40 research outputs found
The imprint of a symbiotic binary progenitor on the properties of Kepler's supernova remnant
We present a model for the Type Ia supernova remnant (SNR) of SN 1604, also
known as Kepler's SNR. We find that its main features can be explained by a
progenitor model of a symbiotic binary consisting of a white dwarf and an AGB
donor star with an initial mass of 4-5 M_sun. The slow, nitrogen rich wind
emanating from the donor star has partially been accreted by the white dwarf,
but has also created a circumstellar bubble. Based on observational evidence,
we assume that the system moves with a velocity of 250 km/s. Due to the
systemic motion the interaction between the wind and the interstellar medium
has resulted in the formation of a bow shock, which can explain the presence of
a one-sided, nitrogen rich shell. We present two-dimensional hydrodynamical
simulations of both the shell formation and the SNR evolution. The SNR
simulations show good agreement with the observed kinematic and morphological
properties of Kepler's SNR. Specifically, the model reproduces the observed
expansion parameters (m=V/(R/t)) of m=0.35 in the north and m=0.6 in the south
of Kepler's SNR. We discuss the variations among our hydrodynamical simulations
in light of the observations, and show that part of the blast wave may have
traversed through the one-sided shell completely. The simulations suggest a
distance to Kepler's SNR of 6 kpc, or otherwise require that SN 1604 was a
sub-energetic Type Ia explosion. Finally, we discuss the possible implications
of our model for Type Ia supernovae and their remnants in general.Comment: 13 pages, 9 figures. Submitted to A&
Results of the COVID-19 mental health international for the general population (COMET-G) study.
INTRODUCTION: There are few published empirical data on the effects of COVID-19 on mental health, and until now, there is no large international study. MATERIAL AND METHODS: During the COVID-19 pandemic, an online questionnaire gathered data from 55,589 participants from 40 countries (64.85% females aged 35.80 ± 13.61; 34.05% males aged 34.90±13.29 and 1.10% other aged 31.64±13.15). Distress and probable depression were identified with the use of a previously developed cut-off and algorithm respectively. STATISTICAL ANALYSIS: Descriptive statistics were calculated. Chi-square tests, multiple forward stepwise linear regression analyses and Factorial Analysis of Variance (ANOVA) tested relations among variables. RESULTS: Probable depression was detected in 17.80% and distress in 16.71%. A significant percentage reported a deterioration in mental state, family dynamics and everyday lifestyle. Persons with a history of mental disorders had higher rates of current depression (31.82% vs. 13.07%). At least half of participants were accepting (at least to a moderate degree) a non-bizarre conspiracy. The highest Relative Risk (RR) to develop depression was associated with history of Bipolar disorder and self-harm/attempts (RR = 5.88). Suicidality was not increased in persons without a history of any mental disorder. Based on these results a model was developed. CONCLUSIONS: The final model revealed multiple vulnerabilities and an interplay leading from simple anxiety to probable depression and suicidality through distress. This could be of practical utility since many of these factors are modifiable. Future research and interventions should specifically focus on them
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