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Articles 8191 - 8220 of 9206
Full-Text Articles in Physical Sciences and Mathematics
A V And I Ccd Mosaic Survey Of The Ursa Minor Dwarf Spheroidal Galaxy, J. T. Kleyna, M. J. Geller, S. J. Kenyon, M. J. Kurtz, J. R. Thorstensen
A V And I Ccd Mosaic Survey Of The Ursa Minor Dwarf Spheroidal Galaxy, J. T. Kleyna, M. J. Geller, S. J. Kenyon, M. J. Kurtz, J. R. Thorstensen
Dartmouth Scholarship
We discuss a Johnson-Cousins V- and I-band CCD mosaic survey of the Ursa Minor dwarf spheroidal galaxy (dSph) to V ~ 22. We covered UMi with 27 105 × 105 overlapping CCD frames, each frame consisting of two 300 s exposures in each of V and I. We also observed several regions ~3° from UMi to obtain an estimate of contamination by galaxies and Galactic stars. We report the first H-R diagram of an entire dSph. Separation of dwarf stars from foreground stars by color allows a robust estimation of the structural parameters of UMi. We examine …
Aquila X-1: A Low-Inclination Soft X-Ray Transient, T. Shahbaz, J. R. Thorstensen, P. A. Charles, N. D. Sherman
Aquila X-1: A Low-Inclination Soft X-Ray Transient, T. Shahbaz, J. R. Thorstensen, P. A. Charles, N. D. Sherman
Dartmouth Scholarship
We have obtained I-band photometry of the neutron star X-ray transient Aql X-1 during quiescence. We find a periodicity at 2.487 cycles d−1, which we interpret as twice the orbital frequency (19.30±0.05 h). Folding the data on the orbital period, we model the light-curve variations as the ellipsoidal modulation of the secondary star. We determine the binary inclination to be 20°–30° (90 per cent confidence) and also determine the 95 per cent upper limits to the radial velocity semi-amplitude and rotational broadening of the secondary star to be 117 and 50 km s−1, respectively.
Search For A New Gauge Boson In Π0 Decays, Nomad Collaboration, J. Altegoer, D. Autiero, A. Baldisseri, M. Baldo-Ceolin, G. Ballocchi, M. Banner, S. Basa, G. Bassompierre, K. Benslama, N. Besson, I. Bird, B. Blumenfeld, F. Bobisut, J. Bouchez, S. Boyd, A. Bueno, S. Bunyatov, L. Camilleri, K. Zuber, Roberto Petti, Et. Al.
Search For A New Gauge Boson In Π0 Decays, Nomad Collaboration, J. Altegoer, D. Autiero, A. Baldisseri, M. Baldo-Ceolin, G. Ballocchi, M. Banner, S. Basa, G. Bassompierre, K. Benslama, N. Besson, I. Bird, B. Blumenfeld, F. Bobisut, J. Bouchez, S. Boyd, A. Bueno, S. Bunyatov, L. Camilleri, K. Zuber, Roberto Petti, Et. Al.
Faculty Publications
A search was made for a new light gauge boson X which might be produced in π0→γ+X decay from neutral pions generated by 450 GeV protons in the CERN SPS neutrino target. The X's would penetrate the downstream shielding and be observed in the NOMAD detector via the Primakoff effect, in the process of X→π0 conversion in the external Coulomb field of a nucleus. With 1.45×1018 protons on target, 20 candidate events with energy between 8 and 140 GeV were found from the analysis of neutrino data. This number is in …
The Two-Dimensional Ising Model: Mean-Field And Monte Carlo Results For Equilibrium And Nonequilibrium Transitions, Kevin Scott Brown
The Two-Dimensional Ising Model: Mean-Field And Monte Carlo Results For Equilibrium And Nonequilibrium Transitions, Kevin Scott Brown
Honors Theses
No abstract provided.
