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Articles 2461 - 2490 of 8856

Full-Text Articles in Astrophysics and Astronomy

Searches For Gravitational Waves From Known Pulsars At Two Harmonics In 2015–2017 Ligo Data, Tiffany Summerscales, Ligo Scientific Collaboration And The Virgo Collaboration Jun 2019

Searches For Gravitational Waves From Known Pulsars At Two Harmonics In 2015–2017 Ligo Data, Tiffany Summerscales, Ligo Scientific Collaboration And The Virgo Collaboration

Faculty Publications

We present a search for gravitational waves from 222 pulsars with rotation frequencies 10 Hz. We use advanced LIGO data from its first and second observing runs spanning 2015–2017, which provides the highest-sensitivity gravitational-wave data so far obtained. In this search we target emission from both the l = m = 2 mass quadrupole mode, with a frequency at twice that of the pulsar's rotation, and the l = 2, m = 1 mode, with a frequency at the pulsar rotation frequency. The search finds no evidence for gravitational-wave emission from any pulsar at either frequency. For the l = …

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On The Balance Between Plasma And Magnetic Pressure Across Equatorial Plasma Depletions, J. Rodríguez-Zuluaga, C. Stolle, Y. Yamazaki, H. Lühr, J. Park, Ludger Scherliess, J. L. Chau Jun 2019

On The Balance Between Plasma And Magnetic Pressure Across Equatorial Plasma Depletions, J. Rodríguez-Zuluaga, C. Stolle, Y. Yamazaki, H. Lühr, J. Park, Ludger Scherliess, J. L. Chau

All Physics Faculty Publications

In magnetized plasmas such as the ionosphere, electric currents develop in regions of strong density gradients to balance the resulting plasma pressure gradients. These currents, usually known as diamagnetic currents decrease the magnetic pressure where the plasma pressure increases, and vice versa. In the low‐latitude ionosphere, equatorial plasma depletions (EPDs) are well known for their steep plasma density gradients and adverse effect on radio wave propagation. In this paper, we use continuous measurements of the magnetic field and electron density from the European Space Agency's Swarm constellation mission to assess the balance between plasma and magnetic pressure across large‐scale EPDs. …

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Rotational Quenching Of Hd Induced By Collisions With H2 Molecules, Yier Wan, Nadulvalath Balakrishnan, B. H. Yang, R. C. Forrey, P. C. Stancil Jun 2019

Rotational Quenching Of Hd Induced By Collisions With H2 Molecules, Yier Wan, Nadulvalath Balakrishnan, B. H. Yang, R. C. Forrey, P. C. Stancil

Chemistry and Biochemistry Faculty Research

Rate coefficients for rotational transitions in HD induced by H2 impact for rotational levels of HD j ≤ 8 and temperatures 10 K ≤ T ≤ 5000 K are reported. The quantum mechanical close-coupling (CC) method and the coupled-states (CS) decoupling approximation are used to obtain the cross-sections employing the most recent highly accurate H2–H2 potential energy surface (PES). Our results are in good agreement with previous calculations for low-lying rotational transitions The cooling efficiency of HD compared with H2 and astrophysical applications are briefly discussed.

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Methanol Masers In Star-Forming Regions, Nicolas Clarisse, Anuj P. Sarma Jun 2019

Methanol Masers In Star-Forming Regions, Nicolas Clarisse, Anuj P. Sarma

DePaul Discoveries

Methanol molecules in star-forming regions emit detectable microwave radiation. In particular, the rotational energy state transitions of methanol are responsible for two types of masers: Class I and Class II, found in the bipolar outflows and accretion disks of star-forming regions, respectively. Masers, being intense point-like sources in our sky, serve as an excellent source of information in further understanding the environment of high-mass star-forming regions due to their intense luminosities. High-mass star formation is still not entirely understood and remains an observational challenge. We have compiled a list of all the methanol maser transitions observed in the literature, in …

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Hierarchical Structure Formation In The Sdss Eboss Ly-Alpha Forests, Devin Becker Jun 2019

Hierarchical Structure Formation In The Sdss Eboss Ly-Alpha Forests, Devin Becker

