EVIDENCE FOR THE DIRECT DETECTION OF THE THERMAL SPECTRUM OF THE NON-TRANSITING HOT GAS GIANT HD 88133 b

Abstract

We target the thermal emission spectrum of the non-transiting gas giant HD 88133 b with high-resolution nearinfrared spectroscopy, by treating the planet and its host star as a spectroscopic binary. For sufficiently deep summed flux observations of the star and planet across multiple epochs, it is possible to resolve the signal of the hot gas giant's atmosphere compared to the brighter stellar spectrum, at a level consistent with the aggregate shot noise of the full data set. To do this, we first perform a principal component analysis to remove the contribution of the Earth's atmosphere to the observed spectra. Then, we use a cross-correlation analysis to tease out the spectra of the host star and HD 88133 b to determine its orbit and identify key sources of atmospheric opacity. In total, six epochs of Keck NIRSPEC L-band observations and three epochs of Keck NIRSPEC K-band observations of the HD 88133 system were obtained. Based on an analysis of the maximum likelihood curves calculated from the multi-epoch cross-correlation of the full data set with two atmospheric models, we report the direct detection of the emission spectrum of the non-transiting exoplanet HD 88133 b and measure a radial projection of the Keplerian orbital velocity of 40±15 km s , and an atmosphere opacity structure at high dispersion dominated by water vapor. This, combined with 11 years of radial velocity measurements of the system, provides the most up-to-date ephemeris for HD 88133.

Detection of Water Vapor in the Thermal Spectrum of the Non-transiting Hot Jupiter Upsilon Andromedae b

“…As in Piskorz et al (2016), all but about 0.1% of the variance in each night's data set is encapsulated by the first principal component. The following results are roughly consistent for data sets with more than the first principal component removed.…”

“…As in Piskorz et al (2016), at this step, we eliminate the K r and K l band orders ranging from 2.3 to 2.4 μm from the analysis since there is high correlation between the stellar and planetary models themselves at these wavelengths. This means we remove any signal from carbon monoxide, and the dominant molecule in the planetary model in the remaining wavelengths is water vapor.…”

“…Analagous to Piskorz et al (2016), we produce a "shuffled" planetary model by randomly rearranging chunks of the planetary model. Cross-correlating our data with a shuffled model should show no peak near 55kms −1 if the planet truly exists with a line-of-sight orbital velocity of 55kms −1 .…”

Time-resolved High Spectral Resolution Observation of 2MASSW J0746425+200032AB

“…We reduced raw data from NIRSEPC using two packages, the IDL-based REDSPEC (Kim et al 2015;Prato et al 2015) and the Python-based PyNIRSPEC (Boogert et al 2002;Piskorz et al 2016). We compared results from the two packages and concluded that the final, calibrated 1-d spectra are similar within measurement uncertainties.…”

Doppler tomography as a tool for detecting exoplanet atmospheres

“…This was followed by the detection of CO molecular absorption from the dayside of the non-transiting hot-Jupiter τ Boo b by both Brogi et al (2012) and Rodler et al (2012) (with water vapour later found for the same planet by Lockwood et al 2014). Since these discoveries, additional detections (including for other molecular species such H 2 O and TiO) have also been reported for 51 Peg b Birkby et al 2017), HD189733b (de Kok et al 2013Birkby et al 2013;Brogi et al 2016;Brogi et al 2018), HD179949b (Brogi et al 2014), upsilon Andromedae b (Piskorz et al 2017), HD88133b (Piskorz et al 2016), and WASP-33b (Nugroho et al 2017).…”