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Cosmology, Relativity, and Gravity

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Articles 91 - 120 of 129

Full-Text Articles in Stars, Interstellar Medium and the Galaxy

Vacuum, Space-Time, Matter And The Models Of Smarandache Geometry, Florentin Smarandache, Hu Chang-Wei Jan 2012

Vacuum, Space-Time, Matter And The Models Of Smarandache Geometry, Florentin Smarandache, Hu Chang-Wei

Branch Mathematics and Statistics Faculty and Staff Publications

Many fundamental concepts in physics remain unsolved:  What is time? Is it pure relative?  What is the vacuum? Is it void space or special medium?  What is mass? Can it be created? I believe that physicists have not got definite answers for the above questions. Isaac Newton said: I was like a boy playing on the sea-shore, and diverting myself now and then finding a smoother pebble or a prettier shell than ordinary, whilst the great ocean of truth lay all undiscovered before me. For instance, we still do not know what the clear definition of time …

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Veritas Observations Of The Unusual Extragalactic Transient Swift J164449.3+573451, P. T. Reynolds, Et Al Aug 2011

Veritas Observations Of The Unusual Extragalactic Transient Swift J164449.3+573451, P. T. Reynolds, Et Al

Physical Sciences Publications

We report on very high energy (>100 GeV) gamma-ray observations of Swift J164449.3+573451, an unusual transient object first detected by the Swift Observatory and later detected by multiple radio, optical, and X-ray observatories. A total exposure of 28 hr was obtained on Swift J164449.3+573451 with the Very Energetic Radiation Imaging Telescope Array System (VERITAS) during 2011 March 28-April 15. We do not detect the source and place a differential upper limit on the emission at 500 GeV during these observations of 1.4 × 10–12 erg cm–2 s–1 (99% confidence level). We also present time-resolved upper limits and use a …

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The Variable Quiescent X-Ray Emission Of The Neutron Star Transient Xte J1701-462, Joel K. Fridriksson, Jeroen Homan, Rudy Wijnands, Edward M. Cackett, Diego Altamirano, Nathalie Degenaar, Edward F. Brown, Mariano Méndez, Tomaso M. Belloni Aug 2011

The Variable Quiescent X-Ray Emission Of The Neutron Star Transient Xte J1701-462, Joel K. Fridriksson, Jeroen Homan, Rudy Wijnands, Edward M. Cackett, Diego Altamirano, Nathalie Degenaar, Edward F. Brown, Mariano Méndez, Tomaso M. Belloni

Physics and Astronomy Faculty Research Publications

We present the results of continued monitoring of the quiescent neutron star low-mass X-ray binary XTE J1701-462 with Chandra and Swift. A new Chandra observation from 2010 October extends our tracking of the neutron star surface temperature from ≃ 800 days to ≃ 1160 days since the end of an exceptionally luminous 19 month outburst. This observation indicates that the neutron star crust may still be slowly cooling toward thermal equilibrium with the core; another observation further into quiescence is needed to verify this. The shape of the overall cooling curve is consistent with that of a broken power law, …

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Quiescent X-Ray Variability From The Neutron Star Transient Aql X-1, E. M. Cackett, J. K. Fridriksson, J. Homan, J. M. Miller, R. Wijnands Jul 2011

Quiescent X-Ray Variability From The Neutron Star Transient Aql X-1, E. M. Cackett, J. K. Fridriksson, J. Homan, J. M. Miller, R. Wijnands

Physics and Astronomy Faculty Research Publications

A number of studies have revealed variability from neutron star low-mass X-ray binaries during quiescence. Such variability is not well characterized, or understood, but may be a common property that has been missed due to lack of multiple observations. One such source where variability has been observed is Aql X-1. Here, we analyse 14 Chandra and XMM-Newton observations of Aql X-1 in quiescence, covering a period of approximately 2 yr. There is clear variability between the epochs, with the most striking feature being a flare-like increase in the flux by a factor of 5. Spectral fitting is inconclusive as to …

