Hα Variability of AB Aur b with the Hubble Space Telescope: Probing the Nature of a Protoplanet Candidate with Accretion Light Echoes
Giant planets generate accretion luminosity as they form. Much of this energy is radiated in strong H α line emission, which has motivated direct imaging surveys at optical wavelengths to search for accreting protoplanets. However, compact disk structures can mimic accreting planets by scattering em...
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| Format: | Article |
| Language: | English |
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IOP Publishing
2025-01-01
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| Series: | The Astronomical Journal |
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| Online Access: | https://doi.org/10.3847/1538-3881/adb6a1 |
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| author | Brendan P. Bowler Yifan Zhou Lauren I. Biddle Lillian Yushu Jiang Jaehan Bae Laird M. Close Katherine B. Follette Kyle Franson Adam L. Kraus Aniket Sanghi Quang Tran Kimberly Ward-Duong Ya-Lin Wu Zhaohuan Zhu |
| author_facet | Brendan P. Bowler Yifan Zhou Lauren I. Biddle Lillian Yushu Jiang Jaehan Bae Laird M. Close Katherine B. Follette Kyle Franson Adam L. Kraus Aniket Sanghi Quang Tran Kimberly Ward-Duong Ya-Lin Wu Zhaohuan Zhu |
| author_sort | Brendan P. Bowler |
| collection | DOAJ |
| description | Giant planets generate accretion luminosity as they form. Much of this energy is radiated in strong H α line emission, which has motivated direct imaging surveys at optical wavelengths to search for accreting protoplanets. However, compact disk structures can mimic accreting planets by scattering emission from the host star. This can complicate the interpretation of H α point sources, especially if the host star itself is accreting. We describe an approach to distinguish accreting protoplanets from scattered-light disk features using “accretion light echoes.” This method relies on variable H α emission from a stochastically accreting host star to search for a delayed brightness correlation with a candidate protoplanet. We apply this method to the candidate protoplanet AB Aur b with a dedicated Hubble Space Telescope Wide Field Camera 3 program designed to sequentially sample the host star and the candidate planet in H α while accounting for the light travel time delay and orbital geometry of the source within the protoplanetary disk. Across five epochs spanning 14 months, AB Aur b is over 20 times more variable than its host star; AB Aur’s H α emission changes by 15% while AB Aur b varies by 330%. These brightness changes are not correlated, which rules out unobstructed scattered starlight from the host star as the only source of AB Aur b’s H α emission and is consistent with tracing emission from an independently accreting protoplanet, inner disk shadowing effects, or a physically evolving compact disk structure. More broadly, accretion light echoes offer a novel tool to explore the nature of protoplanet candidates with well-timed observations of the host star prior to deep imaging in H α . |
| format | Article |
| id | doaj-art-366c4e170dcb41abb4704f23423de14e |
| institution | OA Journals |
| issn | 1538-3881 |
| language | English |
| publishDate | 2025-01-01 |
| publisher | IOP Publishing |
| record_format | Article |
| series | The Astronomical Journal |
| spelling | doaj-art-366c4e170dcb41abb4704f23423de14e2025-08-20T02:16:55ZengIOP PublishingThe Astronomical Journal1538-38812025-01-01169525810.3847/1538-3881/adb6a1Hα Variability of AB Aur b with the Hubble Space Telescope: Probing the Nature of a Protoplanet Candidate with Accretion Light EchoesBrendan P. Bowler0https://orcid.org/0000-0003-2649-2288Yifan Zhou1https://orcid.org/0000-0003-2969-6040Lauren I. Biddle2https://orcid.org/0000-0003-2646-3727Lillian Yushu Jiang3https://orcid.org/0000-0003-4006-102XJaehan Bae4https://orcid.org/0000-0001-7258-770XLaird M. Close5https://orcid.org/0000-0002-2167-8246Katherine B. Follette6https://orcid.org/0000-0002-7821-0695Kyle Franson7https://orcid.org/0000-0003-4557-414XAdam L. Kraus8https://orcid.org/0000-0001-9811-568XAniket Sanghi9https://orcid.org/0000-0002-1838-4757Quang Tran10https://orcid.org/0000-0001-6532-6755Kimberly Ward-Duong11https://orcid.org/0000-0002-4479-8291Ya-Lin Wu12https://orcid.org/0000-0002-4392-1446Zhaohuan Zhu13https://orcid.org/0000-0003-3616-6822Department of Physics, University of California , Santa Barbara, Santa Barbara, CA 93106, USA ; bpbowler@astro.as.utexas.edu; Department