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Register a new userFirst exoplanet transit observation with the Stratospheric Observatory for Infrared Astronomy: Confirmation of Rayleigh scattering in HD 189733 b with HIPO
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Here we report on the first successful exoplanet transit observation with the Stratospheric Observatory for Infrared Astronomy (SOFIA). We observed a single transit of the hot Jupiter HD 189733 b, obtaining two simultaneous primary transit lightcurves in the B and z bands as a demonstration of SOFIAs capability to perform absolute transit photometry. We present a detailed description of our data reduction, in particular the correlation of photometric systematics with various in-flight parameters unique to the airborne observing environment. The derived transit depths at B and z wavelengths confirm a previously reported slope in the optical transmission spectrum of HD 189733 b. Our results give new insights to the current discussion about the source of this Rayleigh scattering in the upper atmosphere and the question of fixed limb darkening coefficients in fitting routines.
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The Stratospheric Observatory for Infrared Astronomy (SOFIA) is an airborne observatory consisting of a specially modified Boeing 747SP with a 2.7-m telescope, flying at altitudes as high as 13.7 km (45,000 ft). Designed to observe at wavelengths from 0.3 micron to 1.6 mm, SOFIA operates above 99.8 % of the water vapor that obscures much of the infrared and submillimeter. SOFIA has seven science instruments under development, including an occultation photometer, near-, mid-, and far-infrared cameras, infrared spectrometers, and heterodyne receivers. SOFIA, a joint project between NASA and the German Aerospace Center DLR, began initial science flights in 2010 December, and has conducted 30 science flights in the subsequent year. During this early science period three instruments have flown: the mid-infrared camera FORCAST, the heterodyne spectrometer GREAT, and the occultation photometer HIPO. This article provides an overview of the observatory and its early performance.
HD 95086 is an intermediate-mass debris-disk-bearing star. VLT/NaCo $3.8 mu m$ observations revealed it hosts a $5pm2 mathrm{M}_{Jup}$ companion (HD 95086 b) at $simeq 56$ AU. Follow-up observations at 1.66 and 2.18 $mu m$ yielded a null detection, suggesting extremely red colors for the planet and the need for deeper direct-imaging data. In this Letter, we report H- ($1.7 mu m$) and $mathrm{K}_1$- ($2.05 mu m$) band detections of HD 95086 b from Gemini Planet Imager (GPI) commissioning observations taken by the GPI team. The planet position in both spectral channels is consistent with the NaCo measurements and we confirm it to be comoving. Our photometry yields colors of H-L= $3.6pm 1.0$ mag and K$_1$-L=$2.4pm 0.7$ mag, consistent with previously reported 5-$sigma$ upper limits in H and Ks. The photometry of HD 95086 b best matches that of 2M 1207 b and HR 8799 cde. Comparing its spectral energy distribution with the BT-SETTL and LESIA planet atmospheric models yields T$_{mathrm{eff}}sim$600-1500 K and log g$sim$2.1-4.5. Hot-start evolutionary models yield M=$5pm2$ M$_{Jup}$. Warm-start models reproduce the combined absolute fluxes of the object for M=4-14 M$_{Jup}$ for a wide range of plausible initial conditions (S$_{init}$=8-13 k$_{B}$/baryon). The color-magnitude diagram location of HD 95086 b and its estimated T$_{mathrm{eff}}$ and log g suggest that the planet is a peculiar L-T transition object with an enhanced amount of photospheric dust.
An updated Science Vision for the SOFIA project is presented, including an overview of the characteristics and capabilities of the observatory and first generation instruments. A primary focus is placed on four science themes: The Formation of Stars and Planets, The Interstellar Medium of the Milky Way, Galaxies and the Galactic Center and Planetary Science.
Multi-wavelength imaging polarimetry at far-infrared wavelengths has proven to be an excellent tool for studying the physical properties of dust, molecular clouds, and magnetic fields in the interstellar medium. Although these wavelengths are only observable from airborne or space-based platforms, no first-generation instrument for the Stratospheric Observatory for Infrared Astronomy (SOFIA) is presently designed with polarimetric capabilities. We study several options for upgrading the High-resolution Airborne Wideband Camera (HAWC) to a sensitive FIR polarimeter. HAWC is a 12 x 32 pixel bolometer camera designed to cover the 53 - 215 micron spectral range in 4 colors, all at diffraction-limited resolution (5 - 21 arcsec). Upgrade options include: (1) an external set of optics which modulates the polarization state of the incoming radiation before entering the cryostat window; (2) internal polarizing optics; and (3) a replacement of the current detector array with two state-of-the-art superconducting bolometer arrays, an upgrade of the HAWC camera as well as polarimeter. We discuss a range of science studies which will be possible with these upgrades including magnetic fields in star-forming regions and galaxies and the wavelength-dependence of polarization.
Giant exoplanets orbiting very close to their parent star (hot Jupiters) are subject to tidal forces expected to synchronize their rotational and orbital periods on short timescales (tidal locking). However, spin rotation has never been measured directly for hot Jupiters. Furthermore, their atmospheres can show equatorial super-rotation via strong eastward jet streams, and/or high-altitude winds flowing from the day- to the night-side hemisphere. Planet rotation and atmospheric circulation broaden and distort the planet spectral lines to an extent that is detectable with measurements at high spectral resolution. We observed a transit of the hot Jupiter HD 189733 b around 2.3 {mu}m and at a spectral resolution of R~10$^5$ with CRIRES at the ESO Very Large Telescope. After correcting for the stellar absorption lines and their distortion during transit (the Rossiter-McLaughlin effect), we detect the absorption of carbon monoxide and water vapor in the planet transmission spectrum by cross-correlating with model spectra. The signal is maximized (7.6{sigma}) for a planet rotational velocity of $(3.4^{+1.3}_{-2.1})$ km/s, corresponding to a rotational period of $(1.7^{+2.9}_{-0.4})$ days. This is consistent with the planet orbital period of 2.2 days and therefore with tidal locking. We find that the rotation of HD 189733 b is longer than 1 day (3{sigma}). The data only marginally (1.5{sigma}) prefer models with rotation versus models without rotation. We measure a small day- to night-side wind speed of $(-1.7^{+1.1}_{-1.2})$ km/s. Compared to the recent detection of sodium blue-shifted by (8$pm$2) km/s, this likely implies a strong vertical wind shear between the pressures probed by near-infrared and optical transmission spectroscopy.
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