28 research outputs found
SMC SMP 24: A newly radio-detected planetary nebula in the small magellanic cloud
In this paper we report new radio-continuum detection of an extragalactic PN:
SMC SMP 24. We show the radio-continuum image of this PN and present the
measured radio data. The newly reduced radio observations are consistent with
the multi-wavelength data and derived parameters found in the literature. SMC
SMP 24 appear to be a young and compact PN, optically thick at frequencies
below 2 GHz.Comment: accepted for publication in Serbian Astronomical Journa
The H\alpha\ surface brightness - radius relation: a robust statistical distance indicator for planetary nebulae
Measuring the distances to Galactic planetary nebulae (PNe) has been an
intractable problem for many decades. We have now established a robust optical
statistical distance indicator, the H surface brightness- radius or S-r
relation, which addresses this problem. We developed this relation from a
critically evaluated sample of primary calibrating PNe. The robust nature of
the method results from our revised calibrating distances with significantly
reduced systematic uncertainties, and the recent availability of high-quality
data, including updated nebular diameters and integrated H fluxes. The
S-r technique is simple in its application, requiring only an angular size, an
integrated H\alpha\ flux, and the reddening to the PN. From these quantities,
an intrinsic radius is calculated, which when combined with the angular size,
yields the distance directly. Furthermore, we have found that optically thick
PNe tend to populate the upper bound of the trend, while optically-thin PNe
fall along the lower boundary in the S-r plane. This enables sub-trends to be
developed which offer even better precision in the determination of distances,
as good as 18 per cent in the case of optically-thin, high-excitation PNe. This
is significantly better than any previous statistical indicator. We use this
technique to create a catalogue of statistical distances for over 1100 Galactic
PNe, the largest such compilation in the literature to date. Finally, in an
appendix, we investigate both a set of transitional PNe and a range of PN
mimics in the S-r plane, to demonstrate its use as a diagnostic tool.
Interestingly, stellar ejecta around massive stars plot on a tight locus in S-r
space with the potential to act as a separate distance indicator for these
objects.Comment: 49 pages, 17 tables, 8 figures. Published in MNRAS; supplementary
tables are included at end of this manuscrip
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
Radio-continuum detections of Galactic Planetary Nebulae I. MASH PNe detected in large-scale radio surveys
We present an updated and newly compiled radio-continuum data-base for MASH
PNe detected in the extant large scale "blind" radio-continuum surveys (NVSS,
SUMSS/MGPS-2 and PMN) and, for a small number of MASH PNe, observed and
detected in targeted radio-continuum observations. We found radio counterparts
for approximately 250 MASH PNe. In comparison with the percentage of previously
known Galactic PNe detected in the NVSS and MGPS-2 radio-continuum surveys and
according to their position on the flux density-angular diameter and the radio
brightness temperature evolutionary diagrams we conclude, unsurprisingly, that
the MASH sample presents the radio-faint end of the known Galactic PNe
population. Also, we present radio-continuum spectral properties of a small
sub-sample of MASH PNe located in the strip between declinations -30arcdeg and
-40arcdeg, that are detected in both the NVSS and MGPS-2 radio surveys.Comment: 13 figures and 7 tables, accepted for publication in MNRA
A catalogue of integrated H\alpha\ fluxes for ~1100 Galactic planetary nebulae
We present new determinations of the integrated H\alpha\ flux for ~1100
Galactic planetary nebulae measured from the Southern H-Alpha Sky Survey Atlas
(SHASSA) and its northern counterpart, the Virginia Tech Spectral-Line Survey
(VTSS). This catalogue is the largest homogeneous database of its kind,
tripling the number of currently available measurements.Comment: 2 pages, 2 figures, presented at the IAU Symposium "Planetary
Nebulae: an Eye to the Future" No. 283, 201
Lead Telluride Doped with Au as a Very Promising Material for Thermoelectric Applications
PbTe single crystals doped with monovalent Au or Cu were grown using the Bridgman method. Far infrared reflectivity spectra were measured at room temperature for all samples and plasma minima were registered. These experimental spectra were numerically analyzed and optical parameters were calculated. All the samples of PbTe doped with Au or Cu were of the ânâ type. The properties of these compositions were analyzed and compared with PbTe containing other dopants. The samples of PbTe doped with only 3.3âat% Au were the best among the PbTe + Au samples having the lowest plasma frequency and the highest mobility of free carriers-electrons, while PbTe doped with Cu was the opposite. Samples with the lowest Cu concentration of 0.23âat% Cu had the best properties. Thermal diffusivity and electronic transport properties of the same PbTe doped samples were also investigated using a photoacoustic (PA) method with the transmission detection configuration. The results obtained with the far infrared and photoacoustic characterization of PbTe doped samples were compared and discussed. Both methods confirmed that when PbTe was doped with 3.3âat% Au, thermoelectric and electrical properties of this doped semiconductor were both significantly improved, so Au as a dopant in PbTe could be used as a new high quality thermoelectric material
