Search Publications
What Are Little Worlds Made Of? Stellar Abundances and the Building Blocks of Planets
Gaidos, Eric
If the photospheres of solar-type stars represent the composition of circumstellar disks from which any planets formed, spectroscopic determinations of stellar elemental abundances offer information on the composition of those planets, including smaller, rocky planets. In particular, the C/O ratio is proposed to be a key determinant of the composi…
Hubble Space Telescope Observations of Sub-damped Lyα Absorbers at z < 0.5, and Implications for Galaxy Chemical Evolution
York, Donald G.; Kulkarni, Varsha P.; Lauroesch, James T. +5 more
We report observations of four sub-damped Lyα (sub-DLA) quasar absorbers at z\lt 0.5 obtained with the Hubble Space Telescope Cosmic Origins Spectrograph. We measure the available neutrals or ions of C, N, O, Si, P, S, Ar, Mn, Fe, and/or Ni. Our data have doubled the sub-DLA metallicity samples at z\lt 0.5 and improved constraints on sub-DLA chemi…
Faraday Tomography of the North Polar Spur: Constraints on the Distance to the Spur and on the Magnetic Field of the Galaxy
Leahy, J. P.; Gaensler, B. M.; McClure-Griffiths, N. M. +9 more
We present radio continuum and polarization images of the North Polar Spur (NPS) from the Global Magneto-ionic Medium Survey conducted with the Dominion Radio Astrophysical Observatory 26 m Telescope. We fit polarization angle versus wavelength squared over 2048 frequency channels from 1280 to 1750 MHz to obtain a Faraday rotation measure (RM) map…
A Measurement of the Black Hole Mass in NGC 1097 Using ALMA
Kohno, K.; Onishi, K.; Iguchi, S. +1 more
We present an estimate of the mass of the supermassive black hole (SMBH) in the nearby type-1 Seyfert galaxy NGC 1097 using Atacamma Large Millimeter/submillimeter Array (ALMA) observations of dense gas kinematics. Dense molecular gas dynamics are traced with HCN(J=1-0) and HC{{O}+}(J=1-0) emission lines. Assuming a host galaxy inclinat…
Light Bridge in a Developing Active Region. II. Numerical Simulation of Flux Emergence and Light Bridge Formation
Toriumi, Shin; Cheung, Mark C. M.; Katsukawa, Yukio
Light bridges, the bright structure dividing umbrae in sunspot regions, show various activity events. In Paper I, we reported on an analysis of multi-wavelength observations of a light bridge in a developing active region (AR) and concluded that the activity events are caused by magnetic reconnection driven by magnetconvective evolution. The aim o…
Feedback from Mass Outflows in Nearby Active Galactic Nuclei. II. Outflows in the Narrow-line Region of NGC 4151
Fischer, Travis C.; Crenshaw, D. Michael; Schmitt, Henrique R. +1 more
We present a detailed study of active galactic nucleus feedback in the narrow-line region (NLR) of the Seyfert 1 galaxy NGC 4151. We illustrate the data and techniques needed to determine the mass outflow rate (\dot{M}out) and kinetic luminosity (L KE) of the outflowing ionized gas as a function of position in the NLR. We fin…
Proper Motions and Trajectories for 16 Extreme Runaway and Hypervelocity Stars
Anderson, Jay; Bond, Howard E.; Geller, Margaret J. +3 more
We measure proper motions with the Hubble Space Telescope for 16 extreme radial velocity stars, mostly unbound B stars in the Milky Way halo. Twelve of these stars have proper motions statistically consistent with zero, and thus have radial trajectories statistically consistent with a Galactic center “hypervelocity star” origin. The trajectory of …
Propagation of the 7 January 2014 CME and Resulting Geomagnetic Non-event
Thompson, B. J.; Möstl, C.; Jian, L. K. +9 more
On 2014 January 7 an X1.2 flare and coronal mass ejection (CME) with a radial speed ≈2500 km s-1 was observed from near an active region close to disk center. This led many forecasters to estimate a rapid arrival at Earth (≈36 hr) and predict a strong geomagnetic storm. However, only a glancing CME arrival was observed at Earth with a t…
Predicting the Arrival Time of Coronal Mass Ejections with the Graduated Cylindrical Shell and Drag Force Model
Zhang, Jie; Ding, Mingde; Cheng, Xin +3 more
Accurately predicting the arrival of coronal mass ejections (CMEs) to the Earth based on remote images is of critical significance for the study of space weather. In this paper, we make a statistical study of 21 Earth-directed CMEs, specifically exploring the relationship between CME initial speeds and transit times. The initial speed of a CME is …
An Ultrasoft X-Ray Flare from 3XMM J152130.7+074916: A Tidal Disruption Event Candidate
Gwyn, Stephen D. J.; Komossa, S.; Lin, Dacheng +6 more
We report on the discovery of an ultrasoft X-ray transient source, 3XMM J152130.7+074916. It was serendipitously detected in an XMM-Newton observation on 2000 August 23, and its location is consistent with the center of the galaxy SDSS J152130.72+074916.5 (z = 0.17901 and dL = 866 Mpc). The high-quality X-ray spectrum can be fitted with…