IGR J12580+0134: A Candidate for Repeating Partial Tidal Disruption Events Supported by Multi-Wavelength Observations

Abstract

Repeating partial tidal disruption events (pTDEs) provide a direct probe of stellar orbits and episodic mass loss around supermassive black holes, but robust identification requires multi-band and multi-epoch evidence. We investigate whether the late-time radio rebrightening of the nuclear transient IGR J12580+0134 in NGC 4845 can be explained as a repeating pTDE, using multi-epoch Karl G. Jansky VLA observations together with X-ray constraints from Swift/XRT and NICER. The radio light curves show two distinct episodes, with the L-band peaks separated by $\approx1513$ days. Modeling the second episode with a synchrotron afterglow framework using Markov Chain Monte Carlo fitting favors a non-relativistic outflow $v\simeq0.03c$, with an isotropic-equivalent kinetic energy of order $10^{50}$ erg propagating in an approximately constant-density circumnuclear medium. No significant contemporaneous brightening is detected by Swift/XRT during the 2016 radio flare, while faint NICER flares in 2023 suggest intermittent low-level accretion. The recurrence timescale and radio energetics therefore make IGR J12580+0134 a possible candidate for a repeating pTDE system, motivating continued sensitive radio and X-ray monitoring to test future reactivations.

Figures (7)

• Figure 1: SDSS image showing the location of NGC 4845 at RA = 12$^\mathrm{h}$58$^\mathrm{m}$01$^\mathrm{s}$, Dec = +01°3433. The image was obtained from the SDSS SkyServer Navigate tool (https://skyserver.sdss.org/dr18/VisualTools/navi2).
• Figure 2: Multi-wavelength light curves of IGR J12580+0134, combining X-ray and radio data. Radio fluxes are plotted for L-band (black hexagons), C-band (pink diamonds), S-band (green triangles), and X-band (purple thin diamonds). Red stars represent the 2011 X-ray flare in the 17.3-80 keV band nikolajuk2013tidal. The Swift/XRT observation (0.5--7 keV) is shown as magenta squares. A faint X-ray flare detected in 2023 via NICER (0.4-10 keV) monitoring is indicated by blue circles and the shaded region indicating the background flux level between 2021 June 15 and 2024 February 28 Danehkar_2025. Early submillimeter measurements from Planck at 100 and 353 GHz are shown as golden pentagons and dark-orange crosses yuan2016catching. The fluxes are plotted on a logarithmic scale to highlight the dynamic range of the event.
• Figure 3: Modeling results for the second radio flare of IGR J12580+0134. The left panel shows the best-fit radio light curves at 1.5, 3, and 6 GHz overlaid on the observational data from Perlman2022, where the flux densities at 3 and 6 GHz are scaled down by factors of $10$ and $10^{2}$ for clarity. The right panel presents the posterior distributions of the synchrotron afterglow parameters derived from MCMC sampling.
• Figure 4: Linear interpolation of L-band flux at MJD 58594. Red circles denote the observed L-band flux densities at two epochs, and the blue square represents the interpolated value at the target date, yielding a flux of 62.0 mJy. The vertical dashed line marks the interpolation time. This value is used to reconstruct the broadband spectrum at a common epoch with the S-band measurement.
• Figure 5: Radio spectral fits of IGR J12580+0134 at two different epochs: 2016-05-21 (blue) and 2019-04-21 (orange). The data points represent observed flux densities at multiple frequencies, while the dashed lines show the best-fit power-law models. The shaded regions indicate the 1$\sigma$ confidence intervals propagated from the uncertainty in the spectral index $\beta$. The steeper slope observed in 2019 suggests a significant spectral evolution over the three-year period. Notably, the flux density decline between 3 and 6 GHz in the 2016 data appears steeper and closely matches the spectral slope of the 2019 epoch. This suggests that by 2016 May 21, the cooling frequency $\nu_c$ had likely decreased below 6 GHz, placing the observing band within the fast-cooling regime.