Astrophysics and Astronomy Commons^™

Fe I And Fe Ii Abundances Of Solar-Type Dwarfs In The Pleiades Open Cluster, Simon C. Schuler, Adele L. Plunkett, Jeremy R. King, Marc H. Pinsonneault

Publications

We have derived Fe abundances of 16 solar-type Pleiades dwarfs by means of an equivalent width analysis of Fe I and Fe II lines in high-resolution spectra obtained with the Hobby - Eberly Telescope and High Resolution Spectrograph. Abundances derived from Fe II lines are larger than those derived from Fe I lines (herein referred to as over-ionization) for stars with Teff < 5400 K, and the dis-crepancy (∆Fe = [Fe II/H] - [Fe I/H]) increases dramatically with decreasing Teff, reaching over 0.8 dex for the coolest stars of our sample. The Pleiades joins the open clusters M34, the Hyades, IC2602, and IC2391, and the Ursa Major moving group, demonstrating ostensible over-ionization trends. The Pleiades ∆Fe abun-dances are correlated with Ca II infrared triplet and Hα chromospheric emission indicators and relative differences therein. Oxygen abundances of our Pleiades sample derived from the high-excitation O I triplet have been previously shown to increase with decreasing Teff, and a comparison with the ∆Fe abundances sug-gests that the over-excitation (larger abundances derived from high excitation lines relative to low excitation lines) and over-ionization effects that have been observed in cool open cluster and disk field main sequence (MS) dwarfs share a common origin. Curiously, a correlation between the Pleiades O I abundances and chromospheric emission indicators does not exist. Star-to-star Fe I abun-dances have low internal scatter (< 0.11 dex), but the abundances of stars with Teff< 5400 K are systematically higher compared to the warmer stars. The cool star [Fe I/H] abundances cannot be connected directly to over-excitation effects, but similarities with the ∆Fe and O I triplet trends suggest the abundances are dubious. Using the [Fe I/H] abundances of five stars with Teff > 5400 K, we derive a mean Pleiades cluster metallicity of [Fe/H] = +0.01 ± 0.02.

Discovery Of Rotational Braking In The Magnetic Helium-Strong Star Sigma Orionis E, R. H.D. Townsend, M. E. Oksala, David H. Cohen, S. P. Owocki, A. Ud-Doula

Physics & Astronomy Faculty Works

We present new U-band photometry of the magnetic helium-strong star sigma Ori E, obtained over 2004-2009 using the SMARTS 0.9 m telescope at Cerro Tololo Inter-American Observatory. When combined with historical measurements, these data constrain the evolution of the star's 1.19 day rotation period over the past three decades. We are able to rule out a constant period at the p(null) = 0.05% level, and instead find that the data are well described (p(null) = 99.3%) by a period increasing linearly at a rate of 77 ms per year. This corresponds to a characteristic spin-down time of 1.34 Myr, in …

Structure Maps For Hcp Metals From First-Principles Calculations, Gus L. W. Hart, Ohad Levy, Stefano Curtarolo

Faculty Publications

The ability to predict the existence and crystal type of ordered structures of materials from their components is a major challenge of current materials research. Empirical methods use experimental data to construct structure maps and make predictions based on clustering of simple physical parameters. Their usefulness depends on the availability of reliable data over the entire parameter space. Recent development of high-throughput methods opens the possibility to enhance these empirical structure maps by ab initio calculations in regions of the parameter space where the experimental evidence is lacking or not well characterized. In this paper we construct enhanced maps for …

The Nature Of The Strong 24 Μmspitzersource J222557+601148: Not A Young Galactic Supernova Remnant, Robert A. Fesen, Dan Milisavljevic

Dartmouth Scholarship

The nebula J222557+601148, tentatively identified by Morris et al. as a young Galactic supernova remnant (SNR) from Spitzer Galactic First Look Survey images and a follow-up mid-infrared spectrum, is unlikely to be an SNR remnant based on Hα, [O III], [S II] images, and low-dispersion optical spectra. The object is seen in Hα and [O III] λ5007 images as a faint, roughly circular ring nebula with dimensions matching that seen in 24 μm Spitzer images. Low-dispersion optical spectra show it to have narrow Hα and [N II] λλ6548,6583 line emissions with no evidence of broad or high-velocity (v ≥ …

