10 research outputs found
Supernova Remnants as Clues to Their Progenitors
Supernovae shape the interstellar medium, chemically enrich their host
galaxies, and generate powerful interstellar shocks that drive future
generations of star formation. The shock produced by a supernova event acts as
a type of time machine, probing the mass loss history of the progenitor system
back to ages of 10 000 years before the explosion, whereas supernova
remnants probe a much earlier stage of stellar evolution, interacting with
material expelled during the progenitor's much earlier evolution. In this
chapter we will review how observations of supernova remnants allow us to infer
fundamental properties of the progenitor system. We will provide detailed
examples of how bulk characteristics of a remnant, such as its chemical
composition and dynamics, allow us to infer properties of the progenitor
evolution. In the latter half of this chapter, we will show how this exercise
may be extended from individual objects to SNR as classes of objects, and how
there are clear bifurcations in the dynamics and spectral characteristics of
core collapse and thermonuclear supernova remnants. We will finish the chapter
by touching on recent advances in the modeling of massive stars, and the
implications for observable properties of supernovae and their remnants.Comment: A chapter in "Handbook of Supernovae" edited by Athem W. Alsabti and
Paul Murdin (18 pages, 6 figures
Radio emission from Supernova Remnants
The explosion of a supernova releases almost instantaneously about 10^51 ergs
of mechanic energy, changing irreversibly the physical and chemical properties
of large regions in the galaxies. The stellar ejecta, the nebula resulting from
the powerful shock waves, and sometimes a compact stellar remnant, constitute a
supernova remnant (SNR). They can radiate their energy across the whole
electromagnetic spectrum, but the great majority are radio sources. Almost 70
years after the first detection of radio emission coming from a SNR, great
progress has been achieved in the comprehension of their physical
characteristics and evolution. We review the present knowledge of different
aspects of radio remnants, focusing on sources of the Milky Way and the
Magellanic Clouds, where the SNRs can be spatially resolved. We present a brief
overview of theoretical background, analyze morphology and polarization
properties, and review and critical discuss different methods applied to
determine the radio spectrum and distances. The consequences of the interaction
between the SNR shocks and the surrounding medium are examined, including the
question of whether SNRs can trigger the formation of new stars. Cases of
multispectral comparison are presented. A section is devoted to reviewing
recent results of radio SNRs in the Magellanic Clouds, with particular emphasis
on the radio properties of SN 1987A, an ideal laboratory to investigate
dynamical evolution of an SNR in near real time. The review concludes with a
summary of issues on radio SNRs that deserve further study, and analyzing the
prospects for future research with the latest generation radio telescopes.Comment: Revised version. 48 pages, 15 figure
Supernova remnants: the X-ray perspective
Supernova remnants are beautiful astronomical objects that are also of high
scientific interest, because they provide insights into supernova explosion
mechanisms, and because they are the likely sources of Galactic cosmic rays.
X-ray observations are an important means to study these objects.And in
particular the advances made in X-ray imaging spectroscopy over the last two
decades has greatly increased our knowledge about supernova remnants. It has
made it possible to map the products of fresh nucleosynthesis, and resulted in
the identification of regions near shock fronts that emit X-ray synchrotron
radiation.
