532 research outputs found
Recent developments and applications of the SEC vidicon for astronomy
The engineering development of the SEC vidicon as an astronomical sensor has continued in parallel with its operational use. One scientific application was the six hour exposure of the quasar PHL-957 at the Coude spectrograph of the 200-inch Hale telescope. The developmental effort includes both the enhancement of the basic attributes that make the SEC an appropriate sensor, namely, high quantum efficiency, low threshold, and long integration; as well as work to broaden its scientific usefulness, such as the development of a MgF2 photocathode window for vacuum ultraviolet sensitivity, and a permanent magnet focus design for thermal compatibility with proposed large space telescopes. Additional details on the characteristics of the SEC tube are discussed, as well as plans to make a larger and higher resolution version
Development of television tubes for the large space telescope
Princeton Observatory has been working for several years under NASA sponsorship to develop television type sensors to use in place of photographic film for space astronomy. The performance of an SEC-vidicon with a 25 mm x 25 mm active area, MgF2 window, and bi-alkali photocathode is discussed. Results from ground based use on the Coude spectrograph of the 200-inch Hale telescope are included. The intended use of this tube in an echelle spectrograph sounding rocket payload and on Stratoscope 2 for direct high resolution imagery is also discussed. The paper also discusses the large space telescope image sensor requirements and the development of a larger television tube for this mission
Study of magnetic perturbations on SEC vidicon tubes
A laboratory measurements program was conducted to determine the tolerances that must be imposed to achieve optimum performance from SEC-vidicon data sensors in the LST mission. These measurements along with other data were used to formulate recommendations regarding the necessary telemetry and remote control for the television data sensors when in orbit. The study encompassed the following tasks: (1) Conducted laboratory measurements of the perturbations which an external magnetic field produces on a magnetically focused, SEC-vidicon. Evaluated shielding approaches. (2) Experimentally evaluated the effects produced on overall performance by variations of the tube electrode potentials, and the focus, deflection and alignment fields. (3) Recommended the extent of ground control of camera parameters and camera parameter telemetry required for optimizing the performance of the television system in orbit. The experimental data are summarized in a set of graphs
Discovery of a Very Young Field L Dwarf, 2MASS J01415823-4633574
While following up L dwarf candidates selected photometrically from the Two
Micron All Sky Survey, we uncovered an unusual object designated 2MASS
J01415823-4633574. Its optical spectrum exhibits very strong bands of vanadium
oxide but abnormally weak absorptions by titanium oxide, potassium, and sodium.
Morphologically such spectroscopic characteristics fall intermediate between
old, field early-L dwarfs (log(g)~5) and very late M giants (log(g)~0), leading
us to favor low gravity as the explanation for the unique spectral signatures
of this L dwarf. Such a low gravity can be explained only if this L dwarf is
much lower in mass than a typical old field L dwarf of similar temperature and
is still contracting to its final radius. These conditions imply a very young
age. Further evidence of youth is found in the near-infrared spectrum,
including a triangular-shaped H-band continuum reminiscent of young brown dwarf
candidates discovered in the Orion Nebula Cluster. Using the above information
along with comparisons to brown dwarf atmospheric and interior models, our
current best estimate is that this L dwarf has an age of 1-50 Myr and a mass of
6-25 M_Jupiter. The location of 2MASS 0141-4633 on the sky coupled with a
distance estimate of ~35 pc and the above age estimate suggests that this
object may be a brown dwarf member of either the 30-Myr-old Tucana/Horologium
Association or the ~12-Myr-old beta Pic Moving Group.Comment: Accepted for publication in the 10 March 2006 issue (volume 639) of
the Astrophysical Journa
Discovery of a Companion at the L/T Transition with the Wide-field Infrared Survey Explorer
We report the discovery of a substellar companion to the nearby solar-type
star HD 46588 (F7V, 17.9 pc, ~3 Gyr). HD 46588 B was found through a survey for
common proper motion companions to nearby stars using data from the Wide-field
Infrared Survey Explorer and the Two-Micron All-Sky Survey. It has an angular
separation of 79.2" from its primary, which corresponds to a projected physical
separation of 1420 AU. We have measured a spectral type of L9 for this object
based on near-infrared spectroscopy performed with TripleSpec at Palomar
Observatory. We estimate a mass of 0.064+0.008/-0.019 Msun from a comparison of
its luminosity to the values predicted by theoretical evolutionary models for
the age of the primary. Because of its companionship to a well-studied star, HD
46588 B is one of the few known brown dwarfs at the L/T transition for which
both age and distance estimates are available. Thus, it offers new constraints
on the properties of brown dwarfs during this brief evolutionary phase. The
discovery of HD 46588 B also illustrates the value of the Wide-field Infrared
Survey Explorer for identifying brown dwarfs in the solar neighborhood via
their proper motions.Comment: Astrophysical Journal, in pres
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