A Flare In The Jet Of Pictor A, Herman L. Marshall, Eric S. Perlman

Aerospace, Physics, and Space Science Faculty Publications

A Chandra X-ray imaging observation of the jet in Pictor A showed a feature that appears to be a flare that faded between 2000 and 2002. The feature was not detected in a follow-up observation in 2009. The jet itself is over 150kpc long and about 1 kpc wide, so finding year-long variability is surprising. Assuming a synchrotron origin of the observed high-energy photons and a minimum energy condition for the outflow, the synchrotron loss time of the X-ray emitting electrons is of order 1200 years, which is much longer than the observed variability timescale. This leads to the possibility …

Bandwidth In Bolometric Interferometry, R. Charlassier, Emory F. Bunn, J.-Ch. Hamilton, J. Kaplan, S. Malu

Physics Faculty Publications

Context. Bolometric interferometry is a promising new technology with potential applications to the detection of B-mode polarization fluctuations of the cosmic microwave background (CMB). A bolometric interferometer will have to take advantage of the wide spectral detection band of its bolometers to be competitive with imaging experiments. A crucial concern is that interferometers are assumed to be significantly affected by a spoiling effect known as bandwidth smearing.

Aims. We investigate how the bandwidth modifies the work principle of a bolometric interferometer and affects its sensitivity to the CMB angular power spectra.

Methods. We obtain analytical expressions for …

Semi-Classical Approaches To Below Threshold Harmonics, James A. Hostetter

Honors Capstones

No abstract provided.

All-Sky Search For Gravitational-Wave Bursts In The First Joint Ligo-Geo-Virgo Run, J. Abadie, B. P. Abbott, R. Abbott, T. Accadia, F. Acernese, R. Adhikari, P. Ajith, B. Allen, G. Allen, E. Amador Ceron, R. S. Amin, S. B. Anderson, W. G. Anderson, F. Antonucci, M. A. Arain, M. Araya, K. G. Arun, Y. Aso, S. Aston, P. Astone, P. Aufmuth, C. Aulbert, S. Babak, P. Baker, G. Ballardin, S. Ballmer, D. Barker, F. Barone, B. Barr, P. Barriga, L. Barsotti, Tiffany Z. Summerscales

Faculty Publications

We present results from an all-sky search for unmodeled gravitational-wave bursts in the data collected by the LIGO, GEO 600 and Virgo detectors between November 2006 and October 2007. The search is performed by three different analysis algorithms over the frequency band 50-6000 Hz. Data are analyzed for times with at least two of the four LIGO-Virgo detectors in coincident operation, with a total live time of 266 days. No events produced by the search algorithms survive the selection cuts. We set a frequentist upper limit on the rate of gravitational-wave bursts impinging on our network of detectors. When combined …

Co And H3 + Toward Mwc 1080, Mwc 349, And Lkhα 101, Erika Gibb, S. Brittain, T Rettig, M Troutman, Theodore Simon, C Kulesa

Physics Faculty Works

We present high-resolution, near-infrared NIRSPEC observations of the fundamental rovibrational CO and H+ 3 R(1,0), R(1,1) u , and Q(1,0) transitions toward three early-type young stars: MWC 1080, MWC 349, and LkHα 101. These observations were performed for the purpose of constraining the physical characteristics of the interstellar material along each line of sight. Toward MWC 1080, we detected strong CO absorption and determined a column density upper limit of 1.4 × 1014 cm–2 for H+ 3. We infer that there is very little diffuse material along the line of sight toward MWC 1080 and that the CO absorption is …

Rapid Cooling Of The Neutron Star In The Quiescent Super-Eddington Transient Xte J1701-462, Joel K. Fridriksson, Jeroen Homan, Rudy Wijnands, Mariano Méndez, Diego Altamirano, Edward M. Cackett, Edward F. Brown, Tomaso M. Belloni, Nathalie Degenaar, Walter H. G. Lewin