In this text all the relevant aspects of X-ray emission from supernova
remnants are reviewed and put into the context of supernova explosion
properties and the physics and evolution of supernova remnants. The first half
of this review has a more tutorial style and discusses the basics of supernova
remnant physics and thermal and non-thermal X-ray emission. The second half
offers a review of the recent advances.The topics addressed there are core
collapse and thermonuclear supernova remnants, SN 1987A, mature supernova
remnants, mixed-morphology remnants, including a discussion of the recent
finding of overionization in some of them, and finally X-ray synchrotron
radiation and its consequences for particle acceleration and magnetic fields.Comment: Published in Astronomy and Astrophysics Reviews. This version has 2
column-layout. 78 pages, 42 figures. This replaced version has some minor
language edits and several references have been correcte
The serotonin hypothesis of pulmonary hypertension revisited
The serotonin hypothesis of pulmonary arterial hypertension (PAH) arose after an outbreak of PAH in patients taking the anorexigenic drugs aminorex and dexfenfluramine. Both of these drugs are serotonin transporter (SERT) substrates and indirect serotinergic agonists. There is now a wealth of evidence to support a role for serotonin in the pathobiology of PAH. Synthesis of serotonin can occur in pulmonary artery endothelial cells by the enzyme tryptophan hydroxylase 1 (TPH1). Serotonin then acts at the 5-HT1B receptor and the SERT to mediate constriction and proliferation of pulmonary artery smooth muscle cells. Downstream signalling molecules which play a role in serotonin-induced constriction and proliferation include reactive oxygen species (ROS), Rho-kinase (ROCK) p38 and extracellular signal-regulated kinase (ERK). There is also evidence to suggest that serotonin may interact with the bone morphogenetic receptor type II (BMPRII) to provide a ‘second hit’ risk factor for PAH
Turbulent amplification of magnetic fields in laboratory laser-produced shock waves
X-ray1-3 and radio4-6 observations of the supernova remnant Cassiopeia A reveal the presence of magnetic fields about 100 times stronger than those in the surrounding interstellar medium. Field coincident with the outer shock probably arises through a nonlinear feedback process involving cosmic rays2,7,8. The origin of the large magnetic field in the interior of the remnant is less clear but it is presumably stretched and amplified by turbulent motions. Turbulence may be generated by hydrodynamic instability at the contact discontinuity between the supernova ejecta and the circumstellar gas9. However, optical observations of Cassiopeia A indicate that the ejecta are interacting with a highly inhomogeneous, dense circumstellar cloud bank formed before the supernova explosion10-12. Herewe investigate the possibility that turbulent amplification is induced when the outer shock overtakes dense clumps in the ambient medium13-15. We report laboratory experiments that indicate the magnetic field is amplified when the shock interacts with a plastic grid. We show that our experimental results can explain the observed synchrotron emission in the interior of the remnant. The experiment also provides a laboratory example of magnetic field amplification by turbulence in plasmas, a physical process thought to occur in many astrophysical phenomena. © 2014 Macmillan Publishers Limited. All rights reserved
Supernova 1604, Kepler’s Supernova, and Its Remnant
Supernova 1604 is the last Galactic supernova for which historical records
exist. Johannes Kepler's name is attached to it, as he published a detailed
account of the observations made by himself and European colleagues. Supernova
1604 was very likely a Type Ia supernova, which exploded 350 pc to 750 pc above
the Galactic plane. Its supernova remnant, known as Kepler's supernova remnant,
shows clear evidence for interaction with nitrogen-rich material in the
north/northwest part of the remnant, which, given the height above the Galactic
plane, must find its origin in mass loss from the supernova progenitor system.
The combination of a Type Ia supernova and the presence of circumstellar
material makes Kepler's supernova remnant a unique object to study the origin
of Type Ia supernovae. The evidence suggests that the progenitor binary system
of supernova 1604 consisted of a carbon- oxygen white dwarf and an evolved
companion star, which most likely was in the (post) asymptotic giant branch of
its evolution. A problem with this scenario is that the companion star must
have survived the explosion, but no trace of its existence has yet been found,
despite a deep search.
1 Introduction; 2 The supernova remnant, its distance and multiwavelength
properties; 2.1 Position, distance estimates and SN1604 as a runaway system;
2.2 X-ray imaging spectroscopy and SN1604 as a Type Ia supernova 2.3 The
circumstellar medium as studied in the optical and infrared; 3 The dynamics of
Kepler's SNR; 3.1 Velocity measurements; 3.2 Hydrodynamical simulations; 4 The
progenitor system of SN 1604; 4.1 Elevated circumstellar nitrogen abundances,
silicates and a single degenerate scenario for SN1604; 4.2 Problems with a
single degenerate Type Ia scenario for SN 1604; 4.3 Was SN 1604 a
core-degenerate Type Ia explosion?; 4.4 What can we learn from the historical
light curve of SN 1604? ; 5 ConclusionsComment: Final draft of a chapter in "Handbook of Supernovae" edited by Athem
W. Alsabti and Paul Murdin (23 pages, 5 figures). V2 has a small mistake
corrected. Final print version can be found here:
http://link.springer.com/referenceworkentry/10.1007/978-3-319-20794-0_49-