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Interpretation Of The Arcade 2 Absolute Sky Brightness Measurement, M. Seiffert, D. J. Fixsen, A. Kogut, S. M. Levin, M. Limon, P. M. Lubin, P. Mirel, Jack Singal, T. Villela, E. Wollack, C. A. Wuensche Jun 2011

Interpretation Of The Arcade 2 Absolute Sky Brightness Measurement, M. Seiffert, D. J. Fixsen, A. Kogut, S. M. Levin, M. Limon, P. M. Lubin, P. Mirel, Jack Singal, T. Villela, E. Wollack, C. A. Wuensche

Physics Faculty Publications

We use absolutely calibrated data between 3 and 90 GHz from the 2006 balloon flight of the ARCADE 2 instrument, along with previous measurements at other frequencies, to constrain models of extragalactic emission. Such emission is a combination of the cosmic microwave background (CMB) monopole, Galactic foreground emission, the integrated contribution of radio emission from external galaxies, any spectral distortions present in the CMB, and any other extragalactic source. After removal of estimates of foreground emission from our own Galaxy, and an estimated contribution of external galaxies, we present fits to a combination of the flat-spectrum CMB and potential spectral …

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Oral Presentation: The Universe In A Box, Jason Jaacks Apr 2011

Oral Presentation: The Universe In A Box, Jason Jaacks

Festival of Communities: UG Symposium (Posters)

When and how galaxies formed throughout the history of the Universe is one of the most fundamental questions of astronomy and astrophysics. As technology improves, astronomers are able to push the frontier of galaxy observation to a period when the Universe was less than 1 billion years old. This is when the first galaxies are beginning to form. However, beyond the limits of observational technology lies data fundamental to our complete understanding of these processes. Using state-of-the-art cosmological hydrodynamic computer codes combined with access to the nation’s largest and fastest supercomputers, we are able to simulate the formation and evolution …

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Further X-Ray Observations Of Exo 0748-676 In Quiescence: Evidence For A Cooling Neutron Star Crust, N. Degenaar, M. T. Wolff, P. S. Ray, K. S. Wood, J. Homan, W. H. G. Lewin, P. G. Jonker, E. M. Cackett, J. M. Miller, E. F. Brown, R. Wijnands Apr 2011

Further X-Ray Observations Of Exo 0748-676 In Quiescence: Evidence For A Cooling Neutron Star Crust, N. Degenaar, M. T. Wolff, P. S. Ray, K. S. Wood, J. Homan, W. H. G. Lewin, P. G. Jonker, E. M. Cackett, J. M. Miller, E. F. Brown, R. Wijnands

Physics and Astronomy Faculty Research Publications

In late 2008, the quasi-persistent neutron star X-ray transient and eclipsing binary EXO 0748-676 started a transition from outburst to quiescence, after it actively accreted for more than 24 yr. In a previous work, we discussed Chandra and Swift observations obtained during the first 5 months of this transition. Here, we report on further X-ray observations of EXO 0748-676, extending the quiescent monitoring to 1.6 yr. Chandra and XMM-Newton data reveal quiescent X-ray spectra composed of a soft, thermal component that is well fitted by a neutron star atmosphere model. An additional hard power-law tail is detected that changes non-monotonically …

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A Fast X-Ray Disk Wind In The Transient Pulsar Igr J17480-2446 In Terzan 5, Jon M. Miller, Dipankar Maitra, Edward M. Cackett, Sudip Bhattacharyya, Tod E. Strohmayer Apr 2011

A Fast X-Ray Disk Wind In The Transient Pulsar Igr J17480-2446 In Terzan 5, Jon M. Miller, Dipankar Maitra, Edward M. Cackett, Sudip Bhattacharyya, Tod E. Strohmayer

