466 research outputs found
Optical detection and spectroscopic confirmation of supernova remnant G213.0-0.6 (now re-designated as G213.3-0.4)
During a detailed search for optical counterparts of known Galactic supernova
remnants (SNRs) using the Anglo Australian Observatory/United Kingdom Schmidt
Telescope (AAO/UKST) HAlpha survey of the southern Galactic plane we have found
characteristic optical HAlpha filaments and associated emission in the area of
SNR G213.0-0.6. Although this remnant was previously detected in the radio as a
non-thermal source, we also confirm emission at 4850 MHz in the Parkes-MIT-NRAO
(PMN) survey and at 1400 MHz in the NRAO/VLA Sky Survey (NVSS). There is an
excellent match in morphological structure between the optical (HAlpha) and
radio emission. We subsequently obtained optical spectroscopy of selected
HAlpha filaments using the South African Astronomical Observatory 1.9-m
telescope which confirmed shock excitation typical of supernova remnants. Our
discovery of HAlpha emission and the positional match with several radio
frequency maps led us to reassign G213.0-0.6 as G213.3-0.4 as these
co-ordinates more accurately reflect the actual centre of the SNR shell and
hence the most probable place of the original supernova explosion. Support for
this new SNR ID comes from the fact that the X-ray source 1RXS J065049.7-003220
is situated in the centre of this new remnant and could be connected with the
supernova explosion.Comment: 9 pages, 8 figures, Accepted for publishing in MNRA
Newly confirmed and high quality candidate Galactic SNRs uncovered from the AAO/UKST HAlpha survey
We present a catalogue of 18 new Galactic supernova remnants (SNRs) uncovered
in the optical regime as filamentary emissions and extended nebulosities on
images of the Anglo Australian Observatory/United Kingdom Schmidt Telescope
(AAO/UKST) HAlpha survey of the southern Galactic plane. Our follow-up spectral
observations confirmed classical optical SNR emission lines for these 18
structures via detection of very strong [SII] at 6717 and 6731A relative to
HAlpha ([SII]/HAlpha> 0.5). Morphologically, 10 of these remnants have
coherent, extended arc or shell structures, while the remaining objects are
more irregular in form but clearly filamentary in nature, typical of optically
detected SNRs.
In 11 cases there was a clear if not complete match between the optical and
radio structures with H filamentary structures registered inside and along the
presumed radio borders. Additionally, ROSAT X-ray sources were detected inside
the optical/radio borders of 11 of these new remnants and 3 may have an
associated pulsar.
The multi-wavelength imaging data and spectroscopy together present strong
evidence to confirm identification of 18 new, mostly senile Galactic SNRs. This
includes G288.7-6.3, G315.1+2.7 and G332.5-5.6, identified only as possible
remnants from preliminary radio observations. We also confirm existence of
radio quiet but optically active supernova remnants.Comment: In original form 21 pages, 29 figures Accepted for MNRA
Multifrequency radio observations of SNR J0536-6735 (N 59B) with associated pulsar
We present a study of new Australian Telescope Compact Array (ATCA)
observations of supernova remnant, SNR J0536-6735. This remnant appears to
follow a shell morphology with a diameter of D=36x29 pc (with 1 pc uncertainty
in each direction). There is an embedded Hii region on the northern limb of the
remnant which made various analysis and measurements (such as flux density,
spectral index and polarisation) difficult. The radio-continuum emission
followed the same structure as the optical emission, allowing for extent and
flux density estimates at 20 cm. We estimate a surface brightness for the SNR
at 1 GHz of 2.55x10^-21 W m^-2 Hz^-1 sr^-1. Also, we detect a distinctive
radio-continuum point source which confirms the previous suggestion of this
remnant being associated with a pulsar wind nebulae (PWN). The tail of this
remnant isn't seen in the radio-continuum images and is only seen in the
optical and X-ray images.Comment: 10 pages 4 figures, accepted for publication in SA
Multi-wavelength study of a new Galactic SNR G332.5-5.6
We present compelling evidence for confirmation of a Galactic supernova
remnant (SNR) candidate, G332.5-5.6, based initially on identification of new,
filamentary, optical emission line nebulosity seen in the arcsecond resolution
images from the AAO/UKST HAlpha survey. The extant radio observations and X-ray
data which we have independently re-reduced, together with new optical
spectroscopy of the large-scale fragmented nebulosity, confirms the
identification. Optical spectra, taken across five different, widely separated
nebula regions of the remnant as seen on the HAlpha images, show average ratios
of [NII]/HAlpha =2.42, [SII]/HAlpha = 2.10, and [SII] 6717/6731 = 1.23, as well
as strong [OI] 6300, 6364A and [OII] 3727A emission. These ratios are firmly
within those typical of SNRs. Here, we also present the radio-continuum
detection of the SNR at 20/13cm from observations with the Australia Telescope
Compact Array (ATCA). Radio emission is also seen at 4850 MHz, in the PMN
survey (Griffith and Wright 1993) and at 843 MHz from the SUMSS survey (Bock,
Large and Sadler 1999). We estimate an angular diameter of ~30 arcmin and
obtain an average radio spectral index of alpha = -0.6 +- 0.1 which indicates
the non-thermal nature of G332.5-5.6. Fresh analysis of existing ROSAT X-ray
data in the vicinity also confirms the existence of the SNR. The distance to
G332.5-5.6 has been independently estimated by Reynoso and Green (2007) as 3.4
kpc based on measurements of the HI lambda21 cm line seen in absorption against
the continuum emission. Our cruder estimates via assumptions on the height of
the dust layer (3.1 kpc) and using the Sigma-D relation (4 kpc) are in good
agreement.Comment: 14 pages, 18 figures. Accepted for publishing in the MNRA
First detection of optical light from SNR G279.0+1.1
This is the initial paper in a series presenting the first optical detections
and subsequent follow-up spectroscopy of known Southern Galactic supernova
remnants (SNRs) previously discovered in the radio. These new detections come
from the AAO/UKST HAlpha survey of the Southern Galactic plane which has opened
up fresh opportunities to study Galactic remnants. Here we present the first
optical imaging and follow-up spectra of Galactic SNR G279.0+1.1 where a series
of 14 small-scale fragmented groups of HAlpha filaments have been discovered in
a ~2.3 deg. area centred on G279.0+1.1. Individually they are somewhat
inconspicuous but collectively they are completely enclosed within the overall
radio contours of this known SNR. Three of these filamentary groupings are
particularly prominent and optical spectra have been obtained across two of
them. Their morphological structure and spectral characteristics are typical of
optically detected SNR filaments. Very strong [S II] emission relative to H has
been detected with [S II]/HAlpha 0.7 and 1.1, confirming strong, shock heated
emission. This is sufficient to classify these filaments in the likely SNR
domain and therefore indicating a direct connection with the radio remnant.
