Physical Sciences and Mathematics Commons^™

Orbital Period Of The Low‐Inclination Sw Sextantis Star V442 Ophiuchi, D. W. Hoard, John R. Thorstensen, Paula Szkody

Dartmouth Scholarship

V442 Ophiuchi is a low-inclination (noneclipsing) nova-like cataclysmic variable. We have obtained medium resolution (1-3.5 Å), time-resolved optical spectroscopy of this interacting binary star spanning an interval of 4 yr, from 1995 August to 1999 June. Using an Hα radial velocity curve constructed from our combined spectroscopic data sets, we have determined that Porb = 0.1243 days for V442 Oph, breaking the long-standing 1 day alias ambiguity in its orbital period. V442 Oph shares many of the characteristics of the group of cataclysmic variables known as the SW Sextantis stars. Its Doppler tomograms and orbital phase-dependent emission-line behavior, including …

Redshift-Distance Survey Of Early-Type Galaxies: Dipole Of The Velocity Field, L. N. Da Costa, M. Bernardi, M. V. Alonso, G. Wegner

Dartmouth Scholarship

We use the recently completed redshift-distance survey of nearby early-type galaxies (ENEAR) to measure the dipole component of the peculiar velocity field to a depth of cz ~ 6000 km s-1. The sample consists of 1145 galaxies brighter than mB = 14.5 and with cz ≤ 7000 km s-1, uniformly distributed over the whole sky, and 129 fainter cluster galaxies within the same volume. Most of the Dn-σ distances were obtained from new spectroscopic and photometric observations conducted by this project, ensuring the homogeneity of the data over the whole sky. These 1274 galaxies are objectively assigned …

Redshift-Distance Survey Of Early-Type Galaxies. I. Sample Selection, Properties, And Completeness, L. N. Da Costa, M. Bernardi, M. V. Alonso, G. Wegner

Dartmouth Scholarship

This is the first in a series of papers describing the recently completed all-sky redshift-distance survey of Early-type NEARby galaxies (ENEAR) carried out for peculiar velocity analysis. The sample is divided into two parts and consists of 1607 elliptical and lenticular galaxies with cz ≤ 7000 km s^-1 and with blue magnitudes brighter than m_B = 14.5 (ENEARm) and of galaxies in clusters (ENEARc). Galaxy distances based on the D_n-σ and fundamental plane (FP) relations are now available for 1359 and 1107 ENEARm galaxies, respectively, with roughly 80% based on new data gathered by …

Enear Redshift-Distance Survey: Cosmological Constraints, Stefano Borgani, Mariangela Bernardi, Luiz N. Da Costa, Gary Wegner

Dartmouth Scholarship

We present an analysis of the ENEAR sample of peculiar velocities of field and cluster elliptical galaxies, obtained with Dn-σ distances. We use the velocity correlation function ψ1(r) to analyze the statistics of the field object's velocities, while the analysis of the cluster data is based on the estimate of their rms peculiar velocity Vrms. The results are compared with predictions from cosmological models using linear theory. The statistics of the model velocity field is parameterized by the amplitude η8 = σ8Ω and by the shape parameter Γ of the cold dark matter-like power spectrum. …

Trading Risk In Mobile-Agent Computational Markets, Jonathan Bredin, David Kotz, Daniela Rus

Dartmouth Scholarship

Mobile-agent systems allow user programs to autonomously relocate from one host site to another. This autonomy provides a powerful, flexible architecture on which to build distributed applications. The asynchronous, decentralized nature of mobile-agent systems makes them flexible, but also hinders their deployment. We argue that a market-based approach where agents buy computational resources from their hosts solves many problems faced by mobile-agent systems. \par In our earlier work, we propose a policy for allocating general computational priority among agents posed as a competitive game for which we derive a unique computable Nash equilibrium. Here we improve on our earlier approach …

Grb 991216 Joins The Jet Set: Discovery And Monitoring Of Its Optical Afterglow, J. P. Halpern, R. Uglesich, N. Mirabal, S. Kassin, J. Thorstenson, W. C. Keel, A. Diercks, J. S. Bloom, F. Harrison, J. Mattox, M. Eracleous

