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Articles 4891 - 4920 of 8860

Full-Text Articles in Astrophysics and Astronomy

Optical And X-Ray Studies Of 10 X-Ray-Selected Cataclysmic Binaries, John R. Thorstensen, Jules Halpern Sep 2013

Optical And X-Ray Studies Of 10 X-Ray-Selected Cataclysmic Binaries, John R. Thorstensen, Jules Halpern

Dartmouth Scholarship

We report on ground-based optical observations of 10 cataclysmic binaries that were discovered through their X-ray emission. Time-resolved radial velocity spectroscopy yields unambiguous orbital periods for eight objects and ambiguous results for the remaining two. The orbital periods range from 87 minutes to 9.38 hr. We also obtained time-series optical photometry for six targets, four of which have coherent pulsations. These periods are 1218 s for 1RXS J045707.4+452751, 628 s for AX J1740.2–2903, 477 s for AX J1853.3–0128, and 935 s for IGR J19267+1325. A total of seven of the sources have coherent oscillations in X-rays or optical, indicating that …

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Multiwavelength Observations And Modeling Of 1es 1959+650 In A Low Flux State, P. T. Reynolds, Et. Al. Sep 2013

Multiwavelength Observations And Modeling Of 1es 1959+650 In A Low Flux State, P. T. Reynolds, Et. Al.

Physical Sciences Publications

We report on the VERITAS observations of the high-frequency peaked BL Lac object 1ES 1959+650 in the period 2007-2011. This source is detected at TeV energies by VERITAS at 16.4 standard deviation (σ) significance in 7.6 hr of observation in a low flux state. A multiwavelength spectral energy distribution (SED) is constructed from contemporaneous data from VERITAS, Fermi-LAT, RXTE PCA, and Swift UVOT. Swift XRT data is not included in the SED due to a lack of simultaneous observations with VERITAS. In contrast to the orphan γ-ray flare exhibited by this source in 2002, the X-ray flux of the source …

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Goals Strategies And First Discoveries Of Ao327 The Arecibo All-Sky 327 Mhz Drift Pulsar Survey, J. S. Deneva, K. Stovall, M. A. Mclaughlin, S. D. Bates, P. C.C. Freire, J. G. Martinez, F. Jenet, M. Bagchi Sep 2013

Goals Strategies And First Discoveries Of Ao327 The Arecibo All-Sky 327 Mhz Drift Pulsar Survey, J. S. Deneva, K. Stovall, M. A. Mclaughlin, S. D. Bates, P. C.C. Freire, J. G. Martinez, F. Jenet, M. Bagchi

Physics & Astronomy Faculty Publications

We report initial results from AO327, a drift survey for pulsars with the Arecibo telescope at 327 MHz. The first phase of AO327 will cover the sky at declinations of -1° to 28°, excluding the region within 5° of the Galactic plane, where high scattering and dispersion make low-frequency surveys sub-optimal. We record data from a 57 MHz bandwidth with 1024 channels and 125 μs sampling time. The 60 s transit time through the AO327 beam means that the survey is sensitive to very tight relativistic binaries even with no acceleration searches. To date we have detected 44 known pulsars …

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The Xmm-Newton Epic X-Ray Light Curve Analysis Of Wr 6., Richard Ignace, K. Gayley, W.-R. Hamann, D. Huenemoerder, L. Oskinova, A. Pollock, M. Mcfall Sep 2013

The Xmm-Newton Epic X-Ray Light Curve Analysis Of Wr 6., Richard Ignace, K. Gayley, W.-R. Hamann, D. Huenemoerder, L. Oskinova, A. Pollock, M. Mcfall

ETSU Faculty Works

We obtained four pointings of over 100 ks each of the well-studied Wolf-Rayet star WR 6 with the XMM-Newton satellite. With a first paper emphasizing the results of spectral analysis, this follow-up highlights the X-ray variability clearly detected in all four pointings. However, phased light curves fail to confirm obvious cyclic behavior on the well-established 3.766 d period widely found at longer wavelengths. The data are of such quality that we were able to conduct a search for "event clustering" in the arrival times of X-ray photons. However, we fail to detect any such clustering. One possibility is that X-rays …

