Perth Observatory

Bickley, Australia

Perth Observatory

Bickley, Australia
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Jordan A.,University of Santiago de Chile | Jordan A.,Millennium Institute of Astrophysics | Brahm R.,University of Santiago de Chile | Brahm R.,Millennium Institute of Astrophysics | And 34 more authors.
Astronomical Journal | Year: 2014

We report the discovery by the HATSouth survey of HATS-4b, an extrasolar planet transiting a V = 13.46 mag G star. HATS-4b has a period of P ≈ 2.5167 days, mass of Mp ≈ 1.32 MJup, radius of Rp ≈ 1.02 RJup, and density of ρp = 1.55 ± 0.16 g cm-3 ≈ 1.24 ρJup. The host star has a mass of 1.00 M⊙, a radius of 0.92 R⊙, and a very high metallicity [Fe/H]=0.43 ± 0.08. HATS-4b is among the densest known planets with masses between 1 and 2 MJ and is thus likely to have a significant content of heavy elements of the order of 75 M⊕. In this paper we present the data reduction, radial velocity measurements, and stellar classification techniques adopted by the HATSouth survey for the CORALIE spectrograph. We also detail a technique for simultaneously estimating vsin i and macroturbulence using high resolution spectra. © 2014. The American Astronomical Society. All rights reserved.

Jacoby G.H.,WIYN Observatory | Kronberger M.,Deepskyhunters Collaboration | Patchick D.,Deepskyhunters Collaboration | Teutsch P.,Deepskyhunters Collaboration | And 10 more authors.
Publications of the Astronomical Society of Australia | Year: 2010

Recent Hα surveys such as SHS and IPHAS have improved the completeness of the Galactic planetary nebula (PN) census. We now know of ∼3000 PNe in the Galaxy, but this is far short of most estimates, typically ∼25 000 or more for the total population. The size of the Galactic PN population is required to derive an accurate estimate of the chemical enrichment rates of nitrogen, carbon, and helium. In addition, a high PN count (>20 000) is strong evidence that most main-sequence stars of mass 1-8 M⊙ will go through a PN phase, while a low count (<10 000) argues that special conditions (e.g. close binary interactions) are required to form a PN. We describe a technique for finding hundreds more PNe using the existing data collections of the digital sky surveys, thereby improving the census of Galactic PNe. © Astronomical Society of Australia 2010.

Beardsley A.P.,University of Washington | Hazelton B.J.,University of Washington | Morales M.F.,University of Washington | Arcus W.,Curtin University Australia | And 59 more authors.
Monthly Notices of the Royal Astronomical Society: Letters | Year: 2013

Using the final 128 antenna locations of the MurchisonWidefield Array (MWA), we calculate its sensitivity to the epoch of reionization (EoR) power spectrum of redshifted 21 cm emission for a fiducial model and provide the tools to calculate the sensitivity for any model. Our calculation takes into account synthesis rotation, chromatic and asymmetrical baseline effects, and excludes modes that will be contaminated by foreground subtraction. For the fiducial model, the MWA will be capable of a 14σ detection of the EoR signal with one full season of observation on two fields (900 and 700 h). © 2012 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society.

Sicardy B.,University of Paris Descartes | Sicardy B.,University Pierre and Marie Curie | Sicardy B.,Institut Universitaire de France | Bolt G.,Craigie | And 33 more authors.
Astronomical Journal | Year: 2011

