Characterizing K2 Candidate Planetary Systems Orbiting Low-mass Stars. III. A High Mass and Low Envelope Fraction for the Warm Neptune K2-55b
K2-55b is a Neptune-sized planet orbiting a K7 dwarf with a radius of 0.715[subscript -0.040][superscript +0.043]R[subscript ⊙], a mass of 0.688 ± 0.069 M[subscript ⊙], and an effective temperature of 4300[subscript -100][superscript +107] K. Having characterized the host star using near-infrared sp...
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| Format: | Article |
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American Astronomical Society
2019
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| Online Access: | https://hdl.handle.net/1721.1/121204 |
| _version_ | 1826189991591542784 |
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| author | Dressing, Courtney D. Sinukoff, Evan Fulton, Benjamin J. Lopez, Eric D. Beichman, Charles A. Howard, Andrew W. Knutson, Heather A. Werner, Michael Benneke, Björn Crossfield, Ian Jm Isaacson, Howard Krick, Jessica Gorjian, Varoujan Livingston, John Petigura, Erik A. Schlieder, Joshua E. Akeson, Rachel L. Batygin, Konstantin Christiansen, Jessie L. Ciardi, David R. Crepp, Justin R. Gonzales, Erica J. Hardegree-Ullman, Kevin Hirsch, Lea A. Kosiarek, Molly Weiss, Lauren M. |
| author2 | Massachusetts Institute of Technology. Department of Physics |
| author_facet | Massachusetts Institute of Technology. Department of Physics Dressing, Courtney D. Sinukoff, Evan Fulton, Benjamin J. Lopez, Eric D. Beichman, Charles A. Howard, Andrew W. Knutson, Heather A. Werner, Michael Benneke, Björn Crossfield, Ian Jm Isaacson, Howard Krick, Jessica Gorjian, Varoujan Livingston, John Petigura, Erik A. Schlieder, Joshua E. Akeson, Rachel L. Batygin, Konstantin Christiansen, Jessie L. Ciardi, David R. Crepp, Justin R. Gonzales, Erica J. Hardegree-Ullman, Kevin Hirsch, Lea A. Kosiarek, Molly Weiss, Lauren M. |
| author_sort | Dressing, Courtney D. |
| collection | MIT |
| description | K2-55b is a Neptune-sized planet orbiting a K7 dwarf with a radius of 0.715[subscript -0.040][superscript +0.043]R[subscript ⊙], a mass of 0.688 ± 0.069 M[subscript ⊙], and an effective temperature of 4300[subscript -100][superscript +107] K. Having characterized the host star using near-infrared spectra obtained at IRTF/SpeX, we observed a transit of K2-55b with Spitzer/Infrared Array Camera (IRAC) and confirmed the accuracy of the original K2 ephemeris for future follow-up transit observations. Performing a joint fit to the Spitzer/IRAC and K2 photometry, we found a planet radius of 4.41[subscript -0.28][superscript +0.32]R[subscript ⊙], an orbital period of 2.84927265[ subscript -6.42×10[superscript -6]][superscript 6.87×10[superscript -6]] days, and an equilibrium temperature of roughly 900 K. We then measured the planet mass by acquiring 12 radial velocity (RV) measurements of the system using the High Resolution Echelle Spectrometer on the 10 m Keck I Telescope. Our RV data set precisely constrains the mass of K2-55b to 43.13[subscript -5.80][superscript +5.98]M[subscript ⊙], indicating that K2-55b has a bulk density of 2.8[subscript -0.6][superscript +0.8]g cm[superscript -3] and can be modeled as a rocky planet capped by a modest H/He envelope (M[subscript envelope] = 12 ± 3% M[subscript p]). K2-55b is denser than most similarly sized planets, raising the question of whether the high planetary bulk density of K2-55b could be attributed to the high metallicity of K2-55. The absence of a substantial volatile envelope despite the high mass of K2-55b poses a challenge to current theories of gas giant formation. We posit that K2-55b may have escaped runaway accretion by migration, late formation, or inefficient core accretion, or that K2-55b was stripped of its envelope by a late giant impact. |
| first_indexed | 2024-09-23T08:33:21Z |
| format | Article |
| id | mit-1721.1/121204 |
| institution | Massachusetts Institute of Technology |
| last_indexed | 2024-09-23T08:33:21Z |
| publishDate | 2019 |
| publisher | American Astronomical Society |
| record_format | dspace |