Radio Pulse Properties Of The Millisecond Pulsar Psr J0437-4715. I. Observations At 20 Centimeters, F. A. Jenet, S. B. Anderson, V. M. Kaspi, T. A. Prince, S. C. Unwin
Radio Pulse Properties Of The Millisecond Pulsar Psr J0437-4715. I. Observations At 20 Centimeters, F. A. Jenet, S. B. Anderson, V. M. Kaspi, T. A. Prince, S. C. Unwin
Physics and Astronomy Faculty Publications and Presentations
We present a total of 48 minutes of observations of the nearby, bright millisecond pulsar PSR J0437-4715 taken at the Parkes Observatory in Australia. The data were obtained at a central radio frequency of 1380 MHz using a high-speed tape recorder that permitted coherent Nyquist sampling of 50 MHz of bandwidth in each of two polarizations. Using the high time resolution available from this voltage recording technique, we have studied a variety of single-pulse properties, many for the first time in a millisecond pulsar. We show that individual pulses are broad band, have pulse widths ranging from ∼ 10 (∼ …
White Dwarf Cosmochronometry. I. Monte Carlo Simulations Of Proper-Motion And Magnitude-Limited Samples Using Schmidt's 1/Vmax Estimator, Matt A. Wood, Terry D. Oswalt
White Dwarf Cosmochronometry. I. Monte Carlo Simulations Of Proper-Motion And Magnitude-Limited Samples Using Schmidt's 1/Vmax Estimator, Matt A. Wood, Terry D. Oswalt
Aerospace, Physics, and Space Science Faculty Publications
Observationally, white dwarf stars are a remarkably homogeneous class with a minimum observed Teff ∼ 4000 K. Theoretically, the physics that determines their cooling timescales is relatively more straightforward than that which determines main-sequence evolutionary timescales. As a result, the white dwarf luminosity function has for the last decade been used as a probe of the age and star formation rate of the Galactic disk, providing an estimated local disk age of ∼ 10 Gyr with estimated total uncertainties of roughly 20%. A long-standing criticism of the technique is that the reality of the reported downturn in the luminosity function …
White Dwarf Cosmochronometry. I. Monte Carlo Simulations Of Proper-Motion ̶ And Magnitude-Limited Samples Using Schmidt’S 1/Vmax Estimator, Matt A. Wood, Terry D. Oswalt
White Dwarf Cosmochronometry. I. Monte Carlo Simulations Of Proper-Motion ̶ And Magnitude-Limited Samples Using Schmidt’S 1/Vmax Estimator, Matt A. Wood, Terry D. Oswalt
Publications
Observationally, white dwarf stars are a remarkably homogeneous class with a minimum observed Teff ~4000 K. Theoretically, the physics that determines their cooling timescales is relatively more straightforward than that which determines main-sequence evolutionary timescales. As a result, the white dwarf luminosity function has for the last decade been used as a probe of the age and star formation rate of the Galactic disk, providing an estimated local disk age of ~10 Gyr with estimated total uncertainties of roughly 20%. A long-standing criticism of the technique is that the reality of the reported downturn in the luminosity function (LF) …
Pg 1002+506: A Be Star Apparently At Z > +10 Kiloparsecs, F. A. Ringwald, W. R. J. Rolleston, R. A. Saffer, John R. Thorstensen
Pg 1002+506: A Be Star Apparently At Z > +10 Kiloparsecs, F. A. Ringwald, W. R. J. Rolleston, R. A. Saffer, John R. Thorstensen
Dartmouth Scholarship
PG 1002+506 is found to be a Be star, one of three found so far by the Palomar-Green survey. Its spectrum is classified as a B5 ± 1 Ve, with Teff = 14,900 ± 1200, log g = 4.2 ± 0.2, and v sin i = 340 ± 50 km s-1. At b = +51°, its height above the Galactic plane would therefore be z = +10.8 kpc, putting this apparently young, rapidly rotating star well into the Galactic halo. Its heliocentric radial velocity is found to be -2 ± 15 km s-1, consistent with …
Cross Sections Spring 1998, Department Of Physics And Astronomy
Cross Sections Spring 1998, Department Of Physics And Astronomy
Cross Sections
No abstract provided.
