Search Publications
Chromospheric UV Bursts and Turbulent-driven Magnetic Reconnection
Wu, Pin
We use Interface Region Imaging Spectrograph (IRIS) spacecraft data to study a group of Chromospheric ultraviolet bursts (UVBs) associated with an active region. We classify the UVBs into two types: smaller ones that can only be measured once by the scanning slit, and larger UVBs that are measured twice by the slit. The UVBs’ optically thin Si IV …
A Recipe for Finding Stellar Radii, Temperatures, Surface Gravities, Metallicities, and Masses Using Spectral Lines
Gray, David F.; Kaur, Taranpreet
A recipe based on physical principles employs the observed equivalent widths of 10 spectral lines to model the photosphere of a target star. Coupled with the visual magnitude and an absolute flux calibration, the recipe yields the angular radius, effective temperature, surface gravity, and metallicity. With the addition of a parallax, a linear rad…
ALMA, ATCA, and Spitzer Observations of the Luminous Extragalactic Supernova SN 1978K
Kotak, R.; Ryder, S. D.; Smith, I. A. +2 more
Only three extragalactic supernovae have been detected at late times at millimeter wavelengths: SN 1987A, SN 1978K, and SN 1996cr. SN 1978K is a remarkably luminous Type IIn supernova that remains bright at all wavelengths 40 years after its explosion. Here, we present Atacama Large Millimeter/submillimeter Array (ALMA) observations taken in 2016 …
Kinetic Theory of Ion Acoustic Waves Observed at Comet 67P/Churyumov-Gerasimenko
Rehman, Saeed ur; Shah, Asif; Haque, Qamar ul
This work presents the resonance interaction of ion acoustic waves with the cometary plasma as observed at comet 67P/Churyumov-Gerasimenko. The plasma is comprised of cold, warm, and suprathermal electron populations and water ions such that the quasineutrality is satisfied. The cold electron population is found to play a dominant role in the damp…
Exploring the Asymmetry of the Solar Corona Electron Density with Very Long Baseline Interferometry
Pavlov, Dmitry; Melnikov, Alexey; Aksim, Dan +1 more
The Sun’s corona has interested researchers for multiple reasons, including the search for a solution to the famous coronal heating problem and a purely practical consideration of predicting geomagnetic storms on Earth. There exist numerous different theories regarding the solar corona; therefore, it is important to be able to perform comparative …
Absolute Dimensions of the Early F-type Eclipsing Binary V506 Ophiuchi
Torres, Guillermo; Fekel, Francis C.; Muterspaugh, Matthew W. +1 more
We report extensive differential V-band photometry and high-resolution spectroscopic observations of the early F-type, 1.06-day detached eclipsing binary V506 Oph. The observations, along with times of minimum light from the literature, are used to derive a very precise ephemeris and the physical properties for the components, with the absolute ma…
Discovery of Two Quasars at z = 5 from the OGLE Survey
Greiner, J.; Soszyński, I.; Udalski, A. +17 more
We used Optical Gravitational Lensing Experiment (OGLE-IV) deep (stacked) images (V ≲ 23 mag, I ≲ 23 mag at 3σ) of the Magellanic System, encompassing an area of ∼670 deg2, to perform a search for high-z quasar candidates. We combined the optical OGLE data with the mid-IR Wide-field Infrared Survey Explorer 3.4/4.6/12 µm data, and…
Adaptive Grid Lens Modeling of the Cosmic Horseshoe Using Hubble Space Telescope Imaging
Cui, Wei; Li, Guoliang; Wiesner, Matthew P. +3 more
The Cosmic Horseshoe gravitational lensing system is an extraordinary example of strong gravitational lensing both due to the nearly complete Einstein ring formed in this system and due to the star-forming nature of the lensed z = 2.38 Lyman-break galaxy. In this paper, we describe the development of a new lens modeling package and the lens models…
The Gemini/HST Galaxy Cluster Project: Environment Effects on the Stellar Populations in the Lynx Clusters at z = 1.27
Toft, Sune; Jørgensen, Inger; Hunter, Laura C. +4 more
Few detailed investigations of stellar populations in passive galaxies beyond z ≈ 1 are based on deep spectroscopic observations, due to the difficulty in obtaining such data. We present a study of stellar populations, structure, and mass-to-light ratios (M/L) of a large sample of bulge-dominated galaxies in the two z = 1.27 clusters Lynx E and Ly…
Identification of Herbig Ae/Be Stars in the Small Magellanic Cloud
Zijlstra, A. A.; Simon, Joshua D.; Oliveira, Joana M. +12 more
Protoplanetary disks orbiting intermediate-mass stars, Herbig Ae/Be stars, that have formed in a metal-poor environment may evolve differently than their Galactic cousins. A study of the planet-formation process in such an environment requires identification and characterization of a sample of candidates. We have observed several stars in the Smal…