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Post Info TOPIC: Tycho's Supernova Remnant

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Posts: 131433
Date:
 RE: Tycho's Supernova Remnant Permalink Title: The Three-Dimensional Expansion of the Ejecta from Tycho's Supernova Remnant Author: Brian J. Williams, Nina M. Coyle, Hiroya Yamaguchi, Joseph Depasquale, Ivo R. Seitenzahl, John W. Hewitt, John M. Blondin, Kazimierz J. Borkowski, Parviz Ghavamian, Robert Petre, Stephen P. Reynolds We present the first three-dimensional measurements of the velocity of various ejecta knots in Tycho's supernova remnant, known to result from a Type Ia explosion. Chandra X-ray observations over a 12-year baseline from 2003 to 2015 allow us to measure the proper motion of nearly 60 "tufts" of Si-rich ejecta, giving us the velocity in the plane of the sky. For the line of sight velocity, we use two different methods: a non-equilibrium ionization model fit to the strong Si and S lines in the 1.2-2.8 keV regime, and a fit consisting of a series of Gaussian lines. These methods give consistent results, allowing us to determine the red or blue shift of each of the knots. Assuming a distance of 3.5 kpc, we find total velocities that range from 2400 to 6600 km s^-1, with a mean of 4430 km s^-1. We find several regions where the ejecta knots have overtaken the forward shock. These regions have proper motions in excess of 6000 km s^-1. Some Type Ia supernova explosion models predict a velocity asymmetry in the ejecta. We find no such velocity asymmetries in Tycho, and discuss our findings in light of various explosion models, favoring those delayed detonation models with relatively vigorous and symmetrical deflagrations. Finally, we compare measurements with models of the remnant's evolution that include both smooth and clumpy ejecta profiles, finding that both ejecta profiles can be accommodated by the observations. Read more (7395kb, PDF) __________________

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Posts: 131433
Date:
 Permalink Title: The Origin of the Iron-Rich Knot in Tycho's Supernova Remnant Author: Hiroya Yamaguchi, John P. Hughes, Carles Badenes, Eduardo Bravo, Ivo R. Seitenzahl, Hector Martnez-Rodrguez, Sangwook Park, Robert Petre X-ray observations of supernova remnants (SNRs) allow us to investigate the chemical inhomogeneity of ejecta, offering unique insight into the nucleosynthesis in supernova explosions. Here we present detailed imaging and spectroscopic studies of the "Fe knot" located along the eastern rim of the Type Ia SNR Tycho (SN 1572) using Suzaku and Chandra long-exposure data. Surprisingly, the Suzaku spectrum of this knot shows no emission from Cr, Mn, or Ni, which is unusual for the Fe-rich regions in this SNR. Within the framework of the canonical delayed-detonation models for SN Ia, the observed mass ratios M_Cr/M_Fe < 0.023, M_Mn/M_Fe < 0.012, and M_Ni/M_Fe < 0.029 (at 90% confidence) can only be achieved for a peak temperature of (5.3-5.7) x 10^9 K and a neutron excess of < 2.0 x 10^-3. These constraints rule out the deep, dense core of a Chandrasekhar-mass white dwarf as the origin of the Fe knot, and favors either incomplete Si burning or the alpha-rich freeze-out regime, probably close to their boundary. An explosive He burning regime is a possible alternative, although this hypothesis is in conflict with the main properties of this SNR.Read more (4342kb, PDF) __________________

