Stars, Interstellar Medium and the Galaxy Commons^™

Constraining The Surface Inhomogeneity And Settling Times Of Metals On Accreting White Dwarfs, Michael H. Montgomery, S.E. Thompson, Ted Von Hippel

Publications

Due to the short settling times of metals in DA white dwarf atmospheres, any white dwarfs with photospheric metals must be actively accreting. It is therefore natural to expect that the metals may not be deposited uniformly on the surface of the star. We present calculations showing how the temperature variations associated with white dwarf pulsations lead to an observable diagnostic of the surface metal distribution, and we show what constraints current data sets are able to provide. We also investigate the effect that time-variable accretion has on the metal abundances of different species, and we show how this can …

A Multiwavelength Analysis Of The Halo Planetary Nebula Dddm‐1, R. B. C. Henry, K. B. Kwitter, R. J. Dufour, J. N. Skinner

Dartmouth Scholarship

We present new HST optical imagery as well as new UV and IR spectroscopic data obtained with the Hubble Space Telescope and Spitzer Space Telescope, respectively, of the halo planetary nebula DdDm-1. For the first time we present a resolved image of this object, which indicates that the morphology of DdDm-1 can be described as two orthogonal elliptical components in the central part surrounded by an extended halo. The extent of the emission is somewhat larger than was previously reported in the literature. We combine the spectral data with our own previously published optical measurements to derive nebular abundances …

Infrared Spectroscopy Of Symbiotic Stars. Vi. Combined Orbits For Two S-Type Systems: V455 Scorpii And Ss 73-90, Francis C. Fekel, Kenneth H. Hinkle, Richard R. Joyce, Peter R. Wood, Ian D. Howarth

Information Systems and Engineering Management Research Publications

We have combined new infrared radial velocities and previously obtained spectropolarimetric observations to compute orbits of the M6 giants in two southern S-type symbiotic systems. The spectropolarimetric data enable the orbital inclinations of the systems to be determined, placing greater constraints on the properties of the components. V455 Sco has a circular orbit with a period of 1398 ± 6 days and an inclination of 94° ± 1°. The orbit of SS 73-90 has a period of 898 ± 5 days, a modest eccentricity of 0.16, and an inclination of 97° ± 7°. The center of mass velocity of each …

Orbits And Pulsations Of The Classical Ζ Aurigae Binaries, Joel A. Eaton, Gregory W. Henry, Andrew P. Odell

Information Systems and Engineering Management Research Publications

We have derived new orbits for ζ Aur, 32 Cyg, and 31 Cyg with observations from the Tennessee State University (TSU) Automatic Spectroscopic Telescope, and used them to identify nonorbital velocities of the cool supergiant components of these systems. We measure periods in those deviations, identify unexpected long-period changes in the radial velocities, and place upper limits on the rotation of these stars. These radial-velocity variations are not obviously consistent with radial pulsation theory, given what we know about the masses and sizes of the components. Our concurrent photometry detected the nonradial pulsations driven by tides (ellipsoidal variation) in both …

Initial Measurements Of Black Hole Spin In Gx 339-4 From Suzaku Spectroscopy, J. M. Miller, C. S. Reynolds, A. C. Fabian, E. M. Cackett, G. Miniutti, J. Raymond, D. Steeghs, R. Reis, J. Homan

Physics and Astronomy Faculty Research Publications

We report on a deep Suzaku observation of the stellar-mass black hole GX 339-4 in outburst. A clear, strong, relativistically shaped iron emission line from the inner accretion disk is observed. The broadband disk reflection spectrum revealed is one of the most sensitive yet obtained from an accreting black hole. We fit the Suzaku spectra with a physically motivated disk reflection model, blurred by a new relativistic line function in which the black hole spin parameter is a variable. This procedure yielded a black hole spin parameter of a=0.89+/-0.04. Joint modeling of these Suzaku spectra and prior XMM-Newton spectra obtained …

Book Review: Guide To Observing Deep-Sky Objects: A Complete Global Resource For Astronomers, T. D. Oswalt

Publications

This document is Dr. Oswalt’s review of Guide to Observing Deep-Sky Objects : a Complete Global Resource for Astronomers by Jeff A. Farinacci. Springer, 2007 189p, 9780387728506 $29.95

The First Mid-Infrared Spectra Of Cool White Dwarfs, Mukremin Kilic, Ted Von Hippel, Et Al.

