Asymmetric Shapes Of Radio Recombination Lines From Ionized Stellar Winds,
2019
East Tennessee State University
Asymmetric Shapes Of Radio Recombination Lines From Ionized Stellar Winds, Richard Ignace
ETSU Faculty Works
Recombination line profile shapes are derived for ionized spherical stellar winds at radio wavelengths. It is assumed that the wind is optically thick owing to free-free opacity. Emission lines of arbitrary optical depth are obtained assuming that the free-free photosphere forms in the outer, constant expansion portion of the wind. Previous works have derived analytic results for isothermal winds when the line and continuum source functions are equal. Here, semi-analytic results are derived for unequal source functions to reveal that line shapes can be asymmetric about line center. A parameter study is presented and applications discussed.
On The Apparent Absence Of Wolf–Rayet+Neutron Star Systems: The Curious Case Of Wr124,
2018
UNAM Campus Morelia
On The Apparent Absence Of Wolf–Rayet+Neutron Star Systems: The Curious Case Of Wr124, Jesus A. Toala, Lidi Oskinova, W.R. Hamann, Richard Ignace, A.A. C. Sander, H. Todt, Y.H. Chu, M. A. Guerrero, R. Hainich, R. Hainich, J. M. Terrejon
ETSU Faculty Works
Among the different types of massive stars in advanced evolutionary stages is the enigmatic WN8h type. There are only a few Wolf–Rayet (WR) stars with this spectral type in our Galaxy. It has long been suggested that WN8h-type stars are the products of binary evolution that may harbor neutron stars (NS). One of the most intriguing WN8h stars is the runaway WR 124 surrounded by its magnificent nebula M1-67. We test the presence of an accreting NS companion in WR 124 using ~100 ks long observations by the Chandra X-ray observatory. The hard X-ray emission from WR 124 with a …
The Dynamical State Of A Young Stellar Cluster,
2018
University of Missouri, St. Louis
The Dynamical State Of A Young Stellar Cluster, Timothy Sullivan
Dissertations
The dynamical state of the young star-forming cluster Rho Ophiuchi is considered, with emphasis on the L1688 cloud. Radial velocities are derived for 32 YSOs, with some being multi-epoch, using Markov-Chain Monte Carlo routines based upon the package emcee. Sources are chosen based upon their spectral index to focus on the earlier stages of star formation, in this case, Class I and Flat spectrum objects, and compared with a sample of Class II and III objects from the same embedded cluster. It is found that the radial velocity dispersion for these younger objects is ∆v = 2.8 ± 0.6 km …
Mirach’S Goblin: Discovery Of A Dwarf Spheroidal Galaxy Behind The Andromeda Galaxy,
2018
Universität Heidelberg
Mirach’S Goblin: Discovery Of A Dwarf Spheroidal Galaxy Behind The Andromeda Galaxy, David Martínez-Delgado, Eva Grebel, Behnam Javanmardi, Walter Boschin, Nicolas Longeard, Julio Carballo-Bello, Dmitry Makarov, Michael Beasley, Giuseppe Donatiello, Martha Haynes, Duncan Forbes, Aaron Romanowsky
Faculty Publications
Context. It is of broad interest for galaxy formation theory to carry out a full inventory of the numbers and properties of dwarf galaxies, both satellite and isolated, in the Local Volume.Aims. Ultra-deep imaging in wide areas of the sky with small amateur telescopes can help to complete the census of these hitherto unknown low-surface-brightness galaxies, which cannot be detected by the current resolved stellar population and HI surveys. We report the discovery of Donatiello I, a dwarf spheroidal galaxy located one degree from the star Mirach (β And) in a deep image taken with an amateur telescope.Methods. The color-magnitude …
