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Full-Text Articles in Physical Sciences and Mathematics
Cooling Of The Crust In The Neutron Star Low-Mass X-Ray Binary Mxb 1659-29, Edward M. Cackett, Rudy Wijnands, Jon M. Miller, Edward F. Brown, Nathalie Degenaar
Cooling Of The Crust In The Neutron Star Low-Mass X-Ray Binary Mxb 1659-29, Edward M. Cackett, Rudy Wijnands, Jon M. Miller, Edward F. Brown, Nathalie Degenaar
Physics and Astronomy Faculty Research Publications
In quasi-persistent neutron star transients, long outbursts cause the neutron star crust to be heated out of thermal equilibrium with the rest of the star. During quiescence, the crust then cools back down. Such crustal cooling has been observed in two quasi-persistent sources: KS 1731-260 and MXB 1659-29. Here we present an additional Chandra observation of MXB 1659-29 in quiescence, which extends the baseline of monitoring to 6.6 yr after the end of the outburst. This new observation strongly suggests that the crust has thermally relaxed, with the temperature remaining consistent over 1000 days. Fitting the temperature cooling curve with …
The Acs Survey Of Galactic Globular Clusters. Iii. The Double Subgiant Branch Of Ngc 1851, A. P. Milone, L. R. Bedin, G. Piotto, J. Anderson, I. R. King, A. Sarajedini, A. Dotter, B. Chaboyer, A. Marin Franch, S. Majewski, A. Aparicio, M. Hempel, N. E.Q Paust, I. N. Reid, A. Rosenberg, M. Siegel
The Acs Survey Of Galactic Globular Clusters. Iii. The Double Subgiant Branch Of Ngc 1851, A. P. Milone, L. R. Bedin, G. Piotto, J. Anderson, I. R. King, A. Sarajedini, A. Dotter, B. Chaboyer, A. Marin Franch, S. Majewski, A. Aparicio, M. Hempel, N. E.Q Paust, I. N. Reid, A. Rosenberg, M. Siegel
Dartmouth Scholarship
Photometry with the Hubble Space Telescope Advanced Camera for Surveys (HST ACS) reveals that the subgiant branch (SGB) of the globular cluster NGC 1851 splits into two well-defined branches. If the split is due only to an age effect, the two SGBs would imply two star formation episodes separated by ~1 Gyr. We discuss other anomalies in NGC 1851 that could be interpreted in terms of a double stellar population. Finally, we compare the case of NGC 1851 with the other two globulars known to host multiple stellar populations, and show that all three clusters differ in several important …
Starlight In The Night: Discovering The Secret Lives Of Stars, Shane L. Larson
Starlight In The Night: Discovering The Secret Lives Of Stars, Shane L. Larson
Public Talks
No abstract provided.
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
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 …
Ages And Metallicities Of Early-Type Void Galaxies From Line Strength Measurements, Gary Wegner, Norman A. Grogin
Ages And Metallicities Of Early-Type Void Galaxies From Line Strength Measurements, Gary Wegner, Norman A. Grogin
Dartmouth Scholarship
We present spectroscopic observations of 26 galaxies of type E and S0, based on their blue morphologies, located in voids by the study of Grogin & Geller in 1999. Measurements of redshift, velocity dispersion, and four Lick line indices, Mg b , Fe5270, Fe5335, and Hβ with their errors are given for all of these galaxies, along with Hβ, [O III], Hα, and [N II] emission line strengths for a subset of these objects. These sources are brighter than M* for low-density regions and tend to be bluer than their counterpart early-type objects in high-density regions. Using the models …
The Enigmatic Young Object: Walker 90/V590 Monocerotis, M. D. Joner, M. R. Perez, B. Mccollum, M. E. Van Dend Ancker
The Enigmatic Young Object: Walker 90/V590 Monocerotis, M. D. Joner, M. R. Perez, B. Mccollum, M. E. Van Dend Ancker
Faculty Publications