Publications

We present the first mid-infrared spectra of two cool white dwarfs obtained with the Spitzer Space Telescope. We also present 3.5–8 μ m photometry for 19 cool white dwarfs with 5000 K ≤T_eff ≤ 9000 K. We perform a detailed model atmosphere analysis of these white dwarfs by fitting their UBVRIJHK and Spitzer photometry with state-of-the-art model atmospheres, and demonstrate that the optical and infrared spectral energy distributions of cool white dwarfs are well reproduced by our grid of models. Our mid-infrared photometry and 7.5-14.5 μm spectrum of WD 0018–267 are consistent with a T_eff = 5720 …

Deep Advanced Camera For Surveys Imaging In The Globular Cluster Ngc 6397: The Cluster Color-Magnitude Diagram And Luminosity Function, Harvey B. Richer, Aaron Dotter, Jarrod Hurley, Jay Anderson

Dartmouth Scholarship

We present the color-magnitude diagram (CMD) from deep Hubble Space Telescope imaging in the globular cluster NGC 6397. The Advanced Camera for Surveys (ACS) was used for 126 orbits to image a single field in two colors (F814W, F606W) 5' SE of the cluster center. The field observed overlaps that of archival WFPC2 data from 1994 and 1997 which were used to proper motion (PM) clean the data. Applying the PM corrections produces a remarkably clean CMD which reveals a number of features never seen before in a globular cluster CMD. In our field, the main-sequence stars appeared to terminate …

The Chromospherically Active, Triple, Ellipsoidal, And Eclipsing Binary Hd 6286 = Be Piscium: A Laboratory For Binary Evolution, Klaus G. Strassmeier, János Bartus, Francis C. Fekel, Gregory W. Henry

Information Systems and Engineering Management Research Publications

Aims. We present a detailed analysis of the star HD 6286 = BE Psc from 16 years of spectroscopic observations and 18 seasons of photometric ones. The star is an evolved, chromospherically active, eclipsing binary, consisting of a K1 giant plus an F6 dwarf/subgiant in a circular orbit with a period of 35.671 days. A faint, close visual companion of spectral type ≈G0 makes the system triple. The orbital inclination of the eclipsing pair is 818.

Methods. We have obtained simultaneous solutions with our extensive set of radial velocities and light curves that include the star spot variability of …

The Extremely Rapid Rotational Braking Of The Magnetic Helium-Strong Star Hd 37776, Zdeněk Mikulášek, Jiří Krtička, Gregory W. Henry, Juraj Zverko, Jozef Žižňovský, David A. Bohlender, Iosif I. Romanyuk, Jan Janík, Hrvoje Božić, D. Korčáková, Miloslav Zejda, Ivan Kh. Iliev, Petr Škoda, Miroslav Šlechta, Tomáš Gráf, Martin Netolický, Michal Ceniga

Information Systems and Engineering Management Research Publications

Context. Light and spectrum variations of the magnetic chemically peculiar (mCP) stars are explained by the oblique rigid rotator model with a rotation period usually assumed to be stable on a long time scale. A few exceptions, such as CU Vir or 56 Ari, have been reported as displaying an increase in their rotation period. A possible increase in the period of light and spectrum variations has also been suggested from observations of the helium-strong mCP star HD 37776 (V901 Ori).

