A Parsec-Scale Transient High-Frequency-Peaked Radio Source in the Very Large Array Sky Survey Brightening and Fading over a Decadal Timescale

@misc{chen2026parsecscale,
  title = {{A Parsec-Scale Transient High-Frequency-Peaked Radio Source in the Very Large Array Sky Survey Brightening and Fading over a Decadal Timescale}},
  author = {Yuyang Chen and B. M. Gaensler and Maria R. Drout and Dillon Z. Dong and Emmanuel Momjian and Tracy Clarke and Wendy Peters and Emil Polisensky and Ariel D. Amaral and Katie Auchettl and Ylva Götberg and Kovi Rose and Peter Senchyna},
  howpublished = {arXiv},
  year = {2026},
  month = oct,
  doi = {10.48550/arxiv.2610.20495},
  eprint = {2610.20495},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2610.20495},
  note = {CC BY 4.0},
}

TY  - UNPB
TI  - A Parsec-Scale Transient High-Frequency-Peaked Radio Source in the Very Large Array Sky Survey Brightening and Fading over a Decadal Timescale
AU  - Yuyang Chen
AU  - B. M. Gaensler
AU  - Maria R. Drout
AU  - Dillon Z. Dong
AU  - Emmanuel Momjian
AU  - Tracy Clarke
AU  - Wendy Peters
AU  - Emil Polisensky
AU  - Ariel D. Amaral
AU  - Katie Auchettl
AU  - Ylva Götberg
AU  - Kovi Rose
AU  - Peter Senchyna
PY  - 2026
DA  - 2026/10/14
PB  - arXiv
DO  - 10.48550/arxiv.2610.20495
UR  - https://arxiv.org/abs/2610.20495
AB  - A subset of active galactic nuclei (AGN) manifests as compact radio sources with peaked radio spectra, commonly referred to as peaked-spectrum (PS) sources. Generally, PS sources are interpreted as young radio jets, but the early evolution of the jet is rarely observed and not fully understood. Here, we present VT J182357-234511 (VT J1823-2345), a radio transient in the Very Large Array Sky Survey (VLASS) that resembles a PS source. Notable properties of VT J1823-2345 include: (i) brightening by a factor of 3 between 1996 and 2021 at 1.4 GHz, (ii) peaked spectra with high frequency peaks at ν_p,obs≳6 GHz, (iii) a peaked 3 GHz light curve that has been fading since 2023, (iv) a resolved Gaussian (major-axis) size of 0.4 mas in 2024, and (v) a linear polarization fraction p_L≃0.73% at 8.8 GHz with an extreme Faraday rotation measure RM_obs ∼ +12,000 rad m^−2. On the sky, VT J1823-2345 coincides with a supernova remnant and an F-type star, but no background galaxy is seen. Based on the multi-wavelength properties, we disfavor Galactic transients, explosive extragalactic transients, and blazar variability as plausible explanations. We argue that VT J1823-2345 is consistent with a "short-lived" parsec-scale PS source with a decades-old jet that does not grow into a large-scale radio galaxy. From comparing the full VLASS light curves, we speculate that VT J1823-2345 is similar to many VLASS nuclear transients reported in the literature, which may represent an emerging class of transient radio jets, perhaps related to episodic AGN activity or jetted tidal disruption events.
ER  -