Papers by Andrew J Williams
International Astronomical Union Colloquium, 1997
Abstract We report on a search for narrowband emissions from the vicinity of 36 solar type (F6 to... more Abstract We report on a search for narrowband emissions from the vicinity of 36 solar type (F6 to K4) target stars and 13 other nonsolar-type stars within 11.5 parsec at five possible interstellar beacon frequencies of pi* f (H), 2pi* f (H), e* f (OH), e*(f (OH)+ f (H)), and He-3 (4.462, 8.925, 4.532, 8.393, and 8.666 GHz respectively). The frequencies were selected by scaling important naturally occurring lines by fundamental constants. The stars were selected for a distance of less than 11.5 parsec to give sufficient time for a nearby ...
Bookmarks Related papers MentionsView impact
IAUC 6849 available at Central Bureau for Astronomical Telegrams.
Bookmarks Related papers MentionsView impact
ABSTRACT
Bookmarks Related papers MentionsView impact
The principal aim of Perth Astronomy Research Group is to automate Perth Observatory'... more The principal aim of Perth Astronomy Research Group is to automate Perth Observatory's main instrument - the Lowell-Perth 61-cm reflector - and equip it with a CCD camera, for the purpose of searching for supernovae in other galaxies and monitoring for other transient astronomical phenomena, particularly stellar flares.
Bookmarks Related papers MentionsView impact
ABSTRACT
Bookmarks Related papers MentionsView impact
IAUC 6912 available at Central Bureau for Astronomical Telegrams.
Bookmarks Related papers MentionsView impact
IAUC 6817 available at Central Bureau for Astronomical Telegrams.
Bookmarks Related papers MentionsView impact
ABSTRACT
Bookmarks Related papers MentionsView impact
ABSTRACT
Bookmarks Related papers MentionsView impact
ABSTRACT
Bookmarks Related papers MentionsView impact
IAUC 7214 available at Central Bureau for Astronomical Telegrams.
Bookmarks Related papers MentionsView impact
ABSTRACT
Bookmarks Related papers MentionsView impact
Bookmarks Related papers MentionsView impact
Bookmarks Related papers MentionsView impact
The Astrophysical Journal, 2015
Bookmarks Related papers MentionsView impact
Monthly Notices of the Royal Astronomical Society, 1992
Bookmarks Related papers MentionsView impact
Brown dwarfs are important objects because they may provide a missing link between stars and plan... more Brown dwarfs are important objects because they may provide a missing link between stars and planets, two populations that have dramatically different formation history. In this paper, we present the candidate binaries with brown dwarf companions that are found by analyzing binary microlensing events discovered during 2004 - 2011 observation seasons. Based on the low mass ratio criterion of q < 0.2, we found 7 candidate events, including OGLE-2004-BLG-035, OGLE-2004-BLG-039, OGLE-2007-BLG-006, OGLE-2007-BLG-399/MOA-2007-BLG-334, MOA-2011-BLG-104/OGLE-2011-BLG-0172, MOA-2011-BLG-149, and MOA-201-BLG-278/OGLE-2011-BLG-012N. Among them, we are able to confirm that the companions of the lenses of MOA-2011-BLG-104/OGLE-2011-BLG-0172 and MOA-2011-BLG-149 are brown dwarfs by determining the mass of the lens based on the simultaneous measurement of the Einstein radius and the lens parallax. The measured mass of the brown dwarf companions are (0.02 +/- 0.01) M_Sun and (0.019 +/- 0.002) M_...
Bookmarks Related papers MentionsView impact
Proceedings of the International Astronomical Union, 2010
Bookmarks Related papers MentionsView impact
We review the current status and future prospects of the PLANET collaboration, an international t... more We review the current status and future prospects of the PLANET collaboration, an international team of astronomers performing high-precision photometric monitoring of microlensing events. Our photometric precision and sampling is characterised and the suitability of the database for variable star studies is discussed. Preliminary results on K-giant stability are presented.
Bookmarks Related papers MentionsView impact
The Astronomical Journal, 2014
ABSTRACT We report the discovery by the HATSouth survey of HATS-4b, an extrasolar planet transiti... more ABSTRACT 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 d, mass of Mp = 1.32 Mj, radius of Rp = 1.02 Rj and density of rho_p = 1.55 +- 0.16 g/cm^3 ~ 1.24 rhoj. The host star has a mass of 1.00 Msun, a radius of 0.92 Rsun and a very high metallicity [Fe/H]= 0.43 +- 0.08. HATS-4b is among the densest known planets with masses between 1-2 Mj and is thus likely to have a significant content of heavy elements of the order of 75 Mearth. In this paper we present the data reduction, radial velocity measurement and stellar classification techniques adopted by the HATSouth survey for the CORALIE spectrograph. We also detail a technique to estimate simultaneously vsini and macroturbulence using high resolution spectra.
Bookmarks Related papers MentionsView impact
Uploads
Papers by Andrew J Williams