Aims. In this paper we attempt to confirm the possible period change of HD 37776 and discuss a possible …

The Nature Of The Ultraluminous Oxygen‐Rich Supernova Remnant In Ngc 4449, Dan Milisavljevic, Robert A. Fesen

Dartmouth Scholarship

Optical images and spectra, both ground based and taken by Hubble Space Telescope (HST), of the young, luminous O-rich supernova remnant in the irregular galaxy NGC 4449 are presented. HST images of the remnant and its local region were obtained with the ACS/WFC using filters F435W, F555W, F814W (B, V, and I, respectively), F502N ([O III]), F658N (Hα + [N II]), F660N ([N II]), and F550M (line-free continuum). These images show an unresolved remnant (FWHM < 0.05'') located within a rich cluster of OB stars which itself is enclosed by a nearly complete interstellar shell seen best in Hα + [N II] emission approximately 8'' × 6'' (150 pc × 110 pc ) in size. The remnant and its associated OB cluster are isolated …

Investigating The Nature Of Absorption Lines In The Chandra X-Ray Spectra Of The Neutron Star Binary 4u 1820-30, E. M. Cackett, J. M. Miller, J. Raymond, J. Homan, M. Van Der Klis, M. Méndez, D. Steeghs, R. Wijnands

Physics and Astronomy Faculty Research Publications

We use four Chandra gratings spectra of the neutron star low-mass X-ray binary 4U 1820-30 to better understand the nature of certain X-ray absorption lines in X-ray binaries, including the Ne II, Ne III, Ne IX, O VII, and O VIII lines. The equivalent widths of the lines are generally consistent between the observations, as expected if these lines originate in the hot interstellar medium. No evidence was found that the lines were blueshifted, again supporting the interstellar medium origin, although this may be due to poor statistics. There is apparent variability in the O VIII Lyα line equivalent width …

Comparing Various Multi-Component Global Heliosphere Models, H.-R. Müller, V. Florinski, J. Heerikhuisen, V. V. Izmodenov

Dartmouth Scholarship

Modeling of the global heliosphere seeks to investigate the interaction of the solar wind with the partially ionized local interstellar medium. Models that treat neutr al hydrogen self-consistently and in great detail, together with the plasma, but that neglect magnetic fields, constitute a sub-category within global heliospheric models. There are several different modeling strategies used for this sub-category in the literature. Differences and commonalities in the modeling results from different strategies are pointed out.

A New Look At The Local White Dwarf Population, J. B. Holberg, E. M. Sion, Terry D. Oswalt, G. P. Mccook, S. Foran, John P. Subasavage

Publications

We have conducted a detailed new survey of the local population of white dwarfs lying within 20 pc of the Sun. A new revised catalog of local white dwarfs containing 122 entries (126 individual degenerate stars) is presented. This list contains 27 white dwarfs not included in a previous list from 2002, as well as new and recently published trigonometric parallaxes. In several cases new members of the local white dwarf population have come to light through accurate photometric distance estimates. In addition, a suspected new double degenerate system (WD 0423+120) has been identified. The 20 pc sample is currently …

A New, Bright, Short-Period, Emission Line Binary In Ophiuchus, M. A. Stark, Richard A. Wade, John R. Thorstensen, Christopher S. Peters

Dartmouth Scholarship

The 11th magnitude star LS IV-08°3 has been classified previously as an OB star in the Luminous Stars survey, or alternatively as a hot subdwarf. It is actually a binary star. We present spectroscopy, spectroscopic orbital elements, and time-series photometry from observations made at the Kitt Peak National Observatory 2.1 m, Steward Observatory 2.3 m, MDM Observatory 1.3 m and 2.4 m, Hobby-Eberly 9.2 m, and Michigan State University 0.6 m telescopes. The star exhibits emission of varying strength in the cores of H and He I absorption lines. Emission is also present at 4686 Å (He II) and near …

De Canum Venaticorum: A Bright, Eclipsing Red Dwarf–White Dwarf Binary, E. J. M. Van Den Besselaar, R. Greimel, L. Morales-Rueda, G. Nelemans, J. R. Thorstensen

