A Late-time Radio Search for Highly Off-axis Jets from PTF Broad-lined Ic Supernovae in GRB-like Host Galaxy Environments

TL;DR

This study targets the existence of highly off-axis relativistic jets in broad-lined SNe Ic-bl by conducting deep late-time radio observations of 14 events from the PTF, chosen for their GRB-like host environments, at rest-frame times of roughly $3$--$4\times10^{3}$ days. The authors combine new VLA/MeerKAT data with archival radio surveys and develop FIREFLY-based off-axis afterglow models to map constraints on jet energy $E$ and circumburst density $n$ as a function of viewing angle $\theta_{obs}$, exploring $\theta_{obs}=30^{\circ},60^{\circ},90^{\circ}$ and frequencies $\nu_{obs}=3,6,10$ GHz. They detect a single source, PTF10tqv, whose late-time radio emission is consistent with an off-axis jet with $E\sim10^{51}$--$10^{51.7}$ erg and $n\gtrsim10^{-2.8}$ cm$^{-3}$; for the other 11 non-detections, the data rule out most classical GRB-like jets at $E\gtrsim10^{51}$ erg for many $n$ values but remain compatible with highly off-axis ($\theta_{obs}\gtrsim60^{\circ}$) jets in low-density environments. The work demonstrates the power and limitations of late-time radio searches for off-axis jets and argues for coordinated, cadence-rich surveys (e.g., ZTF BTS with VLASS/DSA-2000) to robustly probe jets with $E$ down to $\sim10^{50}$ erg across a range of $n$, significantly advancing our ability to test the link between SNe Ic-bl and GRBs.

Abstract

Hydrogen/Helium-poor stripped-envelope core-collapse supernovae with broad lines (SNe Ic-bl) almost always accompany the nearby ($z < 0.3$) jetted relativistic explosions known as long duration gamma-ray bursts (GRBs). However, the majority of SNe Ic-bl have no detected GRB counterpart. At least some of these SNe should harbor off-axis jets, whose afterglow may become detectable at late times, particularly at radio wavelengths. Here, we present Karl G. Jansky Very Large Array radio observations (rest frame times of $\sim 3$-$4\times10^{3}$ days post SN discovery) of a sample of 14 SNe Ic-bl discovered by the Palomar Transient Factory (PTF) that have been demonstrated to originate from the same host environments as the SNe Ic-bl associated with nearby GRBs. Of the 14 SNe, we identify three that are radio detected, one of which (PTF10tqv, $z = 0.0795$) is consistent with an off-axis jet with energy similar to classical GRBs (${\sim 10^{51}}$-${10^{51.7}~}$erg). Using recently developed synchrotron radiation code, we find that for our 11 non-detections, which are among the deepest limits obtained for Ic-bl, we rule out an off-axis jet with an energy of $\gtrsim 10^{51}~{\rm erg}$ in circumburst densities of $\gtrsim 10^{-1}~{\rm cm}^{-3}$. We predict that well-spaced monitoring of newly discovered SNe Ic-bl from $\sim 10~$days to $\sim 10~$years (rest frame) to luminosities of $\sim 10^{27}~{\rm erg~s}^{-1}~{\rm Hz}^{-1}$ will constrain the existence of highly off-axis jets ($\gtrsim60^\circ$) with classical GRB energies. The VLA Sky Survey will probe jets that are $\lesssim 60^\circ$ off-axis, whereas the Deep Synpotic Array 2000 will probe jets out to $\sim 90^\circ$ off-axis, demonstrating the importance of utilizing radio surveys to supplement targeted observations.

Figures (8)