Investigating The Formation Of Extra-Galactic Radio Jets, Casey R. Watson
Investigating The Formation Of Extra-Galactic Radio Jets, Casey R. Watson
Mahurin Honors College Capstone Experience/Thesis Projects
Jets of collimated particles are among the most intriguing characteristics of active galactic nuclei. In this paper two models of particle interactions in active galactic nuclei are used to explore a possible initial acceleration mechanism of the jets: charge separation. Model I ignores the effects of both collisions and electromagnetic forces and does not predict charge separation. Model II incorporates collisions and electromagnetic interactions, and, although it too predicts no charge separation, it provides a more physically sound model of active nucleus than does Model I.
Contribution Of White Dwarfs To Cluster Masses, Ted Von Hippel
Contribution Of White Dwarfs To Cluster Masses, Ted Von Hippel
Publications
I have undertaken a literature search through 1997 July 31 of white dwarfs (WDs) in open and globular clusters. I have tried to make a careful evaluation in each case of the likelihood that the object is a WD and that it is a cluster member. The results are presented for 13 open clusters and 11 globular clusters. Currently there are 36 single WDs and Ðve WDs in binaries known among the open clusters, and 340 single WDs and 11 WDs in binaries known among the globular clusters. From these data, I have calculated WD mass fractions for four open …
Steps Toward Determination Of The Size And Structure Of The Broad-Line Region In Active Galactic Nuclei. Xii. Ground-Based Monitoring Of 3c 390.3, M. Dietrich, Terry D. Oswalt, B. M. Peterson, P. Albrecht, M. Altmann, Et Al.
Steps Toward Determination Of The Size And Structure Of The Broad-Line Region In Active Galactic Nuclei. Xii. Ground-Based Monitoring Of 3c 390.3, M. Dietrich, Terry D. Oswalt, B. M. Peterson, P. Albrecht, M. Altmann, Et Al.
Publications
Results of a ground-based optical monitoring campaign on 3C 390.3 in 1994-1995 are presented. The broadband fluxes (B, V, R, and I), the spectrophotometric optical continuum flux and the Fλ(5177 Å),integrated emission-line fluxes of Hᵪ Hβ, Hᵧ, He I λ5876 and He II λ4686 all show a nearly monotonic increase with episodes of milder short-term variations superposed. The amplitude of the continuum variations increases with decreasing wavelength (4400-9000 Å). The optical continuum variations follow the variations in the ultraviolet and X-ray with time delays, measured from the centroids of the cross-correlation functions, typically around …
Contribution Of White Dwarfs To Cluster Masses, Ted Von Hippel
Contribution Of White Dwarfs To Cluster Masses, Ted Von Hippel
Publications
I have undertaken a literature search through 1997 July 31 of white dwarfs (WDs) in open and globular clusters. I have tried to make a careful evaluation in each case of the likelihood that the object is a WD and that it is a cluster member. The results are presented for 13 open clusters and 11 globular clusters. Currently there are 36 single WDs and Ðve WDs in binaries known among the open clusters, and 340 single WDs and 11 WDs in binaries known among the globular clusters. From these data, I have calculated WD mass fractions for four open …
A Re-Evaluation Of Profile Shapes From Resonance Line Scattering In Spherical Stellar Winds., R. Ignace
A Re-Evaluation Of Profile Shapes From Resonance Line Scattering In Spherical Stellar Winds., R. Ignace
Richard Ignace
It is common to treat the scattering of light by resonance lines as isotropic, but in fact it has been known for some time that general resonance line scattering is partially isotropic and partially dipolar, the relative strength of the two components depending on the specific transition. As a result, the profile shapes of lines that scatter with strong dipole distributions could in principle differ markedly from those that scatter isotropically. This paper explores the consequences of general resonance line scattering in spherically symmetric stellar envelopes. As a simplified example, a resonance line profile arising in a constant expansion wind …