DePaul Discoveries

In this study, we examine hierarchical structure at large redshifts utilizing Sloan Digital Sky Survey (SDSS) Lyman-alpha forest data. Lyman-alpha forests are absorption lines in the spectrum of quasars that serve as tracers for clouds of primordial hydrogen. These data serve as a 1-dimensional probe of the matter density field at high redshift. Using a measure sensitive to hierarchical structure formation assembled around a discrete wavelet transform, we were able to detect hierarchical structure formation in the spectrum of every quasar studied. The nature of the hierarchy seems to pertain to two forms: one that is constant across all scales, …

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Spatially Resolved Stellar Populations And Kinematics With Kcwi: Probing The Assembly History Of The Massive Early-Type Galaxy Ngc 1407, Anna Ferré-Mateu, Duncan Forbes, Richard Mcdermid, Aaron Romanowsky, Jean Brodie Jun 2019

Spatially Resolved Stellar Populations And Kinematics With Kcwi: Probing The Assembly History Of The Massive Early-Type Galaxy Ngc 1407, Anna Ferré-Mateu, Duncan Forbes, Richard Mcdermid, Aaron Romanowsky, Jean Brodie

Faculty Publications

Using the newly commissioned Keck Cosmic Web Imager (KCWI) instrument on the Keck II telescope, we analyze the stellar kinematics and stellar populations of the well-studied massive early-type galaxy (ETG) NGC 1407. We obtained high signal-to-noise integral field spectra for a central and an outer (around one effective radius toward the southeast direction) pointing with integration times of just 600 s and 2400 s, respectively. We confirm the presence of a kinematically distinct core also revealed by VLT/MUSE data of the central regions. While NGC 1407 was previously found to have stellar populations characteristic of massive ETGs (with radially constant …

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How Bright Are Fast Optical Bursts Associated With Fast Radio Bursts?, Yuan-Pei Yang, Bing Zhang, Jian-Yan Wei Jun 2019

How Bright Are Fast Optical Bursts Associated With Fast Radio Bursts?, Yuan-Pei Yang, Bing Zhang, Jian-Yan Wei

Physics & Astronomy Faculty Research

The origin of fast radio bursts (FRBs) is still unknown. Multiwavelength observations during or shortly after the FRB phase would be essential to identify the counterpart of an FRB and to constrain its progenitor and environment. In this work, we investigate the brightness of the “fast optical bursts” (FOBs) associated with FRBs and the prospects of detecting them. We investigate several inverse Compton (IC) scattering processes that might produce an FOB, including both the one-zone and two-zone models. We also investigate the extension of the same mechanism of FRB emission to the optical band. We find that a detectable FOB …

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The Effect Of Binarity On Circumstellar Disk Evolution, S. A. Barenfeld, J. M. Carpenter, A. I. Sargent, A. C. Rizzuto, A. L. Kraus, T. Meshkat, R. L. Akeson, Eric L.N. Jensen, S. Hinkley Jun 2019

The Effect Of Binarity On Circumstellar Disk Evolution, S. A. Barenfeld, J. M. Carpenter, A. I. Sargent, A. C. Rizzuto, A. L. Kraus, T. Meshkat, R. L. Akeson, Eric L.N. Jensen, S. Hinkley

Physics & Astronomy Faculty Works

We present new results on how the presence of stellar companions affects disk evolution based on a study of the 5–11 Myr old Upper Scorpius OB Association. Of the 50 G0-M3 Upper Sco members with disks in our sample, only seven host a stellar companion within 2'' and brighter than K = 15, compared to 35 of 75 members without disks. This matches a trend seen in the 1–2 Myr old Taurus region, where systems with a stellar companion within 40 au have a lower fraction of infrared-identified disks than those without such companions, indicating shorter disk lifetimes in close …

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Thermodynamics Of Neutrons In A Magnetic Field And Its Implications For Neutron Stars, Efrain J. Ferrer, Aric Hackebill Jun 2019

Thermodynamics Of Neutrons In A Magnetic Field And Its Implications For Neutron Stars, Efrain J. Ferrer, Aric Hackebill