Angular Momentum And Galaxy Formation Revisited: Scaling Relations For Disks And Bulges,
2018
Space Telescope Science Institute
Angular Momentum And Galaxy Formation Revisited: Scaling Relations For Disks And Bulges, S. Michael Fall, Aaron Romanowsky
Faculty Publications
We show that the stellar specific angular momentum j, mass M, and bulge fraction of normal galaxies of all morphological types are consistent with a simple model based on a linear superposition of independent disks and bulges. In this model, disks and bulges follow scaling relations of the form and with but offset from each other by a factor of 8 ± 2 over the mass range . Separate fits for disks and bulges alone give and , respectively. This model correctly predicts that galaxies follow a curved 2D surface in the 3D space of , , and . We …
Covariations Of Chromospheric And Photometric Variability Of The Young Sun Analogue Hd 30495: Evidence For And Interpretation Of Mid-Term Periodicities,
2018
Harvard-Smithsonian Center for Astrophysics
Covariations Of Chromospheric And Photometric Variability Of The Young Sun Analogue Hd 30495: Evidence For And Interpretation Of Mid-Term Periodicities, Willie Soon, Victor M. Velasco Herrera, Rodolfo G. Cionco, S. Qiu, Sallie Baliunas, Ricky Egeland, Gregory W. Henry, Ivanka Charvátová
Information Systems and Engineering Management Research Publications
This study reports the synchronization between the chromospheric and photometric variability at time-scale of about 1.6–1.8 yr as observed for the young, rapidly rotating solar analogue HD 30495. In addition, HD 30495 may be presenting evidence of surface differential rotation at time-scales of about 11 d and 21 d, as well as the sunspot-like decadal cycles at 11–12 yr or so. We apply a new gapped wavelet method of time–frequency analysis for studying the variability in a new composite of the chromospheric S-index (1967–2018) and the longest photometric Δ(b + y)/2 index (1993–2018). We discuss and interpret our results in …
The Dragonfly Nearby Galaxies Survey. V. Hst/Acs Observations Of 23 Low Surface Brightness Objects In The Fields Of Ngc 1052, Ngc 1084, M96, And Ngc 4258,
2018
Yale University
The Dragonfly Nearby Galaxies Survey. V. Hst/Acs Observations Of 23 Low Surface Brightness Objects In The Fields Of Ngc 1052, Ngc 1084, M96, And Ngc 4258, Yotam Cohen, Pieter Van Dokkum, Shany Danieli, Aaron Romanowsky, Roberto Abraham, Allison Merritt, Jielai Zhang, Lamiya Mowla, J. Diederik Kruijssen, Charlie Conroy, Asher Wasserman
Faculty Publications
We present Hubble Space Telescope/Advanced Camera for Surveys (ACS) imaging of 23 very low surface brightness (μ e,V ~ 25–27.5) galaxies detected in the fields of four nearby galaxy groups. These objects were selected from deep optical imaging obtained with the Dragonfly Telephoto Array. Seven are newly identified, while most of the others had been seen previously in visual surveys of deep photographic plates and more recent surveys. Few have previously been studied in detail. From the ACS images, we measure distances to the galaxies using both the tip of the red giant branch method and the surface brightness fluctuations …
Bayesian Analysis Of Two Stellar Populations In Galactic Globular Clusters Ii: Ngc 5024, Ngc 5272, And Ngc 6352,
2018
University of Florida
Bayesian Analysis Of Two Stellar Populations In Galactic Globular Clusters Ii: Ngc 5024, Ngc 5272, And Ngc 6352, Rachel Wagner-Kaiser, Ted Von Hippel, David Stenning, Elliot Robinson, Ata Sarajedini, David Van Dyk, Nathan Stein, William H. Jefferys