Semilocal String Formation In Two Dimensions, Ana Achúcarro, Julian Borrill, Andrew R. Liddle
Semilocal String Formation In Two Dimensions, Ana Achúcarro, Julian Borrill, Andrew R. Liddle
Dartmouth Scholarship
We present a toy model for the investigation of the formation of semilocal strings, where a planar symmetry is employed to reduce the system to two dimensions. We approximate the symmetry breaking using an extension of the Vachaspati-Vilenkin algorithm, where we throw down random phases for the scalar fields and then find the gauge field configuration which minimizes gradient energy in this fixed scalar background. We show this procedure reproduces the standard estimate for the formation rate of cosmic strings. For semilocal strings the configurations generated by this method are ambiguous, and we numerically evolve the configurations forward in time …
How To Count Kinks. From The Continuum To The Lattice And Back, Marcelo Gleiser, Hans-Reinhard Muller
How To Count Kinks. From The Continuum To The Lattice And Back, Marcelo Gleiser, Hans-Reinhard Muller
Dartmouth Scholarship
We investigate the matching between (1+1)-dimensional nonlinear field theories coupled to an external stochastic environment and their lattice simulations. In particular, we focus on how to obtain numerical results which are lattice-spacing independent, and on how to extract the correct effective potential which emerges from the simulations. As an application, we study the thermal production of kink-antikink pairs, obtaining a number density of pairs which is lattice-spacing independent and the
Temperature Variations And N/O In The Orion Nebula From Hst Observations, R. H. Rubin, P. G. Martin, R. J. Dufour, Gary J. Ferland, J. A. Baldwin, J. J. Hester, D. K. Walter
Temperature Variations And N/O In The Orion Nebula From Hst Observations, R. H. Rubin, P. G. Martin, R. J. Dufour, Gary J. Ferland, J. A. Baldwin, J. J. Hester, D. K. Walter
Physics and Astronomy Faculty Publications
Using the Goddard High Resolution Spectrograph (GHRS) and the Faint Object Spectrograph (FOS) on the Hubble Space Telescope, we measured the flux of the N II] (2s2p3 5S2 --> 2s22p2 3P2,1) lines at λvac = 2143.45, 2139.68 Å in the Orion Nebula--the first detection of these lines in an H II region. In order to assess the N+/O+ ratio, we also measured the flux of the [O II] (2p32Po1/2,3/2-->2p34So3/2) lines at λvac …
The Ultraviolet-Optical Albedo Of Broad Emission Line Clouds, Kirk Korista, Gary J. Ferland
The Ultraviolet-Optical Albedo Of Broad Emission Line Clouds, Kirk Korista, Gary J. Ferland
Physics and Astronomy Faculty Publications
We explore the effective UV-optical albedos of a variety of types of broad emission line clouds, as well as their possible effects on the observed spectra of active galactic nuclei (AGNs). An important albedo source in moderately ionized ionization-bounded clouds is that which is due to neutral hydrogen: Rayleigh scattering of continuum photons off the extreme damping wings of Lyα. The photons resulting from this scattering mechanism may contribute significantly to the Lyα emission line, especially in the very broad wings. In addition, line photons emitted near 1200 Å (e.g., N V λ1240) that stream toward the neutral portion of …
Chromospherically Active Stars. Xvii. The Double-Lined Binary 54 Camelopardalis (Ae Lyncis), Francis C. Fekel, Joseph J. Eitter, José-Renan De Medeiros, J. Davy Kirkpatrick
Chromospherically Active Stars. Xvii. The Double-Lined Binary 54 Camelopardalis (Ae Lyncis), Francis C. Fekel, Joseph J. Eitter, José-Renan De Medeiros, J. Davy Kirkpatrick
Information Systems and Engineering Management Research Publications
New spectroscopic observations of the double-lined chromospherically active binary 54 Camelopardalis (=AE Lyncis) have been obtained, resulting in improved orbital elements and the determination of the fundamental properties of the system. 54 Cam has a period of 11.06794 days, an eccentricity of 0.125, and a mass ratio of 0.9945. The spectral types are F8 IV-V and G5 IV, positioning the components on opposite sides of the Hertzsprung gap. From a comparison with theoretical evolutionary tracks, the masses are estimated to be 1.60 and 1.59 M_⊙ for the G and F stars, respectively, while the radii are 3.7 and 3.2 R_⊙. …
