A Radio Flaring, Chromospherically Inactive K Dwarf

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...

Full description

Saved in:
Bibliographic Details
Main Authors: 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
Format: Article
Language:English
Published: IOP Publishing 2025-01-01
Series:The Astrophysical Journal
Subjects:
Stellar magnetic fields
Late-type dwarf stars
Radio continuum emission
Star-planet interactions
Online Access:https://doi.org/10.3847/1538-4357/adee14
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary: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.
ISSN:1538-4357

Similar Items