Publications
We use Cycle 21 Hubble Space Telescope (HST) observations and HST archival ACS Treasury observations of Galactic Globular Clusters to find and characterize two stellar populations in NGC 5024 (M53), NGC 5272 (M3), and NGC 6352. For these three clusters, both single and double-population analyses are used to determine a best fit isochrone(s). We employ a sophisticated Bayesian analysis technique to simultaneously fit the cluster parameters (age, distance, absorption, and metallicity) that characterize each cluster. For the two-population analysis, unique population level helium values are also fit to each distinct population of the cluster and the relative proportions of the …
The Extended Planetary Nebula Spectrograph (Epn.S) Early-Type Galaxy Survey: The Kinematic Diversity Of Stellar Halos And The Relation Between Halo Transition Scale And Stellar Mass,
2018
Max Planck Institute for Extraterrestrial Physics
The Extended Planetary Nebula Spectrograph (Epn.S) Early-Type Galaxy Survey: The Kinematic Diversity Of Stellar Halos And The Relation Between Halo Transition Scale And Stellar Mass, C. Pulsoni, O. Gerhard, M. Arnaboldi, L. Coccato, A. Longobardi, N. Napolitano, E. Moylan, C. Narayan, V. Gupta, A. Burkert, M. Capaccioli, A. Chies-Santos, A. Cortesi, K. Freeman, K. Kuijken, M. Merrifield, Aaron Romanowsky, C. Tortora
Faculty Research, Scholarly, and Creative Activity
Context. In the hierarchical two-phase formation scenario, the halos of early type galaxies (ETGs) are expected to have different physical properties from the galaxies’ central regions.Aims. The ePN.S survey characterizes the kinematic properties of ETG halos using planetary nebulae (PNe) as tracers, overcoming the limitations of absorption line spectroscopy at low surface brightness.Methods. We present two-dimensional velocity and velocity dispersion fields for 33 ETGs, including fast (FRs) and slow rotators (SRs). The velocity fields were reconstructed from the measured PN velocities using an adaptive kernel procedure validated with simulations, and extend to a median of 5.6 effective radii (Re). We …
Wide-Field Kinematics Of Globular Clusters In The Leo I Group (Corrigendum),
2018
Michigan State University
Wide-Field Kinematics Of Globular Clusters In The Leo I Group (Corrigendum), G. Bergond, S. Zepf, Aaron Romanowsky, R. Sharples, K. Rhode
Faculty Publications
No abstract provided.
Expected And Achievable Accuracy In Estimating Parameters Of Standing Accretion Shock Instability (Sasi) Fluctuations From Neutrinos And Gravitational Wave Oscillations,
2018
Embry-Riddle Aeronautical University
Expected And Achievable Accuracy In Estimating Parameters Of Standing Accretion Shock Instability (Sasi) Fluctuations From Neutrinos And Gravitational Wave Oscillations, Colter Richardson, Jonathan Westhouse
Undergraduate Research Symposium - Prescott
Core collapse supernovae are one of the most interesting sources of gravitational waves. When the progenitor star is particularly massive, hydrodynamic instability called standing accretion shock instability can develop and it is characterized by deterministic oscillations in the gravitational wave signal as well as in the neutrino luminosity with frequencies of 100hz. In this talk we will review current efforts to extract physical information from the SASI components of the gravitational wave and enhance the detectability of gravitational waves with such components both using laser interferometers and neutrino detectors.