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Two Suns In The Sky: Stellar Multiplicity Influence On Planet Formation, Ji Wang, Debra Fischer Sep 2013

Two Suns In The Sky: Stellar Multiplicity Influence On Planet Formation, Ji Wang, Debra Fischer

Yale Day of Data

We found that a planet is less likely to exist around a binary star, and thus Tatooine may be just a dream.

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Hst Hot Jupiter Transmission Spectral Survey: Detection Of Water In Hat-P-1b From Wfc3 Near-Ir Spatial Scan Observations, Hannah R. Wakeford, David K. Sing, Drake Deming, Neale P. Gibson, Jonathan J. Fortney, Adam Burrows, Gilda E. Ballester, Nikolay Nikolov, Suzanne Aigrain, Gregory W. Henry, Heather Knutson, Alain Lecavelier Des Etangs, Frederic Pont, Adam P. Showman, Alfred Vidal-Madjar, Kevin J. Zahnle Sep 2013

Hst Hot Jupiter Transmission Spectral Survey: Detection Of Water In Hat-P-1b From Wfc3 Near-Ir Spatial Scan Observations, Hannah R. Wakeford, David K. Sing, Drake Deming, Neale P. Gibson, Jonathan J. Fortney, Adam Burrows, Gilda E. Ballester, Nikolay Nikolov, Suzanne Aigrain, Gregory W. Henry, Heather Knutson, Alain Lecavelier Des Etangs, Frederic Pont, Adam P. Showman, Alfred Vidal-Madjar, Kevin J. Zahnle

Information Systems and Engineering Management Research Publications

We present Hubble Space Telescope near-infrared transmission spectroscopy of the transiting hot-Jupiter HAT-P-1b. We observed one transit with Wide Field Camera 3 using the G141 low-resolution grism to cover the wavelength range 1.087–1.678 μm. These time series observations were taken with the newly available spatial-scan mode that increases the duty cycle by nearly a factor of 2, thus improving the resulting photometric precision of the data. We measure a planet-to-star radius ratio of Rp/R* = 0.117 09 ± 0.000 38 in the white light curve with the centre of transit occurring at 245 6114.345 ± 0.000 133 (JD). We achieve …

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Andromeda Dwarfs In Light Of Mond. Ii. Testing Prior Predictions, Stacy S. Mcgaugh Sep 2013

Andromeda Dwarfs In Light Of Mond. Ii. Testing Prior Predictions, Stacy S. Mcgaugh

Faculty Scholarship

We employ recently published measurements of the velocity dispersions in the newly discovered dwarf satellite galaxies of Andromeda to test our previously published predictions of this quantity. The data are in good agreement with our specific predictions for each dwarf made a priori with modified Newtonian dynamics (MOND), with reasonable stellar mass-to-light ratios, and no dark matter, while Newtonian dynamics point to quite large mass discrepancies in these systems. MOND distinguishes between regimes where the internal field of the dwarf, or the external field of the host, dominates. The data appear to recognize this distinction, which is a unique feature …

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Discovery Of High-Frequency Iron K Lags In Ark 564 And Mrk 335, E. Kara, A. C. Fabian, E. M. Cackett, P. Uttley, D. R. Wilkins, A. Zoghbi Sep 2013

Discovery Of High-Frequency Iron K Lags In Ark 564 And Mrk 335, E. Kara, A. C. Fabian, E. M. Cackett, P. Uttley, D. R. Wilkins, A. Zoghbi

