A Radio Flaring, Chromospherically Inactive K Dwarf
We report on an unusual radio source (J180526−292953), initially identified as a steep spectrum, polarized point source toward the Galactic bulge and found to coincide with the nearby K dwarf HD 317101A. We conducted a multiwavelength radio study utilizing new GMRT observations and archival data fro...
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IOP Publishing
2025-01-01
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| Series: | The Astrophysical Journal |
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| Online Access: | https://doi.org/10.3847/1538-4357/adee14 |
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| author | Dale A. Frail Scott D. Hyman Michele L. Silverstein Emil Polisensky Evangelia Tremou Simona Giacintucci Hodari-Sadiki Hubbard-James Jacinda Byam Steve B. Howell Robert F. Wilson Matthew Lastovka Tracy E. Clarke Namir E. Kassim |
| author_facet | Dale A. Frail Scott D. Hyman Michele L. Silverstein Emil Polisensky Evangelia Tremou Simona Giacintucci Hodari-Sadiki Hubbard-James Jacinda Byam Steve B. Howell Robert F. Wilson Matthew Lastovka Tracy E. Clarke Namir E. Kassim |
| author_sort | Dale A. Frail |
| collection | DOAJ |
| description | We report on an unusual radio source (J180526−292953), initially identified as a steep spectrum, polarized point source toward the Galactic bulge and found to coincide with the nearby K dwarf HD 317101A. We conducted a multiwavelength radio study utilizing new GMRT observations and archival data from ASKAP, MeerKAT, and the Very Large Array. At 1.5 GHz, HD 317101A exhibits highly polarized coherent emission with variable activity lasting several hours with an apparent period of 3.7 days, which is consistent with electron cyclotron maser (ECM) emission. The behavior at 3 GHz is distinctive, with a short burst lasting tens of seconds to minutes, a flat spectrum, and no detected polarization, possibly suggesting gyro-synchrotron emission. High-resolution optical spectroscopy from CHIRON/SMARTS confirms HD 317101A as a mature, chromospherically inactive K7V star, while Gaia astrometry, combined with speckle imaging from Zorro/Gemini-S, indicates the presence of a close-in M5.5V companion. We evaluated three possible origins for the combined radio behavior: chromospheric activity, auroral emission (possibly from a star–planet interaction), or an ultralong-period transient. The bulk of the evidence favors an auroral origin, but the dominant stellar source of the ECM emission remains uncertain. Future very-long baseline interferometry observations, long-term TESS monitoring, high-resolution spectroscopy, and further radio characterization will be key to distinguishing between various scenarios. |
| format | Article |
| id | doaj-art-640d7b7c828f4c87b0b4ca8950906eac |
| institution | DOAJ |
| issn | 1538-4357 |
| language | English |
| publishDate | 2025-01-01 |
| publisher | IOP Publishing |
| record_format | Article |
| series | The Astrophysical Journal |
| spelling | doaj-art-640d7b7c828f4c87b0b4ca8950906eac2025-08-20T03:02:52ZengIOP PublishingThe Astrophysical Journal1538-43572025-01-01989218610.3847/1538-4357/adee14A Radio Flaring, Chromospherically Inactive K DwarfDale A. Frail0https://orcid.org/0009-0008-7604-003XScott D. Hyman1https://orcid.org/0009-0006-5070-6329Michele L. Silverstein2https://orcid.org/0000-0003-2565-7909Emil Polisensky3https://orcid.org/0000-0003-3272-9237Evangelia Tremou4https://orcid.org/0000-0002-4039-6703Simona Giacintucci5https://orcid.org/0000-0002-1634-9886Hodari-Sadiki Hubbard-James6https://orcid.org/0000-0003-4568-2079Jacinda Byam7https://orcid.org/0009-0006-7309-1005Steve B. Howell8https://orcid.org/0000-0002-2532-2853Robert F. Wilson9https://orcid.org/0000-0002-4235-6369Matthew Lastovka10https://orcid.org/0009-0009-4693-7783Tracy