Physics & Astronomy Faculty Publications

We investigate the effects of a magnetic field on the thermodynamics of a neutron system at finite density and temperature. Our main motivation is to deepen the understanding of the physics of a class of neutron stars known as magnetars, which exhibit extremely strong magnetic fields. Taking into account two facts, (i) the existence of a pressure anisotropy in the presence of a magnetic field and (ii) that the quantum field theory contribution to the pressure is non-negligible, we show that the maximum value that the inner magnetic field of a star can reach while being in agreement with the …

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Propagation Of A Short Grb Jet In The Ejecta: Jet Launching Delay Time, Jet Structure, And Gw170817/Grb 170817a, Jin-Jun Geng, Bing Zhang, Anders Kölligan, Rolf Kuiper, Yong-Feng Huang Jun 2019

Propagation Of A Short Grb Jet In The Ejecta: Jet Launching Delay Time, Jet Structure, And Gw170817/Grb 170817a, Jin-Jun Geng, Bing Zhang, Anders Kölligan, Rolf Kuiper, Yong-Feng Huang

Physics & Astronomy Faculty Research

We perform a series of relativistic magnetohydrodynamic simulations to investigate how a hot magnetic jet propagates within the dynamical ejecta of a binary neutron star merger, focusing on how the jet structure depends on the delay time of jet launching with respect to the merger time, Δt jet. We find that regardless of the jet-launching delay time, a structured jet with an angle-dependent luminosity and Lorentz factor is always formed after the jet breaks out of the ejecta. On the other hand, the jet-launching delay time has an impact on the jet structure. If the jet-launching delay time is relatively …

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Variability In The Atmosphere Of The Hot Jupiter Kepler-76b, Brian Jackson, Elisabeth Adams, Wesley Sandidge, Steven Kreyche, Jennifer Briggs Jun 2019

Variability In The Atmosphere Of The Hot Jupiter Kepler-76b, Brian Jackson, Elisabeth Adams, Wesley Sandidge, Steven Kreyche, Jennifer Briggs

Physics Faculty Publications and Presentations

No abstract provided.

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The Newborn Planet Population Emerging From Ring-Like Structures In Discs, Giuseppe Lodato, Giovanni Dipierro, Enrico Ragusa, Feng Long, Gregory J. Herczeg, Ilaria Pascucci, Paola Pinilla, Carlo F. Manara, Marco Tazzari, Yao Liu, Gijs D. Mulders, Daniel Harsono, Yann Boehler, François Ménard, Doug Johnstone, Colette Salyk, Gerrit Van Der Plas, Sylvie Cabrit, Suzan Edwards, William J. Fischer, Nathan Hendler, Brunella Nisini, Elisabetta Rigliaco, Henning Avenhaus, Andrea Banzatti, Michael Gully-Santiago Jun 2019

The Newborn Planet Population Emerging From Ring-Like Structures In Discs, Giuseppe Lodato, Giovanni Dipierro, Enrico Ragusa, Feng Long, Gregory J. Herczeg, Ilaria Pascucci, Paola Pinilla, Carlo F. Manara, Marco Tazzari, Yao Liu, Gijs D. Mulders, Daniel Harsono, Yann Boehler, François Ménard, Doug Johnstone, Colette Salyk, Gerrit Van Der Plas, Sylvie Cabrit, Suzan Edwards, William J. Fischer, Nathan Hendler, Brunella Nisini, Elisabetta Rigliaco, Henning Avenhaus, Andrea Banzatti, Michael Gully-Santiago

Astronomy: Faculty Publications

ALMA has observed a plethora of ring-like structures in planet-forming discs at distances of 10–100 au from their host star. Although several mechanisms have been invoked to explain the origin of such rings, a common explanation is that they trace new-born planets. Under the planetary hypothesis, a natural question is how to reconcile the apparently high frequency of gap-carving planets at 10–100 au with the paucity of Jupiter-mass planets observed around main-sequence stars at those separations. Here, we provide an analysis of the new-born planet population emerging from observations of gaps in discs, under the assumption that the observed gaps …

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Differential Photometry Of Active Galactic Nuclei Using Time Resolved Observations With The 1m Nickel Telescope Of Lick Observatory, Chance L. Spencer Jun 2019

