Time Variability of Nonthermal X-Ray Stripes in Tycho's Supernova Remnant with Chandra

• Published in: The Astrophysical journal Vol. 894; no. 1; pp. 50 - 56
• Main Authors: Okuno, Tomoyuki, Tanaka, Takaaki, Uchida, Hiroyuki, Aharonian, Felix A., Uchiyama, Yasunobu, Tsuru, Takeshi Go, Matsuda, Masamune
• Format: Journal Article
• Language: English
• Published: Philadelphia The American Astronomical Society 01.05.2020; IOP Publishing
• Subjects: Astrophysics; Brightening; Cosmic ray sources; Emission; Galactic cosmic rays; Interstellar medium; Knots; Magnetic fields; Spectral analysis; Spectrum analysis; Supernova; Supernova remnants; Synchrotron radiation; Turbulence; Variability; X-ray emissions; X-ray fluxes; X-ray sources; X-rays
• ISSN: 0004-637X; 1538-4357
• DOI: 10.3847/1538-4357/ab837e

Analyzing Chandra data of Tycho's supernova remnant (SNR) taken in 2000, 2003, 2007, 2009, and 2015, we search for time-variable features of synchrotron X-rays in the southwestern part of the SNR, where stripe structures of hard X-ray emission were previously found. By comparing X-ray images obtained at each epoch, we discover a knot-like structure in the northernmost part of the stripe region became brighter particularly in 2015. We also find a bright filamentary structure gradually became fainter and narrower as it moves outward. Our spectral analysis reveals that not only the nonthermal X-ray flux but also the photon indices of the knot-like structure change from year to year. During the period from 2000 to 2015, the small knot shows a brightening of ∼70% and hardening of ΔΓ ∼ 0.45. The time variability can be explained if the magnetic field is amplified to and/or if magnetic turbulence significantly changes with time.