Modeling And Detectability Of Gravitational Wave Waveform Memory From Core Collapse Supernovae,
2018
Embry-Riddle Aeronautical University
Modeling And Detectability Of Gravitational Wave Waveform Memory From Core Collapse Supernovae, Pedro Jesus Quinonez, Emily Grimes
Undergraduate Research Symposium - Prescott
Ever since the discovery of gravitational waves by LIGO, studying these waves have become of utmost importance. This is because gravitational waves have the potential to carry information that have remain unseen by physicist in the past. For example, take the case of a core collapse supernovae. Any information transferred through electromagnetic waves that attempts to escape the inner core of a dying star is blocked out by the intense radiation of its outer shell. For this reason, astronomers have been unable to truly study what goes in the core. However, this is not the case for gravitational waves, which …
Veritas And Fermi-Lat Observations Of Tev Gamma-Ray Sources Discovered By Hawc In The 2hwc Catalog,
2018
Department of Physical Sciences, Cork Institute of Technology, Bishopstown, Cork, Ireland
Veritas And Fermi-Lat Observations Of Tev Gamma-Ray Sources Discovered By Hawc In The 2hwc Catalog, P. T. Reynolds, Et Al
Physical Sciences Publications
The High Altitude Water Cherenkov (HAWC) collaboration recently published their 2HWC catalog, listing 39 very high energy (VHE; >100 GeV) gamma-ray sources based on 507 days of observation. Among these, 19 sources are not associated with previously known teraelectronvolt (TeV) gamma-ray sources. We have studied 14 of these sources without known counterparts with VERITAS and Fermi-LAT. VERITAS detected weak gamma-ray emission in the 1 TeV–30 TeV band in the region of DA 495, a pulsar wind nebula coinciding with 2HWC J1953+294, confirming the discovery of the source by HAWC. We did not find any counterpart for the selected 14 …
Probing The Rotational Velocity Of Galactic Wo Stars With Spectropolarimetry,
2018
University of Sheffied
Probing The Rotational Velocity Of Galactic Wo Stars With Spectropolarimetry, H. F. Stevance, Richard Igance, P. A. Crowther, J. R. Maund, B. Davies, G. Rate
ETSU Faculty Works
Oxygen sequence Wolf-Rayet stars (WO) are thought to be the final evolution phase of some high-mass stars, as such they may be the progenitors of Type Ic SNe as well as potential progenitors of broad-lined Ic and long gamma-ray bursts. We present the first spectropolarimetric observations of the Galactic WO stars WR93b and WR102 obtained with FORS1 on the Very Large Telescope. We find no sign of a line effect, which could be expected if these stars were rapid rotators. We also place constraints on the amplitude of a potentially undetected line effect. This allows us to derive upper limits …
Chromodynamical Analysis Of Lenticular Galaxies Using Globular Clusters And Planetary Nebulae,
2018
Universidade Federal do Rio Grande do Sul
Chromodynamical Analysis Of Lenticular Galaxies Using Globular Clusters And Planetary Nebulae, Emilio Zanatta, Arianna Cortesi, Ana Chies-Santos, Duncan Forbes, Aaron Romanowsky, Adebusola Alabi, Lodovico Coccato, Claudia Mendes De Oliveira, Jean Brodie, Michael Merrifield
Faculty Publications
Recovering the origins of lenticular galaxies can shed light on the understanding of galaxy and compare them with the kinematics of planetary nebulae (PNe). The PNe and GC data come from the Planetary Nebulae Spectrograph and the SLUGGS Surveys. Through photometric spheroid-disc decomposition and PNe kinematics. we find the probability for a given GC to belong to either the spheroid or the disc of its host galaxy or be rejected from the model. We find that there is no correlation between the components that the GCs are likely to belong to and their colours. Particularly, for NGC 2768, we find …
Origins Of Ultradiffuse Galaxies In The Coma Cluster – Ii. Constraints From Their Stellar Populations,
2018
Swinburne University of Technology - Australia
Origins Of Ultradiffuse Galaxies In The Coma Cluster – Ii. Constraints From Their Stellar Populations, Anna Ferre-Mateu, Adebusola Alabi, Duncan Forbes, Aaron Romanowsky, Jean Brodie, Viraj Pandya, Ignacio Mart´In-Navarro, Sabine Bellstedt, Asher Wasserman, Maria Stone, Nobuhiro Okabe
Faculty Publications