Dartmouth Scholarship

The optical light curve of the energetic γ-ray burst GRB 991216 is consistent with jetlike behavior in which a power-law decay steepens from t^-1.22+-0.04 at early times to t^{-1.53 +- 0.05} in a gradual transition at around 2 days. The derivation of the late-time decay slope takes into account the constant contribution of a host or intervening galaxy, which was measured 110 days after the event at R = 24.56 +- 0.14, although the light curve deviates from a single power law whether or not a constant term is included. The early-time spectral energy distribution of the afterglow …

The Peculiar Type Ic Supernova 1997ef: Another Hypernova, Koichi Iwamoto, Takayoshi Nakamura, Ken’Ichi Nomoto, Paolo A. Mazzali, I. John Danziger, Peter Garnavich, Robert Kirshner, Saurabh Jha, David Balam, John Thorstensen

Dartmouth Scholarship

SN 1997ef has been recognized as a peculiar supernova from its light curve and spectral properties. The object was classified as a Type Ic supernova (SN Ic) because its spectra were dominated by broad absorption lines of oxygen and iron, lacking any clear signs of hydrogen or helium line features. The light curve is very different from that of previously known SNe Ic, showing a very broad peak and a slow tail. The strikingly broad line features in the spectra of SN 1997ef, which were also seen in the hypernova SN 1998bw, suggest the interesting possibility that SN 1997ef may …

The Warps Survey. Iii. The Discovery Of An X‐Ray Luminous Galaxy Cluster At Z = 0.833 And The Impact Of X‐Ray Substructure On Cluster Abundance Measurements, H. Ebeling, L. R. Jones, E. Perlman, C. Scharf, D. Horner, G. Wegner

Dartmouth Scholarship

The Wide Angle ROSAT Pointed Survey team reviews the properties and history of the discovery of Cl J0152.7-1357, an X-ray luminous, rich cluster of galaxies at a redshift of z = 0.833. At LX = 8 × 1044h ergs s-1 (0.5-2.0 keV) Cl J0152.7-1357 is the most X-ray luminous cluster known at redshifts z > 0.55. The high X-ray luminosity of the system suggests that massive clusters may begin to form at redshifts considerably greater than unity. This scenario is supported by the high degree of optical and X-ray substructure in Cl J0152.7-1357, which is similarly complex as that …

Restricted Delegation: Seamlessly Spanning Administrative Boundaries, Jon Howell, David Kotz

Dartmouth Scholarship

Historically and currently, access control and authentication is managed through ACLs. Examples include:

• the list of users in /etc/password, the NIS passwd map, or an NT domain

• permissions on Unix files or ACLs on NT objects

• a list of known hosts in .ssh/known hosts

• a list of IP addresses in .rhosts (for rsh) or .htaccess (http)

The limitations of ACLs always cause problems when spanning administrative domains (and often even inside administrative domains). The best example is the inability to express transitive sharing. Alice shares read access to object X with Bob (but not access to …

The Noesy Jigsaw: Automated Protein Secondary Structure And Main-Chain Assignment From Sparse, Unassigned Nmr Data, Chris Bailey-Kellogg, Alik Widge, John J. Kelley Iii, Marcelo J. Berardi, John H. Bushweller, Bruce Randall Donald

Dartmouth Scholarship

High-throughput, data-directed computational protocols for Structural Genomics (or Proteomics) are required in order to evaluate the protein products of genes for structure and function at rates comparable to current gene-sequencing technology. This paper presents the Jigsaw algorithm, a novel high-throughput, automated approach to protein structure characterization with nuclear magnetic resonance (NMR). Jigsaw consists of two main components: (1) graph-based secondary structure pattern identification in unassigned heteronuclear NMR data, and (2) assignment of spectral peaks by probabilistic alignment of identified secondary structure elements against the primary sequence. Jigsaw's deferment of assignment until after secondary structure identification differs greatly from traditional approaches, …

Spectroscopy And Orbital Periods Of The Old Novae V533 Herculis, V446 Herculis And X Serpentis, J. R. Thorstensen, C. J. Taylor

