1,396 research outputs found
Early gray dust formation in the type IIn SN 2005ip
The physical characteristics of dust formed in supernovae is poorly known. In
this paper, we investigate the extinction properties of dust formed in the type
IIn SN 2005ip. The observed light curves of SN 2005ip all exhibit a sudden drop
around 50 days after discovery. This has been attributed to dust formation in
the dense circumstellar medium. We modeled the intrinsic light curves in six
optical bands, adopting a theoretical model for the luminosity evolution of
supernovae interacting with their circumstellar material. From the difference
between the observed and intrinsic light curves, we calculated extinction
curves as a function of time. The total-to-selective extinction ratio, ,
was determined from the extinction in the B and V bands. The resulting
extinction, , increases monotonically up to about 1 mag, 150 days after
discovery. The inferred value also increases slightly with time, but
appears constant in the range 4.5--8, beyond 100 days after discovery. The
analysis confirms that dust is likely formed in SN 2005ip, starting about two
months after explosion. The high value of , that is, gray dust, suggests
dust properties different from of the Milky Way. While this result hinges on
the assumed theoretical intrinsic light curve evolution, it is encouraging that
the fitted light curves are as expected for standard ejecta and circumstellar
medium density structures.Comment: Accepted for publication in A&
Moduli Space Dynamics of a First-Order Vortex System
The moduli space dynamics of vortices in the Jackiw-Pi model where a
non-relativistic Schrodinger field couples minimally to Chern-Simons gauge
field, is considered. It is shown that the difficulties in direct application
of Manton's method to obtain a moduli-space metric in the first order system
can be circumvented by turning the Lagrangian into a second order system. We
obtain exact metrics for some simple cases and describe how the vortices
respond to an external U(1) field. We then construct an effective Lagrangian
describing dynamics of the vortices. In addition, we clarify strong-weak
coupling duality between fundamental particles and vortices.Comment: 9 pages, Latex, Corrections include
The low luminosity behaviour of the 4U 0115+63 Be/X-ray transient
The Be/X-ray transient 4U 0115+63 exhibited a giant, type-II outburst in
October 2015. The source did not decay to its quiescent state but settled in a
meta-stable plateau state (a factor ~10 brighter than quiescence) in which its
luminosity slowly decayed. We used XMM-Newton to observe the system during this
phase and we found that its spectrum can be well described using a black-body
model with a small emitting radius. This suggests emission from hot spots on
the surface, which is confirmed by the detection of pulsations. In addition, we
obtained a relatively long (~7.9 ksec) Swift/XRT observation ~35 days after our
XMM-Newton one. We found that the source luminosity was significantly higher
and, although the spectrum could be fitted with a black-body model the
temperature was higher and the emitting radius smaller. Several weeks later the
system started a sequence of type-I accretion outbursts. In between those
outbursts, the source was marginally detected with a luminosity consistent with
its quiescent level. We discuss our results in the context of the three
proposed scenarios (accretion down to the magnestospheric boundary, direct
accretion onto neutron star magnetic poles or cooling of the neutron star
crust) to explain the plateau phase.Comment: 8 pages, 4 figures, 2 tables, accepted for publication in MNRA
Noncommutative Vortex Solitons
We consider the noncommutative Abelian-Higgs theory and investigate general
static vortex configurations including recently found exact multi-vortex
solutions. In particular, we prove that the self-dual BPS solutions cease to
exist once the noncommutativity scale exceeds a critical value. We then study
the fluctuation spectra about the static configuration and show that the exact
non BPS solutions are unstable below the critical value. We have identified the
tachyonic degrees as well as massless moduli degrees. We then discuss the
physical meaning of the moduli degrees and construct exact time-dependent
vortex configurations where each vortex moves independently. We finally give
the moduli description of the vortices and show that the matrix nature of
moduli coordinates naturally emerges.Comment: 22 pages, 1 figure, typos corrected, a comment on the soliton size is
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