Physics and Astronomy Faculty Research Publications

Accretion disk winds are revealed in Chandra gratings spectra of black holes. The winds are hot and highly ionized (typically composed of He-like and H-like charge states) and show modest blueshifts. Similar line spectra are sometimes seen in "dipping" low-mass X-ray binaries (LMXBs), which are likely viewed edge-on; however, that absorption is tied to structures in the outer disk, and blueshifts are not typically observed. Here, we report the detection of blueshifted He-like Fe XXV (3100 ± 400 km s-1) and H-like Fe XXVI (1000 ± 200 km s-1) absorption lines in a Chandra/HETG spectrum of …

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Multistate Observations Of The Galactic Black Hole Xte J1752-223: Evidence For An Intermediate Black Hole Spin, R. C. Reis, J. M. Miller, A. C. Fabian, E. M. Cackett, D. Maitra, C. S. Reynolds, M. Rupen, D. T. H. Steeghs, R. Wijnands Feb 2011

Multistate Observations Of The Galactic Black Hole Xte J1752-223: Evidence For An Intermediate Black Hole Spin, R. C. Reis, J. M. Miller, A. C. Fabian, E. M. Cackett, D. Maitra, C. S. Reynolds, M. Rupen, D. T. H. Steeghs, R. Wijnands

Physics and Astronomy Faculty Research Publications

The Galactic black hole candidate XTE J1752-223 was observed during the decay of its 2009 outburst with the Suzaku and XMM-Newton observatories. The observed spectra are consistent with the source being in the ‘intermediate’ and ‘low-hard’ states, respectively. The presence of a strong, relativistic iron emission line is clearly detected in both observations and the line profiles are found to be remarkably consistent and robust to a variety of continuum models. This strongly points to the compact object in XTE J1752-223 being a stellar mass black hole accretor and not a neutron star. Physically motivated and self-consistent reflection models for …

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A New Pulsar Instrumentation At The Allen Telescope Array And The Nancay Radio Telescope, G. Desvignes, William C. Barott, I. Cognard, P. Lespagnol, G. Theureau Jan 2011

A New Pulsar Instrumentation At The Allen Telescope Array And The Nancay Radio Telescope, G. Desvignes, William C. Barott, I. Cognard, P. Lespagnol, G. Theureau

Publications

In the prospect of the gravitational wave background detection with high precision pulsar timing, we recently installed a new coherent dedispersion backend at the Allen Telescope Array (ATA) and the Nançay Radio Telescope (NRT).

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On Relativistic Disk Spectroscopy In Compact Objects With X-Ray Ccd Cameras, J. M. Miller, A. D'Aì, M. W. Bautz, S. Bhattacharyya, D. N. Burrows, E. M. Cackett, A. C. Fabian, M. J. Freyberg, F. Haberl, J. Kennea, M. A. Nowak, R. C. Reis, T. E. Strohmayer, M. Tsujimoto Dec 2010

On Relativistic Disk Spectroscopy In Compact Objects With X-Ray Ccd Cameras, J. M. Miller, A. D'Aì, M. W. Bautz, S. Bhattacharyya, D. N. Burrows, E. M. Cackett, A. C. Fabian, M. J. Freyberg, F. Haberl, J. Kennea, M. A. Nowak, R. C. Reis, T. E. Strohmayer, M. Tsujimoto

Physics and Astronomy Faculty Research Publications

X-ray charge-coupled devices (CCDs) are the workhorse detectors of modern X-ray astronomy. Typically covering the 0.3-10.0 keV energy range, CCDs are able to detect photoelectric absorption edges and K shell lines from most abundant metals. New CCDs also offer resolutions of 30-50 (E/ΔE), which is sufficient to detect lines in hot plasmas and to resolve many lines shaped by dynamical processes in accretion flows. The spectral capabilities of X-ray CCDs have been particularly important in detecting relativistic emission lines from the inner disks around accreting neutron stars and black holes. One drawback of X-ray CCDs is that spectra can be …