| spelling | mit-1721.1/1212042022-09-23T12:52:51Z Characterizing K2 Candidate Planetary Systems Orbiting Low-mass Stars. III. A High Mass and Low Envelope Fraction for the Warm Neptune K2-55b Dressing, Courtney D. Sinukoff, Evan Fulton, Benjamin J. Lopez, Eric D. Beichman, Charles A. Howard, Andrew W. Knutson, Heather A. Werner, Michael Benneke, Björn Crossfield, Ian Jm Isaacson, Howard Krick, Jessica Gorjian, Varoujan Livingston, John Petigura, Erik A. Schlieder, Joshua E. Akeson, Rachel L. Batygin, Konstantin Christiansen, Jessie L. Ciardi, David R. Crepp, Justin R. Gonzales, Erica J. Hardegree-Ullman, Kevin Hirsch, Lea A. Kosiarek, Molly Weiss, Lauren M. Massachusetts Institute of Technology. Department of Physics MIT Kavli Institute for Astrophysics and Space Research K2-55b is a Neptune-sized planet orbiting a K7 dwarf with a radius of 0.715[subscript -0.040][superscript +0.043]R[subscript ⊙], a mass of 0.688 ± 0.069 M[subscript ⊙], and an effective temperature of 4300[subscript -100][superscript +107] K. Having characterized the host star using near-infrared spectra obtained at IRTF/SpeX, we observed a transit of K2-55b with Spitzer/Infrared Array Camera (IRAC) and confirmed the accuracy of the original K2 ephemeris for future follow-up transit observations. Performing a joint fit to the Spitzer/IRAC and K2 photometry, we found a planet radius of 4.41[subscript -0.28][superscript +0.32]R[subscript ⊙], an orbital period of 2.84927265[ subscript -6.42×10[superscript -6]][superscript 6.87×10[superscript -6]] days, and an equilibrium temperature of roughly 900 K. We then measured the planet mass by acquiring 12 radial velocity (RV) measurements of the system using the High Resolution Echelle Spectrometer on the 10 m Keck I Telescope. Our RV data set precisely constrains the mass of K2-55b to 43.13[subscript -5.80][superscript +5.98]M[subscript ⊙], indicating that K2-55b has a bulk density of 2.8[subscript -0.6][superscript +0.8]g cm[superscript -3] and can be modeled as a rocky planet capped by a modest H/He envelope (M[subscript envelope] = 12 ± 3% M[subscript p]). K2-55b is denser than most similarly sized planets, raising the question of whether the high planetary bulk density of K2-55b could be attributed to the high metallicity of K2-55. The absence of a substantial volatile envelope despite the high mass of K2-55b poses a challenge to current theories of gas giant formation. We posit that K2-55b may have escaped runaway accretion by migration, late formation, or inefficient core accretion, or that K2-55b was stripped of its envelope by a late giant impact. 2019-06-04T18:38:42Z 2019-06-04T18:38:42Z 2018-07 2018-06 2019-03-15T18:52:17Z Article http://purl.org/eprint/type/JournalArticle 1538-3881 0004-6256 https://hdl.handle.net/1721.1/121204 Dressing, Courtney D. et al. “Characterizing K2 Candidate Planetary Systems Orbiting Low-Mass Stars. III. A High Mass and Low Envelope Fraction for the Warm Neptune K2-55b.” The Astronomical Journal 156, 2 (July 2018): 70 © American Astronomical Society http://dx.doi.org/10.3847/1538-3881/AACF99 Astronomical Journal Article is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use. application/pdf American Astronomical Society The Astrophysical Journal |
| spellingShingle | Dressing, Courtney D. Sinukoff, Evan Fulton, Benjamin J. Lopez, Eric D. Beichman, Charles A. Howard, Andrew W. Knutson, Heather A. Werner, Michael Benneke, Björn Crossfield, Ian Jm Isaacson, Howard Krick, Jessica Gorjian, Varoujan Livingston, John Petigura, Erik A. Schlieder, Joshua E. Akeson, Rachel L. Batygin, Konstantin Christiansen, Jessie L. Ciardi, David R. Crepp, Justin R. Gonzales, Erica J. Hardegree-Ullman, Kevin Hirsch, Lea A. Kosiarek, Molly Weiss, Lauren M. Characterizing K2 Candidate Planetary Systems Orbiting Low-mass Stars. III. A High Mass and Low Envelope Fraction for the Warm Neptune K2-55b |
| title | Characterizing K2 Candidate Planetary Systems Orbiting Low-mass Stars. III. A High Mass and Low Envelope Fraction for the Warm Neptune K2-55b |
| title_full | Characterizing K2 Candidate Planetary Systems Orbiting Low-mass Stars. III. A High Mass and Low Envelope Fraction for the Warm Neptune K2-55b |
| title_fullStr | Characterizing K2 Candidate Planetary Systems Orbiting Low-mass Stars. III. A High Mass and Low Envelope Fraction for the Warm Neptune K2-55b |
| title_full_unstemmed | Characterizing K2 Candidate Planetary Systems Orbiting Low-mass Stars. III. A High Mass and Low Envelope Fraction for the Warm Neptune K2-55b |
| title_short | Characterizing K2 Candidate Planetary Systems Orbiting Low-mass Stars. III. A High Mass and Low Envelope Fraction for the Warm Neptune K2-55b |
| title_sort | characterizing k2 candidate planetary systems orbiting low mass stars iii a high mass and low envelope fraction for the warm neptune k2 55b |
| url | https://hdl.handle.net/1721.1/121204 |
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