Magnesium-rich Ejecta in the SNR G284.3$-$1.8 Around the High-Mass Gamma-Ray Binary 1FGL J1018.6$-$5856

Abstract

We present results from two {\it Chandra} observations of the 16.6 d X-ray/$\gamma$-ray high-mass binary 1FGL J1018.6$-$5856 located at the center of the supernova remnant G284.3$-$1.8. The binary spectra, separated by 0.25 in binary phase, are fit with an absorbed power-law model with $\Gamma \approx 1.7-1.8$ for both observations (the flux during the second observation is a factor of 1.7 smaller). In the high-resolution ACIS-I image we found a hint of extended emission $\approx 2^{\prime \prime }$--$3^{\prime \prime }$ southeast of the binary, significant at the $3\sigma$ level. Binary evolution codes reproduce the system's observed properties with two massive stars with an initial 18-day period, undergoing mass transfer and leaving behind a heavy $\approx 2$ $\msun$ neutron star. The initial mass of the progenitor star in this scenario is 27 $\pm 4$ $\msun$. \emph{Chandra} and {\it XMM-Newton} images of the remnant show it has a relatively low X-ray surface brightness. The two brightest regions of extended X-ray emission, with luminosities $\sim 10^{33}$ erg s${}^{-1}$ for $d=5$ kpc, lie in the northern and western portions and show significantly different spectra. The northern patch is consistent with shocked ISM, with a low temperature and long ionization timescale. However, the western patch is dominated by ejecta, and shows significantly enhanced Mg content relative to other ejecta products. The abundance ratios inferred resemble those from the Large Magellanic Cloud remnant N49B. To our knowledge, this is only the second case of such Mg-rich ejecta found in an SNR. Nucleosynthesis models for core-collapse SNe predict Mg-rich ejecta from very massive progenitors of $>25$ $\msun$.

Accepted for publication in ApJ Letters

References in corpus (5)

• Periodic Emission from the Gamma-ray Binary 1FGL J1018.6-5856
• The Plasma Structure of the Cygnus Loop from the Northeastern Rim to the Southwestern Rim
• Discovery of variable VHE gamma-ray emission from the binary system 1FGL J1018.6-5856
• Spitzer IRS Observations of the XA Region in the Cygnus Loop Supernova Remnant
• Broadband X-ray Properties of the Gamma-ray Binary 1FGL J1018.6-5856

Cited by in corpus (9)

• Progenitor Mass Distribution of Core-Collapse Supernova Remnants in Our Galaxy and Magellanic Clouds based on Elemental Abundances
• Stellar Binaries That Survive Supernovae
• Light curve and SED modeling of the gamma-ray binary 1FGL J1018.6$-$5856: constraints on the orbital geometry and relativistic flow
• Optical spectroscopy of the high-mass gamma-ray binary 1FGL J1018.6-5856: A probable neutron star primary
• Refining the origins of the gamma-ray binary 1FGL J1018.6-5856
• Discovery of a Synchrotron Bubble Associated with PSR J1015-5719
• Spatial Distribution of Mg-Rich Ejecta in LMC Supernova Remnant N49B
• "The Goose" Pulsar Wind Nebula of PSR J1016-5857: The Birth of a Plerion
• The Supernova Remnant G284.3$-$1.8 and Its Relation to the Gamma-ray Binary 1FGL J1018.6$-$5856