E. Clarke11https://orcid.org/0000-0001-6812-7938Namir E. Kassim12https://orcid.org/0000-0001-8035-4906National Radio Astronomy Observatory , P.O. Box O, Socorro, NM 87801, USA ; dfrail@nrao.eduDepartment of Engineering and Physics, Sweet Briar College , Sweet Briar, VA 24595, USAU.S. Naval Research Laboratory , 4555 Overlook Avenue SW, Washington, DC 20375, USAU.S. Naval Research Laboratory , 4555 Overlook Avenue SW, Washington, DC 20375, USANational Radio Astronomy Observatory , P.O. Box O, Socorro, NM 87801, USA ; dfrail@nrao.eduU.S. Naval Research Laboratory , 4555 Overlook Avenue SW, Washington, DC 20375, USAAgnes Scott College , 141 E. College Avenue, Decatur, GA 30030, USAAgnes Scott College , 141 E. College Avenue, Decatur, GA 30030, USANASA Ames Research Center , Moffett Field, CA 94035, USANASA , Goddard Space Flight Center, Mail Code 660 Greenbelt, MD 20771, USADepartment of Astronomy, University of Maryland 4296 Stadium Dr ., College Park, MD 20742-2421, USAU.S. Naval Research Laboratory , 4555 Overlook Avenue SW, Washington, DC 20375, USAU.S. Naval Research Laboratory , 4555 Overlook Avenue SW, Washington, DC 20375, USAWe report on an unusual radio source (J180526−292953), initially identified as a steep spectrum, polarized point source toward the Galactic bulge and found to coincide with the nearby K dwarf HD 317101A. We conducted a multiwavelength radio study utilizing new GMRT observations and archival data from ASKAP, MeerKAT, and the Very Large Array. At 1.5 GHz, HD 317101A exhibits highly polarized coherent emission with variable activity lasting several hours with an apparent period of 3.7 days, which is consistent with electron cyclotron maser (ECM) emission. The behavior at 3 GHz is distinctive, with a short burst lasting tens of seconds to minutes, a flat spectrum, and no detected polarization, possibly suggesting gyro-synchrotron emission. High-resolution optical spectroscopy from CHIRON/SMARTS confirms HD 317101A as a mature, chromospherically inactive K7V star, while Gaia astrometry, combined with speckle imaging from Zorro/Gemini-S, indicates the presence of a close-in M5.5V companion. We evaluated three possible origins for the combined radio behavior: chromospheric activity, auroral emission (possibly from a star–planet interaction), or an ultralong-period transient. The bulk of the evidence favors an auroral origin, but the dominant stellar source of the ECM emission remains uncertain. Future very-long baseline interferometry observations, long-term TESS monitoring, high-resolution spectroscopy, and further radio characterization will be key to distinguishing between various scenarios.https://doi.org/10.3847/1538-4357/adee14Stellar magnetic fieldsLate-type dwarf starsRadio continuum emissionStar-planet interactions |
| spellingShingle | Dale A. Frail Scott D. Hyman Michele L. Silverstein Emil Polisensky Evangelia Tremou Simona Giacintucci Hodari-Sadiki Hubbard-James Jacinda Byam Steve B. Howell Robert F. Wilson Matthew Lastovka Tracy E. Clarke Namir E. Kassim A Radio Flaring, Chromospherically Inactive K Dwarf The Astrophysical Journal Stellar magnetic fields Late-type dwarf stars Radio continuum emission Star-planet interactions |
| title | A Radio Flaring, Chromospherically Inactive K Dwarf |
| title_full | A Radio Flaring, Chromospherically Inactive K Dwarf |
| title_fullStr | A Radio Flaring, Chromospherically Inactive K Dwarf |
| title_full_unstemmed | A Radio Flaring, Chromospherically Inactive K Dwarf |
| title_short | A Radio Flaring, Chromospherically Inactive K Dwarf |
| title_sort | radio flaring chromospherically inactive k dwarf |
| topic | Stellar magnetic fields Late-type dwarf stars Radio continuum emission Star-planet interactions |
| url | https://doi.org/10.3847/1538-4357/adee14 |
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