Pluto and its main satellite, Charon, occulted the same star on 2008 June 22. This event was observed from Australia and La Réunion Island, providing the east and north Charon Plutocentric offset in the sky plane (J2000): X = + 12,070.5 ± 4 km (+ 546.2 ± 0.2 mas), Y = + 4,576.3 ± 24 km (+ 207.1 ± 1.1 mas) at 19:20:33.82 UT on Earth, corresponding to JD 2454640.129964 at Pluto. This yields Charon's true longitude L = 153.483 ± 0. ° 071 in the satellite orbital plane (counted from the ascending node on J2000 mean equator) and orbital radius r = 19,564 ± 14 km at that time. We compare this position to that predicted by (1) the orbital solution of Tholen & Buie (the "TB97" solution), (2) the PLU017 Charon ephemeris, and (3) the solution of Tholen et al. (the "T08" solution). We conclude that (1) our result rules out solution TB97, (2) our position agrees with PLU017, with differences of δL = + 0.073 ± 0. ? 071 in longitude, and δr = + 0.6 ± 14 km in radius, and (3) while the difference with the T08 ephemeris amounts to only δL = 0.033 ± 0. ? 071 in longitude, it exhibits a significant radial discrepancy of δr = 61.3 ± 14 km. We discuss this difference in terms of a possible image scale relative error of 3.35 × 10-3in the 2002-2003 Hubble Space Telescope images upon which the T08 solution is mostly based. Rescaling the T08 Charon semi-major axis, a = 19, 570.45 km, to the TB97 value, a=19636 km, all other orbital elements remaining the same ("T08/TB97" solution), we reconcile our position with the re-scaled solution by better than 12 km (or 0.55 mas) for Charon's position in its orbital plane, thus making T08/TB97 our preferred solution. © 2011. The American Astronomical Society. All rights reserved.

Frew D.J.,Macquarie University | Frew D.J.,Perth Observatory | Madsen G.J.,University of Sydney | O'Toole S.J.,AngloAustralian Observatory | And 2 more authors.
Publications of the Astronomical Society of Australia | Year: 2010

The emission nebula around the subdwarf B (sdB) star PHL 932 is currently classified as a planetary nebula (PN) in the literature. Based on a large body of multi-wavelength data, both new and previously published, we show here that this low-excitation nebula is in fact a small Störmgren sphere (Hii region) in the interstellar medium around this star. We summarise the properties of the nebula and its ionizing star, and discuss its evolutionary status. We find no compelling evidence for close binarity, arguing that PHL 932 is an ordinary sdB star. We also find that the emission nebulae around the hot DO stars PG 0108 + 101 and PG 0109 + 111 are also Störmgren spheres in the ISM, and along with PHL 932, are probably associated with the same extensive region of high-latitude molecular gas in PiscesPegasus. © Astronomical Society of Australia 2010.

Michalska G.,Wrocław University | Michalska G.,University of Concepción | Niemczura E.,Wrocław University | Pigulski A.,Wrocław University | And 3 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2013

Using photometric and spectroscopic observations of the double-lined early-type eclipsing binary system ALS 1135, a member of the distant OB association Bochum 7, we derived the new physical and orbital parameters of its components. The masses of both components were derived with an accuracy better than 1 per cent, and their radii, with an accuracy better than 3 per cent. Since the primary's mass is equal to about 25M⊙, its radius was subsequently used to derive the age of the system which is equal to 4.3 ± 0.5Myr. The result shows that this method represents a viable alternative to isochrone fitting. A photometric search of the field of ALS 1135 resulted in the discovery of 17 variable stars, including 7 pulsating ones. One of them is a slowly-pulsating B (SPB) star belonging to Vel OB1, the other six are δ Scuti stars. Of the six δ Scuti stars three might belong to Vel OB1, the other two are likely members of Bochum 7. Given the age of Bochum 7, these two stars are probably pre-main-sequence pulsators. In addition, we provide UBVIC photometry for about 600 stars in the observed field. © 2012 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society.

Koen C.,University of the Western Cape | Kilkenny D.,University of the Western Cape | Pretorius M.L.,South African Astronomical Observatory | Pretorius M.L.,European Southern Observatory | And 2 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2010

We present photometry which shows that two known hot subdwarf stars, HE 0218-3437 and LB 1516, are variable. LB 1516 exhibits several frequencies in the range 12-25 cycles d-1 (periods of about 1-2 h) with amplitudes less than about 0.003 mag and appears to be a typical slowly pulsating sdB star. Results from a multisite campaign on HE 0218-3437 show the presence of two frequencies only, the lower amplitude variation an apparent subharmonic of the higher amplitude periodicity. It is likely that the star is in a binary system, and that the variability is due to ellipsoidal deformation of the primary star. © 2009 RAS.

Frew D.J.,Macquarie University | Frew D.J.,Perth Observatory | Parker Q.A.,Macquarie University | Parker Q.A.,Anglo Australian Observatory
Publications of the Astronomical Society of Australia | Year: 2010

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. © Astronomical Society of Australia 2010.

