Perth Exoplanet Survey Telescope

Perth, Australia

Perth Exoplanet Survey Telescope

Perth, 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.


Han C.,Chungbuk National University | Udalski A.,University of Warsaw | Choi J.-Y.,Chungbuk National University | Yee J.C.,Ohio State University | And 34 more authors.
Astrophysical Journal Letters | Year: 2013

We report the discovery of a planetary system from observation of the high-magnification microlensing event OGLE-2012-BLG-0026. The lensing light curve exhibits a complex central perturbation with multiple features. We find that the perturbation was produced by two planets located near the Einstein ring of the planet host star. We identify four possible solutions resulting from the well-known close/wide degeneracy. By measuring both the lens parallax and the Einstein radius, we estimate the physical parameters of the planetary system. According to the best-fit model, the two planet masses are ∼0.11 M J and 0.68 MJ and they are orbiting a G-type main-sequence star with a mass ∼0.82 M⊙. The projected separations of the individual planets are beyond the snow line in all four solutions, being ∼3.8 AU and 4.6 AU in the best-fit solution. The deprojected separations are both individually larger and possibly reversed in order. This is the second multi-planet system with both planets beyond the snow line discovered by microlensing. This is the only such system (other than the solar system) with measured planet masses without sin i degeneracy. The planetary system is located at a distance 4.1 kpc from the Earth toward the Galactic center. It is very likely that extra light from stars other than the lensed star comes from the lens itself. If this is correct, it will be possible to obtain detailed information about the planet host star from follow-up observation. © 2013. The American Astronomical Society. All rights reserved.


PubMed | University of Notre Dame, Korea Astronomy and Space Science Institute, Turitea Observatory, Tel Aviv University and 23 more.
Type: Journal Article | Journal: Science (New York, N.Y.) | Year: 2014

Using gravitational microlensing, we detected a cold terrestrial planet orbiting one member of a binary star system. The planet has low mass (twice Earths) and lies projected at ~0.8 astronomical units (AU) from its host star, about the distance between Earth and the Sun. However, the planets temperature is much lower, <60 Kelvin, because the host star is only 0.10 to 0.15 solar masses and therefore more than 400 times less luminous than the Sun. The host itself orbits a slightly more massive companion with projected separation of 10 to 15 AU. This detection is consistent with such systems being very common. Straightforward modification of current microlensing search strategies could increase sensitivity to planets in binary systems. With more detections, such binary-star planetary systems could constrain models of planet formation and evolution.


Mancini L.,Max Planck Institute for Astronomy | Mancini L.,University of Salerno | Ciceri S.,Max Planck Institute for Astronomy | Chen G.,Max Planck Institute for Astronomy | And 56 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2013

We present new ground-based, multi-colour, broad-band photometric measurements of the physical parameters, transmission and emission spectra of the transiting extrasolar planet WASP-19b. The measurements are based on observations of eight transits and four occultations through a Gunn i filter using the 1.54-m Danish Telescope, 14 transits through an Rc filter at the Perth Exoplanet SurveyTelescope (PEST) observatory and one transit observed simultaneously through four optical (Sloan g', r', i', z') and three near-infrared (J,H,K) filters, using the Gamma Ray Burst Optical and Near-Infrared Detector (GROND) instrument on the MPG/ESO 2.2-m telescope. The GROND optical light curves have a point-to-point scatter around the best-fitting model between 0.52 and 0.65 mmag rms. We use these new data to measure refined physical parameters for the system. We find the planet to be more bloated (Rb = 1.410 ± 0.017RJup; Mb = 1.139 ± 0.030MJup) and the system to be twice as old as initially thought. We also used published and archived data sets to study the transit timings, which do not depart from a linear ephemeris. We detected an anomaly in the GROND transit light curve which is compatible with a spot on the photosphere of the parent star. The starspot position, size, spot contrast and temperature were established. Using our new and published measurements, we assembled the planet's transmission spectrum over the 370-2350 nm wavelength range and its emission spectrum over the 750-8000 nm range. By comparing these data to theoretical models we investigated the theoretically predicted variation of the apparent radius of WASP- 19b as a function of wavelength and studied the composition and thermal structure of its atmosphere. We conclude that: (i) there is no evidence for strong optical absorbers at low pressure, supporting the common idea that the planet's atmosphere lacks a dayside inversion; (ii) the temperature of the planet is not homogenized, because the high warming of its dayside causes the planet to be more efficient in re-radiating than redistributing energy to the night side; (iii) the planet seems to be outside of any current classification scheme. © 2013 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.