Physics and Astronomy Faculty Research Publications

We present Rossi X-Ray Timing Explorer and Swift observations made during the final three weeks of the 2006-2007 outburst of the super-Eddington neutron star (NS) transient XTE J1701-462, as well as Chandra and XMM-Newton observations covering the first sime800 days of the subsequent quiescent phase. The source transitioned quickly from active accretion to quiescence, with the luminosity dropping by over 3 orders of magnitude in sime13 days. The spectra obtained during quiescence exhibit both a thermal component, presumed to originate in emission from the NS surface, and a non-thermal component of uncertain origin, which has shown large and irregular variability. …

Quantum Criticality Due To Incipient Phase Separation In The Two-Dimensional Hubbard Model, Ehsan Khatami, K. Mikelsons, D. Galanakis, A. Macridin, J. Moreno, R. Scalettar, M. Jarrell

Faculty Publications

We investigate the two-dimensional Hubbard model with next-nearest-neighbor hopping, t′, using the dynamical cluster approximation. We confirm the existence of a first-order phase-separation transition terminating at a second-order critical point at filling nc(t′) and temperature Tps(t′). We find that as t′ approaches zero, Tps(t′) vanishes and nc(t′) approaches the filling associated with the quantum critical point separating the Fermi liquid from the pseudogap phase. We propose that the quantum critical point under the superconducting dome is the zero-temperature limit of the line of second-order critical points.

Satellite Motion In A Non-Singular Gravitational Potential, Ioannis Haranas, Spiros Pagiatakis

Physics and Computer Science Faculty Publications

We study the effects of a non-singular gravitational potential on satellite orbits by deriving the corresponding time rates of change of its orbital elements. This is achieved by expanding the non-singular potential into power series up to second order. This series contains three terms, the first been the Newtonian potential and the other two, here R₁ (first order term) and R₂ (second order term), express deviations of the singular potential from the Newtonian. These deviations from the Newtonian potential are taken as disturbing potential terms in the Lagrange planetary equations that provide the time rates of change of …

Co And H+3 Toward Mwc 1080, Mwc 349, And Lkhα 101, E L. Gibb, Sean D. Brittain, T W. Rettig, M Troutman, Theodore Simon, C Kulesa

Publications

We present high-resolution, near-infrared NIRSPEC observations of the fundamental rovibrational CO and H+ 3 R(1,0), R(1,1) u , and Q(1,0) transitions toward three early-type young stars: MWC 1080, MWC 349, and LkHα 101. These observations were performed for the purpose of constraining the physical characteristics of the interstellar material along each line of sight. Toward MWC 1080, we detected strong CO absorption and determined a column density upper limit of 1.4 × 1014 cm–2 for H+ 3. We infer that there is very little diffuse material along the line of sight toward MWC 1080 and that the CO absorption is …

Multiwavelength Observations Of 1rxh J173523.7-354013: Revealing An Unusual Bursting Neutron Star, N. Degenaar, P. G. Jonker, M. A. P. Torres, R. Kaur, N. Rea, G. L. Israel, A. Patruno, G. Trap, E. M. Cackett, P. D'Avanzo, G. Lo Curto, G. Novara, H. Krimm, S. T. Holland, A. De Luca, P. Esposito, R. Wijnands

Physics and Astronomy Faculty Research Publications

On 2008 May 14, the Burst Alert Telescope onboard the Swift mission triggered on a type-I X-ray burst from the previously unclassified ROSAT object 1RXH J173523.7-354013, establishing the source as a neutron star X-ray binary. We report on X-ray, optical and near-infrared observations of this system. The X-ray burst had a duration of ~2 h and belongs to the class of rare, intermediately long type-I X-ray bursts. From the bolometric peak flux of ~3.5 × 10^-8ergcm^-2s^-1, we infer a source distance of D <~ 9.5 kpc. Photometry of the field reveals an optical counterpart that declined from R = 15.9 during the X-ray burst to R = 18.9 thereafter. Analysis of post-burst Swift/X-ray Telescope observations as well as archival XMM-Newton and ROSAT data suggests that the system is persistent at a 0.5-10 keV luminosity of ~2 × 10³⁵ (D/9.5 kpc)²ergs^-1. Optical and infrared photometry …

Observing Mesospheric Gravity Waves With Nasa’S Awe Mission And Correlating To Gnss Tec Maps, Jaime Aguilar Guerrero, Björn Bergsson, Sehin Mesfin, Pavel Inchin, Matthew Zettergren, Ludger Scherliess, Yucheng Zhao, Dominique Pautet