Dartmouth Scholarship

Close white dwarf - red dwarf binaries must have gone through a common-envelope phase during their evolution. DE CVn is a detached white dwarf - red dwarf binary with a relatively short (~8.7 hours) orbital period. Its brightness and the presence of eclipses makes this system ideal for a more detailed study. From a study of photometric and spectroscopic observations of DE CVn we derive the system parameters which we discuss in the frame work of common-envelope evolution. Photometric observations of the eclipses are used to determine an accurate ephemeris. From a model fit to an average low-resolution spectrum of …

Relativistic Iron Emission Lines In Neutron Star Low-Mass X-Ray Binaries As Probes Of Neutron Star Radii, Edward M. Cackett, Jon M. Miller, Sudip Bhattacharyya, Jonathan E. Grindlay, Jeroen Homan, Michiel Van Der Klis, M. Coleman Miller, Tod E. Strohmayer, Rudy Wijnands

Physics and Astronomy Faculty Research Publications

Using Suzaku observations of three neutron star low-mass X-ray binaries (Ser X-1, 4U 1820-30, and GX 349+2) we have found broad, asymmetric, relativistic Fe K emission lines in all three objects. These Fe K lines can be well fit by a model for lines from a relativistic accretion disk (``diskline''), allowing a measurement of the inner radius of the accretion disk and hence an upper limit on the neutron star radius. These upper limits correspond to 14.5-16.5 km for a 1.4 M_solar neutron star. The inner disk radii that we measure with Fe K lines are in good agreement …

Optical Imaging And Spectroscopy Of The Galactic Supernova Remnant 3c 58 (G130.7+3.1), Robert Fesen, Gwen Rudie, Alan Hurford, Aljeandro Soto

Dartmouth Scholarship

We present a comprehensive imaging and spectroscopic survey of optical emission knots associated with the young Galactic supernova remnant 3C 58. Hα images show hundreds of clumpy filaments and knots arranged in a complex structure covering a nearly circular area roughly 400'' in diameter. A quite different emission structure is seen in [O III], where the brightest features are less clumpy and largely confined to the remnant's northwest quadrant. Measured radial velocities of over 450 knots reveal two distinct kinematic populations; one with average and peak expansion velocities of 770 and 1100 km s⁻¹, respectively, forming a thick …

Masses, Luminosities, And Orbital Coplanarities Of The Μ Orionis Quadruple-Star System From Phases Differential Astrometry, Matthew W. Muterspaugh, Benjamin F. Lane, Francis C. Fekel, Maciej Konacki, Bernard F. Burke, Shrinivas R. Kulkarni, Mark M. Colavita, Michael Shao, Sloane J. Wiktorowicz

Information Systems and Engineering Management Research Publications

μ Orionis was identified by spectroscopic studies as a quadruple-star system. Seventeen high-precision differential astrometry measurements of μ Ori have been collected by the Palomar High-precision Astrometric Search for Exoplanet Systems (PHASES). These show both the motion of the long-period binary orbit and short-period perturbations superimposed on that caused by each of the components in the long-period system being themselves binaries. The new measurements enable the orientations of the long-period binary and short-period subsystems to be determined. Recent theoretical work predicts the distribution of relative inclinations between inner and outer orbits of hierarchical systems to peak near 40 and 140 …

The Extinction Toward The Galactic Bulge From Rr Lyrae Stars, Andrea Kunder, Piotr Popowski, Kem H. Cook, Brian Chaboyer

Dartmouth Scholarship

We present mean reddenings toward 3525 RR0 Lyrae stars from the Galactic bulge fields of the MACHO Survey. These reddenings are determined using the color at minimum V-band light of the RR0 Lyrae stars themselves and are found to be in general agreement with extinction estimates at the same location obtained from other methods. Using 3256 stars located in the Galactic Bulge, we derive the selective extinction coefficient R_V,VR = A_V/E(V − R) = 4.3 ± 0.2. This value is what is expected for a standard extinction law with R …

New Precision Orbits Of Bright Double-Lined Spectroscopic Binaries. Ii. Hr 2962, Hd 214686, And 16 Psc, Jocelyn Tomkin, Francis C. Fekel

