6,924 research outputs found
High speed electrostatic photomultiplier tube for the 1.06 micrometer wavelength. Cup and slat dynode chain combined with flat cathode and coax output produces 0.25 nsec rise time
The Varian cup and slat dynode chain was modified to have a flat cathode. These modifications were incorporated in an all-electrostatic photomultiplier tube having a rise time of 0.25 n sec. The tube delivered under the contract had a flat S-20 opaque cathode with a useful diameter of 5 mm. The design of the tube is such that a III to V cathode support is mounted in place of the existing cathode substrate. This cathode support is designed to accept a transferred III to V cathode and maintain the cathode surface in the same position as the S-20 photocathode
Line strength variations in beta Cephei
The line strength variations of the resonance line of C IV (1550A, 2s 2S - 2P) observed by OAO-2 were confirmed by IUE observations. In addition, the NV resonance line (1204A, 2s 2S - 2P), the Si III line (1206A, 3p 1P-1D, multiplet 11) and the Si IV resonance line (1395A, 3s 2S - 2P) all vary in line strength essentially in phase with the C IV variation. The (preliminary) period of the variation is 6.02/12.04 days
Dust and ionized gas in active radio elliptical galaxies
The authors present broad and narrow bandwidth imaging of three southern elliptical galaxies which have flat-spectrum active radio cores (NGC 1052, IC 1459 and NGC 6958). All three contain dust and extended low excitation optical line emission, particularly extensive in the case of NGC 1052 which has a large H alpha + (NII) luminosity. Both NGC 1052 and IC 1459 have a spiral morphology in emission-line images. All three display independent strong evidence that a merger or infall event has recently occurred, i.e., extensive and infalling HI gas in NGC 1052, a counter-rotating core in IC 1459 and Malin-Carter shells in NGC 6958. This infall event is the most likely origin for the emission-line gas and dust, and the authors are currently investigating possible excitation mechanisms (Sparks et al. 1990)
A Search for Candidate Light Echoes: Photometry of Supernova Environments
Supernova (SN) light echoes could be a powerful tool for determining
distances to galaxies geometrically, Sparks 1994. In this paper we present CCD
photometry of the environments of 64 historical supernovae, the first results
of a program designed to search for light echoes from these SNe. We commonly
find patches of optical emission at, or close to, the sites of the supernovae.
The color distribution of these patches is broad, and generally consistent with
stellar population colors, possibly with some reddening. However there are in
addition patches with both unusually red and unusually blue colors. We expect
light echoes to be blue, and while none of the objects are quite as blue in V-R
as the known light echo of SN1991T, there are features that are unusually blue
and we identify these as candidate light echoes for follow-on observations.Comment: 13 pages, Latex, 5 Postscript Tables, 42 Postscript figures, accepted
for publication in the A&AS. Figures 1 through 36 are available at the web
address: http://www.stsci.edu/~boffi
The design and implementation of a smartphone illuminance meter
Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Architecture, 2013.Cataloged from PDF version of thesis.Includes bibliographical references (p. 14-15).The proliferation of consumer smartphones has offered new opportunities for environmental sensing and mobile computation. Recent smartphone models - equipped with GPS trackers, accelerometers, megapixel cameras and rich software stacks - offer the possibility of emulating specialized tools completely in software. This paper documents recent efforts to build a robust, smartphone-based illuminance meter application, and describes its prototype implementation. Though hardware and software constraints prevent the complete development of such a prototype, its use and potential are demonstrated.by Devon D. Sparks.S.B
IC5063: A merger with a hidden luminous active nucleus
IC5063 is a nearby galaxy classified as an SO and containing a system of dust lanes parallel to its major optical axis (Danziger, Goss and Wellington, 1981; Bergeron, Durret and Boksenberg, 1983). Extended emission line regions with high excitation properties have been detected over distances of up to 19 kpc from the nucleus. This galaxy has been classified as Seyfert 2 on the basis of its emission line spectrum. These characteristics make IC5063 one of the best candidates for a merger remnant and an excellent candidate for a hidden luminous active nucleus. Based on new broad and narrow band images and long-slit spectroscopy obtained at the ESO 3.6 m telescope, the authors present some preliminary results supporting this hypothesis
The Regression of Good Faith in Maryland Commercial Law
“Good faith,” in the affirmative or as the absence of bad faith, has always been a challenge to define and judge as a matter of conduct, motive, or both. Different tests apply a subjective standard, an objective standard, or even a combination of the two. Some parties may be held to different expectations than others. This determination of good faith has always been fact-driven and somewhat transcendental. Until recently, however, the question invoked a construct of fairness, resting on a two-pronged metric, at least insofar as several key titles of the Maryland Uniform Commercial Code were concerned. Since June 1, 2012, the various Maryland Uniform Commercial Code definitions of good faith have been stripped to the bare, subjective “honesty in fact.”1 The ramifications of this deviation from the Uniform Law Commission’s2 promulgated Uniform Commercial Code (“UCC”) and decades of jurisprudence with consistency among most states have yet to unfold; the bench and bar are just discovering the change. This comment explores how this occurred and what the potential consequences are and also recommends remediation of Maryland’s statutory language to conform to the UCC
Low radiative efficiency accretion at work in active galactic nuclei: the nuclear spectral energy distribution of NGC4565
We derive the spectral energy distribution (SED) of the nucleus of the
Seyfert galaxy NGC4565. Despite its classification as a Seyfert2, the nuclear
source is substantially unabsorbed. The absorption we find from Chandra data
(N_H=2.5 X 10^21 cm^-2) is consistent with that produced by material in the
galactic disk of the host galaxy. HST images show a nuclear unresolved source
in all of the available observations, from the near-IR H band to the optical U
band. The SED is completely different from that of Seyfert galaxies and QSO, as
it appears basically ``flat'' in the IR-optical region, with a small drop-off
in the U-band. The location of the object in diagnostic planes for low
luminosity AGNs excludes a jet origin for the optical nucleus, and its
extremely low Eddington ratio L_o/L_Edd indicates that the radiation we observe
is most likely produced in a radiatively inefficient accretion flow (RIAF).
This would make NGC4565 the first AGN in which an ADAF-like process is
identified in the optical. We find that the relatively high [OIII] flux
observed from the ground cannot be all produced in the nucleus. Therefore, an
extended NLR must exist in this object. This may be interpreted in the
framework of two different scenarios: i) the radiation from ADAFs is sufficient
to give rise to high ionization emission-line regions through photoionization,
or ii) the nuclear source has recently ``turned-off'', switching from a
high-efficiency accretion regime to the present low-efficiency state.Comment: 7 pages, 6 figures, accepted for publication in the Astrophysical
Journa
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