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Relativistic Lines And Reflection From The Inner Accretion Disks Around Neutron Stars, Edward M. Cackett, Jon M. Miller, David R. Ballantyne, Didier Barret, Sudip Bhattacharyya, Martin Boutelier, M. Coleman Miller, Tod E. Strohmayer, Rudy Wijnands Sep 2010

Relativistic Lines And Reflection From The Inner Accretion Disks Around Neutron Stars, Edward M. Cackett, Jon M. Miller, David R. Ballantyne, Didier Barret, Sudip Bhattacharyya, Martin Boutelier, M. Coleman Miller, Tod E. Strohmayer, Rudy Wijnands

Physics and Astronomy Faculty Research Publications

A number of neutron star low-mass X-ray binaries (LMXBs) have recently been discovered to show broad, asymmetric Fe K emission lines in their X-ray spectra. These lines are generally thought to be the most prominent part of a reflection spectrum, originating in the inner part of the accretion disk where strong relativistic effects can broaden emission lines. We present a comprehensive, systematic analysis of Suzaku and XMM-Newton spectra of 10 neutron star LMXBs, all of which display broad Fe K emission lines. Of the 10 sources, 4 are Z sources, 4 are atolls, and 2 are accreting millisecond X-ray pulsars …

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Discovery Of Very High Energy Gamma-Ray Emission From The Snr G54.1+0.3, P. T. Reynolds, Et Al Jul 2010

Discovery Of Very High Energy Gamma-Ray Emission From The Snr G54.1+0.3, P. T. Reynolds, Et Al

Physical Sciences Publications

We report the discovery of very high energy (VHE) gamma-ray emission from the direction of the SNR G54.1+0.3 using the VERITAS ground-based gamma-ray observatory. The TeV signal has an overall significance of 6.8σ and appears pointlike given the resolution of the instrument. The integral flux above 1 TeV is 2.5% of the Crab Nebula flux and significant emission is measured between 250 GeV and 4 TeV, well described by a power-law energy spectrum dN/dE ~ E –Γ with a photon index Γ = 2.39 ± 0.23stat ± 0.30sys. We find no evidence of time variability among observations …

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Central Compact Objects, Trevor Meek Mar 2010

Central Compact Objects, Trevor Meek

Physics

Central compact objects (CCOs) are point-like sources found near the center of supernova remnants (SNRs). They emit X-rays, but show no radio or gamma ray counterpart. Typical CCO candidates have emission radii on the order of 0.2-3.0 km. This is much smaller than the typical radius of a neutron star, making CCOs a difficult astronomical phenomenon to identify.

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Discovery Of Variability In The Very High Energy Gamma-Ray Emission Of 1es 1218+304 With Veritas, P. T. Reynolds, Et Al Jan 2010

Discovery Of Variability In The Very High Energy Gamma-Ray Emission Of 1es 1218+304 With Veritas, P. T. Reynolds, Et Al

Physical Sciences Publications

We present results from an intensive VERITAS monitoring campaign of the high-frequency peaked BL Lac object 1ES 1218+304 in 2008/2009. Although 1ES 1218+304 was detected previously by MAGIC and VERITAS at a persistent level of ~6% of the Crab Nebula flux, the new VERITAS data reveal a prominent flare reaching ~20% of the Crab. While very high energy (VHE) flares are quite common in many nearby blazars, the case of 1ES 1218+304 (redshift z = 0.182) is particularly interesting since it belongs to a group of blazars that exhibit unusually hard VHE spectra considering their redshifts. When correcting the measured …

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Begin The Adventure : How To Break The Light Barrier By A.D. 2079 (3rd Ed.), Florentin Smarandache, Homer B. Tilton Jan 2010

Begin The Adventure : How To Break The Light Barrier By A.D. 2079 (3rd Ed.), Florentin Smarandache, Homer B. Tilton