Physics and Astronomy Faculty Research Publications

We use archival XMM-Newton observations of Ark 564 and Mrk 335 to calculate the frequency-dependent time lags for these two well-studied sources. We discover high-frequency Fe K lags in both sources, indicating that the red wing of the line precedes the rest-frame energy by roughly 100 and 150 s for Ark 564 and Mrk 335, respectively. Including these two new sources, Fe K reverberation lags have been observed in seven Seyfert galaxies. We examine the low-frequency lag-energy spectrum, which is smooth, and shows no feature of reverberation, as would be expected if the low-frequency lags were produced by distant reflection …

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Detecting The Rapidly Expanding Outer Shell Of The Crab Nebula: Where To Look, Xiang Wang, Gary J. Ferland, J. A. Baldwin, E. D. Loh, C. T. Richardson Sep 2013

Detecting The Rapidly Expanding Outer Shell Of The Crab Nebula: Where To Look, Xiang Wang, Gary J. Ferland, J. A. Baldwin, E. D. Loh, C. T. Richardson

Physics and Astronomy Faculty Publications

We present a range of steady-state photoionization simulations, corresponding to different assumed shell geometries and compositions, of the unseen postulated rapidly expanding outer shell to the Crab Nebula. The properties of the shell are constrained by the mass that must lie within it, and by limits to the intensities of hydrogen recombination lines. In all cases the photoionization models predict very strong emissions from high ionization lines that will not be emitted by the Crab's filaments, alleviating problems with detecting these lines in the presence of light scattered from brighter parts of the Crab. The near-NIR [Ne VI] λ7.652 μ …

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Nitrogen Abundances And The Distance Moduli Of The Pleiades And Hyades, Blake Miller, Jeremy R. King, Yu Chen, Ann Merchant Boesgaard Sep 2013

Nitrogen Abundances And The Distance Moduli Of The Pleiades And Hyades, Blake Miller, Jeremy R. King, Yu Chen, Ann Merchant Boesgaard

Publications

Recent reanalyses of HIPPARCOS parallax data confirm a previously noted discrepancy with the Pleiades distance modulus estimated from main-sequence fitting in the color-magnitude diagram. One proposed explanation of this distance modulus discrepancy is a Pleiades He abundance that is significantly larger than the Hyades value. We suggest that, based on our theoretical and observational understanding of Galactic chemical evolution, nitrogen abundances may serve as a proxy for helium abundances of disk stars. Utilizing high-resolution near-UV Keck/HIRES spectroscopy, we determine N abundances in the Pleiades and Hyades dwarfs from NH features in the λ3330 region. While our Hyades N abundances show …

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Nsf Funds Study Of Cosmic Dust, Kim Hill Sep 2013

Nsf Funds Study Of Cosmic Dust, Kim Hill

News and Events (Discontinued Series)

No abstract provided.

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The Biophysical Effects Of Deuterium Oxide On Biomolecules And Living Cells Through Open Notebook Science., Anthony Salvagno Sep 2013

The Biophysical Effects Of Deuterium Oxide On Biomolecules And Living Cells Through Open Notebook Science., Anthony Salvagno

Physics & Astronomy ETDs

This dissertation explores various effects of deuterium oxide (D2O also known as heavy water) in nature. Water is everywhere and interacts with just about everything. As such, it would be quite a daunting task to characterize every effect that water exhibits on everything in the universe. This research is a small piece of the puzzle, and provides some fundamental understanding of how water interacts with other molecules. This is done from two viewpoints: (1) the effects of heavy water on living cells and (2) the effects of heavy water on molecules. Varying concentrations of deuterium oxide were used as the …

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A Change In The Quiescent X-Ray Spectrum Of The Neutron Star Low-Mass X-Ray Binary Mxb 1659-29, E. M. Cackett, E. F. Brown, A. Cumming, N. Degenaar, J. K. Fridriksson, J. Homan, J. M. Miller, R. Wijnands Sep 2013

A Change In The Quiescent X-Ray Spectrum Of The Neutron Star Low-Mass X-Ray Binary Mxb 1659-29, E. M. Cackett, E. F. Brown, A. Cumming, N. Degenaar, J. K. Fridriksson, J. Homan, J. M. Miller, R. Wijnands