Roy R.,Aryabhatta Research Institute of Observational science ARIES | Kumar B.,Aryabhatta Research Institute of Observational science ARIES | Moskvitin A.S.,Special Astrophysical Observatory | Benetti S.,Instituto Nazionale Of Astrofisica | And 11 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2011

We present BVRI photometric and low-resolution spectroscopic investigation of the Type II core-collapse supernova (SN) 2008gz, which occurred in a star-forming arm and within a half-light radius (solar metallicity region) of the nearby spiral galaxy NGC 3672. The SN event was detected late, and a detailed investigation of its light curves and spectra spanning 200d suggest that it is an event of Type IIP similar to the archetypal SNe 2004et and 1999em. However, in contrast to other events of its class, SN 2008gz exhibits a rarely observed Vmagnitude drop of 1.5 over the period of a month during the plateau to nebular phase. Using an AV of 0.21mag as a lower limit and a distance of 25.5Mpc, we estimate a synthesized 56Ni mass of 0.05 ± 0.01M⊙, a mid-plateau MV of -16.6 ± 0.2mag and a total radiant energy of ~1049erg. The photospheric velocity is observed to be higher than observed for SN 2004et at similar epochs, indicating that the explosion energy was comparable to or higher than that of SN 2004et. A similar trend was also seen for the expansion velocity of H envelopes. By comparing the properties of SN 2008gz with other well-studied events, as well as by using a recent simulation of pre-SN models by Dessart, Livne & Waldman, we infer an explosion energy range of 2-3 × 1051erg, and this coupled with the observed width of the forbidden [Oi] 6300-6364Å line at 275d after the explosion gives an upper limit for the main-sequence (non-rotating, solar metallicity) progenitor mass of 17M⊙. Our narrow-band Hα observation, taken nearly 560d after the explosion, and the presence of an emission kink at zero velocity in the Doppler-corrected spectra of SN indicate that the event took place in a low-luminosity star-forming Hii region. © 2011 The Authors Monthly Notices of the Royal Astronomical Society © 2011 RAS.

Biggs J.D.,Curtin University Australia | Biggs J.D.,Perth Observatory | Fouche T.,Curtin University Australia | Bilki F.,Micromine | Zadnik M.G.,Curtin University Australia
Monthly Notices of the Royal Astronomical Society | Year: 2012

In order to study the light pollution produced in the city of Perth, Western Australia, we have used a hand-held sky brightness meter to measure the night sky brightness across the city. The data acquired facilitated the creation of a contour map of night sky brightness across the 2400km 2 area of the city - the first such map to be produced for a city. Importantly, this map was created using a methodology borrowed from the field of geophysics - the well proven and rigorous techniques of geostatistical analysis and modelling. A major finding of this study is the effect of land use on night sky brightness. By overlaying the night sky brightness map on to a suitably processed Landsat satellite image of Perth we found that locations near commercial and/or light industrial areas have a brighter night sky, whereas locations used for agriculture or having high vegetation coverage have a fainter night sky than surrounding areas. Urban areas have intermediate amounts of vegetation and are intermediate in brightness compared with the above-mentioned land uses. Regions with a higher density of major highways also appear to contribute to increased night sky brightness. When corrected for the effects of direct illumination from high buildings, we found that the night sky brightness in the central business district (CBD) is very close to that expected for a city of Perth's population from modelling work and observations obtained in earlier studies. Given that our night sky brightness measurements in Perth over 2009 and 2010 are commensurate with that measured in Canadian cities over 30 years earlier implies that the various lighting systems employed in Perth (and probably most other cities) have not been optimised to minimize light pollution over that time. We also found that night sky brightness diminished with distance with an exponent of approximately -0.25 ± 0.02 from 3.5 to 10km from the Perth CBD, a region characterized by urban and commercial land use. For distances from 10 out to about 40km from the CBD the radial variation of night sky brightness steepens to have an exponent value of approximately -1.8 ± 0.2. This steepening is associated with land use because vegetation cover increases with further distance from the CBD. © 2012 The Authors Monthly Notices of the Royal Astronomical Society © 2012 RAS.

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