Gamma rays and neutrinos from supernovae of type Ib and Ic with late time emission

Observations of some supernovae (SNe), such as SN 2014C, in the x-ray and radio wavebands revealed a rebrightening over a timescale of about a year since their detection. Such a discovery hints towards the evolution of a hydrogen-poor SN of type Ib/Ic into a hydrogen-rich SN of type IIn, the late time activity being attributed to the interaction of the SN ejecta with a dense hydrogen-rich circumstellar medium (CSM) far away from the stellar core. We compute the neutrino and $\gamma$-ray emission from these SNe, considering interactions between the shock accelerated protons and the nonrelativistic CSM protons. Assuming three CSM models inspired by recent electromagnetic observations, we explore the dependence of the expected multimessenger signals on the CSM characteristics. The detection prospects of existing and upcoming $\gamma$-ray (Fermi-Large Area Telescope (LAT) and Cherenkov Telescope Array) and neutrino (IceCube and IceCube-Gen2) telescopes are also outlines. Our findings are in agreement with the nondetection of neutrinos and $\gamma$-rays from past SNe exhibiting late time emission. Nevertheless, the detection prospects of SNe with late time emission in $\gamma$-rays and neutrinos with the Cherenkov Telescope Array and IceCube-Gen2 (Fermi-LAT and IceCube) are promising and could potentially provide new insight into the CSM properties, if the SN burst should occur within 10 Mpc (4 Mpc).

Figure 1

Temporal evolution of the flux of muon neutrinos (thin blue) and $\gamma$-rays (thick red) at Earth from SN model B1 (see also Table 1). The left plot extends up to 250 days, and it shows the early emission from SN Ib/Ic; the right panel shows the LT emission, i.e., beyond 250 days. The $y$ axis of the right panel is rescaled by a factor ${10}^5$ at 250 days. The continuous and dashed line styles represent the minimum ($f=1$) and maximum ($f=0.1$) CSM asymmetry, respectively. Note that the $\gamma$-ray distributions do not take into account absorption. One can see that the early time emission from SNe Ib/Ic is significantly smaller than the corresponding LT emission. The other SN models (A and B2) show a similar temporal evolution and are therefore not shown.

Figure 2

Top: time snapshots of $\gamma$-ray (on the left) and muon neutrino (on the right) fluxes as functions of the energy for SN model B1 (see Table 1 for more details on the model parameters). The different curves indicate the flux at 255, 1000, 1500, and 2000 days. We consider the asymmetry factor to be $f=0.5$ to describe the typical spectral variation over the late emission phase. After the onset of the LT interaction, the fluxes increase with time. The fluxes averaged over 2000 days have also been shown by the black curves. The $\gamma$-ray fluxes between $1–{10}^3\mathrm{TeV}$ are attenuated by pair production on the SN thermal photons. The amount of absorption is initially large, but it becomes smaller with time as the thermal photon density falls rapidly with the radius. Bottom: the fluxes of $\gamma$-rays (left) and neutrinos (right) averaged over 2000 days for model A (medium thick), B1 (thinnest), and B2 (thickest) are shown for guidance.

Figure 3

Left: time averaged $\gamma$-ray flux for different CSM models (see Table 1). The red band represents the time-averaged flux of SN Ib/Ic LT obtained considering the uncertainties in the model parameters (${\epsilon }_P\sim {10}^{-2}–{10}^{-1}$, ${\epsilon }_B\sim {10}^{-3}–{10}^{-2}$ and $f\sim 0.1–1$), while the other model parameters are kept fixed as detailed in Table 1. The uncertainty band has been obtained as follows: for the upper limit, we take $\alpha =2.0$, ${\epsilon }_{\mathrm{p}}={10}^{-1}$, ${\epsilon }_{\mathrm{B}}={10}^{-2}$, and $f=1$ for model B1; for the lower limit, we choose $\alpha =2.0$, ${\epsilon }_{\mathrm{p}}={10}^{-2}$, ${\epsilon }_{\mathrm{B}}={10}^{-3}$, and $f=0.1$ for model B2. The red continuous and dotted curves show the fluxes for model B1 and model B2, respectively, for $f=0.5$. The pink dashed curve represents the flux for model A. The sensitivities of Fermi-LAT (4 years) and CTA (50 hours) are plotted in brown and green, respectively. CTA may be able to detect $\gamma$-rays from SNe closer than $\simeq 15\mathrm{Mpc}$. Right: corresponding neutrino flux and sensitivities of IceCube (6 years with 90% CL) [61], IceCube-Gen2 (6 years with 90% CL) [62]. The blue band represents the uncertainty in the model parameters. The sensitivity chosen for IceCube corresponds to the one at the declination of 0° where IceCube is most sensitive. Neutrinos from SNe Ib/Ic LT may be detectable for bursts occurring closer than 15 Mpc.

Figure 4

Left: detection horizon (see main text for details) in $\gamma$-rays for SNe Ib/Ic LT. The time-averaged $\gamma$-ray flux has been integrated over energy in the range $5\times {10}^{-2}–5\times {10}^1\mathrm{TeV}$ for SN model B1 (red) and model B2 (red dotted) for an asymmetry factor $f=0.5$. The pink dashed line represents the flux for SN model A, slightly overlapping with the SN model B1 flux. The red band corresponds to the uncertainties in the parameters $\alpha \in [2.0-2.2]$, ${\epsilon }_P\in [{10}^{-2},{10}^{-1}]$, ${\epsilon }_B\in [{10}^{-3},{10}^{-2}]$, and $f\in [0.1,1]$. The horizontal dotted line represents the CTA sensitivity. The detection horizon is about 10 Mpc. Right: corresponding detection horizon for neutrinos. The blue band represents the time-averaged flux integrated in the range ${10}^2–{10}^4\mathrm{TeV}$. The purple dashed, blue, and light blue dotted lines show the fluxes for the SN model A, model B1, and model B2, respectively. The 90% CL sensitivity bands of different detectors are obtained by considering the variation of the declination angle ($\delta$) of the source. The band for IceCube corresponds to the minimum detector sensitivity for $\delta =-60°$ [60] and maximum detector sensitivity, $\delta =0°$ [61]. Similarly, we consider $\delta =30°$ (minimum) and $\delta =0°$ (maximum) for IceCube-Gen2 [62]; IceCube-Gen2 has the potential to detect SNe Ib/Ic LT up to 10 Mpc, while IceCube can only probe SNe up to 3 Mpc. For guidance, the black data points in both panels show the fluxes of recent nearby SN Ib/Ic LTe: SN 2014C and SN 2019yvr.

Figure 5

Acceleration time scale versus different cooling timescales.