Aims. We assess the evolutionary status of the intriguing object Walker 90/V590 Mon, which is located about 20 arcmin northwest of the Cone Nebula near the center of the open cluster NGC 2264. This object, according to its most recent optical spectral type determination (B7), which we confirmed, is at least 3 mag too faint in V for the cluster distance, but it shows the classical signs of a young pre-main sequence object, such as highly variable H emission, Mg II emission, IR excess, UV continuum, and optical variability. Methods. We analyzed a collection of archival and original data on …
Metallicity And Effective Temperature Of The Secondary Or Rs Ophicuhi, R. L. Pearson Iii, Ya. V. Pavlenko, A. Evans, T. Kerr, L. Yakovina, C. E. Woodward, D. Lynch, R. Rudy, R. W. Russell
Metallicity And Effective Temperature Of The Secondary Or Rs Ophicuhi, R. L. Pearson Iii, Ya. V. Pavlenko, A. Evans, T. Kerr, L. Yakovina, C. E. Woodward, D. Lynch, R. Rudy, R. W. Russell
Faculty Publications
Context. The recurrent nova RS Ophiuchi undergoes nova eruptions every 10-20 years as a result of thermonuclear runaway on the surface of a white dwarf close to the Chandrasekhar limit. Both the progress of the eruption and its aftermath depend on the (poorly known) composition of the red giant in the RS Oph system. Aims. Our aim is to understand better the effect of the giant secondary on the recurrent nova eruption. Methods. Synthetic spectra were computed for a grid of M-giant model atmospheres having a range of effective temperatures 3200 < Teff < 4400 K, gravities 0 < log g < 1 and abundances -4 < [Fe/H] < 0.5, and fit to infrared spectra of RS Oph as it returned to quiescence after its 2006 eruption. We have modelled the infrared spectrum in the range 1.4-2.5µm to determine metallicity and effective temperature of the red giant. Results. We find Teff= 4100 ±100 K, log g = 0.0 ±0.5, [Fe/H] = 0.0 ±0.5, [C/H] = -0.8 ±0.2, [N/H] = +0.6 ±0.3 in the atmosphere of the secondary, and demonstrate that inclusion of some dust "veiling" in the spectra cannot improve our fits.
Clouds Search For Variability In Brown Dwarf Atmospheres: Infrared Spectroscopic Time Series Of L/T Transition Brown Dwarfs, D. Stephens, B. Goldman, M. C. Cushing, M. S. Marley, E. Artigau, K. S. Baliyan, V. J. S. Bejar, J. A. Caballero, N. Chanover, M. Connelley, R. Doyon, T. Forveille, S. Ganesh, C. R. Gelino, H. B. Hammel, J. Holtzman, S. Joshi, U. C. Joshi, S. K. Leggett, M. C. Liu
Clouds Search For Variability In Brown Dwarf Atmospheres: Infrared Spectroscopic Time Series Of L/T Transition Brown Dwarfs, D. Stephens, B. Goldman, M. C. Cushing, M. S. Marley, E. Artigau, K. S. Baliyan, V. J. S. Bejar, J. A. Caballero, N. Chanover, M. Connelley, R. Doyon, T. Forveille, S. Ganesh, C. R. Gelino, H. B. Hammel, J. Holtzman, S. Joshi, U. C. Joshi, S. K. Leggett, M. C. Liu
Faculty Publications
L-type ultra-cool dwarfs and brown dwarfs have cloudy atmospheres that could host weather-like phenomena. The detection of photometric or spectral variability would provide insight into unresolved atmospheric heterogeneities, such as holes in a global cloud deck. Indeed, a number of ultra-cool dwarfs have been reported to vary. Additional time-resolved spectral observations of brown dwarfs offer the opportunity for further constraining and characterising atmospheric variability. Aims. It has been proposed that growth of heterogeneities in the global cloud deck may account for the L- to T-type transition when brown dwarf photospheres evolve from cloudy to clear conditions. Such a mechanism is …
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
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
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 Msolar neutron star. The inner disk radii that we measure with Fe K lines are in good agreement …