of Astronomy, The University of Texas at Austin , Austin, TX 78712, USADepartment of Astronomy, University of Virginia , 530 McCormick Road, Charlottesville, VA 22904, USADepartment of Astronomy, The University of Texas at Austin , Austin, TX 78712, USADepartment of Astronomy, The University of Texas at Austin , Austin, TX 78712, USADepartment of Astronomy, University of Florida , Gainesville, FL 32611, USADepartment of Astronomy, University of Arizona , 933 N. Cherry Avenue, Tucson, AZ 85718, USAAmherst College , Department of Physics and Astronomy, USADepartment of Astronomy, The University of Texas at Austin , Austin, TX 78712, USADepartment of Astronomy, The University of Texas at Austin , Austin, TX 78712, USACahill Center for Astronomy and Astrophysics, California Institute of Technology , 1200 E. California Boulevard, MC 249-17, Pasadena, CA 91125, USADepartment of Astronomy, Yale University , New Haven, CT 06511, USAFive College Astronomy Department , Amherst College, Amherst, MA 01002, USADepartment of Physics, National Taiwan Normal University , Taipei 116, TaiwanDepartment of Physics and Astronomy, University of Nevada , Las Vegas, 4505 South Maryland Parkway, Las Vegas, NV 89154-4002, USAGiant planets generate accretion luminosity as they form. Much of this energy is radiated in strong H α line emission, which has motivated direct imaging surveys at optical wavelengths to search for accreting protoplanets. However, compact disk structures can mimic accreting planets by scattering emission from the host star. This can complicate the interpretation of H α point sources, especially if the host star itself is accreting. We describe an approach to distinguish accreting protoplanets from scattered-light disk features using “accretion light echoes.” This method relies on variable H α emission from a stochastically accreting host star to search for a delayed brightness correlation with a candidate protoplanet. We apply this method to the candidate protoplanet AB Aur b with a dedicated Hubble Space Telescope Wide Field Camera 3 program designed to sequentially sample the host star and the candidate planet in H α while accounting for the light travel time delay and orbital geometry of the source within the protoplanetary disk. Across five epochs spanning 14 months, AB Aur b is over 20 times more variable than its host star; AB Aur’s H α emission changes by 15% while AB Aur b varies by 330%. These brightness changes are not correlated, which rules out unobstructed scattered starlight from the host star as the only source of AB Aur b’s H α emission and is consistent with tracing emission from an independently accreting protoplanet, inner disk shadowing effects, or a physically evolving compact disk structure. More broadly, accretion light echoes offer a novel tool to explore the nature of protoplanet candidates with well-timed observations of the host star prior to deep imaging in H α .https://doi.org/10.3847/1538-3881/adb6a1Exoplanet formationProtoplanetary disks |
| spellingShingle | Brendan P. Bowler Yifan Zhou Lauren I. Biddle Lillian Yushu Jiang Jaehan Bae Laird M. Close Katherine B. Follette Kyle Franson Adam L. Kraus Aniket Sanghi Quang Tran Kimberly Ward-Duong Ya-Lin Wu Zhaohuan Zhu Hα Variability of AB Aur b with the Hubble Space Telescope: Probing the Nature of a Protoplanet Candidate with Accretion Light Echoes The Astronomical Journal Exoplanet formation Protoplanetary disks |
| title | Hα Variability of AB Aur b with the Hubble Space Telescope: Probing the Nature of a Protoplanet Candidate with Accretion Light Echoes |
| title_full | Hα Variability of AB Aur b with the Hubble Space Telescope: Probing the Nature of a Protoplanet Candidate with Accretion Light Echoes |
| title_fullStr | Hα Variability of AB Aur b with the Hubble Space Telescope: Probing the Nature of a Protoplanet Candidate with Accretion Light Echoes |
| title_full_unstemmed | Hα Variability of AB Aur b with the Hubble Space Telescope: Probing the Nature of a Protoplanet Candidate with Accretion Light Echoes |
| title_short | Hα Variability of AB Aur b with the Hubble Space Telescope: Probing the Nature of a Protoplanet Candidate with Accretion Light Echoes |
| title_sort | hα variability of ab aur b with the hubble space telescope probing the nature of a protoplanet candidate with accretion light echoes |
| topic | Exoplanet formation Protoplanetary disks |
| url | https://doi.org/10.3847/1538-3881/adb6a1 |
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