Other typical SNR emission lines such as [O II] at 3727A, HBeta, [O III] at
4959 and 5007A, HAlpha and [N II] at 6548 and 6584A were also detected, lending
strong support to an SNR origin of these optical filaments. The value and
insights that these optical data can provide for known remnants are discussed
along with their relevance to the Galactic nitrogen abundance. A serendipitous
discovery of an adjacent H II region is also briefly described.Comment: 11 Pages. Accepted for publication in MNRA
The planetary nebula Abell 48 and its [WN4] central star
We have conducted a multi-wavelength study of the planetary nebula Abell 48
and give a revised classification of its nucleus as a hydrogen-deficient star
of type [WN4]. The surrounding nebula has a morphology typical of PNe and
importantly, is not enriched in nitrogen, and thus not the 'peeled atmosphere'
of a massive star. Indeed, no WN4 star is known to be surrounded by such a
compact nebula. The ionized mass of the nebula is also a powerful discriminant
between the low-mass PN and high-mass WR ejecta interpretations. The ionized
mass would be impossibly high if a distance corresponding to a Pop I star was
adopted, but at a distance of 2 kpc, the mass is quite typical of moderately
evolved PNe. At this distance, the ionizing star then has a luminosity of ~5000
Lsolar, again rather typical for a PN central star. We give a brief discussion
of the implications of this discovery for the late-stage evolution of
intermediate-mass stars.Comment: EUROWD12 Proceeding
Confirmation of G6.31+0.54 as a part of a Galactic supernova remnant
A combination of archival multi-frequency radio observations with narrow-band
HAlpha optical imagery and new confirmatory optical spectroscopy have shown
that candidate supernova remnant G6.31+0.54 can now be confirmed as part of a
Galactic supernova remnant (SNR). It has non-thermal emission, an optical
emission line spectrum displaying shock excitation and standard SNR line
ratios, fine filamentary structures in HAlpha typical of optical remnants and
closely overlapping radio and optical footprints. An X-ray ROSAT source 1RXS
J175752.1-231105 was also found that matches the radio and optical emission
though a definite association is not proven. Nevertheless, taken together, all
these observed properties point to a clear SNR identification for this source.
We provide a rough estimate for the kinematic distance to G6.31+0.54 of
~4.5kpc. The detected optical filaments are some ~10arcminutes in extent (or
about 13 pc at the assumed distance). However, as only a partial arcuate
structure of the SNR can be seen (and not a full shell) the full angular extent
of the SNR is unclear. Hence the physical extent of the observed partial shell
is also difficult to estimate. If we assume an approximately circular shell
then a conservative fit to the optical arc shaped filaments gives an angular
diameter of ~20 arcminutes corresponding to a physical diameter of ~26 pc that
shows this to be an evolved remnant.Comment: Accepted for publishing in MNRAS 8 pages, 8 figure
In vitro antifungal and demelanizing activity of Nepeta rtanjensis essential oil against the human pathogen Bipolaris spicifera
The antifungal activity of Nepeta rtanjensis DikliÄ & MilojeviÄ essential oil was tested against the human pathogenic fungus Bipolaris spicifera (Bainier) Subramanian via mycelial growth assay and conidia germination assay. The minimally inhibitory concentration (MIC) of the oil was determined at 1.0 Ī¼g ml-1, while the MIC for the antifungal drug Bifonazole in a positive control was determined at 10.0 Ī¼g ml-1. The maximum of conidia germination inhibition was accomplished at 0.6 Ī¼g ml-1. In addition, at 0.6 Ī¼g ml-1 and 0.8 Ī¼g ml-1 the oil was able to cause morphophysiological changes in B. spicifera. The most significant result is the bleaching effect of the melanized conidial apparatus of the test fungi, since the melanin is the virulence factor in human pathogenic fungi. These results showed the strong antifungal properties of N. rtanjensis essential oil, supporting its possible rational use as an alternative source of new antifungal compounds
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