31 research outputs found
An Infrared Camera for Leuschner Observatory and the Berkeley Undergraduate Astronomy Lab
We describe the design, fabrication, and operation of an infrared camera
which is in use at the 30-inch telescope of the Leuschner Observatory. The
camera is based on a Rockwell PICNIC 256 x 256 pixel HgCdTe array, which is
sensitive from 0.9-2.5 micron. The primary purpose of this telescope is for
undergraduate instruction. The cost of the camera has been minimized by using
commercial parts whereever practical. The camera optics are based on a modified
Offner relay which forms a cold pupil where stray thermal radiation from the
telescope is baffled. A cold, six-position filter wheel is driven by a
cryogenic stepper motor, thus avoiding any mechanical feed throughs. The array
control and readout electronics are based on standard PC cards; the only custom
component is a simple interface card which buffers the clocks and amplifies the
analog signals from the array.Comment: 13 pages, 17 figures. Submitted to Publications of the Astronomical
Society of the Pacific: 2001 Jan 10, Accepted 2001 Jan 1
Search for Nanosecond Near-infrared Transients around 1280 Celestial Objects
Stars and planetary system
Panoramic optical and near-infrared SETI instrument: prototype design and testing
The Pulsed All-sky Near-infrared Optical Search for ExtraTerrestrial
Intelligence (PANOSETI) is an instrument program that aims to search for fast
transient signals (nano-second to seconds) of artificial or astrophysical
origin. The PANOSETI instrument objective is to sample the entire observable
sky during all observable time at optical and near-infrared wavelengths over
300 - 1650 nm. The PANOSETI instrument is designed with a number of modular
telescope units using Fresnel lenses (0.5m) arranged on two geodesic
domes in order to maximize sky coverage. We present the prototype design
and tests of these modular Fresnel telescope units. This consists of the design
of mechanical components such as the lens mounting and module frame. One of the
most important goals of the modules is to maintain the characteristics of the
Fresnel lens under a variety of operating conditions. We discuss how we account
for a range of operating temperatures, humidity, and module orientations in our
design in order to minimize undesirable changes to our focal length or angular
resolution.Comment: 12 pages, 8 figures, 1 tabl
UBVRI Photometry of the Type Ia SN 1994D in NGC 4526
We present optical photometry for the type Ia SN 1994D in NGC 4526 from 1994 March 7 to June 4 starting 13 days before B-band maximum. The light curves of this SN resemble closely those of the normal type Ia events SNe 1989B and 1980N, differing only in a slightly faster decline after maximum in VRI. The optical absolute magnitudes of SN 1994D, however, are significantly brighter than those of its near twins, and brighter than those predicted by Phillips\u27 [ApJ, 413, L105 (1993)] relationship between decline rate and luminosity. Our small amount of IR photometry of SN 1994D is not inconsistent with that of other type IA SNe
BVRI Photometry of Supernovae
We present optical photometry of one Type IIn supernova (1994Y) and nine Type
Ia supernovae (1993Y, 1993Z, 1993ae, 1994B, 1994C, 1994M, 1994Q, 1994ae, and
1995D). SN 1993Y and SN 1993Z appear to be normal SN Ia events with similar
rates of decline, but we do not have data near maximum brightness. The colors
of SN 1994C suggest that it suffers from significant reddening or is
intrinsically red. The light curves of SN 1994Y are complicated; they show a
slow rise and gradual decline near maximum brightness in and numerous
changes in the decline rates at later times. SN 1994Y also demonstrates color
evolution similar to that of the SN IIn 1988Z, but it is slightly more luminous
and declines more rapidly than SN 1988Z. The behavior of SN1994Y indicates a
small ejecta mass and a gradual strengthening of the H emission
relative to the continuum.Comment: 29 pages, 10 jpg figures, 6 eps figures, 8 tables; note added in
proo
A High Intrinsic Peculiarity Rate Among Type Ia Supernovae
We have compiled a sample of 45 Type Ia supernovae (SNe Ia) discovered by the
Lick Observatory Supernova Search (LOSS) and the Beijing Astronomical
Observatory Supernova Survey (BAOSS), and determined the rate of
spectroscopically peculiar SNe Ia (i.e., SN 1986G-like, SN 1991bg-like, and SN
1991T-like objects) and the luminosity function of SNe Ia. Because of the
nature of the two surveys (distance-limited with small baselines and deep
limiting magnitudes), nearly all SNe Ia have been discovered in the sample
galaxies of LOSS and BAOSS; thus, the observed peculiarity rate and luminosity
function of SNe Ia are intrinsic. We find that 369% of nearby SNe Ia are
peculiar; specifically, the luminosity function of SNe Ia consists of 20% SN
1991T-like, 64% normal, and 16% SN 1991bg-like objects. We have compared our
results to those found by earlier studies, and to those found at high redshift.
The apparent dearth of SN 1991T-like objects at high redshift may be due to
extinction, and especially to the difficulty of recognizing them from spectra
obtained past maximum brightness or from spectra with low signal-to-noise
ratios. Implications of the high peculiarity rate for the progenitor systems of
SNe Ia are also briefly discussed.Comment: 20 pages, 7 figures, accepted for publication in the Ap
Panoramic SETI: on-sky results from prototype telescopes and instrumental design
The Panoramic SETI (Search for Extraterrestrial Intelligence) experiment (PANOSETI) aims to detect and quantify optical transients from nanosecond to second precision over a large field-of-view (âŒ4,450 square-degrees). To meet these challenging timing and wide-field requirements, the PANOSETI experiment will use two assemblies of âŒ45 telescopes to reject spurious signals by coincidence detection, each one comprising custom-made fast photon-counting hardware combined with (f/1.32) focusing optics. Preliminary on-sky results from pairs of PANOSETI prototype telescopes (100 sq.deg.) are presented in terms of instrument performance and false alarm rates. We found that a separation of >1 km between telescopes surveying the same field-of-view significantly reduces the number of false positives due to nearby sources (e.g., Cherenkov showers) in comparison to a side- by-side configuration of telescopes. Design considerations on the all-sky PANOSETI instrument and expected field-of-views are reported
The Subluminous Type Ia Supernova 1998de in NGC 252
We present spectroscopic and extensive photometric observations of supernova
(SN) 1998de in the S0 galaxy NGC 252, discovered during the course of the Lick
Observatory Supernova Search. These data, which span a time period of 8 days
before to 76 days after -band maximum, unambigously establish SN 1998de as a
peculiar and subluminous SN Ia with strong similarities to SN 1991bg, the
prototype of these intrinsically dim SNe Ia. We find that subluminous SNe Ia
with the same Delta m_{15}(B) can have slightly different light curves at
longer wavelengths. The notable spectroscopic similarities between SN 1998de
and SN 1991bg are the wide Ti II trough at 4100-4500 A, the strong Ca II
features, and the early onset of the nebular phase. We observe that
spectroscopic deviations of SN 1998de from SN 1991bg increase toward redder
wavelenghts. These deviations include the absence of the conspicuous Na I D
absorption found in SN 1991 at 5700 A, and the evolution of a region (6800-7600
A) from featureless to feature-rich. Several lines of evidence suggest that SN
1998de was a slightly more powerful explosion than SN 1991bg. We discuss the
implications of our observations for progenitor models and the explosion
mechanism of peculiar, subluminous SNe Ia. The extensive photometric data make
SN 1998de a better template than SN 1991bg for calibrating the low-luminosity
end of the luminosity vs. decline-rate relationship.Comment: 15 pages, 10 figures, AASTeX V5.0, to appear in PAS