Reddy V.,Planetary Science Institute | Vokrouhlicky D.,Charles University | Bottke W.F.,Southwest Research Institute | Pravec P.,Academy of Sciences of the Czech Republic | And 14 more authors.
Icarus | Year: 2015

We explored the statistical and compositional link between Chelyabinsk meteoroid and potentially hazardous Asteroid (86039) 1999 NC43 to investigate their proposed relation proposed by Borovička et al. (Borovička, J., et al. [2013]. Nature 503, 235-237). First, using a slightly more detailed computation we confirm that the orbit of the Chelyabinsk impactor is anomalously close to the Asteroid 1999 NC43. We find ~(1-3)×10-4 likelihood of that to happen by chance. Taking the standpoint that the Chelyabinsk impactor indeed separated from 1999 NC43 by a cratering or rotational fission event, we run a forward probability calculation, which is an independent statistical test. However, we find this scenario is unlikely at the ~(10-3-10-2) level. Secondly, we note that efforts to conclusively prove separation of the Chelyabinsk meteoroid from (86039) 1999 NC43 in the past needs to meet severe criteria: relative velocity ≃1-10m/s or smaller, and ≃100km distance (i.e. about the Hill sphere distance from the parent body). We conclude that, unless the separation event was an extremely recent event, these criteria present an insurmountable difficulty due to the combination of strong orbital chaoticity, orbit uncertainty and incompleteness of the dynamical model with respect to thermal accelerations. This situation leaves the link of the two bodies unresolved and calls for additional analyses. With that goal, we revisit the presumed compositional link between (86039) 1999 NC43 and the Chelyabinsk body. Borovička et al. (Borovička, J., et al. [2013]. Nature 503, 235-237) noted that given its Q-type taxonomic classification, 1999 NC43 may pass this test. However, here we find that while the Q-type classification of 1999 NC43 is accurate, assuming that all Q-types are LL chondrites is not. Our experiment shows that not all ordinary chondrites fall under Q-taxonomic type and not all LL chondrites are Q-types. Spectral curve matching between laboratory spectra of Chelyabinsk and 1999 NC43 spectrum shows that the spectra do not match. Mineralogical analysis of Chelyabinsk (LL chondrite) and (8) Flora (the largest member of the presumed LL chondrite parent family) shows that their olivine and pyroxene chemistries are similar to LL chondrites. Similar analysis of 1999 NC43 shows that its olivine and pyroxene chemistries are more similar to L chondrites than LL chondrites (like Chelyabinsk). Analysis of the spectrum using Modified Gaussian Model (MGM) suggests 1999 NC43 is similar to LL or L chondrite although we suspect this ambiguity is due to lack of temperature and phase angle corrections in the model. While some asteroid pairs show differences in spectral slope, there is no evidence for L and LL chondrite type objects fissioning out from the same parent body. We also took photometric observations of 1999 NC43 over 54 nights during two apparitions (2000, 2014). The lightcurve of 1999 NC43 resembles simulated lightcurves of tumblers in Short-Axis Mode (SAM) with the mean wobbling angle 20°-30°. The very slow rotation of 1999 NC43 could be a result of slow-down by the Yarkovsky-O'Keefe-Radzievskii-Paddack (YORP) effect. While, a mechanism of the non-principal axis rotation excitation is unclear, we can rule out the formation of asteroid in disruption of its parent body as a plausible cause, as it is unlikely that the rotation of an asteroid fragment from catastrophic disruption would be nearly completely halted. Considering all these facts, we find the proposed link between the Chelyabinsk meteoroid and the Asteroid 1999 NC43 to be unlikely. © 2015 Elsevier Inc.


Brahm R.,University of Santiago de Chile | Brahm R.,Millennium Institute of Astrophysics | Jordan A.,University of Santiago de Chile | Jordan A.,Millennium Institute of Astrophysics | And 25 more authors.
Astronomical Journal | Year: 2015

We report the discovery of two transiting extrasolar planets by the HATSouth survey. HATS-9b orbits an old (10.8 ± 1.5 Gyr) V = 13.3 G dwarf star with a period days. The host star has a mass of 1.03 M⊙, radius of 1.503 R⊙, and effective temperature 5366 ± 70 K. The planetary companion has a mass of 0.837 Mj and radius of 1.065 Rj, yielding a mean density of 0.85g cm-3. HATS-10b orbits a V = 13.1 G dwarf star with a period days. The host star has a mass of 1.1 M⊙, radius of 1.11 R⊙, and effective temperature 5880 ± 120 K. The planetary companion has a mass of 0.53 and radius of 0.97 , yielding a mean density of 0.7 g cm-3. Both planets are compact in comparison with planets receiving similar irradiation from their host stars and lie in the nominal coordinates of Field 7 of K2, but only HATS-9b falls on working silicon. Future characterization of HATS-9b with the exquisite photometric precision of the Kepler telescope may provide measurements of its reflected light signature. © 2015. The American Astronomical Society. All rights reserved.