In this second paper of the series we study, with new Keck/DEIMOS spectra, the stellar populations of seven spectroscopically confirmed ultradiffuse galaxies (UDGs) in the Coma cluster. We find intermediate to old ages (∼7 Gyr), low metallicities ([Z/H] ∼ −0.7 dex) and mostly supersolar abundance patterns ([Mg/Fe] ∼ 0.13 dex). These properties are similar to those of low-luminosity (dwarf) galaxies inhabiting the same area in the cluster and are mostly consistent with being the continuity of the stellar mass scaling relations of more massive galaxies. These UDGs’ star formation histories imply a relatively recent infall into the Coma cluster, consistent …
A Bayesian Analysis Of The Ages Of Four Open Clusters,
2018
BYU
A Bayesian Analysis Of The Ages Of Four Open Clusters, Elizabeth Jeffery, Ted Von Hippel, David A. Van Dyk, David C. Stenning, Elliot Robinson, Nathan Sten, William H. Jefferys
Publications
In this paper we apply a Bayesian technique to determine the best fit of stellar evolution models to find the main sequence turn off age and other cluster parameters of four intermediate-age open clusters: NGC 2360, NGC 2477, NGC 2660, and NGC 3960. Our algorithm utilizes a Markov chain Monte Carlo technique to fit these various parameters, objectively finding the best-fit isochrone for each cluster. The result is a high-precision isochrone fit. We compare these results with the those of traditional “by-eye” isochrone fitting methods. By applying this Bayesian technique to NGC 2360, NGC 2477, NGC 2660, and NGC 3960, …
Mapping Debris Disks At Extreme Contrast: Near-Ir Polarimetric Differential Imaging With The Gemini Planet Imager.,
2018
The University of Western Ontario
Mapping Debris Disks At Extreme Contrast: Near-Ir Polarimetric Differential Imaging With The Gemini Planet Imager., Juan Sebastian Bruzzone
Electronic Thesis and Dissertation Repository
Debris disks are gas-poor evolved circumstellar disks that show decreased near- to mid- infrared thermal excess emission because of lack of material close to the star. Regarded as massive analogues to the Main Asteroid or Kuiper Belts in the Solar System, these often young dust-rich disks comprise second-generation dust created by disruptive collisions of planetesimals and the decay products of asteroids and comets. Of the dozen or so directly imaged planets to date many share a distinctive characteristic: they reside in stellar systems known to also possess circumstellar dust. High-angular resolution characterization of debris disks, whose morphology is thought to …
Separated Fringe Packet Observations With The Chara Array. Iii. The Very High-Eccentricity Binary Hr 7345,
2018
CHARA Array of Georgia State University
Separated Fringe Packet Observations With The Chara Array. Iii. The Very High-Eccentricity Binary Hr 7345, Chris D. Farrington, Francis C. Fekel, Gail Schaefer, Theo A. Ten Brummelaar
Information Systems and Engineering Management Research Publications
After an 11-year observing campaign, we present the combined visual–spectroscopic orbit of the formerly unremarkable bright star HR 7345 (HD 181655, HIP 94981, GJ 754.2). Using the Separated Fringe Packet method with the CHARA Array, we were able to determine a difficult-to-complete orbital period of 331.609 ± 0.004 days. The 11-month period causes the system to be hidden from interferometric view behind the Sun for three years at a time. Due to the high-eccentricity orbit of about 90% of a year, after 2018 January the periastron phase will not be observable again until late 2021. Hindered by its extremely high …
Origins Of Ultradiffuse Galaxies In The Coma Cluster – I. Constraints From Velocity Phase Space,
2018
University of California Observatories
Origins Of Ultradiffuse Galaxies In The Coma Cluster – I. Constraints From Velocity Phase Space, Adebusola Alabi, Anna Ferré-Mateu, Aaron Romanowsky, Jean Brodie, Duncan Forbes, Asher Wasserman, Sabine Bellstedt, Ignacio Martín-Navarro, Viraj Pandya, Maria Stone, Nobuhiro Okabe
Faculty Publications
We use Keck/DEIMOS spectroscopy to confirm the cluster membership of 16 ultradiffuse galaxies (UDGs) in the Coma cluster, bringing the total number of spectroscopically confirmed UDGs from the Yagi et al. (Y16) catalogue to 25. We also identify a new cluster background UDG, confirming that most (∼95 per cent) of the UDGs in the Y16 catalogue belong to the Coma cluster. In this pilot study of Coma UDGs in velocity phase space, we find evidence of a diverse origin for Coma cluster UDGs, similar to normal dwarf galaxies. Some UDGs in our sample are consistent with being late infalls into …
