Indication of a Pulsar Wind Nebula in the Hard X-Ray Emission from SN 1987A

Abstract

Since the day of its explosion, SN 1987A (SN87A) was closely monitored with the aim to study its evolution and to detect its central compact relic. The detection of neutrinos from the supernova strongly supports the formation of a neutron star (NS). However, the constant and fruitless search for this object has led to different hypotheses on its nature. To date, the detection in the Atacama Large Millimeter/submillimeter Array data of a feature that is somehow compatible with the emission arising from a proto-pulsar wind nebula (PWN) is the only hint of the existence of such elusive compact object. Here we tackle this 33 yr old issue by analyzing archived observations of SN87A performed by Chandra and NuSTAR in different years. We firmly detect nonthermal emission in the 10–20 kev energy band, due to synchrotron radiation. The possible physical mechanism powering such emission is twofold: diffusive shock acceleration (DSA) or emission arising from an absorbed PWN. By relating a state-of-the-art magnetohydrodynamic simulation of SN87A to the actual data, we reconstruct the absorption pattern of the PWN embedded in the remnant and surrounded by cold ejecta. We found that, even though the DSA scenario cannot be firmly excluded, the most likely scenario that well explains the data is that of PWN emission.

Spectral Evolution of the X-Ray Remnant of SN 1987A: A High-Resolution $Chandra$ HETG Study

“…Recently, NuSTAR observations of SNR 1987A showed evidence for hard X-ray emission up to E ∼ 20 keV (Alp et al 2021;Greco et al 2021). The NuSTAR-detected hard X-ray spectrum may be attributed to either nonthermal (PL with photon index Γ ∼ 2.5, Greco et al 2021) or thermal (kT ∼ 4 keV, Alp et al 2021) origins.…”

“…These multi-wavelength observations show that the remnant of SN 1987A is now entering a new phase, where the blast wave has started probing outside the ER, while the reverse shock may be closing in on the metal-rich ejecta towards the center. Recently, NuSTAR observations of SNR 1987A have showed evidence for hard X-ray emission up to E ∼ 20 keV (Greco et al 2021;Alp et al 2021). While its origins are still unclear, either nonthermal (Greco et al 2021) or thermal (Alp et al 2021) origins have been suggested.…”

“…Recently, NuSTAR observations of SNR 1987A have showed evidence for hard X-ray emission up to E ∼ 20 keV (Greco et al 2021;Alp et al 2021). While its origins are still unclear, either nonthermal (Greco et al 2021) or thermal (Alp et al 2021) origins have been suggested.…”

The morphology of the ejecta of SN 1987A at 31 years from 1150 to 10000 Å

“…For a review of the insights gained in the decades of observation, see . The neutron star itself has not definitively been found yet due to high extinction by the ejecta (Orlando et al 2015;Alp et al 2018), although some authors (Zanardo et al 2014;Cigan et al 2019;Greco et al 2021) have reported signs of a possible neutron star remnant (but see also Alp et al 2021).…”

Statistical tests of young radio pulsars with/without supernova remnants: implying two origins of neutron stars

“…The associations between the pulsars and supernova remnants (SNRs) have been of considerable interest topics in neutron stars (NSs) astrophysics, since the radio pulses were firstly observed in the Crab Nebula in 1968 (Staelin & Reifenstein 1968), as well as the discovery of the Vela pulsar (Large, Vaughan, & Mills 1968). The story is continuing with identifying the potential NS in SN 1987A (Page et al 2020;Greco et al 2021;Soker 2021). Thanks the efforts and developments of astronomical facilities in recent years, the number of pulsars and SNRs has increased significantly.…”