Physical Sciences and Mathematics | Open Access Articles

A Rosat Hri Observation Of The Supernova Remnant G109.1 – 1.0, Alan P. Hurford, Robert A. Fesen

Dartmouth Scholarship

We present results of a search using ROSAT HRI data for X-ray spatial substructures in the galactic supernova remnant G109.1 – 1.0 which might indicate a connection between the remnant’s bright X-ray blob and its X-ray pulsar, 1E2259 + 586. A 0.1 – 2.4 keV HRI image, created by combining separate 28- and 22-ks pointings, reveals the presence of a few small-scale X-ray features, including a NE-SW emission ridge in the remnant’s X-ray blob. Two diffuse knots in the X-ray blob, previously suggested as being aligned with the X-ray pulsar, appear to be statistical fluctuations in the Einstein HRI data. …

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Determination Of Malmquist Bias And Selection Effects From Monte Carlo Simulations, Wolfram Freudling, Luiz N. Da Costa, Gary Wegner, Riccardo Giovanelli

Dartmouth Scholarship

Maps of the peculiar velocity field derived from distance relations are affected by Malmquist type bias and selection effects. Because of the large number of interdependent effects, they are in most cases difficult to treat analytically. Monte Carlo simulations are used to understand and evaluate these effects. In these simulations the "true" spatial distribution and relevant properties of galaxies as well as selection effects and observational uncertainties are realistically modeled. The results of the simulation can be directly applied to correct observed peculiar velocity maps. The simulation is used to investigate biases in samples of measured peculiar velocities by Lynden-Bell …

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Discovery Of Extreme-Ultraviolet Radiation From The Seyfert Galaxy Ton S180 (=Euve J0057−223), Stéphane Vennes, Elisha Polomski, Stuart Bowyer, John R. Thorstensen

Dartmouth Scholarship

We report the detection of intense EUV radiation from the Seyfert 1 galaxy Ton S180. The source EUVE J0057-223, discovered in the Extreme-Ultraviolet Explorer all-sky survey, is only 25'' away from its optical counterpart, well within the position error circle. We present a complete broadband energy distribution of Ton S180 using infrared (IRAS), optical, ultraviolet (IUE) and X-ray (ROSAT) flux measurements, and we find that the measured EUV flux, corrected for neutral hydrogen and helium absorption in the Galaxy, suggests the presence of a strong EUV to soft X-ray flux excess. We briefly discuss …

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The Orbital Period Of The Pre-Cataclysmic Binary Re 2013+400 And A Study Of The Atmosphere Of The Dao White Dwarf Primary, M. A. Barstow, M. R. Burleigh, T. A. Fleming, J. B. Holberg, D. Koester, M. C. Marsh, S. R. Rosen, R. G.M. Rutten, S. Sakai, R. W. Tweedy, G. Wegner

Dartmouth Scholarship

Several pre-cataclysmic binaries, comprising a hot white dwarf with a red dwarf companion, have been discovered as a result of the optical identification of EUV sources from the ROSAT all-sky survey. The optical spectra have the steep blue continuum and Balmer absorption typical of a hot white dwarf, but there are bright, narrow emission lines of H I (and sometimes He I and Ca II) superimposed. An intense campaign of follow-up observations has been devoted to these binary systems. So far, only RE 2013+400 has exhibited any measurable changes in the radial velocities of the emission components, from which it …

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Orbital Studies Of The Cataclysmic Variables Cz Orionis, V1193 Orionis And Bz Ursae Majoris, F. A. Ringwald, J. R. Thorstensen, R. M. Hamwey

Dartmouth Scholarship

Time-resolved spectroscopy reveals the orbital periods of three cataclysmic variables. CZ Ori has an orbital period of 0.2189 d. This is within 3 per cent of a prediction relating orbital period and dwarf nova outburst decline time. We find the M2.5 ± 1.0 secondary, and infer an absolute magnitude for CZ Ori in RKc of 8.5 ± 1.0 and a distance of 260 ± 110 pc. V1193 Ori, also called Hamuy's Blue Variable, has an orbital period of 0.165 d. In 1988, Ha emission line profile variations suggested red star illumination. In 1989, this line's red wing flared at orbital …

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Photoelectric And Ccd Photometry Of E And S0 Galaxies, M. Colless, D. Burstein, G. Wegner, R. P. Saglia

Dartmouth Scholarship

We present BR photoelectric photometry for 352 E and S0 galaxies that are part of a large survey of the properties and peculiar motions of galaxies in distant clusters. Repeat measurements show our internal errors to be 2 – 3 per cent in B and R and 1 – 2 per cent in B– R. Comparisons of BR and BVR reductions for 10 galaxies also observed in V show small systematic errors due to differences between the spectral energy distributions of stars and galaxies. External comparisons with B– V colours in the literature confirm that these colours are …

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Distinguishing A Charged Higgs Signal From A Heavy Wr Signal, David I. Kaiser

Dartmouth Scholarship

It is shown that non-Standard Model bosons should obey an observable asymmetry in their decays to taus. This asymmetry enables a distinction to be made between charged Higgsboson signalsand heavy right-handed Wboson signals,by reconstructing the orientation of the z with respect to the beam axis.