Branch Mathematics and Statistics Faculty and Staff Publications

This edition, the third, has undergone a subtle name change, going from "A.D. 2070" in the title to A.D. 2079 as the timeline is fine-tuned. Because of the almost universal failure to recognize the distinction between physical (reality-based, dynamical) and visual (appearance-based, kinematical) variables, a tremendous volume of mythology arose over the past 100 years centered around Einstein's reality view of the distortions of special relativity. To get a sense of it, we point the reader to Paul J. Nahin's heroic book, Time Machines, 2nd ed.,- to these Tech Notes in particular: TN#6. "A High-Speed Rocket Is a One-Way Time …

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On Neutral Absorption And Spectral Evolution In X-Ray Binaries, J. M. Miller, E. M. Cackett, R. C. Reis Dec 2009

On Neutral Absorption And Spectral Evolution In X-Ray Binaries, J. M. Miller, E. M. Cackett, R. C. Reis

Physics and Astronomy Faculty Research Publications

Current X-ray observatories make it possible to follow the evolution of transient and variable X-ray binaries across a broad range in luminosity and source behavior. In such studies, it can be unclear whether evolution in the low-energy portion of the spectrum should be attributed to evolution in the source, or instead to evolution in neutral photoelectric absorption. Dispersive spectrometers make it possible to address this problem. We have analyzed a small but diverse set of X-ray binaries observed with the Chandra High Energy Transmission Grating Spectrometer across a range in luminosity and different spectral states. The column density in individual …

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Measuring The Spin Of Grs 1915+105 With Relativistic Disk Reflection, J. L. Blum, J. M. Miller, A. C. Fabian, M. C. Miller, J. Homan, M. Van Der Klis, E. M. Cackett, R. C. Reis Nov 2009

Measuring The Spin Of Grs 1915+105 With Relativistic Disk Reflection, J. L. Blum, J. M. Miller, A. C. Fabian, M. C. Miller, J. Homan, M. Van Der Klis, E. M. Cackett, R. C. Reis

Physics and Astronomy Faculty Research Publications

GRS 1915+105 harbors one of the most massive known stellar black holes in the Galaxy. In 2007 May, we observed GRS 1915+105 for ~117 ks in the low/hard state using Suzaku. We collected and analyzed the data with the Hard X-ray Detector/Positive Intrinsic Negative and X-ray Spectrometer cameras spanning the energy range from 2.3 to 55 keV. Fits to the spectra with simple models reveal strong disk reflection through an Fe K emission line and a Compton backscattering hump. We report constraints on the spin parameter of the black hole in GRS 1915 + 105 using relativistic disk reflection models. …

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Detection Of Extended Vhe Gamma Ray Emission From G106.3+2.7 With Veritas, P. T. Reynolds, Et Al Aug 2009

Detection Of Extended Vhe Gamma Ray Emission From G106.3+2.7 With Veritas, P. T. Reynolds, Et Al

Physical Sciences Publications

We report the detection of very-high-energy (VHE) gamma-ray emission from supernova remnant (SNR) G106.3+2.7. Observations performed in 2008 with the VERITAS atmospheric Cherenkov gamma-ray telescope resolve extended emission overlapping the elongated radio SNR. The 7.3σ (pre-trials) detection has a full angular extent of roughly 06 by 04. Most notably, the centroid of the VHE emission is centered near the peak of the coincident 12CO (J = 1-0) emission, 04 away from the pulsar PSR J2229+6114, situated at the northern end of the SNR. Evidently the current-epoch particles from the pulsar wind nebula are not participating in the gamma-ray production. …

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Chandra And Swift Observations Of The Quasi-Persistent Neutron Star Transient Exo 0748-676 Back To Quiescence, N. Degenaar, R. Wijnands, M. T. Wolff, P. S. Ray, K. S. Wood, J. Homan, W. H. G. Lewin, P. G. Jonker, E. M. Cackett, J. M. Miller, E. F. Brown Jun 2009

Chandra And Swift Observations Of The Quasi-Persistent Neutron Star Transient Exo 0748-676 Back To Quiescence, N. Degenaar, R. Wijnands, M. T. Wolff, P. S. Ray, K. S. Wood, J. Homan, W. H. G. Lewin, P. G. Jonker, E. M. Cackett, J. M. Miller, E. F. Brown