Information Systems and Engineering Management Research Publications

Radial velocities from the 2.1 m telescope at McDonald Observatory and the coudé feed telescope at Kitt Peak National Observatory are used to determine new spectroscopic orbits for the double-lined spectroscopic binaries HR 2962 (F5V), HD 214686 (F8IV), and 16 Psc (F6Vb vw). The new orbital dimensions (a1sin i and a2sin i) and minimum masses (m1sin3i and m2sin3i) have accuracies of 0.1–1%. In the case of HD 214686, which has components of nearly the same mass (m1/m2 = 1.0080 ± 0.0013), we confirm that the component labeled as the primary in previous spectroscopic studies of this system is the slightly …

The Crab Nebula's Dynamical Age As Measured From Its Northern Filamentary Jet, G. C. Rudie, R. A. Fesen, T. Yamada

Dartmouth Scholarship

We present a deep [O III] 4959,5007 image of the northern filamentary jet in the Crab Nebula taken with the 8.2m Subaru telescope. Using this image and an image taken with the KPNO 4m in 1988 (Fesen & Staker 1993), we have computed proper motions for 35 locations in the jet. The results suggest that when compared to the main body of the remnant, the jet experienced less outward acceleration from the central pulsar's rapidly expanding synchrotron nebula. The jet's apparent expansion rate yields an undecelerated explosion date for the Crab Nebula of 1055 plus or minus 24 C.E., a …

Phase-Dependent X-Ray Observations Of The Beta Lyrae System: No Eclipse In The Soft Band., Richard Ignace, L. Oskinova, W. Waldron, J. Hoffman, W.-R. Hamann

ETSU Faculty Works

Aims.We report on observations of the eclipsing and interacting binary beta Lyrae from the Suzaku X-ray telescope. This system involves an early B star embedded in an optically and geometrically thick disk that is siphoning atmospheric gases from a less massive late B II companion. Methods.Motivated by an unpublished X-ray spectrum from the Einstein X-ray telescope suggesting unusually hard emission, we obtained time with Suzaku for pointings at three different phases within a single orbit. Results.From the XIS detectors, the softer X-ray emission appears typical of an early-type star. What is surprising is the remarkably unchanging character …

White Dwarf Luminosity And Mass Functions From Sloan Digital Sky Survey Spectra, Steven Degennaro, Ted Von Hippel, D. E. Winget, S. O. Kepler, Atsuko Nitta, Detlev Koester, Leandro Althaus

Publications

We present the first phase in our ongoing work to use Sloan Digital Sky Survey (SDSS) data to create separate white dwarf (WD) luminosity functions (LFs) for two or more different mass ranges. In this paper, we determine the completeness of the SDSS spectroscopic WD sample by comparing a proper-motion selected sample of WDs from SDSS imaging data with a large catalog of spectroscopically determined WDs. We derive a selection probability as a function of a single color (g − i) and apparent magnitude (g) that covers the range −1.0 < g − i < 0.2 and 15 < g < 19.5. We address the observed upturn in log g for WDs with Teff 12,000 K and offer arguments that the problem is limited to the line profiles and is not present in the continuum. We offer an empirical method of removing the upturn, recovering a reasonable mass function for WDs with Teff < 12,000 K. Finally we present a WD LF with nearly an order of magnitude (3358) more spectroscopically confirmed WDs than any previous work.

Starspots And Relativity: Applied Doppler Imaging For The Gravity Probe B Mission, Stephen C. Marsden, Svetlana V. Berdyugina, Jean-Francois Donati, Joel A. Eaton, Michael H. Williamson

Information Systems and Engineering Management Research Publications

We present Doppler images and surface differential rotation measurements for the primary of the RS CVn binary IM Pegasi, the guide star for the Gravity Probe B experiment. The data used is a subset of that taken during optical support of the mission and was obtained almost nightly over a near three year period from the Automatic Spectroscopic Telescope operated by Tennessee State University. Using the technique of least-squares deconvolution to increase the signal-to-noise ratio of the data, we have reconstructed 31 maximum entropy Doppler images of the star. The images show that the spot features are relatively stable for …