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The 14.8-H Orbital Period Of Gx339-4, P. J. Callanan, P. A. Charles, W. B. Honey, J. R. Thorstensen

Dartmouth Scholarship

We present the results of photometric observations of the black hole candidate GX339-4, obtained while the system was in an 'off' state. We show that a 14.8-h modulation was present, and provide evidence for a similar periodicity in the 'high' state from a reanalysis of previously published photometry and spectroscopy. The presence of the same period in both states implies that it is likely to be the orbital period of the system. The spectroscopy analysis provides evidence for an apparent change in the systemic velocity of the system. The amplitude of the observed radial velocity variations, however, permits only crude …

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Uv Observations Of The Cool Dbqa5 White Dwarf Lds 678a - Limits On The Atmospheric Composition, Pressure Shift, And Gravitational Redshift Derived From C I 2479, Terry D. Oswalt, Edward M. Sion, Gordon Hammond, Gerard Vauclair, James W. Liebert, Gary Wegner

Dartmouth Scholarship

A high-resolution ultraviolet spectrum of the helium-rich degenerate LDS 678A, obtained with the International Ultraviolet Explorer (IUE) satellite, is presented. LDS 678A is the coolest metallic line degenerate (DQ or DZ) yet observed with the IUE echelle. These observations provide a detailed line profile of the strong C I 2479 absorption line and equivalent width W2479 = 2.35 + or - 0.06 A from which theoretical profile fits yield a carbon abundance of log C/He = (-6.7 + or- 0.2). The presence of carbon in a He-rich atmosphere lends credence to the notion that LDS 678A is a transitional case …

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Optical Variability Of The Black Hole Candidate Gx339-4 (X1659-487, V821 Ara) - Limits On Periodic Modulation, R. H. D. Corbet, J. R. Thorstensen, P. A. Charles, W. B. Honey

Dartmouth Scholarship

We present results of extensive CCD optical photometry (over 1000 frames representing ~150 hr of integration time) of the optical counterpart of the X-ray source GX339–4 obtained during the high (soft) state. The source was seen to be significantly variable. We do not, however, detect any periodic modulation with semi-amplitude greater than ~0.03 mag for periods less than ~0.5 day or semi-amplitude greater than ~0.07 mag for longer periods. An optical spectrum obtained shortly after GX339–4 made a transition from a ‘low’ to a ‘high’ state is also presented and compared with previous results. The width of the He II …

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The Orbital Period Of The Optical/X-Ray Burster X1735-444 (V926 Sco), R. H. D. Corbet, J. R. Thorstensen, P. A. Charles, J. W. Menzies

Dartmouth Scholarship

We present extensive CCD photometry of the optical counterpart of X1735–444 which reveals the orbital period of the system. It is periodically variable with a period of 4.654 hr and a full amplitude of 0.15 mag. The mean modulation is quasi-sinusoidal; there are, however, also significant intrinsic deviations from the mean light curve.

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Spectroscopic Studies Of 4u1735 – 44; Evidence For Binary Motion, A. P. Smale, P. A. Charles, I. R. Tuohy, J. R. Thorstensen

Dartmouth Scholarship

We have obtained optical spectroscopy of the X-ray burst source 4U1735 – 44 with spectral resolution of ∼ 1.6 Å and a time resolution of ∼ 30 min. There is strong evidence for cyclic He II velocity variations, but we are unable to confirm or deny either of the previously reported possible binary periodicities in the source. However, kinematic arguments suggest that the companion can be classified as being of spectral type F0–K5 V and the presence of the Ca II K interstellar absorption line at λ 3933 leads to a lower limit on the distance of the source of …

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Photometric And Spectroscopic Observations Of An Optical Candidate For The X-Ray Source H 0544 - 665, M. Van Der Klis, J. Van Paradijs, P. A. Charles, J. R. Thorstensen

Dartmouth Scholarship

We present the results of spectroscopic and UBV observations of the brightest star in the error box of the X-ray source H 0544–665. This object is a B0–1 V star and a member of the LMC. It shows correlated variations in brightness and colour indices. We suggest that it is a Be-type star observed during a stage of low emission strength. Although a relation between this star and the X-ray source has still to be proven the present data add considerable support to the proposed identification.