Dartmouth Scholarship

We report spectroscopic orbital periods of 0.147 d (= 3.53 h) for V533 Her, 0.207 d (= 4.97 h) for V446 Her and 1.478 d for X Ser. V533 Her (Nova Herculis 1963) shows absorption features in its He i and Balmer lines which appear only in a limited range of orbital phase, suggesting that it is a low-inclination SW Sextantis star. V446 Her is unusual in that it has started normal dwarf nova eruptions after a nova outburst, but we find nothing else unusual about it — in particular, a distance estimate based on its dwarf nova outbursts agrees …

A Newly-Discovered Cataclysmic Binary Near The Rosat Galactic Plane Source Rx J1910.8+2856, J R. Thorstensen, F Haberl

Dartmouth Scholarship

We report the discovery of a new cataclysmic binary star from the ROSAT Galactic Plane Survey. The star has V >∼ 18.5atminimumlightandwehavemeasureditasbrightasV = 15.7. Spectroscopy shows broad hydrogen and helium emission lines; HeII λ4686 is not detected. Hα radial velocities yield an orbital period of 0.1429 ± 0.0004 d (3.430 ± 0.010 h). Time- series photometry covering one orbital cycle near maximum light shows irregular variability, but no evidence of an eclipse. ThesystemappearstobeanewdwarfnovaoftheUGemorZ Cam type, and is unlikely to be a magnetic system. Its period is unusually short for a U Gem star.

Curiously, the new cataclysmic binary is 83′′ …

Spatially Resolved Spectroscopy Of Coma Cluster Early–Type Galaxies, D. Mehlert, R. P. Saglia, R. Bender, G. Wegner

Dartmouth Scholarship

We present long slit spectra for a magnitude limited sample of 35 E and S0 galaxies of the Coma cluster. The high quality of the data allowed us to derive spatially resolved spectra for a substantial sample of Coma galaxies for the first time. From these spectra we obtained rota- tion curves, the velocity dispersion profiles and the H3 and H4 coefficients of the Hermite decomposition of the line of sight velocity distribution. Moreover, we derive the radial line index profiles of Mg, Fe and Hβ line indices out to R ≈ 1re − 3re with high signal-to-noise ratio. We …

Associations Among Hospital Capacity, Utilization, And Mortality Of Us Medicare Beneficiaries, Controlling For Sociodemographic Factors., E. S. Fisher, J. E. Wennberg, T. A. Stukel, J. S. Skinner, S. M. Sharp

Dartmouth Scholarship

To explore whether geographic variations in Medicare hospital utilization rates are due to differences in local hospital capacity, after controlling for socioeconomic status and disease burden, and to determine whether greater hospital capacity is associated with lower Medicare mortality rates.

Correlation Analysis Of Sfi Peculiar Velocities, Stefano Borgani, Luiz N. Da Costa, Idit Zehavi, Riccardo Giovanelli, Martha P. Haynes, Wolfram Freudling, Gary Wegner, John J. Salzer

Dartmouth Scholarship

We present results of a statistical analysis of the SFI catalog of peculiar velocities, a recently completed survey of spiral field galaxies with I-band Tully-Fisher distances. The velocity field statistic utilized is the velocity correlation function, ψ₁(r), originally introduced by Górski et al. The analysis is performed in redshift space so as to circumvent potential ambiguities connected with inhomogeneous Malmquist bias corrections. The results from the SFI sample are compared with linear-theory predictions for a class of cosmological models. We generate a large set of mock samples, extracted from N-body simulations, which are used …

Detection Of Co And Dust Emission In Near-Infrared Spectra Of Sn 1998s, Christopher L. Gerardy, Robert A. Fesen, Peter Höflich, J. Craig Wheeler

Dartmouth Scholarship

Near-infrared spectra (0.95 – 2.4 μ m) of the peculiar Type IIn supernova 1998S in NGC 3877 from 95 to 355 days after maximum light are presented. K -band data taken at days 95 and 225 show the presence of the first overtone of CO emission near 2.3 μ m, which is gone by day 355. An apparent extended blue wing on the CO profile in the day 95 spectrum could indicate a large CO expansion velocity (≈ 2000 – 3000 km s − 1). This is the third detection of infrared CO emission in nearly as many Type II …