Search Publications
The Optical Counterpart of NGC 1313 X-1
Feng, Hua; Kaaret, Philip; Yang, Lin
We identify the optical counterpart of the ultraluminous X-ray source (ULX) NGC 1313 X-1 and discuss constraints on its physical nature from multiband optical spectra. There is a single object on Hubble Space Telescope images within the aspect-corrected Chandra X-ray error circle; a fainter, possibly extended, feature lies near the edge of the err…
Chandra Evidence for Extended X-Ray Structure in RY Tau
Skinner, Stephen L.; Güdel, Manuel; Audard, Marc
We report results of a sensitive Chandra ACIS-S observation of the classical T Tauri star RY Tau. Previous studies have shown that it drives a spectacular bipolar jet whose blueshifted component is traced optically along P.A. ≈ 295° at separations of 1farcs5-31'' from the star. Complex X-ray emission is revealed, including a very soft non-variable…
Temperature Equilibration Behind the Shock Front: An Optical and X-Ray Study Of RCW 86
Vink, J.; Bassa, C. G.; Helder, E. A.
We study the electron-proton temperature equilibration behind several shocks of the RCW 86 supernova remnant. To measure the proton temperature, we use published and new optical spectra, all from different locations on the remnant. For each location, we determine the electron temperature from X-ray spectra, and correct for temperature equilibratio…
The Rotation of the White Light Solar Corona at Height 4 R sun from 1996 to 2010: A Tomographical Study of Large Angle and Spectrometric Coronagraph C2 Observations
Morgan, Huw
Solar rotational tomography is applied to Large Angle and Spectrometric Coronagraph (LASCO) C2/Solar and Heliospheric Observatory (SOHO) observations covering the period 1996-2010, resulting in a set of electron density maps at a height of 4 R sun from which rotation rates can be calculated. Large variation of rotation rates is measured…
Revisiting the Solar Tachocline: Average Properties and Temporal Variations
Basu, Sarbani; Antia, H. M.
The tachocline is believed to be the region where the solar dynamo operates. With over a solar cycle's worth of data available from the Michelson Doppler Imager and Global Oscillation Network Group instruments, we are in a position to investigate not merely the average structure of the solar tachocline, but also its time variations. We determine t…
One-dimensional Modeling for Temperature-dependent Upflow in the Dimming Region Observed by Hinode/EUV Imaging Spectrometer
Shimizu, T.; Hara, H.; Watanabe, T. +4 more
We previously found a temperature-dependent upflow in the dimming region following a coronal mass ejection observed by the Hinode EUV Imaging Spectrometer (EIS). In this paper, we reanalyzed the observations along with previous work on this event and provided boundary conditions for modeling. We found that the intensity in the dimming region drama…
Testing a Scale-independent Method to Measure the Mass of Black Holes
Titarchuk, L.; Satyapal, S.; Gliozzi, M. +2 more
Estimating the black hole mass at the center of galaxies is a fundamental step not only for understanding the physics of accretion, but also for the cosmological evolution of galaxies. Recently, a new method, based solely on X-ray data, was successfully applied to determine the black hole mass in Galactic systems. Since X-rays are thought to be pr…
On the Spin-down and Magnetic Field of the X-ray Pulsar 1E 1207.4-5209
Gotthelf, E. V.; Halpern, J. P.
We analyze all of the archival X-ray timing data from the years 2000-2008 on the weakly magnetized central compact object (CCO) pulsar 1E 1207.4-5209 in an attempt to measure its dipole magnetic field strength via spin-down. because most of these observations were not planned for the purpose of phase-coherent timing, the resulting ephemeris is not…
Fokker-Planck Models for M15 Without a Central Black Hole: The Role of the Mass Function
Cohn, Haldan N.; Lugger, Phyllis M.; Murphy, Brian W.
We have developed a set of dynamically evolving Fokker-Planck models for the collapsed-core globular star cluster M15, which directly address the issue of whether a central black hole is required to fit Hubble Space Telescope (HST) observations of the stellar spatial distribution and kinematics. As in our previous work reported by Dull et al., we …
Disentangling the Environment of the FU Orionis Candidate HBC 722 with Herschel
Henning, Thomas; Skinner, Stephen L.; Güdel, Manuel +16 more
We analyze the submillimeter emission surrounding the new FU Orionis-type object, HBC 722. We present the first epoch of observations of the active environs of HBC 722, with imaging and spectroscopy from PACS, SPIRE, and HIFI on board the Herschel Space Observatory, as well as CO J = 2-1 and 350 µm imaging (SHARC-II) with the Caltech Submill…