Search Publications
The Pulsar/White Dwarf/Planet System in M4: Improved Astrometry
Richer, Harvey B.; Ibata, Rodrigo; Fahlman, Gregory G. +1 more
A young and undermassive white dwarf has been identified as the possible companion to the millisecond pulsar PSR B1620-26 in M4. This association is important since it then helps constrain the mass of the third body in the system to be of order a few times that of Jupiter. The presence of this planet in M4 has critical implications for planetary f…
A Deep Chandra X-Ray Observation of NGC 1637
Leonard, Douglas C.; Wang, Q. Daniel; Immler, Stefan +1 more
We present a deep (168 ks) Chandra observation of the nearby face-on spiral galaxy NGC 1637 and study the X-ray source population. A total of 32 X-ray sources are detected within the D25 ellipse of NGC 1637, each of which is found to be variable during the 629 day period covered by the observations. Deep Hubble Space Telescope WFPC2 obs…
Constraints from Infrared Space Observatory Data on the Velocity Law and Clumpiness of WR 136
Ignace, R.; Cassinelli, J. P.; Quigley, M. F.
Observations with the Infrared Space Observatory (ISO) SWS spectrometer are used to constrain the velocity law and wind clumping of the well-studied Wolf-Rayet (W-R) star WR 136 (HD 192163, WN6). Because the free-free continuum opacity in W-R winds increases steadily with wavelength in the IR, each point in the continuous spectrum may be regarded …
An XMM-Newton Observation during the 2000 Outburst of SAX J1808.4-3658
Wijnands, Rudy
I present an XMM-Newton observation of the accretion-driven millisecond X-ray pulsar SAX J1808.4-3658 during its 2000 outburst. The source was conclusively detected, albeit at a level of only ~2×1032 ergs s-1. The source spectrum could be fitted with a power-law model (with a photon index of ~2.2), a neutron star atmosphere m…
Solar Coronal Heating and the Magnetic Flux Content of the Network
Falconer, D. A.; Moore, R. L.; Porter, J. G. +1 more
We investigate the heating of the quiet corona by measuring the increase of coronal luminosity with the amount of magnetic flux in the underlying network at solar minimum when there were no active regions on the face of the Sun. The coronal luminosity is measured from Fe IX/X-Fe XII pairs of coronal images from SOHO/EIT, under the assumption that …
A Unique Small-Scale Gravitational Arc in A1201
Smith, Graham P.; Treu, Tommaso; van Dokkum, Pieter G. +4 more
We present a snapshot Hubble Space Telescope (HST) image of the galaxy cluster A1201 (z=0.169), revealing a tangential arc 2" from the brightest cluster galaxy (BCG). Keck Echelle Spectrograph and Imager (ESI) spectroscopy confirms that the arc is gravitational in nature and that the source galaxy lies at z=0.451. We construct a model of the gravi…
Mass and Dust in the Disk of a Spiral Lens Galaxy
Hall, Patrick B.; Winn, Joshua N.; Schechter, Paul L.
Gravitational lensing is a potentially important probe of spiral galaxy structure, but only a few cases of lensing by spiral galaxies are known. We present Hubble Space Telescope and Magellan observations of the two-image quasar PMN J2004-1349, revealing that the lens galaxy is a spiral galaxy. One of the quasar images passes through a spiral arm …
Infrared Space Observatory Long-Wavelength Spectrometer Spectroscopy of Star-forming Regions in M33
Stacey, G. J.; Higdon, S. J. U.; Higdon, J. L. +1 more
We present Infrared Space Observatory (ISO) Long-Wavelength Spectrometer (LWS) far-infrared (FIR) spectra of the nucleus and six giant H II regions in M33 (NGC 595, IC 142, NGC 592, NGC 604, NGC 588, and IC 133). The seven fine-structure lines observed in the FIR are used to model the H II and photodissociation regions (PDRs). There is no observed…
Hubble Space Telescope/NICMOS Near-Infrared Imaging of the Proto-Planetary Nebula OH 231.8+4.2
Hora, J. L.; Tielens, A. G. G. M.; Latter, W. B. +2 more
We present observations of the bipolar nebula OH 231.8+4.2, made with the Hubble Space Telescope (HST) NICMOS camera, in three wide filter bands (F205W, F160W, and F110W). The images have excellent dynamic range after removal of low-level instrumental artifacts. In the F205W filter (λ~2.04 µm), we achieve a peak/rms of greater than 8000 with…
The 2001 April Burst Activation of SGR 1900+14: Pulse Properties and Torque
Frontera, F.; Hurley, K.; Mereghetti, S. +10 more
We report on observations of SGR 1900+14 made with the Rossi X-Ray Timing Explorer (RXTE) and BeppoSAX during the 2001 April burst activation of the source. Using these data, we measure the spin-down torque on the star and confirm earlier findings that the torque and burst activity are not directly correlated. We compare the X-ray pulse profile to…