Liang Yun-Feng | Searcharxiv

arXiv2021

Is TOL 1326-379 a Prototype of gamma-ray Emitting FR0 Radio Galaxy?

With the possible spacial association to the Fermi/LAT source 3FGL J1330.0-3818, TOL 1326-379 may be the first one that is identified as a gamma-ray emitting Fanaroff-Riley type 0 radio galaxy (FR0 RG). We analyze the ~12 yr Fermi/LAT observation data of this gamma-ray source and examine its association to TOL 1326-379. We show that the gamma-ray source (named as J1331.0-3818) is tentatively detected with a TS value of 28.7, 3FGL J1330.0-3818 is out of the 95% containment of J1331.0-3818, and their positions are spatially separated ~0.2 degr. 4FGL J1331.3-3818 falls into the 68% containment of J1331.0-3818, suggesting that our result agrees with that reported in the Fourth Fermi LAT Source Catalog. TOL 1326-379 is out of the 95% containment of J1331.0-3818, and their positions are spatially separated ~0.4 degr, indicating that the association between J1331.0-3818 and TOL 1326-379 is quite ambiguous. However, we do not find other possible potential radio or X-ray counterpart within the circle centered at J1331.0-3818 with a radius of 0.4 degr. The spectral energy distribution (SED) of TOL 1326-379 shows a bimodal feature as seen in the gamma-ray emitting RGs. We fit the SED with the one-zone leptonic model and find that the average energy spectrum of J1331.0-3818 agrees with the model prediction. Assuming that J1331.0-3818 is an unidentified gamma-ray source, we derive the upper-limit of the gamma-ray flux for TOL 1326-379. It is not tight enough to exclude this possibility with the SED modeling. Based on these results, we cautiously argue that the gamma-ray source J1331.0-3818 is associated with TOL 1326-379 and its jet radiation physic is similar to those gamma-ray emitting RGs.

astro-ph.HE↗

arXiv2021

Nearby SN-Associated GRB~190829A: Environment, Jet Structure, and VHE Gamma-Ray Afterglows

We present a self-consistent paradigm for interpreting the striking features of nearby low-luminosity GRB~190829A. Its prompt gamma-ray lightcurve has two separated pulses. We propose that the interaction of the hard prompt gamma-ray photons ($E_p= 624_{-303}^{+2432}$ keV) of its initial pulse with the dusty medium ($A_{\rm V}=2.33$) does not only result in the second soft gamma-ray pulse ($E_p\sim 12$ keV), but also makes a pre-accelerated $e^{\pm}$-rich medium shell via the $γγ$ annihilation.In this paradigm, we show that the observed radio, optical, and X-ray afterglow lightcurves are well fit with the forward shock model. Its jet is almost isotropic ($θ_j>1.0$ rad) with a Lorentz factor of $\sim 35$, and the electron density of the $e^{\pm}$-rich medium shell is $\sim 15$ cm$^{-3}$, about 7~times higher than the electron density of its normal surrounding medium. The GRB ejecta catches up with and propagates into the $e^{\pm}$-rich medium shell at a region of $R=(4.07-6.46)\times 10^{16}~\rm cm$, resulting in a bright afterglow bump at $\sim 10^3$ seconds post the GRB trigger. The predicted very high energy (VHE) gamma-ray emission from the synchrotron self-Compton process agrees with the H.E.S.S. observation. The derived broadband spectral energy distribution shows that GRB~190829A like nearby GRBs would be promising targets of the VHE gamma-ray telescopes, such as H.E.S.S., MAGIC, and CTA (Cherenkov Telescope Arrays).

astro-ph.HE↗