Physics and Astronomy Faculty Research Publications

The quasi-persistent neutron star low-mass X-ray binary MXB 1659-29 went into quiescence in 2001, and we have followed its quiescent X-ray evolution since. Observations over the first 4 yr showed a rapid drop in flux and temperature of the neutron star atmosphere, interpreted as cooling of the neutron star crust which had been heated during the 2.5 yr outburst. However, observations taken approximately 1400 and 2400 days into quiescence were consistent with each other, suggesting the crust had reached thermal equilibrium with the core. Here we present a new Chandra observation of MXB 1659-29 taken 11 yr into quiescence and …

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Discovery Of High-Frequency Iron K Lags In Ark 564 And Mrk 335, E. Kara, A. C. Fabian, E. M. Cackett, P. Uttley, D. R. Wilkins, A. Zoghbi Sep 2013

Discovery Of High-Frequency Iron K Lags In Ark 564 And Mrk 335, E. Kara, A. C. Fabian, E. M. Cackett, P. Uttley, D. R. Wilkins, A. Zoghbi

Physics and Astronomy Faculty Research Publications

We use archival XMM-Newton observations of Ark 564 and Mrk 335 to calculate the frequency-dependent time lags for these two well-studied sources. We discover high-frequency Fe K lags in both sources, indicating that the red wing of the line precedes the rest-frame energy by roughly 100 and 150 s for Ark 564 and Mrk 335, respectively. Including these two new sources, Fe K reverberation lags have been observed in seven Seyfert galaxies. We examine the low-frequency lag-energy spectrum, which is smooth, and shows no feature of reverberation, as would be expected if the low-frequency lags were produced by distant reflection …

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Ua66 Ogden College Of Science & Engineering Newsletter, Cheryl Stevens, Dean Sep 2013

Ua66 Ogden College Of Science & Engineering Newsletter, Cheryl Stevens, Dean

Ogden College of Science & Engineering Publications

No abstract provided.

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Gas Lines From The 5-Myr Old Optically Thin Disk Around Hd141569a, W F. Thi, C Pinte, E Pantin, J C. Augereau, G Meeus, F Menard, C Martin-Zaidi, P Woitke, P Riviere-Marichalar, I Kamp, A Carmona, G Sandell, C Eiroa, W Dent, B Montesinos, G Aresu, R Meijerink, M Spaans, G White, D Ardila, J Lebreton, I Mendigutia, Sean D. Brittain Sep 2013

Gas Lines From The 5-Myr Old Optically Thin Disk Around Hd141569a, W F. Thi, C Pinte, E Pantin, J C. Augereau, G Meeus, F Menard, C Martin-Zaidi, P Woitke, P Riviere-Marichalar, I Kamp, A Carmona, G Sandell, C Eiroa, W Dent, B Montesinos, G Aresu, R Meijerink, M Spaans, G White, D Ardila, J Lebreton, I Mendigutia, Sean D. Brittain

Publications

At the distance of 99-116 pc, HD141569A is one of the nearest HerbigAe stars that is surrounded by a tenuous disk, probably in transition between a massive primordial disk and a debris disk. We observed the fine-structure lines of OI at 63 and 145 micron and the CII line at 157 micron with the PACS instrument onboard the Herschel Space Telescope as part of the open-time large programme GASPS. We complemented the atomic line observations with archival Spitzer spectroscopic and photometric continuum data, a ground-based VLT-VISIR image at 8.6 micron, and 12CO fundamental ro-vibrational and pure rotational J=3-2 observations. We …

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Continued Neutron Star Crust Cooling Of The 11 Hz X-Ray Pulsar In Terzan 5: A Challenge To Heating And Cooling Models?, N. Degenaar, R. Wijnands, E. F. Brown, D. Altamirano, E. M. Cackett, J. Fridriksson, J. Homan, C. O. Heinke, J. M. Miller, D. Pooley, G. R. Sivakoff Sep 2013

