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Primary Velocity and Orbital Phase Effects on Planetary Detectability from Small Epoch Number Data Sets

Buzard, Cam and Pelletier, Stefan and Piskorz, Danielle and Benneke, Björn and Blake, Geoffrey A. (2021) Primary Velocity and Orbital Phase Effects on Planetary Detectability from Small Epoch Number Data Sets. Astronomical Journal, 162 (1). Art. No. 26. ISSN 0004-6256. doi:10.3847/1538-3881/abf7b9.

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Cross-correlation analyses of high-resolution spectroscopic data have recently shown great success in directly detecting planetary signals and enabling the characterization of their atmospheres. One such technique aims to observe a system at multiple epochs and combine the measured planetary radial velocities from each epoch into a measurement of the planetary Keplerian orbital velocity K_p, constituting a direct detection of the planetary signal. Recent work has shown that in few-epoch (~5) data sets, unintended structure can arise at a high level, obscuring the planetary detection. In this work, we look to simulations to examine whether there are ways to reduce this structured noise in few-epoch data sets by careful planning of observations. The choice of observation date allows observers to select the primary (stellar) velocity through a set systemic velocity and chosen barycentric velocity and the planetary orbital phase so we focus on the effects of these two parameters. We find that epochs taken when the primary velocity is near zero and the stellar lines remain relatively fixed to the telluric rest-frame greatly reduce the level of structured noise and allow for much stronger planetary detections, on average more than twice the significance of detections made with epochs using randomly selected primary velocities. Following these results, we recommend that observers looking to build up high-resolution multi-epoch data sets target nights when their system has a near-zero primary velocity.

Item Type:Article
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URLURL TypeDescription Paper
Buzard, Cam0000-0002-9943-6124
Pelletier, Stefan0000-0002-8573-805X
Piskorz, Danielle0000-0003-4451-2342
Benneke, Björn0000-0001-5578-1498
Blake, Geoffrey A.0000-0003-0787-1610
Additional Information:© 2021. The Author(s). Published by the American Astronomical Society. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. Received 2021 January 21; revised 2021 April 2; accepted 2021 April 12; published 2021 June 22. 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. The data presented herein were 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. This work has made use of data from the European Space Agency (ESA) mission Gaia (, processed by the Gaia Data Processing and Analysis Consortium (DPAC, Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement. This work was partially supported by funding from the NASA Exoplanet Research Program (grant NNX16AI14G, G.A. Blake P.I.). Finally, we would like to thank an anonymous reviewer who pointed us in interesting new directions and by doing so improved the content of this paper.
Funding AgencyGrant Number
W. M. Keck FoundationUNSPECIFIED
Gaia Multilateral AgreementUNSPECIFIED
Subject Keywords:Exoplanet atmospheres; Radial velocity; High resolution spectroscopy
Issue or Number:1
Classification Code:Unified Astronomy Thesaurus concepts: Exoplanet atmospheres (487); Radial velocity (1332); High resolution spectroscopy (2096)
Record Number:CaltechAUTHORS:20210626-225301508
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Official Citation:Cam Buzard et al 2021 AJ 162 26
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:109618
Deposited By: George Porter
Deposited On:28 Jun 2021 20:42
Last Modified:16 Nov 2021 19:37

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