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Posts: 131433
Date:
 Tycho's SN1572 Permalink Title: Newly Determined Explosion Center of Tycho's Supernova and the Implications for Proposed Ex-Companion Stars of the Progenitor Author: Zhichao Xue, Bradley E. Schaefer Star G', near the center of the supernova remnant of Tycho's SN1572, has been claimed to be the ex-companion star of the exploding white dwarf, thus pointing to the progenitor being like a recurrent nova. This claim has been controversial, but there have been no confident proofs or disproofs. Previously, no has seriously addressed the question as to the exact explosion site in 1572. We now provide accurate measures of the supernova position by two radically different methods. Our first method is to use the 42 measured angular distances between the supernova in 1572 and bright nearby stars, with individual measures being as good as 84 arc-seconds, and all resulting in a position with a 1-sigma error radius of 39 arc-seconds (including systematic uncertainties). Our second method is to use a detailed and realistic expansion model for 19 positions around the edge of the remnant, where the swept-up material has measured densities, and we determine the center of expansion with a chi-square fit to the 19 measured radii and velocities. This method has a 1-sigma error radius of 7.5 arc-seconds. Both measures are substantially offset from the geometric center, and both agree closely, proving that neither has any significant systematic errors. Our final combined position for the site of the 1572 explosion is J2000 alpha=0h 25m 15.36s, delta=64°8'40.2", with a 7.3 arc-second 1-sigma uncertainty. Star G is rejected at the 8.2-sigma confidence level. Our new position lies mostly outside the region previously searched for ex-companion stars. Read more (137kb, PDF) __________________

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Posts: 131433
Date:
 Supernova 1572 Permalink Title: Azimuthal Density Variations Around the Rim of Tycho's Supernova Remnant Authors: Brian J. Williams, Kazimierz J. Borkowski, Parviz Ghavamian, John W. Hewitt, S. Alwin Mao, Robert Petre, Stephen P. Reynolds, John M. Blondin Spitzer images of Tycho's supernova remnant in the mid-infrared reveal limb-brightened emission from the entire periphery of the shell and faint filamentary structures in the interior. As with other young remnants, this emission is produced by dust grains, warmed to ~ 100 K in the post-shock environment by collisions with energetic electrons and ions. The ratio of the 70 to 24 µm fluxes is a diagnostic of the dust temperature, which in turn is a sensitive function of the plasma density. We find significant variations in the 70/24 flux ratio around the periphery of Tycho's forward shock, implying order-of-magnitude variations in density. While some of these are likely localised interactions with dense clumps of the interstellar medium, we find an overall gradient in the ambient density surrounding Tycho, with densities 3-10 times higher in the NE than in the SW. This large density gradient is qualitatively consistent with the variations in the proper motion of the shock observed in radio and X-ray studies. Overall, the mean ISM density around Tycho is quite low (~ 0.1-0.2 cm^{-3}), consistent with the lack of thermal X-ray emission observed at the forward shock. We perform two-dimensional hydrodynamic simulations of a Type Ia SN expanding into a density gradient in the ISM, and find that the overall round shape of the remnant is still easily achievable, even for explosions into significant gradients. However, this leads to an offset of the center of the explosion from the geometric center of the remnant of up to 20%, although lower values of 10% are preferred. The best match with hydrodynamical simulations is achieved if Tycho is located at a large (3-4 kpc) distance in a medium with a mean preshock density of ~ 0.2 cm^{-3}. Such preshock densities are obtained for highly (\ga 50%) porous ISM grains. Read more (2088kb, PDF) __________________

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Posts: 131433
Date:
 Tycho's Supernova Remnant Permalink Tycho Brahe discovered Supernova 1572 on the 11th November, 1572 __________________

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Posts: 131433
Date:
 SN 1572 Permalink Title: A Quadruple or Triple Origin For Tycho B and SN 1572 Authors: Todd A. Thompson, Andrew Gould Kerzendorf et al. (2012) recently reported the startling discovery of a metal-poor ([Fe/H]=-1 ± 0.4) A-type star near the center of the Tycho supernova remnant. We propose two possible explanations. In the first, Tycho B is a blue straggler, formed from the merger of a close K- or G-type binary system, which was previously in a quadruple system with the binary that produced SN 1572. Both binaries were likely brought to tidal contact by Kozai-Lidov oscillations acting in concert with tidal friction. Analogous progenitor systems may include CzeV343, VW LMi, and KIC 4247791. In the second, Tycho B is the surviving tertiary component of a triple system, which was also likely affected by Kozai-Lidov oscillations. Rates are briefly discussed. Problems with each evolutionary scenario are presented. Finally, a chance alignment between Tycho B and the supernova remnant is not excluded. Read more (9kb, PDF) __________________