Continued Neutron Star Crust Cooling Of The 11 Hz X-Ray Pulsar In Terzan 5: A Challenge To Heating And Cooling Models?, N. Degenaar, R. Wijnands, E. F. Brown, D. Altamirano, E. M. Cackett, J. Fridriksson, J. Homan, C. O. Heinke, J. M. Miller, D. Pooley, G. R. Sivakoff

Physics and Astronomy Faculty Research Publications

The transient neutron star low-mass X-ray binary and 11 Hz X-ray pulsar IGR J17480-2446 in the globular cluster Terzan 5 exhibited an 11 week accretion outburst in 2010. Chandra observations performed within five months after the end of the outburst revealed evidence that the crust of the neutron star became substantially heated during the accretion episode and was subsequently cooling in quiescence. This provides the rare opportunity to probe the structure and composition of the crust. Here, we report on new Chandra observations of Terzan 5 that extend the monitoring to sime2.2 yr into quiescence. We find that the thermal …

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A Stis Atlas Of Ca Ii Triplet Absorption Line Kinematics In Galactic Nuclei, Daniel P. Batcheldor, David Axon, Monica Valluri, Jocelyn Mandalou, David Merritt Sep 2013

A Stis Atlas Of Ca Ii Triplet Absorption Line Kinematics In Galactic Nuclei, Daniel P. Batcheldor, David Axon, Monica Valluri, Jocelyn Mandalou, David Merritt

Aerospace, Physics, and Space Science Faculty Publications

The relations observed between supermassive black holes and their host galaxies suggest a fundamental link in the processes that cause these two objects to evolve. A more comprehensive understanding of these relations could be gained by increasing the number of supermassive black hole mass (M•) measurements. This can be achieved, in part, by continuing to model the stellar dynamics at the centers of galactic bulges using data of the highest possible spatial resolution. Consequently, we present here an atlas of galaxies in the Space Telescope Imaging Spectrograph (STIS) data archive that may have spectra suitable for new M• estimates. Archived …

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Moving Objects In The Hubble Ultra Deep Field, Mukremin Kilic, Alexandros Gianninas, Ted Von Hippel Sep 2013

Moving Objects In The Hubble Ultra Deep Field, Mukremin Kilic, Alexandros Gianninas, Ted Von Hippel

Publications

We identify proper motion objects in the Hubble Ultra Deep Field (UDF) using the optical data from the original UDF program in 2004 and the near-infrared data from the 128 orbit UDF 2012 campaign. There are 12 sources brighter than I = 27 mag that display >3σ significant proper motions. We do not find any proper motion objects fainter than this magnitude limit. Combining optical and near-infrared photometry, we model the spectral energy distribution of each point-source using stellar templates and state-of-the-art white dwarf models. For I ≤ 27 mag, we identify 23 stars with K0-M6 spectral types and two …

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Book Review: Heart Of Darkness: Unraveling The Mysteries Of The Invisible Universe, T. D. Oswalt Sep 2013

Book Review: Heart Of Darkness: Unraveling The Mysteries Of The Invisible Universe, T. D. Oswalt

Publications

This document is Dr. Oswalt’s review of Heart of Darkness : Unraveling the Mysteries of the Invisible Universe by Jeremiah P. Ostriker and Simon Mitton Princeton, 2013 299p, 9780691134307 $27.95, 9781400844647 $27.95