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Extreme Variability In The Be-Type, Periodic Recurrent X-Ray Transient A0538 - 66: A Highly Eccentric Interacting Binary, P. A. Charles, L. Booth, R. H. Densham, G. T. Bath, J. R. Thorstensen

Dartmouth Scholarship

We present optical spectroscopy and photometry and IUE spectroscopy of the counterpart of the extremely powerful LMC recurrent X-ray transient A0538 – 66. During one 16.6 day outburst cycle at the end of 1980 December the optical spectra show steadily increasing Balmer and He I emission (indicative of an expanding envelope) superposed on a B2 III–IV spectrum. There is a substantial optical brightness increase of 2 mag at the peak, accompanied by the sudden turn-on of He IIλ 4686. These and other optical spectra show significant radial velocity changes but we can find no clear correlation with the 16.6 …

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Full-Text Articles in Physical Sciences and Mathematics

A Rosat Hri Observation Of The Supernova Remnant G109.1 – 1.0, Alan P. Hurford, Robert A. Fesen

Dartmouth Scholarship

Determination Of Malmquist Bias And Selection Effects From Monte Carlo Simulations, Wolfram Freudling, Luiz N. Da Costa, Gary Wegner, Riccardo Giovanelli

Dartmouth Scholarship

Discovery Of Extreme-Ultraviolet Radiation From The Seyfert Galaxy Ton S180 (=Euve J0057−223), Stéphane Vennes, Elisha Polomski, Stuart Bowyer, John R. Thorstensen

Dartmouth Scholarship

The Orbital Period Of The Pre-Cataclysmic Binary Re 2013+400 And A Study Of The Atmosphere Of The Dao White Dwarf Primary, M. A. Barstow, M. R. Burleigh, T. A. Fleming, J. B. Holberg, D. Koester, M. C. Marsh, S. R. Rosen, R. G.M. Rutten, S. Sakai, R. W. Tweedy, G. Wegner

Dartmouth Scholarship

Orbital Studies Of The Cataclysmic Variables Cz Orionis, V1193 Orionis And Bz Ursae Majoris, F. A. Ringwald, J. R. Thorstensen, R. M. Hamwey

Dartmouth Scholarship

Photoelectric And Ccd Photometry Of E And S0 Galaxies, M. Colless, D. Burstein, G. Wegner, R. P. Saglia

Dartmouth Scholarship

Distinguishing A Charged Higgs Signal From A Heavy Wr Signal, David I. Kaiser

Dartmouth Scholarship

The 14.8-H Orbital Period Of Gx339-4, P. J. Callanan, P. A. Charles, W. B. Honey, J. R. Thorstensen

Dartmouth Scholarship

Uv Observations Of The Cool Dbqa5 White Dwarf Lds 678a - Limits On The Atmospheric Composition, Pressure Shift, And Gravitational Redshift Derived From C I 2479, Terry D. Oswalt, Edward M. Sion, Gordon Hammond, Gerard Vauclair, James W. Liebert, Gary Wegner

Dartmouth Scholarship

Optical Variability Of The Black Hole Candidate Gx339-4 (X1659-487, V821 Ara) - Limits On Periodic Modulation, R. H. D. Corbet, J. R. Thorstensen, P. A. Charles, W. B. Honey

Dartmouth Scholarship

The Orbital Period Of The Optical/X-Ray Burster X1735-444 (V926 Sco), R. H. D. Corbet, J. R. Thorstensen, P. A. Charles, J. W. Menzies

Dartmouth Scholarship

Spectroscopic Studies Of 4u1735 – 44; Evidence For Binary Motion, A. P. Smale, P. A. Charles, I. R. Tuohy, J. R. Thorstensen

Dartmouth Scholarship

Photometric And Spectroscopic Observations Of An Optical Candidate For The X-Ray Source H 0544 - 665, M. Van Der Klis, J. Van Paradijs, P. A. Charles, J. R. Thorstensen

Dartmouth Scholarship

Extreme Variability In The Be-Type, Periodic Recurrent X-Ray Transient A0538 - 66: A Highly Eccentric Interacting Binary, P. A. Charles, L. Booth, R. H. Densham, G. T. Bath, J. R. Thorstensen

Dartmouth Scholarship