VLASS Discovery of a Luminous Galactic Radio Transient Evolving on Decade Timescales
9 affiliations
- 1California Institute of Technology
- 2National Radio Astronomy Observatory
- 3Center for Astrophysics—Harvard & Smithsonian
- 4University of California
- 5Kavli Institute for Particle Astrophysics and Cosmology
- 6University of California Santa Cruz
- 7University of Toronto
- 8Michigan State University
- 9The Hebrew University of Jerusalem
Abstract
We present a multiwavelength analysis of the radio transient VT J1906+0849, discovered as a 70 mJy source in Epoch 1 of the Very Large Array Sky Survey (VLASS), 21 yr after an NRAO VLA Sky Survey (NVSS) nondetection. Radio observations reveal the source was first detected in 2005, peaking at ≳200 mJy in 2014, then declining until a late 2025 rebrightening. The transient sits at a Galactic latitude of ≈0.74 ∘ and the properties of its optical-infrared counterpart support a Galactic origin. At d ≳ 15 kpc, the extreme radio luminosity is likely powered by sustained accretion onto a compact object. However, a Swift-XRT nondetection shows it is X-ray faint relative to the Galactic X-ray binary population, and the radio emission is distinct from X-ray binaries in its temporal and spectral behavior. Broadband radio spectra suggest synchrotron self-absorption, but size constraints from equipartition and very long baseline interferometry show little to no expansion in the radio-emitting region over 5 yr, despite significant spectral evolution. Near-infrared spectroscopy reveals a single broad emission line with a stable centroid but variable width and luminosity. We attribute this feature to blueshifted Br γ tracing a persistent asymmetric ≈2000 km s ⁻¹ outflow. These properties are unlike any previously identified Galactic radio source. One possible interpretation is that VT J1906+0849 is a young analog of the microquasar SS 433, with a dense disk wind confining a continuously powered synchrotron outflow. This jet–wind interaction explains the compact, slowly expanding radio source and may contribute to the absence of bright X-ray emission.
Related
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- Discovery of 26 new Galactic radio transients by MeerTRAP
BibTeX
@article{miller2026vlass,
title = {{VLASS Discovery of a Luminous Galactic Radio Transient Evolving on Decade Timescales}},
author = {Jessie M. Miller and Gregg Hallinan and Dillon Dong and Adolfo S. Carvalho and S. T. Myers and Jean Somalwar and Casey Law and B. M. Gaensler and Vikram Ravi and Laura Chomiuk and Assaf Horesh and Delina Levine and Yuyang Chen},
journal = {The Astrophysical Journal},
year = {2026},
month = oct,
doi = {10.3847/1538-4357/aea0d5},
url = {https://iopscience.iop.org/article/10.3847/1538-4357/aea0d5},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - VLASS Discovery of a Luminous Galactic Radio Transient Evolving on Decade Timescales
AU - Jessie M. Miller
AU - Gregg Hallinan
AU - Dillon Dong
AU - Adolfo S. Carvalho
AU - S. T. Myers
AU - Jean Somalwar
AU - Casey Law
AU - B. M. Gaensler
AU - Vikram Ravi
AU - Laura Chomiuk
AU - Assaf Horesh
AU - Delina Levine
AU - Yuyang Chen
PY - 2026
DA - 2026/10/14
JO - The Astrophysical Journal
DO - 10.3847/1538-4357/aea0d5
UR - https://iopscience.iop.org/article/10.3847/1538-4357/aea0d5
AB - We present a multiwavelength analysis of the radio transient VT J1906+0849, discovered as a 70 mJy source in Epoch 1 of the Very Large Array Sky Survey (VLASS), 21 yr after an NRAO VLA Sky Survey (NVSS) nondetection. Radio observations reveal the source was first detected in 2005, peaking at ≳200 mJy in 2014, then declining until a late 2025 rebrightening. The transient sits at a Galactic latitude of ≈0.74 ∘ and the properties of its optical-infrared counterpart support a Galactic origin. At d ≳ 15 kpc, the extreme radio luminosity is likely powered by sustained accretion onto a compact object. However, a Swift-XRT nondetection shows it is X-ray faint relative to the Galactic X-ray binary population, and the radio emission is distinct from X-ray binaries in its temporal and spectral behavior. Broadband radio spectra suggest synchrotron self-absorption, but size constraints from equipartition and very long baseline interferometry show little to no expansion in the radio-emitting region over 5 yr, despite significant spectral evolution. Near-infrared spectroscopy reveals a single broad emission line with a stable centroid but variable width and luminosity. We attribute this feature to blueshifted Br γ tracing a persistent asymmetric ≈2000 km s ⁻¹ outflow. These properties are unlike any previously identified Galactic radio source. One possible interpretation is that VT J1906+0849 is a young analog of the microquasar SS 433, with a dense disk wind confining a continuously powered synchrotron outflow. This jet–wind interaction explains the compact, slowly expanding radio source and may contribute to the absence of bright X-ray emission.
SN - 0004-637X
SN - 1538-4357
ER -