• Figure 1: The 5--$10\,{\rm GHz}$ light curves and upper limits of our PTF sample (green, with observations presented in this paper filled in), compared to SNe Ic-bl samples from 2016ApJ...830...42C and 2023ApJ...953..179C. Also shown are off-axis 10 GHz afterglow models generated by the FIREFLY code for three off-axis angles ($\theta_{\rm obs} = 30, 60, 90^\circ$; orange, pink, purple, respectively) and for two $n$-$E$ pairs ($E = 2\times 10^{51}~{\rm erg}$, $n = 10^{-2}~{\rm cm}^{-3}$, solid lines and $E = 2\times 10^{52}~{\rm erg}$, $n = 10^{-3}~{\rm cm}^{-3}$, dashed lines). Points represent detections and triangles represent upper limits ($3 \sigma$ unless otherwise stated). The detections of PTF10tqv are represented as stars. We also label two SNe Ic-bl, PTF11qcj and PTF11cmh 2014ApJ...782...42C2016ApJ...830...42C2019ApJ...872..201P2021ApJ...910...16P, whose luminous radio emission is thought to arise from CSM interaction, as well as the SNe Ic-bl with the deepest luminosity limits in our sample, PTF10vgv.
• Figure 2: Left: SDSS image of the host galaxy of PTF10tqv (SDSS J224654.99+174728.5). Crosshairs represent the optical location of PTF10tqv. Middle: The 10 GHz VLA image of the location of PTF10tqv, obtained on 2020 August 01 ($\Delta t = 3623$ days, observer frame). Right: The 3.1 GHz MeerKAT image of the location of PTF10tqv, obtained on 2025 March 01 ($\Delta t = 5296$ days, observer frame). For the VLA and MeerKAT images, contours represent the $5\sigma$ level of the image and crosses represent the location of the brightest pixel near the location of PTF10tqv. These contours are also overplotted on the SDSS image to demonstrate the location of the radio source. The length scale is the same for all three panels, and stated in the top right of the left panel. The observing frequency is stated in the top left. When available, the beam size is represented as an ellipse in the bottom left, and the observation date is stated on the bottom right of each image.
• Figure 3: The interstellar medium density ($n$) vs jet energy ($E$) parameter space for three off-axis observer angles ($\theta_{\rm obs} = 30, 60, 90^\circ$), from models generated by the FIREFLY code. Lines represent the constraints on the parameter space from each of our 11 non-detections, where the upper right of each line is ruled out and the lower left of each line is still allowed. We similarly display the constraints that can be placed on the $n$-$E$ parameter space given our suggested observational strategy of future SNe Ic-bl (Section \ref{['sec:Discussion']}, green). Also shown are the beaming corrected kinetic energy and $n$ values for some on-axis GRBs 2002ApJ...571..779P2021ApJ...911...14K.
• Figure 4: Left: The 10 GHz (black) and 3.1 GHz (white) radio detections of PTF10tqv. Also shown are off-axis afterglow models consistent within $2\sigma$ of the detections, for off-axis angles of $\theta_{\rm obs} = 30, 60, 90^\circ$ (purple, orange, pink, respectively), where solid lines represent 10 GHz models and dashed lines represent 3 GHz models. Right: The circumburst density ($n$) vs total jet energy ($E$) space for the off-axis models generated by FIREFLY. Shaded regions represent the space consistent within $2 \sigma$ of the radio detections of the counterpart to PTF10tqv.
• Figure 5: Rest frame light curves for 10 GHz afterglow models at off-axis angles of $\theta_{\rm obs} = 30, 60, 90^\circ$ (lines, orange, pink, purple, respectively) for $E = 2 \times 10^{51}~{\rm erg}$ and $n = 0.01~{\rm cm}^{-3}$ generated by the FIREFLY code 2024ApJ...976..252D. The light curves of PTF10bzf 2016ApJ...830...42C and PTF10tqv (this work, stars) are shown in green. Also shown are the radio non-detections presented in 2023ApJ...953..179C for a sample of ZTF SNe Ic-bl (grey, triangles represent $3\sigma$ upper limits), as well as the radio light curves of several supernova: SN 1998bw 1998Natur.395..663K1998ApJ...497..288W, SN 2006aj 2006Natur.442.1014S, SN 2009bb 2010Natur.463..513S, SN 2012ap 2015ApJ...805..187C, and SN 2020bvc 2020ApJ...902...86H. The sampling of PTF10bzf represents a well-spaced observational strategy to constrain the existence of off-axis jets at any $\theta_{\rm obs}$. The $5 \sigma$ depth of a 1 hr 10 GHz VLA observation at our proposed cadence (black horizontal dashed lines), a 3 GHz VLASS observation at $\sim 1$--$2~{\rm year}$ (black horizontal dotted line) and a 1.4 GHz observation with the Deep Synoptic Array 2000 (DSA-2000) between $\sim 0.3$--$14~$year, at the median ZTF BTS Ic-bl redshift of $z = 0.04$ are presented for reference.