220 research outputs found
Relativistic Jet Dynamics and Calorimetry of Gamma-Ray Bursts
We present numerical solutions of the 2D relativistic hydrodynamics equations
describing the deceleration and expansion of highly relativistic conical jets,
of opening angles 0.05<theta<0.2, propagating into a medium of uniform density.
Jet evolution is followed from a collimated relativistic outflow through to the
quasi-spherical non-relativistic phase. We show that relativistic sideways
expansion becomes significant beyond the radius R at which the expansion
Lorentz factor drops to 1/theta. This is consistent with simple analytic
estimates, which predict faster sideways expansion than has been claimed based
on earlier numerical modeling. For t>R/c the emission of radiation from the jet
blast wave is similar to that of a spherical blast wave carrying the same
energy. Thus, the total (calorimetric) energy of GRB blast waves may be
estimated with only a small fractional error based on t>R/c observations.Comment: 5 pages, 5 figure
Constraints on the Progenitor of SN 2010jl and Pre-Existing Hot Dust in its Surrounding Medium
A search for the progenitor of SN~2010jl, an unusually luminous core-collapse
supernova of Type~IIn, using pre-explosion {\it Hubble}/WFPC2 and {\it
Spitzer}/IRAC images of the region, yielded upper limits on the UV and
near-infrared (IR) fluxes from any candidate star. These upper limits constrain
the luminosity and effective temperature of the progenitor, the mass of any
preexisting dust in its surrounding circumstellar medium (CSM), and dust
proximity to the star. A {\it lower} limit on the CSM dust mass is required to
hide a luminous progenitor from detection by {\it Hubble}. {\it Upper} limits
on the CSM dust mass and constraints on its proximity to the star are set by
requiring that the absorbed and reradiated IR emission not exceed the IRAC
upper limits. Using the combined extinction-IR emission constraints we present
viable combinations, where and are the CSM dust mass and
its inner radius. These depend on the CSM outer radius, dust composition and
grain size, and the properties of the progenitor. The results constrain the
pre-supernova evolution of the progenitor, and the nature and origin of the
observed post-explosion IR emission from SN~2010jl. In particular, an
~Car-type progenitor will require at least 4~mag of visual extinction to
avoid detection by the {\it Hubble}. This can be achieved with dust masses
~\msun\ (less than the estimated 0.2-0.5~\msun\ around
~Car) which must be located at distances of ~cm from the
star to avoid detection by {\it Spitzer}.Comment: Accepted for publication in the ApJ. 14 pages 10 figures. The
complete figure set for Figure 10 (24 images) is available in the online
journa
Asphericity, Interaction, and Dust in the Type II-P/II-L Supernova 2013ej in Messier 74
SN 2013ej is a well-studied core-collapse supernova (SN) that stemmed from a
directly identified red supergiant (RSG) progenitor in galaxy M74. The source
exhibits signs of substantial geometric asphericity, X-rays from persistent
interaction with circumstellar material (CSM), thermal emission from warm dust,
and a light curve that appears intermediate between supernovae of Types II-P
and II-L. The proximity of this source motivates a close inspection of these
physical characteristics and their potential interconnection. We present
multi-epoch spectropolarimetry of SN 2013ej during the first 107 days, and deep
optical spectroscopy and ultraviolet through infrared photometry past ~800
days. SN 2013ej exhibits the strongest and most persistent continuum and line
polarization ever observed for a SN of its class during the recombination
phase. Modeling indicates that the data are consistent with an oblate
ellipsoidal photosphere, viewed nearly edge-on, and probably augmented by
optical scattering from circumstellar dust. We suggest that interaction with an
equatorial distribution of CSM, perhaps the result of binary evolution, is
responsible for generating the photospheric asphericity. Relatedly, our
late-time optical imaging and spectroscopy shows that asymmetric CSM
interaction is ongoing, and the morphology of broad H-alpha emission from
shock-excited ejecta provides additional evidence that the geometry of the
interaction region is ellipsoidal. Alternatively, a prolate ellipsoidal
geometry from an intrinsically bipolar explosion is also a plausible
interpretation of the data, but would probably require a ballistic jet of
radioactive material capable of penetrating the hydrogen envelope early in the
recombination phase (abridged).Comment: Post-proof edit. Accepted to ApJ on Nov. 23 2016; 21 pages, 16
figure
- …