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Physical Parameters of the Multiplanet Systems HD 106315 and GJ 9827

Kosiarek, Molly R. and Berardo, David A. and Crossfield, Ian J. M. and Laguna, Cesar and Murphy, Joseph M. Akana and Howell, Steve B. and Henry, Gregory W. and Isaacson, Howard and Weiss, Lauren M. and Petigura, Erik A. and Fulton, Benjamin and Behmard, Aida and Hirsch, Lea A. and Teske, Johanna and Burt, Jennifer A. and Mills, Sean M. and Chontos, Ashley and Mocnik, Teo and Howard, Andrew W. and Werner, Michael and Livingston, John H. and Krick, Jessica and Beichman, Charles and Gorjian, Varoujan and Kreidberg, Laura and Morley, Caroline and Christiansen, Jessie L. and Morales, Farisa Y. and Scott, Nicholas J. and Crane, Jeffrey D. and Rosenthal, Lee J. and Grunblatt, Samuel K. and Rubenzahl, Ryan A. and Dalba, Paul A. and Giacalone, Steven and Villanueva, Chiara Dane and Liu, Qingtian and Dai, Fei and Hill, Michelle L. and Rice, Malena and Kane, Stephen R. and Mayo, Andrew W. (2021) Physical Parameters of the Multiplanet Systems HD 106315 and GJ 9827. Astronomical Journal, 161 (1). Art. No. 147. ISSN 1538-3881. doi:10.3847/1538-3881/abca39.

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HD 106315 and GJ 9827 are two bright, nearby stars that host multiple super-Earths and sub-Neptunes discovered by K2 that are well suited for atmospheric characterization. We refined the planets' ephemerides through Spitzer transits, enabling accurate transit prediction required for future atmospheric characterization through transmission spectroscopy. Through a multiyear high-cadence observing campaign with Keck/High Resolution Echelle Spectrometer and Magellan/Planet Finder Spectrograph, we improved the planets' mass measurements in anticipation of Hubble Space Telescope transmission spectroscopy. For GJ 9827, we modeled activity-induced radial velocity signals with a Gaussian process informed by the Calcium II H&K lines in order to more accurately model the effect of stellar noise on our data. We measured planet masses of M_b = 4.87 ± 0.37 M_⊕, M_c = 1.92 ± 0.49 M_⊕, and M_d = 3.42 ± 0.62 M_⊕. For HD 106315, we found that such activity radial velocity decorrelation was not effective due to the reduced presence of spots and speculate that this may extend to other hot stars as well (T_(eff) > 6200 K). We measured planet masses of M_b = 10.5 ± 3.1 M_⊕ and M_c = 12.0 ± 3.8 M_⊕. We investigated all of the planets' compositions through comparison of their masses and radii to a range of interior models. GJ 9827 b and GJ 9827 c are both consistent with a 50/50 rock-iron composition, GJ 9827 d and HD 106315 b both require additional volatiles and are consistent with moderate amounts of water or hydrogen/helium, and HD 106315 c is consistent with a ~10% hydrogen/helium envelope surrounding an Earth-like rock and iron core.