Physics and Astronomy Faculty Research Publications

The quasi-persistent neutron star X-ray transient and eclipsing binary EXO 0748-676 recently started the transition to quiescence following an accretion outburst that lasted more than 24 years. We report on two Chandra and 12 Swift observations performed within five months after the end of the outburst. The Chandra spectrum is composed of a soft, thermal component that fits to a neutron star atmosphere model with kT∞ ~ 0.12keV, joined by a hard power-law tail that contributes ~20 per cent of the total 0.5-10 keV unabsorbed flux. The combined Chandra/Swift data set reveals a relatively hot and luminous quiescent system …

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Suzaku Observations Of The Black Hole H1743-322 In Outburst, J. L. Blum, J. M. Miller, E. Cackett, K. Yamaoka, H. Takahashi, J. Raymond, C. S. Reynolds, A. C. Fabian Apr 2009

Suzaku Observations Of The Black Hole H1743-322 In Outburst, J. L. Blum, J. M. Miller, E. Cackett, K. Yamaoka, H. Takahashi, J. Raymond, C. S. Reynolds, A. C. Fabian

Physics and Astronomy Faculty Research Publications

We observed the Galactic black hole candidate H1743-322 with Suzaku for approximately 32 ks, while the source was in a low/hard state during its 2008 outburst. We collected and analyzed the data with the HXD/PIN, HXD/GSO, and XIS cameras spanning the energy range 0.7-200 keV. Fits to the spectra with simple models fail to detect narrow Fe XXV and Fe XXVI absorption lines, with 90% confidence upper limits of 3.5 and 2.5 eV on the equivalent width, respectively. These limits are commensurate with those in the very high state, but are well below the equivalent widths of lines detected in …

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Broad Relativistic Iron Emission Line Observed In Sax J1808.4-3658, E. M. Cackett, D. Altamirano, A. Patruno, J. M. Miller, M. Reynolds, M. Linares, R. Wijnands Mar 2009

Broad Relativistic Iron Emission Line Observed In Sax J1808.4-3658, E. M. Cackett, D. Altamirano, A. Patruno, J. M. Miller, M. Reynolds, M. Linares, R. Wijnands

Physics and Astronomy Faculty Research Publications

During the 2008 September-October outburst of the accreting millisecond pulsar SAX J1808.4-3658, the source was observed by both Suzaku and XMM-Newton approximately 1 day apart. Spectral analysis reveals a broad relativistic Fe Kα emission line which is present in both data sets, as has recently been reported for other neutron star low-mass X-ray binaries. The properties of the Fe K line observed during each observation are very similar. From modeling the Fe line, we determine the inner accretion disk radius to be 13.2 ± 2.5 GM c-2. The inner disk radius measured from the Fe K line suggests …

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Neutrosophic Logic, Wave Mechanics, And Other Stories: Selected Works 2005-2008, Florentin Smarandache, Victor Christianto Mar 2009

Neutrosophic Logic, Wave Mechanics, And Other Stories: Selected Works 2005-2008, Florentin Smarandache, Victor Christianto

Branch Mathematics and Statistics Faculty and Staff Publications

There is beginning for anything; we used to hear that phrase. The same wisdom word applies to us too. What began in 2005 as a short email on some ideas related to interpretation of the Wave Mechanics results in a number of papers and books up to now. Some of these papers can be found in Progress in Physics or elsewhere. It is often recognized that when a mathematician meets a physics-inclined mind then the result is either a series of endless debates or publication. In our story, we prefer to publish rather than perish. Therefore, our purpose with this …

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A Deep Xmm-Newton Observation Of The Quasar 3c 287, G. Salvesen, J. M. Miller, E. Cackett, A. Siemiginowska Feb 2009

A Deep Xmm-Newton Observation Of The Quasar 3c 287, G. Salvesen, J. M. Miller, E. Cackett, A. Siemiginowska

