopic features are needed to establish the optimal resolution and wavelength regions for exoplanet characterization. Other initiatives from our proposed ERS program include testing the instrument brightness limits and performing phase-curve observations. The latter are a unique challenge compared to transit observations because of their significantly longer durations. Using only a single mode, we propose to observe a full-orbit phase curve of one of the previously characterized, short-orbital-period planets to evaluate the facility-level aspects of long, uninterrupted time-series observations.
- Published
- 2016
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274. SECONDARY ECLIPSE PHOTOMETRY OF WASP-4b WITH WARM SPITZER.
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Beerer, Ingrid M., Knutson, Heather A., Burrows, Adam, Fortney, Jonathan J., Agol, Eric, Charbonneau, David, Cowan, Nicolas B., Deming, Drake, Desert, Jean-Michel, Langton, Jonathan, Laughlin, Gregory, Lewis, Nikole K., and Showman, Adam P.
- Published
- 2011
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275. WARM SPITZER PHOTOMETRY OF THE TRANSITING EXOPLANETS CoRoT-1 AND CoRoT-2 AT SECONDARY ECLIPSE.
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Deming, Drake, Knutson, Heather, Agol, Eric, Desert, Jean-Michel, Burrows, Adam, Fortney, Jonathan J., Charbonneau, David, Cowan, Nicolas B., Laughlin, Gregory, Langton, Jonathan, Showman, Adam P., and Lewis, Nikole K.
- Published
- 2011
- Full Text
- View/download PDF
276. A MODEL FOR THERMAL PHASE VARIATIONS OF CIRCULAR AND ECCENTRIC EXOPLANETS.
- Author
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Cowan, Nicolas B. and Agol, Eric
- Published
- 2011
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277. A survey of exoplanet phase curves with Ariel.
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Charnay, Benjamin, Mendonça, João M., Kreidberg, Laura, Cowan, Nicolas B., Taylor, Jake, Bell, Taylor J., Demangeon, Olivier, Edwards, Billy, Haswell, Carole A., Morello, Giuseppe, Mugnai, Lorenzo V., Pascale, Enzo, Tinetti, Giovanna, Tremblin, Pascal, and Zellem, Robert T.
- Subjects
- *
ATMOSPHERIC circulation , *STATISTICAL sampling , *EXTRASOLAR planets - Abstract
The ESA-Ariel mission will include a tier dedicated to exoplanet phase curves corresponding to ∼ 10 % of the science time. We present here the current observing strategy for studying exoplanet phase curves with Ariel. We define science questions, requirements and a list of potential targets. We also estimate the precision of phase curve reconstruction and atmospheric retrieval using simulated phase curves. Based on this work, we found that full-orbit phase variations for 35-40 exoplanets could be observed during the 3.5-yr mission. This statistical sample would provide key constraints on atmospheric dynamics, composition, thermal structure and clouds of warm exoplanets, complementary to the scientific yield from spectroscopic transits/eclipses measurements. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
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