Asteroseismology Of A Star Cooled By Neutrino Emission: The Pulsating Pre-White Dwarf Pg 0122 + 200, Marlea Sean O'Brien, Matt A. Wood
Asteroseismology Of A Star Cooled By Neutrino Emission: The Pulsating Pre-White Dwarf Pg 0122 + 200, Marlea Sean O'Brien, Matt A. Wood
Aerospace, Physics, and Space Science Faculty Publications
Observation of g-rnode pulsations in the variable pre-white dwarf (GW Virginis) stars provides a unique means to probe their interiors and to study the late stages of stellar evolution. Multisite campaigns have in several cases proved highly successful in decoding pre-white dwarf light curves. Three previous attempts to untangle the pulsation spectrum of the coolest GW Virginis star, PG 0122+200, confirmed the existence of multiple g-modes but left the fundamental period spacing and therefore the star's mass and luminosity in doubt. We present an analysis based on new observations of PG 0122+200 obtained during a Whole Earth Telescope (WET) campaign …
Understanding The Cool Da White Dwarf Pulsator, G29-38, Scot J. Kleinman, Matt A. Wood
Understanding The Cool Da White Dwarf Pulsator, G29-38, Scot J. Kleinman, Matt A. Wood
Aerospace, Physics, and Space Science Faculty Publications
The white dwarfs are promising laboratories for the study of cosmochronology and stellar evolution. Through observations of the pulsating white dwarfs, we can measure their internal structures and compositions, critical to understanding post-main-sequence evolution, along with their cooling rates, which will allow us to calibrate their ages directly. The most important set of white dwarf variables to measure are the oldest of the pulsators, the cool DA variables (DAVs), which have not been explored previously through asteroseismology due to their complexity and instability. Through a time-series photometry data set spanning 10 yr, we explore the pulsation spectrum of the cool …
The Warps Survey. Ii. The Log N –Log S Relation And The X‐Ray Evolution Of Low‐Luminosity Clusters Of Galaxies, L. R. Jones, C. Scharf, H. Ebeling, E. Perlman, G. Wegner, M. Malkan, D. Horner
The Warps Survey. Ii. The Log N –Log S Relation And The X‐Ray Evolution Of Low‐Luminosity Clusters Of Galaxies, L. R. Jones, C. Scharf, H. Ebeling, E. Perlman, G. Wegner, M. Malkan, D. Horner
Dartmouth Scholarship
The strong negative evolution observed in previous X-ray-selected surveys of clusters of galaxies is evidence in favor of hierarchical models of the growth of structure in the universe. A large recent survey has, however, contradicted the low-redshift results, finding no evidence for evolution at z < 0.3. Here we present the first results from an X-ray-selected, flux- and surface brightness-limited deep survey for high-redshift clusters and groups of galaxies based on ROSAT PSPC pointed data. The log N-log S relation of all clusters in this survey is consistent with that of most previous surveys, but it occupies a flux range not previously covered (greater than 6 × 10-14 ergs cm-2 s-1 total flux in the 0.5-2 keV band). At high redshifts ( …
A Late-Time Optical Detection Of Sn 1985l In Ngc 5033, Robert A. Fesen
A Late-Time Optical Detection Of Sn 1985l In Ngc 5033, Robert A. Fesen
Dartmouth Scholarship
An apparent late-time optical recovery of SN 1985L (Type II-L) in the Sb galaxy NGC 5033 is presented and discussed. An Hα emission point source is found within 1'' of both SN 1985L's historically reported position 70'' west and 55'' north of NGC 5033's center and its late-time, radio-measured position. This Hα source is not visible on V-band or narrow red continuum (7000 ± 125 Å) images, but is detected using a 6510 Å filter (FWHM = 30 Å). Its detection at 6510 Å can be attributed to blueshifted Hα emission because of a broad (±5000 km s-1 …
The Nomad Experiment At The Cern Sps, Nomad Collaboration, J. Altegoer, M. Anfreville, C. Angelini, P. Astier, M. Authier, D. Autiero, A. Baldisseri, M. Baldo-Ceolin, G. Ballocchi, M. Banner, S. Basa, G. Bassompierre, K. Benslama, I. Bird, B. Blumenfeld, F. Bobisut, J. Bouchez, S. Bunyatov, S. Boyd, Roberto Petti, Et. Al.