Differential Photometry Of Active Galactic Nuclei Using Time Resolved Observations With The 1m Nickel Telescope Of Lick Observatory, Chance L. Spencer

Physics

Active galactic nuclei (AGNs) are exotic objects in the center of some galaxies with luminosities that can greatly outshine the stars of the host galaxy across the entire electromagnetic spectrum. The origin of the UV/optical light is thought to be due to accretion of material onto the supermassive black hole in their centers. Since these objects are too far away to resolve the gravitational sphere of influence of the black hole directly, we make use of a method called reverberation mapping. We measure the lag between the AGN power-law continuum emitted by the accretion disk and the Doppler-broadened emission lines …

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Microcontroller Differential Gps To Subtract Signal Delay Due To Ambient Free Electrons In The Ionosphere, Diana Jane Swanson Jun 2019

Microcontroller Differential Gps To Subtract Signal Delay Due To Ambient Free Electrons In The Ionosphere, Diana Jane Swanson

Physics

The goal of this project is to create a Global Positioning System (GPS) receiver that is more precise than one GPS receiver on its own. The technique is to take the difference between a GPS receiver’s measured position and its actual position, then use radio frequency (RF) communication to send that differential value to another microcontroller GPS receiver. This differential value will be added to the measured second location to get a more accurate position for the second GPS receiver, thus creating a differential GPS.

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Multi-Wavelength Investigation Of Energy Release And Chromospheric Evaporation In Solar Flares, Viacheslav M. Sadykov May 2019

Multi-Wavelength Investigation Of Energy Release And Chromospheric Evaporation In Solar Flares, Viacheslav M. Sadykov

Dissertations

For a comprehensive understanding of the energy release and chromospheric evaporation processes in solar flares it is necessary to perform a combined multi-wavelength analysis using observations from space-based and ground-based observatories, and compare the results with predictions of the radiative hydrodynamic (RHD) flare models. Initially, the case study of spatially-resolved chromospheric evaporation properties for an M 1.0-class solar flare (SOL2014-06-12T21:12) using data form IRIS (Interface Region Imaging Spectrograph), HMI/SDO (Helioseismic and Magnetic Imager onboard Solar Dynamics Observatory), and VIS/GST (Visible Imaging Spectrometer at Goode Solar Telescope), demonstrate a complicated nature of evaporation and its connection to the magnetic field topology. …

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A Tight Relation Between Spiral Arm Pitch Angle And Protplanetary Disk Mass, Si-Yue Yu, Luis C. Ho, Zhaohuan Zhu May 2019

A Tight Relation Between Spiral Arm Pitch Angle And Protplanetary Disk Mass, Si-Yue Yu, Luis C. Ho, Zhaohuan Zhu

Physics & Astronomy Faculty Research

We use two-dimensional Fourier transformation to measure the pitch angle () of the dominant spiral Fourier mode of well-defined spiral arms in 13 protoplanetary disks, making use of near-infrared scattered-light images of AB Aur, SAO 206462, MWC 758, V1247 Ori, HD 142527, DZ Cha, LkHα 330, and HD 100453, and ALMA millimeter continuum images of Elias 2-27, IM Lup, AS 205, and HT Lup. We find that the measured pitch angle correlates strongly with disk mass (M D ), such that more massive protoplanetary disks have smaller pitch angles, following . Interestingly, four disks with a known companion (HD 142527, …

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A Hard Look At Ngc 5347: Revealing A Nearby Compton-Thick Agn, E. S. Kammoun, J. M. Miller, A. Zoghbi, K. Oh, M. Koss, R. F. Muchotzky, L. W. Brenneman, W. N. Brandt, Daniel Proga, A. M. Lohfink, J. S. Kaastra, D. Barret, E. Behar, D. Stern May 2019

A Hard Look At Ngc 5347: Revealing A Nearby Compton-Thick Agn, E. S. Kammoun, J. M. Miller, A. Zoghbi, K. Oh, M. Koss, R. F. Muchotzky, L. W. Brenneman, W. N. Brandt, Daniel Proga, A. M. Lohfink, J. S. Kaastra, D. Barret, E. Behar, D. Stern