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The Deep2 Galaxy Redshift Survey: Design, Observations, Data Reduction, And Redshifts, Jeffery A. Newman, Michael C. Cooper, Marc Davis, S. M. Faber, Alison L. Coil, Puragra Guhathakurta, David C. Koo, Andrew C. Phillips, Charlie Conroy, Aaron A. Dutton, Douglas P. Finkbeiner, Brian F. Gerke, David J. Rosario, Benjamin J. Weiner, Renbin Yan, Justin J. Harker, Susan A. Kassin, N. P. Konidaris, Kamson Lai, Darren S. Madgwick, K. G. Noeske, Gregory D. Wirth, A. J. Connolly, N. Kaiser, Evan N. Kirby, Brian C. Lemaux, Lihwai Lin, Jennifer M. Lotz, G. A. Luppino, C. Marinoni Aug 2013

The Deep2 Galaxy Redshift Survey: Design, Observations, Data Reduction, And Redshifts, Jeffery A. Newman, Michael C. Cooper, Marc Davis, S. M. Faber, Alison L. Coil, Puragra Guhathakurta, David C. Koo, Andrew C. Phillips, Charlie Conroy, Aaron A. Dutton, Douglas P. Finkbeiner, Brian F. Gerke, David J. Rosario, Benjamin J. Weiner, Renbin Yan, Justin J. Harker, Susan A. Kassin, N. P. Konidaris, Kamson Lai, Darren S. Madgwick, K. G. Noeske, Gregory D. Wirth, A. J. Connolly, N. Kaiser, Evan N. Kirby, Brian C. Lemaux, Lihwai Lin, Jennifer M. Lotz, G. A. Luppino, C. Marinoni

Physics and Astronomy Faculty Publications

We describe the design and data analysis of the DEEP2 Galaxy Redshift Survey, the densest and largest high-precision redshift survey of galaxies at z ~ 1 completed to date. The survey was designed to conduct a comprehensive census of massive galaxies, their properties, environments, and large-scale structure down to absolute magnitude MB = –20 at z ~ 1 via ~90 nights of observation on the Keck telescope. The survey covers an area of 2.8 deg2 divided into four separate fields observed to a limiting apparent magnitude of RAB = 24.1. Objects with z ≲ 0.7 are readily …

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Shadows In Time: A Study Of Temporal Metaphysics Through Hard Science Fiction And Its Restrictions On The Past And Future, Lindsey E. Mitchell Aug 2013

Shadows In Time: A Study Of Temporal Metaphysics Through Hard Science Fiction And Its Restrictions On The Past And Future, Lindsey E. Mitchell

Oglethorpe Journal of Undergraduate Research

Through a series of essays, this body of work explores the varying theories concerning the nature of time and how each theory affects the possibility and outcome of time travel. Following these essays, a collection of short stories focuses on what the author considers the most probable theories concerning time and expands on how they might affect a time traveler's decisions and fate.

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A Bayesian Approach To Deriving Ages Of Individual Field White Dwarfs, Erin M. O'Malley, Ted Von Hippel, David A. Van Dyk Aug 2013

A Bayesian Approach To Deriving Ages Of Individual Field White Dwarfs, Erin M. O'Malley, Ted Von Hippel, David A. Van Dyk

Dartmouth Scholarship

We apply a self-consistent and robust Bayesian statistical approach to determine the ages, distances, and zero-age main sequence (ZAMS) masses of 28 field DA white dwarfs (WDs) with ages of approximately 4-8 Gyr. Our technique requires only quality optical and near-infrared photometry to derive ages with <15% uncertainties, generally with little sensitivity to our choice of modern initial-final mass relation. We find that age, distance, and ZAMS mass are correlated in a manner that is too complex to be captured by traditional error propagation techniques. We further find that the posterior distributions of age are often asymmetric, indicating that the standard approach to deriving WD ages can yield misleading results.