Item Type:Article
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URLURL TypeDescription Paper
Kosiarek, Molly R.0000-0002-6115-4359
Berardo, David A.0000-0001-6298-412X
Crossfield, Ian J. M.0000-0002-1835-1891
Laguna, Cesar0000-0003-1314-7514
Murphy, Joseph M. Akana0000-0001-8898-8284
Howell, Steve B.0000-0002-2532-2853
Henry, Gregory W.0000-0003-4155-8513
Isaacson, Howard0000-0002-0531-1073
Weiss, Lauren M.0000-0002-3725-3058
Petigura, Erik A.0000-0003-0967-2893
Fulton, Benjamin0000-0003-3504-5316
Behmard, Aida0000-0003-0012-9093
Hirsch, Lea A.0000-0001-8058-7443
Burt, Jennifer A.0000-0002-0040-6815
Mills, Sean M.0000-0002-4535-6241
Chontos, Ashley0000-0003-1125-2564
Mocnik, Teo0000-0003-4603-556X
Howard, Andrew W.0000-0001-8638-0320
Livingston, John H.0000-0002-4881-3620
Krick, Jessica0000-0002-2413-5976
Beichman, Charles0000-0002-5627-5471
Gorjian, Varoujan0000-0002-8990-2101
Kreidberg, Laura0000-0003-0514-1147
Morley, Caroline0000-0002-4404-0456
Christiansen, Jessie L.0000-0002-8035-4778
Morales, Farisa Y.0000-0001-9414-3851
Scott, Nicholas J.0000-0003-1038-9702
Crane, Jeffrey D.0000-0002-5226-787X
Rosenthal, Lee J.0000-0001-8391-5182
Grunblatt, Samuel K.0000-0003-4976-9980
Rubenzahl, Ryan A.0000-0003-3856-3143
Dalba, Paul A.0000-0002-4297-5506
Giacalone, Steven0000-0002-8965-3969
Dai, Fei0000-0002-8958-0683
Hill, Michelle L.0000-0002-0139-4756
Rice, Malena0000-0002-7670-670X
Kane, Stephen R.0000-0002-7084-0529
Mayo, Andrew W.0000-0002-7216-2135
Alternate Title:Physical Parameters of the Multi-Planet Systems HD 106315 and GJ 9827
Additional Information:© 2020 The American Astronomical Society. Received 2020 September 7; revised 2020 November 9; accepted 2020 November 11; published 2020 December 31. Based on observations obtained at the W. M. Keck Observatory, which is operated jointly by the University of California and the California Institute of Technology. This paper includes data gathered with the 6.5 meter Magellan Telescopes located at Las Campanas Observatory, Chile. We thank the anonymous reviewer for their time and helpful comments. M.R.K is supported by the NSF Graduate Research Fellowship, grant No. DGE 1339067. C.P. is supported by the Technologies for Exo-Planetary Science (TEPS) CREATE program and further acknowledges financial support by the Fonds de Recherche QuébécoisNature et Technologie (FRQNT; Québec). G.W.H. acknowledges long-term support from NASA, NSF, Tennessee State University, and the State of Tennessee through its Centers of Excellence program. L.M.W. is supported by the Beatrice Watson Parrent Fellowship and NASA ADAP grant 80NSSC19K0597. P.D. acknowledges support from a National Science Foundation Astronomy and Astrophysics Postdoctoral Fellowship under award AST-1903811. J.M.A.M. gratefully acknowledges support from the National Science Foundation Graduate Research Fellowship Program under grant No. DGE-1842400. J.M.A.M. also thanks the LSSTC Data Science Fellowship Program, which is funded by LSSTC, NSF Cybertraining grant No. 1829740, the Brinson Foundation, and the Moore Foundation; his participation in the program has benefited this work. 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. Some of the observations in the paper made use of the High-Resolution Imaging instrument Zorro. Zorro was funded by the NASA Exoplanet Exploration Program and built at the NASA Ames Research Center by Steve B. Howell, Nic Scott, Elliott P. Horch, and Emmett Quigley. Zorro is mounted on the Gemini South telescope of the international Gemini Observatory, a program of NSFs OIR Lab, which is managed by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with the National Science Foundation. This work is based in part on observations made with the Spitzer Space Telescope, which was operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA. Support for this work was provided by NASA through an award issued by JPL/Caltech. This research has made use of the Exoplanet Follow-up Observing Program (ExoFOP), which is operated by the California Institute of Technology, under contract with the National Aeronautics and Space Administration. Part of the research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration (80NM0018D0004). 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. Facilities: Keck:I(HIRES) - KECK I Telescope, Magellan:Clay(PFS) - Magellan II Landon Clay Telescope, Spitzer - Spitzer Space Telescope satellite, APF - , TSU:AIT - , Gemini:South(Zorro). - Software: radvel (Fulton et al. 2018), batman (Kreidberg 2015), SpecMatch-Emp (Yee et al. 2017), isoclassify (Huber et al. 2017), spock (Tamayo et al. 2020), rebound (Rein & Liu 2011), numpy (van der Walt et al. 2011), astropy (Astropy Collaboration et al. 2013), emcee (Foreman-Mackey et al. 2013).
Group:Astronomy Department, Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
NSF Graduate Research FellowshipDGE-1339067
Technologies for Exo-Planetary Science (TEPS)UNSPECIFIED
Fonds de recherche du Québec – Nature et technologies (FRQNT)UNSPECIFIED
Tennessee State UniversityUNSPECIFIED
State of Tennessee Centers of Excellence programUNSPECIFIED
Beatrice Watson Parrent FellowshipUNSPECIFIED
NSF Astronomy and Astrophysics FellowshipAST-1903811
NSF Graduate Research FellowshipDGE-1842400
LSSTC Institutional MembersUNSPECIFIED
Brinson FoundationUNSPECIFIED
Gordon and Betty Moore FoundationUNSPECIFIED
Gaia Multilateral AgreementUNSPECIFIED
Subject Keywords:Radial velocity ; Exoplanets ; Mini Neptunes ; Transit photometry ; Gaussian Processes regression ; Super Earths
Issue or Number:1
Classification Code:Unified Astronomy Thesaurus concepts: Radial velocity (1332); Exoplanets (498); Mini Neptunes (1063); Transit photometry (1709); Gaussian Processes regression (1930); Super Earths (1655)
Record Number:CaltechAUTHORS:20200916-112905779
Persistent URL:
Official Citation:Molly R. Kosiarek et al 2021 AJ 161 47
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:105416
Deposited By: George Porter
Deposited On:24 Sep 2020 18:55
Last Modified:16 Nov 2021 18:42

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