Physics & Astronomy Faculty Research

Current measurements show that the observed fraction of Compton-thick (CT) active galactic nuclei (AGN) is smaller than the expected values needed to explain the cosmic X-ray background. Prior fits to the X-ray spectrum of the nearby Seyfert-2 galaxy NGC 5347 (z = 0.00792, D = 35.5 Mpc ) have alternately suggested a CT and Compton-thin source. Combining archival data from Suzaku, Chandra, and—most importantly—new data from NuSTAR, ... See full text for complete abstract

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Long-Term Dust Formation By Core Collapse Supernovae, Kelsie Marie Krafton May 2019

Long-Term Dust Formation By Core Collapse Supernovae, Kelsie Marie Krafton

LSU Doctoral Dissertations

Studying long-term dust formation by CCSNe is an important step toward understanding the large dust masses found in early galaxies. The amazing new discovery of approximately a solar mass of cold dust in the ejecta of SN 1987A has caused a complete re-evaluation of dust formation in core collapse supernovae (CCSNe). CCSNe form only a small amount of dust after three years, but SN 1987A has a dust mass that is several orders of magnitude larger after 25 years. A recent study of SN 2010jl by Gall et al. (2014) made the fascinating suggestion that dust is continuously forming in …

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One Solution To The Mass Budget Problem For Planet Formation: Optically Thick Disks With Dust Scattering, Zhaohuan Zhu, Shangjia Zhang, Yan-Fei Jiang, Akimasa Kataoka, Tilman Birnstiel, Cornelis P. Dullemond, Sean M. Andrews, Jane Huang, Laura M. Perez, John M. Carpenter, Xue-Ning Bai, David J. Wilner, Luca Ricci May 2019

One Solution To The Mass Budget Problem For Planet Formation: Optically Thick Disks With Dust Scattering, Zhaohuan Zhu, Shangjia Zhang, Yan-Fei Jiang, Akimasa Kataoka, Tilman Birnstiel, Cornelis P. Dullemond, Sean M. Andrews, Jane Huang, Laura M. Perez, John M. Carpenter, Xue-Ning Bai, David J. Wilner, Luca Ricci

Physics & Astronomy Faculty Research

Atacama Large Millimeter Array (ALMA) surveys have suggested that the dust in Class II disks may not be enough to explain the averaged solid mass in exoplanets, under the assumption that the mm disk continuum emission is optically thin. This optically thin assumption seems to be supported by recent Disk Substructures at High Angular Resolution Project (DSHARP) observations where the measured optical depths are mostly less than one. However, we point out that dust scattering can considerably reduce the emission from an optically thick region. If that scattering is ignored, an optically thick disk with scattering can be misidentified as …

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Galaxy Classification: A Machine Learning Analysis Of Gama Catalogue Data, Aleke Nolte, Lingyu Wang, Maciej Bilicki, Benne W. Holwerda, Michael Biehl May 2019

Galaxy Classification: A Machine Learning Analysis Of Gama Catalogue Data, Aleke Nolte, Lingyu Wang, Maciej Bilicki, Benne W. Holwerda, Michael Biehl

Faculty and Staff Scholarship

We present a machine learning analysis of five labelled galaxy catalogues from the Galaxy And Mass Assembly (GAMA): The SersicCatVIKING and SersicCatUKIDSS catalogues containing morphological features, the GaussFitSimplecatalogue containing spectroscopic features, the MagPhys catalogue including physical parameters for galaxies, and the Lambdar catalogue, which contains photometric measurements. Extending work previously presented at the ESANN 2018 conference – in an analysis based on Generalized Relevance Matrix Learning Vector Quantization and Random Forests – we find that neither the data from the individual catalogues nor a combined dataset based on all 5 catalogues fully supports the visual-inspection-based galaxy classification scheme employed to …

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Modeling The Light Curves Of The Luminous Type Ic Supernova 2007d, Shan-Qin Wang, Zach Cano, Long Li, Liang-Duan Liu, Ling-Jun Wang, Weikang Zheng, Zi-Gao Dai, En-Wei Liang, Alexei V. Filippenko May 2019