Structure Formation Inside Triaxial Dark Matter Halos: Galactic Disks, Bulges, And Bars, Clayton Heller, Isaac Shlosman, Evangelie Athanassoula

Physics & Astronomy: Faculty Publications

We investigate formation and evolution of galactic disks immersed in assembling live DM halos. Models have been evolved from cosmological initial conditions and represent the collapse of an isolated density perturbation. The baryons include gas participating in star formation (SF) and stars with the energy feedback onto the ISM. We find that (1) the triaxial halo figure tumbling is insignificant and the angular momentum (J) is channeled into the internal circulation, while the baryonic collapse is stopped by the centrifugal barrier; (2) density response of the (disk) baryons is out of phase with DM, thus washing out the …

The Orbits Of The Quadruple Star System 88 Tauri A From Phases Differential Astrometry And Radial Velocity, Benjamin F. Lane, Matthew W. Muterspaugh, Francis C. Fekel, Michael H. Williamson, Stanley Browne, Maciej Konacki, Bernard F. Burke, Mark M. Colavita, Shrinivas R. Kulkarni, Michael Shao

Information Systems and Engineering Management Research Publications

We have used high-precision differential astrometry from the Palomar High-precision Astrometric Search for Exoplanet Systems (PHASES) project and radial velocity measurements covering a time span of 20 years to determine the orbital parameters of the 88 Tau A system. 88 Tau is a complex hierarchical multiple system comprising a total of six stars; we have studied the brightest four, consisting of two short-period pairs orbiting each other with an ~18 yr period. We present the first orbital solution for one of the short-period pairs, and determine the masses of the components and distance to the system to the level of …

Agn Reddening And Ultraviolet Extinction Curves From Hubble Space Telescope Spectra, C. Martin Gaskell, A. J. Benkler

C. Martin Gaskell Publications

We present intrinsic extinction curves for 14 AGNs. The AGNs have reddenings, E(B-V), of up to 0.36 mag. The majority (13 out of 14) of the extinction curves are not steep in the UV. Of the seven best determined extinction curves, five have extinction curves that are as flat as the standard Galactic curve in the optical and near UV, but flatter in the far UV, and without the λ2175 feature. One AGN, B3 0754+394, has a steep SMC-like extinction curve, and another, Mrk 304, has an LMC-like extinction curve, including a probable λ2175 bump. The remaining seven, lower-quality, extinction …

Neon Abundances From A Spitzer/Irs Survey Of Wolf-Rayet Stars., Richard Ignace, J. Cassinelli, G. Tracy, E. Churchwell, H. J. Lamers

ETSU Faculty Works

We report on neon abundances derived from Spitzer high resolution spectral data of eight Wolf-Rayet (WR) stars using the forbidden line of [Ne III] 15.56 μm. Our targets include four WN stars of subtypes 4–7, and four WC stars of subtypes 4–7. We derive ion fraction abundances γ of Ne2+ for the winds of each star. The ion fraction abundance is a product of the ionization fraction Qi in stage i and the abundance by number AE of element E relative to all nuclei. Values generally consistent with solar are obtained for the WN stars, and values in excess of …

Chromospherically Active Stars. Xxvi. The Double-Lined Late-Type Binary Hd 19485 = Wz Arietis, Francis C. Fekel, Charles Thomas Bolton

Information Systems and Engineering Management Research Publications

We have used spectroscopic observations to determine the orbital elements and some basic properties of the double-lined spectroscopic binary HD 19485 = WZ Ari. The orbital period is 6.247854 days, and the orbit is circular. The G5 V primary and K0 V secondary are chromospherically active. One star or possibly both are synchronously rotating. Based on the Hipparcos parallax and the magnitude differences derived in this work, we find that both components are approximately 1 mag above the zero-age main sequence, a result that is inconsistent with the assumption that the components are coeval. We discuss some possible solutions to …