43,678 research outputs found
Out of the frying pan: a young pulsar with a long radio trail emerging from SNR G315.9-0.0
The faint radio supernova remnant SNR G315.9-0.0 is notable for a long and
thin trail that extends outward perpendicular from the edge of its
approximately circular shell. In a search with the Parkes telescope we have
found a young and energetic pulsar that is located at the tip of this
collimated linear structure. PSR J1437-5959 has period P = 61 ms,
characteristic age tau_c = 114 kyr, and spin-down luminosity dE/dt = 1.4e36
erg/s. It is very faint, with a flux density at 1.4 GHz of about 75 uJy. From
its dispersion measure of 549 pc/cc, we infer d ~ 8 kpc. At this distance and
for an age comparable to tau_c, the implied pulsar velocity in the plane of the
sky is V_t = 300 km/s for a birth at the center of the SNR, although it is
possible that the SNR/pulsar system is younger than tau_c and that V_t > 300
km/s. The highly collimated linear feature is evidently the pulsar wind trail
left from the supersonic passage of PSR J1437-5959 through the interstellar
medium surrounding SNR G315.9-0.0.Comment: accepted for publication in ApJ Letter
Radio spectrum of the AXP J1810-197 and of its profile components
As part of a European Pulsar Network (EPN) multi-telescope observing
campaign, we performed simultaneous multi-frequency observations at 1.4, 4.9
and 8.4 GHz during July 2006 and quasi-simultaneous multi-frequency
observations from Decem- ber 2006 until July 2007 at 2.7, 4.9, 8.4, 14.6 and 32
GHz, in order to obtain flux density measurements and spectral features of the
5.5-sec radio-emitting magnetar AXP J1810-197. We monitored the spectral
evolution of its pulse shape which consists of a main pulse (MP) and an
interpulse (IP). We present the flux density spectrum of the average profile
and of the separate pulse components of this first-known radio-emitting
transient anomalous X-ray pulsar. We observe a decrease of the flux density by
a factor of 10 within 8 months and follow the disappearance of one of the two
main components. Although the spectrum is generally flat, we observe large
fluctuations of the spectral index with time. For that reason we have made some
measurements of modulation indices for individual pulses in order to also
investigate the origin of these fluctuations.Comment: accepted for publication in MNRAS, 9 pages, 7 figures, 5 table
Rewriting Modulo SMT and Open System Analysis
Rewriting modulo SMT is a new technique that combines the power of SMT solving, rewriting modulo theories, and model checking. Rewriting modulo SMT is ideally suited to model and analyze reachability properties of infinite-state open systems, i.e., systems that interact with a nondeterministic environment. Such systems exhibit both internal nondeterminism, which is proper to the system, and external nondeterminism, which is due to the environment. In a reflective formalism, such as rewriting logic, rewriting modulo SMT can be reduced to standard rewriting. Hence, rewriting modulo SMT naturally extends rewriting-based reachability analysis techniques, which are available for closed systems, to open systems. In this talk, I will be discussing the main conceptual and technical ideas behind rewriting modulo SMT, its state of implementation in the Maude system, and some research challenges to be tackled during the next few years.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech
Expanding plasmas from Anti de Sitter black holes
We introduce a new foliation of AdS black holes such that the conformal
boundary takes the form of a -dimensional FLRW spacetime with scale factor
. The foliation employs Eddington-Finkelstein-like coordinates and is
applicable to a large class of AdS black holes, supported by matter fields or
not, considerably extending previous efforts in the literature. We argue that
the holographic dual picture of a CFT plasma on a FLRW background provides an
interesting prototype to study the nonequilibrium dynamics of expanding plasmas
and use holographic renormalization to extract the renormalized energy-momentum
tensor of the dual plasma. We illustrate the procedure for three black holes of
interest, namely AdS-Schwarzschild, AdS-Gauss-Bonnet, and
AdS-Reissner-Nordstr\"om. For the latter, as a by-product, we show that the
nonequilibrium dynamics of a CFT plasma subject to a quench in the chemical
potential (i.e., a time-dependent chemical potential) resembles a cosmological
evolution with the scale factor being inversely related to the quench
profile.Comment: 16 pages, no figures; V2: references updated; V3: version to appear
in EPJ
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