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Contrast and Temperature Dependence of Multi-epoch High-resolution Cross-correlation Exoplanet Spectroscopy

Finnerty, Luke and Buzard, Cam and Pelletier, Stefan and Piskorz, Danielle and Lockwood, Alexandra C. and Bender, Chad F. and Benneke, Björn and Blake, Geoffrey A. (2021) Contrast and Temperature Dependence of Multi-epoch High-resolution Cross-correlation Exoplanet Spectroscopy. Astronomical Journal, 161 (3). Art. No. 104. ISSN 1538-3881. doi:10.3847/1538-3881/abd6ec.

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While high-resolution cross-correlation spectroscopy (HRCCS) techniques have proven effective at characterizing the atmospheres of transiting and nontransiting hot Jupiters, the limitations of these techniques are not well understood. We present a series of simulations of one HRCCS technique, which combines the cross-correlation functions from multiple epochs, to place temperature and contrast limits on the accessible exoplanet population for the first time. We find that planets approximately Saturn-sized and larger within ~0.2 au of a Sun-like star are likely to be detectable with current instrumentation in the L band, a significant expansion compared with the previously studied population. Cooler (T_(eq) ≤ 1000 K) exoplanets are more detectable than suggested by their photometric contrast alone as a result of chemical changes that increase spectroscopic contrast. The L-band CH₄ spectrum of cooler exoplanets enables robust constraints on the atmospheric C/O ratio at T_(eq) ~ 900 K, which have proven difficult to obtain for hot Jupiters. These results suggest that the multi-epoch approach to HRCCS can detect and characterize exoplanet atmospheres throughout the inner regions of Sun-like systems with existing high-resolution spectrographs. We find that many epochs of modest signal-to-noise ratio (S/N_(epoch) ~ 1500) yield the clearest detections and constraints on C/O, emphasizing the need for high-precision near-infrared telluric correction with short integration times.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Finnerty, Luke0000-0002-1392-0768
Buzard, Cam0000-0002-9943-6124
Pelletier, Stefan0000-0002-8573-805X
Piskorz, Danielle0000-0003-4451-2342
Bender, Chad F.0000-0003-4384-7220
Benneke, Björn0000-0001-5578-1498
Blake, Geoffrey A.0000-0003-0787-1610
Additional Information:© 2021 The American Astronomical Society. Received 2020 August 23; revised 2020 December 15; accepted 2020 December 26; published 2021 February 4. We thank the anonymous reviewer for their helpful suggestions to improve this paper. The simulations presented herein made use of data obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. This work was partially supported by funding from the NASA Exoplanet Research Program (grant NNX16AI14G, G.A. Blake P.I.). L.F. acknowledges the support of the Lynne Booth and Kent Kresa SURF fellowship. S.P. acknowledges funding from the Technologies for Exo-Planetary Science (TEPS) CREATE program. B.B. acknowledges financial support from the Natural Sciences and Engineering Research Council (NSERC) of Canada and the Fond de Recherche Québécois-Nature et Technologie (FRQNT; Québec). Facility: Keck:II (NIRSPEC). - Software: astropy (Astropy Collaboration et al. 2013, 2018).
Funding AgencyGrant Number
W. M. Keck FoundationUNSPECIFIED
Caltech Summer Undergraduate Research Fellowship (SURF)UNSPECIFIED
Technologies for Exo-Planetary Science (TEPS)UNSPECIFIED
Natural Sciences and Engineering Research Council of Canada (NSERC)UNSPECIFIED
Fonds de recherche du Québec - Nature et technologies (FRQNT)UNSPECIFIED
Subject Keywords:Exoplanet atmospheres ; Exoplanet detection methods ; Hot Jupiters
Issue or Number:3
Classification Code:Unified Astronomy Thesaurus concepts: Exoplanet atmospheres (487); Exoplanet detection methods (489); Hot Jupiters (753)
Record Number:CaltechAUTHORS:20210107-134620839
Persistent URL:
Official Citation:Luke Finnerty et al 2021 AJ 161 104
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:107369
Deposited By: Tony Diaz
Deposited On:08 Jan 2021 19:21
Last Modified:16 Nov 2021 19:02

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