The MeerKAT 1.3 GHz Survey of the Small Magellanic Cloud
We present new radio continuum images and a source catalogue from the MeerKAT survey in the direction of the Small Magellanic Cloud (SMC). The observations, at a central frequency of 1.3 GHz across a bandwidth of 0.8 GHz, encompass a field of view ~7 x 7 degrees and result in images with resolution of 8 arcsec. The median broad-band Stokes I image Root Mean Squared noise value is ~11 microJy/beam. The catalogue produced from these images contains 108,330 point sources and 517 compact extended sources. We also describe a UHF (544-1088 MHz) single pointing observation. We report the detection of a new confirmed Supernova Remnant (SNR) (MCSNR J0100-7211) with an X-ray magnetar at its centre and 10 new SNR candidates. This is in addition to the detection of 21 previously confirmed SNRs and two previously noted SNR candidates. Our new SNR candidates have typical surface brightness an order of magnitude below those previously known, and on the whole they are larger. The high sensitivity of the MeerKAT survey also enabled us to detect the bright end of the SMC Planetary Nebulae (PNe) sample - point-like radio emission is associated with 38 of 102 optically known PNe, of which 19 are new detections. Lastly, we present the detection of three foreground radio stars amidst 11 circularly polarised sources, and a few examples of morphologically interesting background radio galaxies from which the radio ring galaxy ESO 029-G034 may represent a new type of radio object
Discovery of a pulsar-powered bow shock nebula in the Small Magellanic Cloud supernova remnant DEMS5
We report the discovery of a new Small Magellanic Cloud pulsar wind nebula (PWN) at the edge of the supernova remnant (SNR) DEMS5. The pulsar powered object has a cometary morphology similar to the Galactic PWN analogues PSR B1951+32 and ÂŽthe mouseÂŽ. It is travelling supersonically through the interstellar medium.We estimate the pulsar kick velocity to be in the range of 700-2000 km s-1 for an age between 28 and 10 kyr. The radio spectral index for this SNR-PWN-pulsar system is flat (-0.29 ± 0.01) consistent with other similar objects. We infer that the putative pulsar has a radio spectral index of -1.8, which is typical for Galactic pulsars. We searched for dispersion measures up to 1000 cm-3 pc but found no convincing candidates with an S/N greater than 8. We produce a polarization map for this PWN at 5500 MHz and find a mean fractional polarization of P ⌠23 per cent. The X-ray power-law spectrum (Ï âŒ 2) is indicative of non-thermal synchrotron emission as is expected from PWN-pulsar system. Finally, we detect DEMS5 in infrared (IR) bands. Our IR photometric measurements strongly indicate the presence of shocked gas that is expected for SNRs. However, it is unusual to detect such IR emission in an SNR with a supersonic bow shock PWN.We also find a low-velocity HI cloud of âŒ107 km s-1 that is possibly interacting with DEMS5. SNR DEMS5 is the first confirmed detection of a pulsar-powered bow shock nebula found outside the Galaxy.Fil: Alsaberi, Rami Z. E.. Western Sydney University; AustraliaFil: Maitra, C.. Max Planck Institut FĂŒr Extraterrestrische Physik; AlemaniaFil: Filipovic, M. D.. Western Sydney University; AustraliaFil: Bozzetto, L.M.. Western Sydney University; AustraliaFil: Haberl, F.. Max Planck Institut FĂŒr Extraterrestrische Physik; AlemaniaFil: Maggi, P.. UniversitĂ© de Strasbourg; FranciaFil: Sasaki, M.. Universitat Erlangen-Nuremberg; AlemaniaFil: Manjolovic, P.. Western Sydney University; AustraliaFil: Velovic, V.. University Of Belgrade; SerbiaFil: Kavanagh, P.. Dublin Institute For Advanced Studies; IrlandaFil: Maxted, N. I.. University Of New South Wales (unsw) Australia; AustraliaFil: Urosevic, D.. Isaac Newton Institute Of Chile; ChileFil: Rowell, G. P.. University of Adelaide; AustraliaFil: Wong, G. F.. University Of New South Wales (unsw) Australia; AustraliaFil: For, B. Q.. The University Ofwestern Australia; AustraliaFil: O'Brien, A. N.. Western Sydney University; AustraliaFil: Galvin, T. J.. Western Sydney University; AustraliaFil: Staveley-Smith, L.. The University Ofwestern Australia; AustraliaFil: Norris, R. P.. Western Sydney University; AustraliaFil: Jarrett, T.. University Of Cape Town; SudĂĄfricaFil: Kothes, R.. National Research Council Canada; CanadĂĄFil: Luken, K. J.. Western Sydney University; AustraliaFil: Hurley-Walker, N.. Curtin University; AustraliaFil: Sano, H.. Nagoya University; JapĂłnFil: Onic, D.. University Of Belgrade; SerbiaFil: Dai, S. T.. Australia Telescope National Facility; AustraliaFil: Pannuti, G.. Morehead State University; Estados UnidosFil: Tothill, N. F. H.. Western Sydney University; AustraliaFil: Crawford, Evan. Western Sydney University; AustraliaFil: Yew, M.. Western Sydney University; AustraliaFil: Bojicic, I.. Western Sydney University; AustraliaFil: DĂ©nes, H.. Netherlands Foundation For Research In Astronomy; BĂ©lgicaFil: McClure-Griffiths, N.. Australian National University; AustraliaFil: Gurovich, Sebastian. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - CĂłrdoba. Instituto de AstronomĂa TeĂłrica y Experimental. Universidad Nacional de CĂłrdoba. Observatorio AstronĂłmico de CĂłrdoba. Instituto de AstronomĂa TeĂłrica y Experimental; ArgentinaFil: Fukui, Y.. Nagoya University; JapĂł
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