The Nomad Experiment At The Cern Sps, Nomad Collaboration, J. Altegoer, M. Anfreville, C. Angelini, P. Astier, M. Authier, D. Autiero, A. Baldisseri, M. Baldo-Ceolin, G. Ballocchi, M. Banner, S. Basa, G. Bassompierre, K. Benslama, I. Bird, B. Blumenfeld, F. Bobisut, J. Bouchez, S. Bunyatov, S. Boyd, Roberto Petti, Et. Al.
Faculty Publications
The NOMAD experiment is a short base-line search for νμ − ντ oscillations in the CERN neutrino beam. The ντ's are searched for through their charged current interactions followed by the observation of the resulting τ− through its electronic, muonic or hadronic decays. These decays are recognized using kinematical criteria necessitating the use of a light target which enables the reconstruction of individual particles produced in the neutrino interactions. This paper describes the various components of the NOMAD detector: the target and muon drift chambers, the electromagnetic and hadronic calorimeters, the preshower and transition radiation …
Redshifted Neutral Hydrogen 21 Centimeter Absorption Toward Red Quasars, C L. Carilli, Karl M. Menten, Mark J. Reid, M P. Rupen, Min S. Yun
Redshifted Neutral Hydrogen 21 Centimeter Absorption Toward Red Quasars, C L. Carilli, Karl M. Menten, Mark J. Reid, M P. Rupen, Min S. Yun
Min S. Yun
We have searched for redshifted neutral hydrogen 21 cm absorption toward sources from the Stickel et al. "red quasar" subsample. The red quasar subsample is taken from the 1 Jy sample of flat-spectrum radio sources and is comprised of the 15 sources that are undetected on the POSS. Five of these red quasars have been searched for redshifted H I 21 cm absorption to optical depth levels of a few percent, and four show strong absorption, with neutral hydrogen column densities between 4 and 80 × 1018 × (Ts/f) cm-2. This 80% success rate for the red quasars compares to …
Thermal Equilibrium Of Warm Clouds Of Charge With Small Aspect Ratio, Deborah L. Paulson, Ross L. Spencer
Thermal Equilibrium Of Warm Clouds Of Charge With Small Aspect Ratio, Deborah L. Paulson, Ross L. Spencer
Faculty Publications
Global thermal equilibrium computations are presented for non-neutral plasmas whose radial size is much larger than their axial thickness. Axial and radial density profiles are computed for both ideal and nonideal Penning trap fields. Simple results are obtained in the limits of both low and high central density. Comparison is made to the grid calculations of Mason et al. [Phys. Plasmas 3 (5), 1502 (1996)].