Space Dynamics Laboratory Publications

The Atmosphere Waves Experiment (AWE) is a NASA mission launched on November 9, 2023, and installed on the International Space Station (ISS). Its primary goal is to detect and characterize atmospheric gravity waves (AGWs) by measuring Earth’s mesospheric hydroxyl (OH) airglow with its key instrument, the Advanced Mesospheric Temperature Mapper (AMTM). Since its deployment, AWE has been quantifying the seasonal and regional variability of AGWs, investigating their occurrence and potential sources, and enabling the assessment of their broader impact on the atmosphere by comparing measurements at different altitudes by other instruments. AWE has collected extensive imagery and temperature data capturing …

Extrasolar Planet Detection Through Analysis Of K-Giant Radial Velocity Data, Floyd D. Linayao

Physics

Extrasolar planet detection is an ongoing and growing field of scientific research. To date, there are over 400 planet candidates discovered by various means of detection. Currently, astronomers taking observations at Lick Observatory are searching for potential extrasolar planets around K-giant stars. The project was originally developed to monitor stars to be used in the astrometric grid for NASA’s Space Interferometry Mission (SIM). While using the radial velocity method to test if the astrometric centers of K-giants were stable, astronomers came to the realization that the same process could be used for extrasolar planet detection. Of the 373 K-giants being …

Velocity Distribution Of Dark Matter Halos: A Critical Test For The Λ Cold Dark Matter Model, Robert Jo Thompson

UNLV Theses, Dissertations, Professional Papers, and Capstones

The existence of a bullet cluster (such as 1E0657-56) poses a challenge to the concordance cold dark matter model. Here we investigate the velocity distribution of dark matter halo pairs in large N-body simulations with differing box sizes and resolutions. We examine various basic statistics such as halo masses, relative halo velocities, collisional angles, and separation distances in our simulations. We then compare the results to the observational properties of 1E0657-56. Our results suggest that it is very difficult to produce such a halo pair with such a high relative velocity at a redshift of z=0. The relative velocities increase …

Pulsational Mapping Of Calcium Across The Surface Of A White Dwarf, Susan E. Thompson, Ted Von Hippel, Et Al.

Publications

We constrain the distribution of calcium across the surface of the white dwarf star G29-38 by combining time-series spectroscopy from Gemini-North with global time-series photometry from the Whole Earth Telescope. G29-38 is actively accreting metals from a known debris disk. Since the metals sink significantly faster than they mix across the surface, any inhomogeneity in the accretion process will appear as an inhomogeneity of the metals on the surface of the star. We measure the flux amplitudes and the calcium equivalent width amplitudes for two large pulsations excited on G29-38 in 2008. The ratio of these amplitudes best fits a …

Cluster Solver For Dynamical Mean-Field Theory With Linear Scaling In Inverse Temperature, Ehsan Khatami, C. Lee, Z. Bai, R. Scalettar, M. Jarrell

Faculty Publications

Dynamical mean-field theory and its cluster extensions provide a very useful approach for examining phase transitions in model Hamiltonians and, in combination with electronic structure theory, constitute powerful methods to treat strongly correlated materials. The key advantage to the technique is that, unlike competing real-space methods, the sign problem is well controlled in the Hirsch-Fye (HF) quantum Monte Carlo used as an exact cluster solver. However, an important computational bottleneck remains; the HF method scales as the cube of the inverse temperature, β. This often makes simulations at low temperatures extremely challenging. We present here a method based on determinant …

Neutrosophic Physics: More Problems, More Solutions, Florentin Smarandache

Branch Mathematics and Statistics Faculty and Staff Publications

When considering the laws of theoretical physics, one of the physicists says that these laws – the actual expressions of the laws of mathematics and logics being applied to physical phenomena – should be limited according to the physical meaning we attribute to the phenomena. In other word, there is an opinion that a theoretical physicist should put some limitations onto mathematics, in order to “reduce” it to the observed reality. No doubt, we can do it. However, if following this way, we would arrive at only mathematical models of already known physical phenomena. Of course, this might be useful …