Neutron star cooling implications and magnetic field of the Vela Junior central compact object from all XMM-Newton and Chandra spectra

TL;DR

This study analyzes all available XMM-Newton and Chandra spectra of the Vela Junior neutron star to determine its surface temperature, magnetic field, and cooling behavior, revealing a high-mass neutron star with a magnetic field of about 3x10^10 G.

Contribution

The paper provides the first comprehensive spectral analysis of the Vela Junior CCO using all available data, estimating its magnetic field and surface temperatures to infer its high mass and cooling processes.

Findings

Vela Junior CCO has a hydrogen atmosphere with a hot spot at 3.5 million K.

Detected absorption lines suggest a magnetic field of ~3x10^10 G.

The neutron star is colder and likely more massive than typical young neutron stars.

Abstract

The central compact object (CCO) in the Vela Junior supernova remnant is a young neutron star whose relatively low X-ray flux and small distance suggest it has a mass high enough to activate fast neutrino cooling processes. Here we analyse all XMM-Newton MOS and pn and Chandra ACIS-S spectra of the Vela Junior CCO, with observations taking place over the 9 years from 2001 to 2010. We find that the best-fit flux and spectral model parameters do not vary significantly when treating each observation independently, and therefore we fit all the spectra simultaneously using various spectral models to characterize the predominantly thermal emission from the neutron star surface. Our results indicate the Vela Junior CCO has an atmosphere composed of hydrogen, a hot spot temperature (unredshifted) of 3.5x10^6 K, and a colder surface temperature of (6.6-8.8)x10^5 K. Possible absorption lines at ~0.6 keV and 0.9 keV provide evidence for the first-time of an average surface magnetic field B~3x10^10 G for this CCO, which is similar to the magnetic field of other CCOs. At the accurate new Vela Junior distance of 1.4 kpc, the observed luminosity that is dominated by the hot spot is ~5x10^32 erg s^-1. The luminosity from the rest of the colder surface is (1.3-4.0)x10^32 erg s^-1. The cool luminosity and temperature imply the Vela Junior CCO is indeed colder than many other young neutron stars and probably has a high mass that triggered fast neutrino cooling.