Physics and Astronomy Faculty Research Publications

We report on an XMM-Newton observation of the z = 1.055 quasar and Gigahertz Peaked Spectrum (GPS) source 3C 287. Our 62.3 ks observation provides an exceptional X-ray view of a prominent member of this important subclass of active galactic nuclei (AGNs). The X-ray spectra of 3C 287 are consistent with a simple absorbed power law with a spectral index of Γ = 1.72 ± 0.02. Our fits imply a bolometric luminosity of L = 5.8 ± 0.2 × 1045 erg s-1 over the 0.3-10.0 keV band; this gives a mass lower limit of M BH min >= …

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Grb060602b = Swift J1749.4-2807: An Unusual Transiently Accreting Neutron-Star X-Ray Binary, R. Wijnands, E. Rol, E. Cackett, R. L. C. Starling, R. A. Remillard Feb 2009

Grb060602b = Swift J1749.4-2807: An Unusual Transiently Accreting Neutron-Star X-Ray Binary, R. Wijnands, E. Rol, E. Cackett, R. L. C. Starling, R. A. Remillard

Physics and Astronomy Faculty Research Publications

We present an analysis of the Swift Burst Alert Telescope (BAT) and X-ray telescope (XRT) data of GRB060602B, which is most likely an accreting neutron star in a binary system and not a gamma-ray burst. Our analysis shows that the BAT burst spectrum is consistent with a thermonuclear flash (type I X-ray burst) from the surface of an accreting neutron star in a binary system. The X-ray binary nature is further confirmed by the report of a detection of a faint point source at the position of the XRT counterpart of the burst in archival XMM-Newton data approximately six year …

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A Search For Iron Emission Lines In The Chandra X-Ray Spectra Of Neutron Star Low-Mass X-Ray Binaries, E. M. Cackett, J. M. Miller, J. Homan, M. Van Der Klis, W. H. G. Lewin, M. Méndez, J. Raymond, D. Steeghs, R. Wijnands Jan 2009

A Search For Iron Emission Lines In The Chandra X-Ray Spectra Of Neutron Star Low-Mass X-Ray Binaries, E. M. Cackett, J. M. Miller, J. Homan, M. Van Der Klis, W. H. G. Lewin, M. Méndez, J. Raymond, D. Steeghs, R. Wijnands

Physics and Astronomy Faculty Research Publications

While iron emission lines are well studied in black hole systems, both in X-ray binaries and active galactic nuclei, there has been less of a focus on these lines in neutron star low-mass X-ray binaries (LMXBs). However, recent observations with Suzaku and XMM-Newton have revealed broad, asymmetric iron line profiles in three neutron star LMXBs, confirming an inner disk origin for these lines in neutron star systems. Here, we present a search for iron lines in six neutron star LMXBs. For each object we have simultaneous Chandra and RXTE observations at two separate epochs, allowing for both a high-resolution spectrum …

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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 Jun 2008

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 …

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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 Apr 2008

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 …

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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 Feb 2008

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 …

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Quantization In Astrophysics, Brownian Motion, And Supersymmetry, Florentin Smarandache, Victor Christianto Jan 2007

Quantization In Astrophysics, Brownian Motion, And Supersymmetry, Florentin Smarandache, Victor Christianto

Branch Mathematics and Statistics Faculty and Staff Publications

The present book discusses, among other things, various quantization phenomena found in Astrophysics and some related issues including Brownian Motion. With recent discoveries of exoplanets in our galaxy and beyond, this Astrophysics quantization issue has attracted numerous discussions in the past few years. Most chapters in this book come from published papers in various peer-reviewed journals, and they cover different methods to describe quantization, including Weyl geometry, Supersymmetry, generalized Schrödinger, and Cartan torsion method. In some chapters Navier-Stokes equations are also discussed, because it is likely that this theory will remain relevant in Astrophysics and Cosmology While much of the …

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