Search Publications
The Discovery of a Second Luminous Low-Mass X-Ray Binary in the Globular Cluster M15
White, Nicholas E.; Angelini, Lorella
We report an observation by the Chandra X-Ray Observatory of 4U 2127+119, the X-ray source identified with the globular cluster M15. The Chandra observation reveals that 4U 2127+119 is in fact two bright sources, separated by 2.7". One source is associated with AC 211, the previously identified optical counterpart to 4U 2127+119, a low-mass X-ray …
Erupting Solar Magnetic Flux Ropes: Theory and Observation
Thompson, B. J.; Chen, J.; Howard, R. A. +2 more
Measurements of coronograph (LASCO) and extreme-ultraviolet (EIT) images are presented for 11 coronal mass ejection (CME) events. Detailed measurements of these events, selected because they have flux-rope-like morphological features, show excellent agreement with results from a theoretical model of erupting flux-rope dynamics. Here, data are used…
An XMM-Newton Observation of the Luminous Seyfert 1 Galaxy Markarian 509
Reeves, James; Nayakshin, Sergei; O'Brien, Paul +3 more
We present the spectral analysis of an early XMM-Newton observation of the luminous Seyfert 1 galaxy Mrk 509. We find the hard (2-10 keV) continuum slope, including reflection, to be somewhat flatter (Γ=1.75) than that of a typical broad-line Seyfert 1 galaxy. The most obvious feature in the hard X-ray spectrum is a narrow emission line near 6.4 k…
Spectroscopic Diagnostics of Nanoflare-heated Loops
Klimchuk, J. A.; Cargill, P. J.
To evaluate the usefulness of spectroscopic techniques for diagnosing realistic solar plasmas and to better understand the physical origin of coronal heating, we have simulated observations of model coronal loops that are heated randomly and impulsively by nanoflares. We find that the emission measures, densities, and filling factors that are infe…
Far-Ultraviolet and Hα Imaging of Nearby Spiral Galaxies: The OB Stellar Population in the Diffuse Ionized Gas
Hoopes, Charles G.; Bothun, Gregory D.; Walterbos, René A. M.
We have compared Hα and far-ultraviolet (FUV) images of 10 nearby spirals, with the goal of understanding the contribution of field OB stars to the ionization of the diffuse ionized gas (DIG) in spiral galaxies. The FUV images were obtained by the Ultraviolet Imaging Telescope (UIT), and the Hα images were obtained using various ground-based teles…
NGC 1614: A Laboratory for Starburst Evolution
Rieke, G. H.; Alonso-Herrero, A.; Quillen, A. C. +2 more
The modest extinction and reasonably face-on viewing geometry make the luminous infrared galaxy NGC 1614 an ideal laboratory for the study of a powerful starburst. Hubble Space Telescope/near-infrared camera and multiobject spectrometer (NICMOS) observations show (1) deep CO stellar absorption, tracing a starburst nucleus about 45 pc in diameter (…
Hubble Space Telescope Proper-Motion Measurements of the η Carinae Nebula
Davidson, Kris; Bally, John; Balick, Bruce +3 more
We present proper-motion measurements of the bipolar lobes and equatorial disk features ejected from η Carinae during the last century and deduce their relative ages in order to determine the likelihood of multiple ejection events. Hubble Space Telescope Wide Field Planetary Camera 2 images taken in 1994, 1995, and 1999 were compared, and the moti…
NICMOS Observations of Extragalactic Cepheids. I. Photometry Database and a Test of the Standard Extinction Law
Calzetti, D.; Stetson, P. B.; Persson, S. E. +8 more
We present the results of near-infrared observations of extragalactic Cepheids made with the Near-Infrared Camera and Multi-Object Spectrometer on board the Hubble Space Telescope (HST). The variables are located in the galaxies IC 1613, IC 4182, M31, M81, M101, NGC 925, NGC 1365, NGC 2090, NGC 3198, NGC 3621, NGC 4496A, and NGC 4536. All fields w…
Discovery of Extended X-Ray Emission from the Planetary Nebula NGC 7027 by the Chandra X-Ray Observatory
Soker, Noam; Kastner, Joel H.; Vrtilek, Saeqa D.
We report the discovery of X-ray emission from NGC 7027, a prototypical object for the study of the formation and evolution of planetary nebulae. Observations with the Advanced CCD Imaging Spectrometer (ACIS) aboard the Chandra X-Ray Observatory show that the X-ray emission from NGC 7027 is extended and is bipolar in morphology. The ACIS spectrum …
M Dwarfs from Hubble Space Telescope Star Counts. IV.
Gould, Andrew; Salim, Samir; Bahcall, John N. +2 more
We study a sample of about 1400 disk M dwarfs that are found in 148 fields observed with the Wide Field Camera 2 (WFC2) on the Hubble Space Telescope and 162 fields observed with pre-repair Planetary Camera 1 (PC1), of which 95 of the WFC2 fields are newly analyzed. The method of maximum likelihood is applied to derive the luminosity function and …