Search Publications
Resolved Kinematics of Runaway and Field OB Stars in the Small Magellanic Cloud
Lennon, D. J.; Oey, M. S.; Castro, N. +6 more
We use Gaia Data Release 2 proper motions of field OB stars from the Runaways and Isolated O-Type Star Spectroscopic Survey of the Small Magellanic Cloud (SMC) to study the kinematics of runaway stars. The data reveal that the SMC Wing has a systemic peculiar motion relative to the SMC Bar of ({v}α ,{v}δ ) =(62+/- 7,-18+/- 5)…
The Charge State of Polycyclic Aromatic Hydrocarbons across a Reflection Nebula, an H II Region, and a Planetary Nebula
Boersma, C.; Allamandola, L. J.; Bregman, J.
Low-resolution Spitzer-IRS spectral map data of a reflection nebula (NGC 7023), H II region (M17), and planetary nebula (NGC 40), totaling 1417 spectra, are analyzed using the data and tools available through the NASA Ames PAH IR Spectroscopic Database. The polycyclic aromatic hydrocarbon (PAH) emission is broken down into PAH charge and size subc…
Accretion Disk Size Measurement and Time Delays in the Lensed Quasar WFI 2033-4723
Kochanek, Christopher S.; Bonvin, Vivien; Courbin, Frederic +5 more
We present 13 seasons of R-band photometry of the quadruply lensed quasar WFI 2033-4723 from the 1.3 m SMARTS telescope at CTIO and the 1.2 m Euler Swiss Telescope at La Silla, in which we detect microlensing variability of ∼0.2 mag on a timescale of ∼6 years. Using a Bayesian Monte Carlo technique, we analyze the microlensing signal to obtain a m…
Nearby High-speed Stars in Gaia DR2
Geller, Margaret J.; Brown, Warren R.; Kenyon, Scott J. +1 more
We investigate the nature of nearby (10-15 kpc) high-speed stars in the Gaia DR2 archive identified on the basis of parallax, proper motion and radial velocity. Together with a consideration of their kinematic, orbital, and photometric properties, we develop a novel strategy for evaluating whether high-speed stars are statistical outliers of the b…
On the Stellar Velocity Distribution in the Solar Neighborhood in Light of Gaia DR2
Pérez-Villegas, Angeles; Barros, Douglas A.; Michtchenko, Tatiana A. +2 more
The aim of this Letter is to contribute to the understanding of the stellar velocity distribution in the solar neighborhood (SN). We propose that the structures on the U-V planes, known as the moving groups, can be mainly explained by the spiral arms perturbations. The applied model of the Galactic disk and spiral arms, with the parameters defined…
Recoiling Supermassive Black Hole in Changing-look AGN Mrk 1018
Kim, D. -C.; Evans, A. S.; Yoon, Ilsang
The spectral type of Mrk 1018 changed from Type 1.9 to 1 and returned back to 1.9 over a period of 40 years. We have investigated physical mechanisms responsible for the spectral change in Mrk 1018 by analyzing archival spectral and imaging data. Two kinematically distinct broad-line components, blueshifted and redshifted components, are found fro…
Parameterizations of Chromospheric Condensations in dG and dMe Model Flare Atmospheres
Kowalski, Adam F.; Allred, Joel C.
The origin of the near-ultraviolet and optical continuum radiation in flares is critical for understanding particle acceleration and impulsive heating in stellar atmospheres. Radiative-hydrodynamic (RHD) simulations in 1D have shown that high energy deposition rates from electron beams produce two flaring layers at T ∼ 104 K that develo…
IRIS Observations of Magnetic Interactions in the Solar Atmosphere between Preexisting and Emerging Magnetic Fields. I. Overall Evolution
Young, Peter R.; Murabito, Mariarita; Guglielmino, Salvo L. +2 more
We report multiwavelength ultraviolet observations taken with the IRIS satellite, concerning the emergence phase in the upper chromosphere and transition region of an emerging flux region (EFR) embedded in the preexisting field of active region NOAA 12529 in the Sun. IRIS data are complemented by full-disk observations of the Solar Dynamics Observ…
Statistical Study of Magnetic Nonpotential Measures in Confined and Eruptive Flares
Ravindra, B.; Doddamani, V. H.; Vemareddy, P. +1 more
Using Solar Dynamics Observatory/Helioseismic and Magnetic Imager vector magnetic field observations, we studied the relation between the degree of magnetic non-potentiality with the observed flare/coronal mass ejection (CME) in active regions (ARs). From a sample of 77 flare/CME cases, we found in general that the degree of non-potentiality is po…
HST Grism Observations of a Gravitationally Lensed Redshift 9.5 Galaxy
Hoag, A.; Bradač, M.; Brammer, G. +11 more
We present deep spectroscopic observations of a Lyman break galaxy (LBG) candidate (hereafter MACS1149-JD) at z ∼ 9.5 with the Hubble Space Telescope (HST) WFC3/IR grisms. The grism observations were taken at four distinct position angles, totaling 34 orbits with the G141 grism, although only 19 of the orbits are relatively uncontaminated along th…