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Posts: 131433
Date:
 Tycho's Supernova Permalink Title: A High-Resolution Spectroscopic Search for the Remaining Donor for Tycho's Supernova Authors: Wolfgang E. Kerzendorf, David Yong, Brian P. Schmidt, Joshua D. Simon, C. Simon Jeffery, Jay Anderson, Philipp Podsiadlowski, Avishay Gal-Yam, Jeffrey M. Silverman, Alexei V. Filippenko, Ken'ichi Nomoto, Simon J. Murphy, Michael S. Bessell, Kim A. Venn, Ryan J. Foley In this paper, we report on our analysis using Hubble Space Telescope astrometry and Keck-I HIRES spectroscopy of the central six stars of Tycho's supernova remnant (SN 1572). With these data, we measured the proper motions, radial velocities, rotational velocities, and chemical abundances of these objects. Regarding the chemical abundances, we do not confirm the unusually high [Ni/Fe] ratio previously reported for Tycho-G. Rather, we find that for all metrics in all stars, none exhibit the characteristics expected from traditional SN Ia single-degenerate-scenario calculations. The only possible exception is Tycho-B, a rare, metal-poor A-type star; however, we are unable to find a suitable scenario for it. Thus, we suggest that SN 1572 cannot be explained by the standard single-degenerate model. Read more (2857kb, PDF) __________________

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Posts: 131433
Date:
 Permalink NASA's Fermi Shows That Tycho's Star Shines in Gamma RaysIn early November 1572, observers on Earth witnessed the appearance of a "new star" in the constellation Cassiopeia, an event now recognised as the brightest naked-eye supernova in more than 400 years. It's often called "Tycho's supernova" after the great Danish astronomer Tycho Brahe, who gained renown for his extensive study of the object. Now, years of data collected by NASA's Fermi Gamma-Ray Space Telescope reveal that the shattered star's remains shine in high-energy gamma rays.The detection gives astronomers another clue in understanding the origin of cosmic rays, subatomic particles -- mainly protons -- that move through space at nearly the speed of light. Exactly where and how these particles attain such incredible energies has been a long-standing mystery because charged particles speeding through the galaxy are easily deflected by interstellar magnetic fields. This makes it impossible to track cosmic rays back to their sources.Read more __________________

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Posts: 131433
Date:
 Tycho's Supernova Remnant Permalink Hamlet | Act 1, Scene 1 BERNARDO    Last night of all,    When yond same star that's westward from the pole    Had made his course to illume that part of heaven    Where now it burns, Marcellus and myself,    The bell then beating one,-- __________________

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Posts: 131433
Date:
 Permalink Title: Fermi-LAT Detection of the Young SuperNova Remnant TychoAuthors: F. Giordano, M. Naumann-Godo, J. Ballet, K. Bechtol, S. Funk, J. Lande, M. N. Mazziotta, S. Raino, T. Tanaka, O. Tibolla, Y. UchiyamaAfter almost three years of data taking in sky survey mode, the Fermi-LAT has detected \gamma-ray emission toward the Tycho's Supernova Remnant (SNR). The Tycho SNR is among the youngest remnants in the Galaxy, originating from a Type Ia Supernova in AD 1572. The \gamma-ray integral flux from 400 MeV up to 100 GeV has been measured to be (3.5 ±1.1_{stat}±0.7_{syst}) x 10^{-9} cm^{-2}s^{-1} with a photon index of 2.3±0.2_{stat}±0.1_{syst}. Read more (716kb, PDF) __________________
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