19 research outputs found
A reconnaissance of the possible donor stars to the Kepler supernova
The identity of Type Ia supernova progenitors remains a mystery, with various
lines of evidence pointing towards either accretion from a non-degenerate
companion, or the rapid merger of two degenerate stars leading to the
thermonuclear destruction of a white dwarf. In this paper we spectroscopically
scrutinize 24 of the brightest stars residing in the central 38" x 38" of the
SN 1604 (Kepler) supernova remnant to search for a possible surviving companion
star. We can rule out, with high certainty, a red giant companion star - a
progenitor indicated by some models of the supernova remnant. Furthermore, we
find no star that exhibits properties uniquely consistent with those expected
of a donor star down to L>10Lsun. While the distribution of star properties
towards the remnant are consistent with unrelated stars, we identify the most
promising candidates for further astrometric and spectroscopic follow-up. Such
a program would either discover the donor star, or place strong limits on
progenitor systems to luminosities with L<<Lsun.Comment: accepted by Ap
Galaxy emission line classification using 3D line ratio diagrams
Two-dimensional (2D) line ratio diagnostic diagrams have become a key tool in
understanding the excitation mechanisms of galaxies. The curves used to
separate the different regions - HII-like or else excited by an active galactic
nucleus (AGN) - have been refined over time but the core technique has not
evolved significantly. However, the classification of galaxies based on their
emission line ratios really is a multi-dimensional problem. Here we exploit
recent software developments to explore the potential of three-dimensional (3D)
line ratio diagnostic diagrams. We introduce a specific set of 3D diagrams, the
ZQE diagrams, which separate the oxygen abundance and the ionisation parameter
of HII region-like spectra, and which also enable us to probe the excitation
mechanism of the gas. By examining these new 3D spaces interactively, we define
a new set of 2D diagnostics, the ZE diagnostics, which can provide the
metallicity of objects excited by hot young stars, and which cleanly separate
HII region-like objects from the different classes of AGNs. We show that these
ZE diagnostics are consistent with the key log[NII]/H vs.
log[OIII]/H diagnostic currently used by the community. They also have
the advantage of attaching a probability that a given object belongs to one
class or to the other. Finally, we discuss briefly why ZQE diagrams can provide
a new way to differentiate and study the different classes of AGNs in
anticipation of a dedicated follow-up study.Comment: 21 pages, 15 figures, accepted for publication in ApJ. Due to size
limitations, the supplementary STL file for the 3D-printable diagram is
available here: http://www.mso.anu.edu.au/~fvogt/online_material.htm
Synthesis of new 1- 2-azido-2-(2,4-dichlorophenyl)ethyl -1H/-imidazoles and in vitro evaluation of their antifungal activity
International audienc
Diffusion of implanted <sup>195</sup>Au radiotracer atoms in amorphous silicon under irradiation with 1 MeV-N<sup>+</sup> ions
Anomalous self-diffusion, structural and energy relaxations and temporal scaling laws in pure tantalum and pure vanadium metallic glasses
Amorphous Fe targets for transient field measurements with heavy-ion beams.
This article try to solve the University uncontrol cost collect for newest programs (example E-learning) and for the student who want to go back to the university. The System was analysed for the high school fee by the State and the differents students status who show us the uncontrolled economic factor (heavy founds) but also the management, institution and politic problems. Few orientations can help us to decide the cost for the level of degree and preserved the first notion of public service in high school