Search Publications
Probing the Ionization Structure of the Narrow-Line Region in the Seyfert 1 Galaxy NGC 4151
Kraemer, S. B.; Crenshaw, D. M.; Schmitt, H. R.
We present a study of the distribution of [O III] λ5007 and [O II] λ3727 emission in the narrow-line region (NLR) of the Seyfert 1 galaxy NGC 4151. While the NLR of NGC 4151 exhibits an overall structure consistent with the unified model of Seyfert galaxies, narrowband [O III] and [O II] images obtained with the Wide Field and Planetary Camera 2 a…
Constraints on the Emission and Viewing Geometry of the Transient Anomalous X-Ray Pulsar XTE J1810-197
Gotthelf, E. V.; Perna, Rosalba
The temporal decay of the flux components of the transient anomalous X-ray pulsar XTE J1810-197 following its 2002 outburst presents a unique opportunity to probe the emission geometry of a magnetar. Toward this goal, we model the magnitude of the pulsar's modulation in narrow spectral bands over time. Following previous work, we assume that the p…
Discovery of a Young, Energetic 70.5 ms Pulsar Associated with the TeV Gamma-Ray Source HESS J1837-069
Gotthelf, E. V.; Halpern, J. P.
We report the discovery of 70.5 ms pulsations from the X-ray source AX J1838.0-0655 using the Rossi X-Ray Timing Explorer ( RXTE). PSR J1838-0655 is a rotation-powered pulsar with spin-down luminosity Ė = 5.5 × 1036 ergs s-1, characteristic age τc ≡ P/2dot P = 23 kyr, and surface dipole magnetic field strength B
A New Hubble Space Telescope Distance to NGC 1569: Starburst Properties and IC 342 Group Membership
Mack, Jennifer; Aloisi, Alessandra; van der Marel, Roeland P. +8 more
We present deep HST ACS/WFC photometry of the dwarf irregular galaxy NGC 1569, one of the closest and strongest nearby starburst galaxies. These data allow us, for the first time, to unequivocally detect the tip of the red giant branch and thereby determine the distance to NGC 1569. We find that this galaxy is 3.36 +/- 0.20 Mpc away, considerably …
XMM-Newton Observations of Radio Pulsars B0834+06 and B0826-34 and Implications for the Pulsar Inner Accelerator
Haberl, F.; Zhang, B.; Gil, J. +3 more
We report the X-ray observations of two radio pulsars with drifting subpulses, B0834+06 and B0826-34, using XMM-Newton. PSR B0834+06 was detected with a total of 70 counts from the three EPIC instruments over 50 ks exposure time. Its spectrum is best described as that of a blackbody (BB), with temperature Ts = (2.0+ 2.0-…
Characterizing the Near-UV Environment of M Dwarfs
Hawley, Suzanne L.; Johns-Krull, Christopher M.; Walkowicz, Lucianne M.
We report the results of our Hubble Space Telescope (HST) snapshot survey with the ACS HRC PR200L prism, designed to measure the near-UV emission in a sample of nearby M dwarfs. Thirty-three stars were observed, spanning the mass range from 0.1 to 0.6 solar masses (Teff ~ 2200-4000 K) where the UV energy distributions vary widely betwee…
Rotational Feature of Vega Revealed from Spectral Line Profiles
Takeda, Yoichi; Kawanomoto, Satoshi; Ohishi, Naoko
In order to establish Vega's absolute rotational velocity, ve, as distinct from the inclination angle, i, we conducted a detailed profile study on a large number (~200) of weak lines based on very high signal-to-noise ratio spectrum data, making use of the fact that the lines' characteristic shapes may contain information about rotation…
Solar Cycle Related Changes at the Base of the Convection Zone
Basu, Sarbani; Baldner, Charles S.
The frequencies of solar oscillations are known to change with solar activity. We use principal component analysis to examine these changes with high precision. In addition to the well-documented changes in solar normal mode oscillations with activity as a function of frequency, which originate in the surface layers of the Sun, we find a small but…
SWAS Observations of Water in Molecular Outflows
Bergin, Edwin A.; Neufeld, David A.; Kaufman, Michael J. +4 more
We present detections of the ground-state 110→ 101 transition of ortho-H2O at 557 GHz in 18 molecular outflows based on data from the Submillimeter Wave Astronomy Satellite (SWAS). These results are combined with ground-based observations of the J = 1-0 transitions of 12CO and 13CO obtained at…
Titan's Tropical Storms in an Evolving Atmosphere
McKay, Christopher P.; Griffith, Caitlin A.; Ferri, Francesca
The Huygens probe landed in a damp lake bed fed by fluvial channels, indicative of past rainfall. Such washes, interspersed with vast dunes, are typical of Titan's tropical landscape. Yet, Cassini-Huygens measurements reveal a highly stable tropical atmosphere devoid of deep convective storms, and the formation of washes in dune fields is not unde…