6 research outputs found
Spectroscopy of planetary nebulae in M33
Spectroscopic observations of 48 emission-line objects of M33 have been
obtained with the multi-object, wide field, fibre spectrograph AF2/WYFFOS at
the 4.2m WHT telescope (La Palma, Spain). Line intensities and logarithmic
extinction, cbeta, are presented for 42 objects. Their location in the Sabbadin
& D'Odorico diagnostic diagram (Halpha/[SII] vs Hlapha/[NII]) suggests that
>70% of the candidates are Planetary Nebulae (PNe). Chemical abundances and
nebular physical parameters have been derived for the three of the six PNe
where the 4363A [OIII] emission line was measurable. These are disc PNe,
located within a galactocentric distance of 4.1 kpc, and, to date, they are the
farthest PNe with a direct chemical abundance determination. No discrepancy in
the Helium, Oxygen and Argon abundances has been found in comparison with
corresponding abundances of PNe in our Galaxy. Only a lower limit to the
sulphur abundance has been obtained since we could not detect any [SIII] line.
N/H appears to be lower than the Galactic value; some possible explanations for
this under-abundance are discussed.Comment: 18 pages, 1 JPEG figure and 3 Postscript figures, Accepted for
publication in A&
Influence of the remnant magnetization, size distribution and content of soft magnetic reinforcement in micro-mechanical behavior of polymer matrix composites
In this work, the influence of the remnant magnetization, size distribution and content of soft magnetic reinforcement in micro-mechanical behavior of polymer matrix composites (Fe81Ga19/silicone) are evaluated. Melt spinning ribbons were pulverized in a planetary milling machine to act as composite particle reinforcement. The instrumented microindentation behavior (Young's modulus and Vickers micro-hardness), the pseudo-creep and relaxation phenomena as a function of the microstructure have been studied. In general, the micro-hardness, stiffness and elastic recovery of the studied composite materials increased with the filler content. Magnetic saturation did not change with the milling technique, and composite remnant magnetization increased with either contend or particle size. Additionally, the magnetization process improved the Vickers micro-hardness and Young's modulus of composites. Finally, pseudo-creep and stress relaxation behavior was also dependent on Fe81Ga19 content and size distribution
Planetary Nebulae: Observational Properties, Mimics, and Diagnostics
The total number of true, likely and possible planetary nebulae (PN) now
known in the Milky Way is nearly 3000, double the number known a decade ago.
The new discoveries are a legacy of the recent availability of wide field,
narrowband imaging surveys, primarily in the light of H-alpha. In this paper,
we summarise the various PN discovery techniques, and give an overview of the
many types of objects which mimic PN and which appear as contaminants in both
Galactic and extragalactic samples. Much improved discrimination of classical
PN from their mimics is now possible based on the wide variety of high-quality
multiwavelength data sets that are now available. We offer improved taxonomic
and observational definitions for the PN phenomenon based on evaluation of
these better diagnostic capabilities. However, we note that evidence is
increasing that the PN phenomenon is heterogeneous, and PN are likely to be
formed from multiple evolutionary scenarios. In particular, the relationships
between some collimated symbiotic outflows and bipolar PN remain uncertain.Comment: 25 pages, 6 figures; presentation at the workshop on the Legacies of
the Macquarie/AAO/Strasbourg H-alpha Planetary Nebula project, accepted by
the Publications of the Astronomical Society of Australia (PASA