Modeling The Light Curves Of The Luminous Type Ic Supernova 2007d, Shan-Qin Wang, Zach Cano, Long Li, Liang-Duan Liu, Ling-Jun Wang, Weikang Zheng, Zi-Gao Dai, En-Wei Liang, Alexei V. Filippenko

Physics & Astronomy Faculty Research

SN 2007D is a nearby (redshift z = 0.023146), luminous Type Ic supernova (SN) having a narrow light curve (LC) and high peak luminosity. Previous research based on the assumption that it was powered by the 56Ni cascade decay suggested that the inferred 56Ni mass and the ejecta mass are ~1.5 M ⊙ and ~3.5 M ⊙, respectively. In this paper, we employ some multiband LC models to model the R-band LC and the color (V − R) evolution of SN 2007D to investigate the possible energy sources powering them. We find that the pure 56Ni model is disfavored; the …

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Real-Time Rfi Mitigation In Radio Astronomy, Emily Ramey, Nick Joslyn, Richard Prestage, Michael Lam, Luke Hawkins, Tim Blattner, Mark Whitehead May 2019

Real-Time Rfi Mitigation In Radio Astronomy, Emily Ramey, Nick Joslyn, Richard Prestage, Michael Lam, Luke Hawkins, Tim Blattner, Mark Whitehead

Senior Honors Papers / Undergraduate Theses

As the use of wireless technology has increased around the world, Radio Frequency Interference (RFI) has become more and more of a problem for radio astronomers. Preventative measures exist to limit the presence of RFI, and programs exist to remove it from saved data, but the use of algorithms to detect and remove RFI as an observation is occurring is much less common. Such a method would be incredibly useful for observations in which the data must undergo several rounds of processing before being saved, as in pulsar timing studies. Strategies for real-time mitigation have been discussed and tested with …

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Arecibo Message, Joshua P. Tan May 2019

Arecibo Message, Joshua P. Tan

Open Educational Resources

This two week assignment asks students to interpret and analyze the 1974 Arecibo Message sent by Drake and Sagan. Week 1 introduces the concepts behind the construction of the message and engages with a critical analysis of the architecture and the contents of the message. Week 2 asks students to develop software in a Jupyter Notebook (available for free from the Anaconda Python Distribution) to interpret messages that were similar to those produced by Drake and Sagan.

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Relativistic Astronomy. Ii. In-Flight Solution Of Motion And Test Of Special Relativity Light Aberration, Jin-Ping Zhu, Bing Zhang, Yuan-Pei Yang May 2019

Relativistic Astronomy. Ii. In-Flight Solution Of Motion And Test Of Special Relativity Light Aberration, Jin-Ping Zhu, Bing Zhang, Yuan-Pei Yang

Physics & Astronomy Faculty Research

The Breakthrough Starshot project aims to send centimeter-sized, gram-scale "StarChip" probes to Alpha Centauri at a speed of ~0.2 c. On the other hand, Zhang & Li recently proposed that transrelativistic cameras may be sent to any direction to study astronomical objects and test special relativity. To conduct such "relativistic astronomy," one needs to solve the motion of the probe in flight. We solve the motion of the probe (including the moving direction and the velocity) by comparing the positions of three or more point sources observed in the Earth rest frame and in the probe's comoving frame. When the …

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Cosmology-Independent Estimate Of The Fraction Of Baryon Mass In The Igm From Fast Radio Burst Observations, Zhengxiang Li, He Gao, Jun-Jie Wei, Yuan-Pei Yang, Bing Zhang, Zong-Hong Zhu May 2019

Cosmology-Independent Estimate Of The Fraction Of Baryon Mass In The Igm From Fast Radio Burst Observations, Zhengxiang Li, He Gao, Jun-Jie Wei, Yuan-Pei Yang, Bing Zhang, Zong-Hong Zhu

Physics & Astronomy Faculty Research

The excessive dispersion measure (DM) of fast radio bursts (FRBs) has been proposed to be a powerful tool to study intergalactic medium (IGM) and to perform cosmography. One issue is that the fraction of baryons in the IGM, f IGM, is not properly constrained. Here, we propose a method of estimating f IGM using a putative sample of FRBs with the measurements of both DM and luminosity distance d L. The latter can be obtained if the FRB is associated with a distance indicator (e.g., a gamma-ray burst or a gravitational-wave event), or the redshift z of the FRB is …

