18 research outputs found
VLBI detection of an Infrared-Faint Radio Source
Infrared-Faint Radio Sources represent a new and unexpected class of object
which is bright at radio wavelengths but unusually faint at infrared
wavelengths. If, like most mJy radio sources, they were either conventional
active or star-forming galaxies in the local Universe, we would expect them to
be detectable at infrared wavelengths, and so their non-detection by the
Spitzer Space Telescope is surprising. Here we report the detection of one of
these sources using Very Long Baseline Interferometry, from which we conclude
that the sources are driven by Active Galactic Nuclei. We suggest that these
sources are either normal radio-loud quasars at high redshift or abnormally
obscured radio galaxies.Comment: accepted by MNRA
The ROTSE-III Robotic Telescope System
The observation of a prompt optical flash from GRB990123 convincingly
demonstrated the value of autonomous robotic telescope systems. Pursuing a
program of rapid follow-up observations of gamma-ray bursts, the Robotic
Optical Transient Search Experiment (ROTSE) has developed a next-generation
instrument, ROTSE-III, that will continue the search for fast optical
transients. The entire system was designed as an economical robotic facility to
be installed at remote sites throughout the world. There are seven major system
components: optics, optical tube assembly, CCD camera, telescope mount,
enclosure, environmental sensing & protection and data acquisition. Each is
described in turn in the hope that the techniques developed here will be useful
in similar contexts elsewhere.Comment: 19 pages, including 4 figures. To be published in PASP in January,
2003. PASP Number IP02-11
Characterisation of the Mopra Radio Telescope at 16--50 GHz
We present the results of a programme of scanning and mapping observations of
astronomical masers and Jupiter designed to characterise the performance of the
Mopra Radio Telescope at frequencies between 16-50 GHz using the 12-mm and 7-mm
receivers. We use these observations to determine the telescope beam size, beam
shape and overall telescope beam efficiency as a function of frequency. We find
that the beam size is well fit by / over the frequency range with a
correlation coefficient of ~90%. We determine the telescope main beam
efficiencies are between ~48-64% for the 12-mm receiver and reasonably flat at
~50% for the 7-mm receiver. Beam maps of strong HO (22 GHz) and SiO masers
(43 GHz) provide a means to examine the radial beam pattern of the telescope.
At both frequencies the radial beam pattern reveals the presence of three
components, a central `core', which is well fit by a Gaussian and constitutes
the telescopes main beam, and inner and outer error beams. At both frequencies
the inner and outer error beams extend out to approximately 2 and 3.4 times the
full-width half maximum of the main beam respectively. Sources with angular
sizes a factor of two or more larger than the telescope main beam will couple
to the main and error beams, and therefore the power contributed by the error
beams needs to be considered. From measurements of the radial beam power
pattern we estimate the amount of power contained in the inner and outer error
beams is of order one-fifth at 22 GHz rising slightly to one-third at 43 GHz.Comment: Accepted for publication in PAS
Making It Rain: How Giving Me Telescope Time Can Reduce Drought
In this paper we assess the correlation between recent observing runs (2018
and 2019) and inclement weather, and demonstrate that these observing runs have
seen much more rainfall than would otherwise be expected, an increase of over
200%. We further look at a number of observatory sites in areas that are facing
or will face drought, and suggest that a strong environmental benefit would
follow from telescope allocation committees providing us an inordinate amount
of telescope time at facilities located around the globe.Comment: 8 pages, 3 figures, 3 tables. Submitted to Acta Prima Aprili
Making It Rain: How Giving Me Telescope Time Can Reduce Drought
In this paper we assess the correlation between recent observing runs (2018 and 2019) and inclement weather, and demonstrate that these observing runs have seen much more rainfall than would otherwise be expected, an increase of over 200%. We further look at a number of observatory sites in areas that are facing or will face drought, and suggest that a strong environmental benefit would follow from telescope allocation committees providing us an inordinate amount of telescope time at facilities located around the globe
The ESO Key-Programme ``A Homogeneous Bright QSO Survey'' - I The Methods and the ``Deep'' Fields
This is the first paper in a series aimed at defining a statistically
significant sample of QSOs in the range and .
The selection is carried out using direct plates obtained at the ESO and UK
Schmidt Telescopes, scanned with the COSMOS facility and searched for objects
with an ultraviolet excess. Follow-up spectroscopy, carried out at ESO La
Silla, is used to classify each candidate. In this initial paper, we describe
the scientific objectives of the survey; the selection and observing techniques
used. We present the first sample of 285 QSOs () in a 153 deg
area, covered by the six ``deep'' fields, intended to obtain significant
statistics down with unprecedented photometric accuracy. From
this database, QSO counts are determined in the magnitude range .Comment: 21 pages uuencoded compressed postscript, to appear in Astronomy and
Astrophysics Supplements, 199
The Odd Comet 157P/Tritton and Its Misunderstood Fragmentation
Comet 157P is a faint object with a history of being prone to unfortunate
situations, circumstances, and/or coincidences. Several weeks after its 1978
discovery the comet disappeared and remained lost nonstop for twenty five
years. Rediscovered in 2003 as a new comet, it was about 500 times brighter
than in 1978, caught apparently in one of its outbursts. The comet was not
detected 200 days after its 2016 perihelion, being fainter than mag 20, but 80
days later it was mag 16 and gradually fading back to mag 20 over a period of
four months. The comet did not miss the opportunity to have a close encounter
with Jupiter, having approached it to less than 0.3 AU on 2020 February 10. The
2017 outburst or surge of activity appears to have accompanied an event of
nuclear fragmentation. The birth of a second companion is dated to the months
following the Jupiter encounter. The series of weird episodes culminated near
the 2022 perihelion, when one companion brightened to become observable for two
weeks and after another two weeks the other flared up to be seen for the next
two weeks. Unnoticed, this incredible coincidence fooled some experts into
believing that a single object, designated 157P-B, was involved, even though
its orbit left large residuals. I now offer representative fragmentation
solutions for the two companions, the mean residuals amounting to +/-0".4 and
+/-1".0, respectively.Comment: 7 pages, 5 figures, 5 table