Zhou G.,Australian National University | Bayliss D.,Australian National University | Hartman J.D.,Princeton University | Hartman J.D.,Harvard - Smithsonian Center for Astrophysics | And 18 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2014

We report the discovery of four transiting F-M binary systems with companions between 0.1 and 0.2M⊙ in mass by the HATSouth survey. These systems have been characterized via a global analysis of the HATSouth discovery data, combined with high-resolution radial velocities and accurate transit photometry observations. We determined the masses and radii of the component stars using a combination of two methods: isochrone fitting of spectroscopic primary star parameters and equating spectroscopic primary star rotation velocity with spin-orbit synchronization. These new very low mass companions are HATS550- 016B (0.110+0.005 -0.006M⊙, 0.147+0.003 -0.004 R⊙), HATS551-019B (0.17+0.01 -0.01M⊙, 0.18+0.01 -0.01 R⊙), HATS551-021B (0.132+0.014 -0.005M⊙, 0.154+0.006 -0.008 R⊙) and HATS553-001B (0.20+0.01 -0.02M⊙, 0.22+0.01 -0.01 R⊙). We examine our sample in the context of the radius anomaly for fully convective low-mass stars. Combining our sample with the 13 other well-studied very low mass stars, we find a tentative 5 per cent systematic deviation between the measured radii and theoretical isochrone models. © 2013 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society.


Hartman J.D.,Princeton University | Bayliss D.,Australian National University | Brahm R.,University of Santiago de Chile | Brahm R.,Millennium Institute of Astrophysics | And 28 more authors.
Astronomical Journal | Year: 2015

We report the discovery by the HATSouth survey of HATS-6b, an extrasolar planet transiting a V = 15.2 mag, i = 13.7 mag M1V star with a mass of 0.57 and a radius of 0.57 . HATS-6b has a period of P = 3.3253 d, mass of = 0.32 , radius of = 1.00 , and zero-albedo equilibrium temperature of = 712.8 ±5.1 K. HATS-6 is one of the lowest mass stars known to host a close-in gas giant planet, and its transits are among the deepest of any known transiting planet system. We discuss the follow-up opportunities afforded by this system, noting that despite the faintness of the host star, it is expected to have the highest K-band S/N transmission spectrum among known gas giant planets with K. In order to characterize the star we present a new set of empirical relations between the density, radius, mass, bolometric magnitude, and V-, J-, H- and K-band bolometric corrections for main sequence stars with , or spectral types later than K5. These relations are calibrated using eclipsing binary components as well as members of resolved binary systems. We account for intrinsic scatter in the relations in a self-consistent manner. We show that from the transit-based stellar density alone it is possible to measure the mass and radius of a ∼0.6 star to ∼7 and ∼2% precision, respectively. Incorporating additional information, such as the color, or an absolute magnitude, allows the precision to be improved by up to a factor of two. © 2015. The American Astronomical Society. All rights reserved..


Martin J.C.,University of Illinois at Springfield | Hambsch F.-J.,Remote Observatory | Margutti R.,Harvard - Smithsonian Center for Astrophysics | Tan T.G.,Perth Exoplanet Survey Telescope | And 2 more authors.
Astronomical Journal | Year: 2015

The supernova (SN) impostor SN 2009ip has re-brightened several times since its initial discovery in 2009 August. During its last outburst in late 2012 September, it reached a peak brightness of mv ∼13.5 (Mv brighter than -18), causing some to speculate that it had undergone a terminal core-collapse SN. Relatively high-cadence multi-wavelength photometry of the post-peak decline revealed bumps in brightness infrequently observed in other SNe IIn. These bumps occurred synchronously in all ultraviolet (UV) and optical bands with amplitudes of 0.1-0.4 mag at intervals of 10-30 days. Episodic continuum brightening and dimming in the UV and optical with these characteristics is not easily explained within the context of models that have been proposed for the late September 2012 outburst of SN 2009ip. We also present evidence that the post-peak fluctuations in brightness occur at regular intervals and raise more questions about their origin. © 2015. The American Astronomical Society. All rights reserved.

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