Collimated Jet Or Expanding Outflow: Possible Origins of GRBs And X-Ray Flashes Page: 1 of 51
This article is part of the collection entitled: Office of Scientific & Technical Information Technical Reports and was provided to UNT Digital Library by the UNT Libraries Government Documents Department.
Extracted Text
The following text was automatically extracted from the image on this page using optical character recognition software:
slac-pub-12052
astro-ph/0607544
August 2006
Collimated Jet or Expanding Outflow: Possible Origins of GRBs
and X-Ray Flashes
Akira Mizuta"2'3, Tatsuya Yamasakil, Shigehiro Nagatakil4, and Shin Mineshigel
ABSTRACT
We investigate the dynamics of an injected outflow propagating in a progeni-
tor in the context of the collapsar model for gamma-ray bursts (GRBs) through
two dimensional axisymmetric relativistic hydrodynamic simulations. Initially,
we locally inject an outflow near the center of a progenitor. We calculate 25
models, in total, by fixing its total input energy to be 1051ergs s-1 and radius
of the injected outflow to be 7 x 107 cm while varying its bulk Lorentz factor,
Fo = 1.05 - 5, and its specific internal energy, Eo/c2 = 0.1 - 30 (with c being
speed of light). The injected outflow propagates in the progenitor and drives a
large-scale outflow or jet. We find a smooth but dramatic transition from a colli-
mated jet to an expanding outflow among calculated models. The opening angle
of the outflow (Osim) is sensitive to Fo; we find 0sim < 2 for Fo > 3. The maxi-
mum Lorentz factor is, on the other hand, sensitive to both of Fo and 6o; roughly
Fmax - Fo(1 + Eo/c2). In particular, a very high Lorentz factor of Tmax > 100 is
achieved in one model. A variety of opening angles can arise by changing Co, even
when the maximum Lorentz factor is fixed. The jet structure totally depends on
Fo. When Fo is high, a strong bow shock appears and generates a back flow.
High pressure progenitor gas heated by the bow shock collimates the outflow to
form a narrow, relativistic jet. A number of internal oblique shocks within the
jet are generated by the presence of the back flow and/or shear instability. When
Fo is low, on the contrary, the outflow expands soon after the injection, since the
bow shock is weak and thus the pressure of the progenitor gas is not high enough
1Yukawa Institute for Theoretical Physics, Kyoto University, Oiwake-cho Kitashirakawa, Sakyo-ku, Kyoto,
606-8502 Japan.
2Max-Planck-Institute fur Astrophysik Karl-Schwarzschild-Str. 1, 85741 Garching, Germany
3E-mail:mizuta@MPA-Garching.MPG.DE
4KIPAC, Stanford University, P.O.Box 20450, MS 29, Stanford, CA, 94309, USA
Submitted to Astrophys.J.
Work supported in part by Department of Energy contract DE-AC02-76SF00515
Upcoming Pages
Here’s what’s next.
Search Inside
This article can be searched. Note: Results may vary based on the legibility of text within the document.
Tools / Downloads
Get a copy of this page or view the extracted text.
Citing and Sharing
Basic information for referencing this web page. We also provide extended guidance on usage rights, references, copying or embedding.
Reference the current page of this Article.
Mizuta, Akira; /Kyoto U., Yukawa Inst., Kyoto /Garching, Max Planck Inst.; Yamasaki, Tatsuya; /Kyoto U., Yukawa Inst., Kyoto; Nagataki, Shigehiro; /Kyoto U., Yukawa Inst., Kyoto /KIPAC, Menlo Park et al. Collimated Jet Or Expanding Outflow: Possible Origins of GRBs And X-Ray Flashes, article, August 10, 2006; [Menlo Park, California]. (https://digital.library.unt.edu/ark:/67531/metadc873434/m1/1/: accessed April 19, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.