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Haro 11, Pox 186, And Vcc 1313: The Enigmatic Behavior Of Hi Non-Emitters, Sarah H. Taft May 2019

Haro 11, Pox 186, And Vcc 1313: The Enigmatic Behavior Of Hi Non-Emitters, Sarah H. Taft

Macalester Journal of Physics and Astronomy

We present neutral hydrogen (HI) observations from the Very Large Array (VLA) telescope of the galaxies Haro 11, Pox 186, and VCC 1313. 24 hours of deep spectral line observation at the 21 cm line were obtained from the program 17B-287 of Haro 11, the primary galaxy studied in this capstone, and 176 and 203 respective minutes of archival VLA data at the 21 cm line were obtained from the program AS0832 of Pox 186 and VCC 1313, the secondary and tertiary sources of study for this capstone. Haro 11 is one of a very small number of local dwarf …

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Binary Neutron Star Merger Rates. Predictions From Observations Of Dwarf Galaxies And Observable Rates With Ground-Based Gravitational-Wave Detectors, Karen Perez Sarmiento May 2019

Binary Neutron Star Merger Rates. Predictions From Observations Of Dwarf Galaxies And Observable Rates With Ground-Based Gravitational-Wave Detectors, Karen Perez Sarmiento

Macalester Journal of Physics and Astronomy

Binary Neutron Star (BNS) mergers are interesting events in the field of multi-messenger astronomy since they are sources of detectable gravitational wave signals and electromagnetic transients. Here I introduce a new method to calculate a conservative, lower-limit for the rate of BNS merger events that is proportional to the stellar mass and is based on evidence of an r-process event in the dwarf galaxy Reticulum II. Two estimates of the stellar mass in the nearby universe were made using a Schechter Mass Function and a modified version of the 2MASS Extended Source Catalog (2MASS XSC). The BNS merger event rates …

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Uv Led System For Pl Measurements On Gan Samples, Dona H. Pantova May 2019

Uv Led System For Pl Measurements On Gan Samples, Dona H. Pantova

Macalester Journal of Physics and Astronomy

Gallium Nitride materials are direct bandgap semiconductors with important applications, such as in the production of light-emitting diodes and transistors. The process of photoluminescence, in which excited electron and holes emit electro-magnetic radiation when they recombine, can be used to study the structure and quality of Gallium Nitride materials. Due to the size of the bandgap in these materials (3.4eV), ultraviolet light is required to create electron-hole pairs in GaN. We designed and built a system, which uses ultraviolet light, to take measurements on GaN samples provided by a local company, Lightwave Photonics, who were interested in the quality of …

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Investigation On The Electrical Properties Of Cdo/Zno Thin Films Using Thz Spectroscopy, Ramon Molina May 2019

Investigation On The Electrical Properties Of Cdo/Zno Thin Films Using Thz Spectroscopy, Ramon Molina

Macalester Journal of Physics and Astronomy

In this work, we study the electrical properties of transparent conducting oxides using physical and optical techniques. The objective is to characterize the conductivity of a series of cadmium oxide zinc-oxide thin films with varying cadmium concentrations using three methods. The Hall Effect estimates carrier concentration, sheet conductivity, and carrier mobility. Optical methods, such as FTIR spectroscopy, can provide estimates of the plasma frequency, which describes a metal’s transition from being transparent to opaque to light. THz spectroscopy extracts the complex conductivity of materials in the far infrared spectrum and provides insights on the optical transport properties of conductors. Our …

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Understanding Solar Activity During The Last 400 Years, Sam Q. Hollenbach May 2019

Understanding Solar Activity During The Last 400 Years, Sam Q. Hollenbach

Macalester Journal of Physics and Astronomy

The solar cycle has a profound effect on both terrestrial and extra-terrestrial operations. Understanding the history of the solar cycle is necessary for studying long term trends, however older data is difficult to calibrate due to the sparsity of observations. In this paper we propose a new method for calibrating sunspot number data that does not rely on observational overlap. Initial testing shows promise in this method’s success, though more work must be done to ensure calibration consistency across all observers.

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