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Supermassive Black Hole Formation At High Redshifts Via Direct Collapse: Physical Processes In The Early Stage, Jun-Hwan Choi, Isaac Shlosman, Mitchell C. Begelman Aug 2013

Supermassive Black Hole Formation At High Redshifts Via Direct Collapse: Physical Processes In The Early Stage, Jun-Hwan Choi, Isaac Shlosman, Mitchell C. Begelman

Physics and Astronomy Faculty Publications

We use numerical simulations to explore whether direct collapse can lead to the formation of supermassive black hole (SMBH) seeds at high redshifts. Using the adaptive mesh refinement code ENZO, we follow the evolution of gas within slowly tumbling dark matter (DM) halos of Mvir ~ 2 × 108 M☉ and Rvir ~ 1 kpc. For our idealized simulations, we adopt cosmologically motivated DM and baryon density profiles and angular momentum distributions. Our principal goal is to understand how the collapsing flow overcomes the centrifugal barrier and whether it is subject to fragmentation which can potentially …

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Salt Long-Slit Spectroscopy Of Luminous Obscured Quasars: An Upper Limit On The Size Of The Narrow-Line Region?, Kevin N. Hainline, Ryan Hickox, Jenny E. Greene, Adam D. Myers, Nadia L. Zakamska Aug 2013

Salt Long-Slit Spectroscopy Of Luminous Obscured Quasars: An Upper Limit On The Size Of The Narrow-Line Region?, Kevin N. Hainline, Ryan Hickox, Jenny E. Greene, Adam D. Myers, Nadia L. Zakamska

Dartmouth Scholarship

We present spatially resolved long-slit spectroscopy from the Southern African Large Telescope (SALT) to examine the spatial extent of the narrow-line regions (NLRs) of a sample of 8 luminous obscured quasars at 0.10 < z < 0.43. Our results are consistent with an observed shallow slope in the relationship between NLR size and L_[OIII], which has been interpreted to indicate that NLR size is limited by the density and ionization state of the NLR gas rather than the availability of ionizing photons. We also explore how the NLR size scales with a more direct measure of instantaneous AGN power using mid-IR photometry from WISE, which probes warm to hot dust near the central black hole and so, unlike [OIII], does not depend on the properties of the NLR. Using our results as well as samples from the literature, we obtain a power-law relationship between NLR size and L_8micron that is significantly steeper than that observed for NLR size and L_[OIII]. We find that the size of the NLR goes approximately as L^(1/2)_8micron, as expected from the simple scenario of constant-density clouds illuminated by a central ionizing source. We further see tentative evidence for a flattening of the relationship between NLR size and L_8micron at the high luminosity end, and propose that we are seeing a limiting NLR size of 10 - 20 kpc, beyond which the availability of gas to ionize becomes too low. We find that L_[OIII] ~ L_8micron^(1.4), consistent with a picture in which the L_[OIII] is dependent on the volume of the NLR. These results indicate that high-luminosity quasars have a strong effect in ionizing the available gas in a galaxy.

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First Magnetic Seismology Of The Cme Reconnection Outflow Layer In The Low Corona With 2.5-D Mhd Simulations Of The Kelvin-Helmholtz Instability, Katariina Nykyri, Claire Foullon Aug 2013

First Magnetic Seismology Of The Cme Reconnection Outflow Layer In The Low Corona With 2.5-D Mhd Simulations Of The Kelvin-Helmholtz Instability, Katariina Nykyri, Claire Foullon

Publications

For conditions observed in the low corona, we perform 2.5-D magnetohydrodynamic (MHD) simulations of the Kelvin-Helmholtz instability (KHI) at the surface of a coronal mass ejection (CME). We match the observed time development of the KHI with simulated growth from 110 MHD experiments representing a parametric range of realistic magnetic field strengths and orientations and two key values of the velocity shear, ΔV, inferred from observations. The results are field strengths Be≈ 8–9 G and Bs≈ 10–11 G in the CME reconnection outflow layer and the surrounding sheath, respectively, for ΔV≈770kms−1; for nearly perpendicular orientation (1° tilt) of Bs with …

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Impact Of Mhd Shock Physics On Magnetosheath Symmetry And Kelvin-Helmholtz Instability, K. Nykyri Aug 2013

Impact Of Mhd Shock Physics On Magnetosheath Symmetry And Kelvin-Helmholtz Instability, K. Nykyri