A Photometric And Spectroscopic Study Of The Cataclysmic Variable Sx Leonis Minoris In Quiescence And Superoutburst, R. Mark Wagner, John R. Thorstensen, R. K. Honeycutt, S. B. Howell
A Photometric And Spectroscopic Study Of The Cataclysmic Variable Sx Leonis Minoris In Quiescence And Superoutburst, R. Mark Wagner, John R. Thorstensen, R. K. Honeycutt, S. B. Howell
Dartmouth Scholarship
We present CCD imaging, CCD photometry on long and short timescales, and time-resolved spectroscopy of SX LMi, a new SU Ursae Majoris type dwarf nova. The quiescent optical spectrum shows broad double-peaked Balmer, He I, and He II emission lines, similar to other quiescent dwarf novae. Absorption lines from a late-type secondary are not detected. Time-resolved spectra obtained in quiescence reveal radial velocity variations of the Balmer emission lines on a period of 0.06717 ± 0.00011 days, or 96.72 ± 0.16 minutes, with only a slight possibility of a daily cycle-count error. Optical photometry obtained between 1987 and 1991 shows …
Inference Of Steady Stellar Wind V(R) Laws From Optically Thin Emission Lines Ii. Occultation Effects And The Determination Of Intrinsic Stellar Properties., R. Ignace, J. C. Brown, L. L. Richardson, J. P. Cassinelli
Inference Of Steady Stellar Wind V(R) Laws From Optically Thin Emission Lines Ii. Occultation Effects And The Determination Of Intrinsic Stellar Properties., R. Ignace, J. C. Brown, L. L. Richardson, J. P. Cassinelli
Richard Ignace
This paper extends previous work on the inversion of line profiles to obtain wind velocity laws to a case that includes the occultation of light from the far side of the star. The velocity law v(r) is assumed to be from a wind that is steady and spherically symmetric. The wind is also assumed to be optically thin in the emission line profile. The major result here is the derivation of an analytic inversion formula. The effects of stellar occultation are shown to produce a significant change in the analysis from paper I, and by accounting for the occultation, the …
A Search For Optical Afterglow From Grb 970828, P. J. Groot, T. J. Galama, J. Van Paradijs, C. Kouveliotou, R. A. M. J. Wijers, J. Bloom, N. Tanvir, R. Vanderspek, J. Greiner, A. J. Castro-Tirado, J. Gorosabel, T. Von Hippel, M. Lehnert, K. Kuijken, H. Hoekstra, N. Metcalfe, C. Howk, C. Conselice, J. Telting, R. G. M. Rutten, J. Rhoads, A. Cole, D. J. Pisano, R. Naber, R. Schwarz
A Search For Optical Afterglow From Grb 970828, P. J. Groot, T. J. Galama, J. Van Paradijs, C. Kouveliotou, R. A. M. J. Wijers, J. Bloom, N. Tanvir, R. Vanderspek, J. Greiner, A. J. Castro-Tirado, J. Gorosabel, T. Von Hippel, M. Lehnert, K. Kuijken, H. Hoekstra, N. Metcalfe, C. Howk, C. Conselice, J. Telting, R. G. M. Rutten, J. Rhoads, A. Cole, D. J. Pisano, R. Naber, R. Schwarz
Publications
We report on the results of R-band observations of the error box of the g-ray burst of 1997 August 28 made between 4 hr and 8 days after this burst occurred. No counterpart was found varying by more than 0.2 mag down to R 5 23.8. We discuss the consequences of this nondetection for relativistic blast wave models of g-ray bursts and the possible effect of redshift on the relation between optical absorption and the low-energy cutoff in the X-ray afterglow spectrum.
Molecular Gas In The Inner 100 Parces Of M51, N Z. Scoville, Min S. Yun, L Armus, H Ford
Molecular Gas In The Inner 100 Parces Of M51, N Z. Scoville, Min S. Yun, L Armus, H Ford
Min S. Yun
We report imaging of CO (2-1) emission in the nucleus of M51 at 1'' (47 pc) resolution. Molecular gas is found closely associated with the nuclear radio jet and the X-shaped dust absorption feature seen in the Hubble Space Telescope images. The CO emission lies along the side of the nuclear radio continuum "jet." The strongest molecular emission is not symmetric in either position or velocity with respect to the nucleus—the dominant feature is at redshifted velocities and peaks 1'' to the west of the radio/optical nucleus. The CO (2-1) emission has an integrated flux implying a molecular gas mass …