Publications

We have performed 13 three-dimensional global magnetohydrodynamic (MHD) simulations of the magnetosheath plasma and magnetic field properties for Parker spiral (PS) and ortho-Parker spiral interplanetary magnetic field (IMF) orientations corresponding to a wide range of solar wind plasma conditions. To study the growth of the Kelvin-Helmholtz instability on the dawn and dusk flank magnetopause, we have performed 26 local two-dimensional MHD simulations, with the initial conditions taken from global simulations on both sides of the velocity shear layer at the dawn-dusk terminator. These simulations indicate that while the MHD physics of the fast shocks does not directly lead to strong …

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Ice And Dust In The Prestellar Dark Cloud Lynds 183: Preplanetary Matter At The Lowest Temperatures, David Horne, D. Whittet, C Poteet, J. Chiar, L. Paganini, V Bajaj, S. Shenoy, A Adamson Aug 2013

Ice And Dust In The Prestellar Dark Cloud Lynds 183: Preplanetary Matter At The Lowest Temperatures, David Horne, D. Whittet, C Poteet, J. Chiar, L. Paganini, V Bajaj, S. Shenoy, A Adamson

Physics Faculty Works

Dust grains are nucleation centers and catalysts for the growth of icy mantles in quiescent interstellar clouds, the products of which may accumulate into preplanetary matter when new stars and solar systems form within the clouds. In this paper, we present the first spectroscopic detections of silicate dust and the molecular ices H2O, CO, and CO2 in the vicinity of the prestellar core L183 (L134N). An infrared photometric survey of the cloud was used to identify reddened background stars, and we present spectra covering solid-state absorption features in the wavelength range 2-20 μm for nine of them. The mean composition …

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Polarimetry And The High-Energy Emission Mechanisms In Quasar Jets: The Case Of Pks 1136-135, Mihai Cara, Eric S. Perlman Aug 2013

Polarimetry And The High-Energy Emission Mechanisms In Quasar Jets: The Case Of Pks 1136-135, Mihai Cara, Eric S. Perlman

Aerospace, Physics, and Space Science Faculty Publications

Since the discovery of kiloparsec-scale X-ray emission from quasar jets, the physical processes responsible for their high-energy emission have been poorly defined. A number of mechanisms are under active debate, including synchrotron radiation, inverse-Comptonized cosmic microwave background (IC/CMB) emission, and other Comptonization processes. In a number of cases, the optical and X-ray emission of jet regions are inked by a single spectral component, and in those, high-resolution multi-band imaging and polarimetry can be combined to yield a powerful diagnostic of jet emission processes. Here we report on deep imaging photometry of the jet of PKS 1136−135 obtained with the Hubble …

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The Einstein@Home Search For Radio Pulsars And Psr J2007+2722 Discovery, B. Allen, B. Knispel, J. M. Cordes, J. S. Deneva, J. W.T. Hessels, D. Anderson, C. Aulbert, O. Bock, Fredrick A. Jenet, Kevin Stovall Aug 2013

The Einstein@Home Search For Radio Pulsars And Psr J2007+2722 Discovery, B. Allen, B. Knispel, J. M. Cordes, J. S. Deneva, J. W.T. Hessels, D. Anderson, C. Aulbert, O. Bock, Fredrick A. Jenet, Kevin Stovall

Physics & Astronomy Faculty Publications

Einstein@Home aggregates the computer power of hundreds of thousands of volunteers from 193 countries, to search for new neutron stars using data from electromagnetic and gravitational-wave detectors. This paper presents a detailed description of the search for new radio pulsars using Pulsar ALFA survey data from the Arecibo Observatory. The enormous computing power allows this search to cover a new region of parameter space; it can detect pulsars in binary systems with orbital periods as short as 11 minutes. We also describe the first Einstein@Home discovery, the 40.8 Hz isolated pulsar PSR J2007+2722, and provide a full timing model. PSR …

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