Search Publications
Ongoing Massive Star Formation in the Bulge of M51
Panagia, N.; Spaans, M.; Romaniello, M. +4 more
We present a study of Hubble Space Telescope Wide Field Planetary Camera 2 observations of the inner kiloparsec of the interacting galaxy M51 in six bands from 2550 to 8140 Å. The images show an oval-shaped area (which we call the ``bulge'') of about 11''×16'', or 450×650 pc, around the nucleus that is dominated by a smooth `…
The Host Galaxies of Radio-loud Active Galactic Nuclei: The Black Hole-Galaxy Connection
Urry, C. Megan; O'Dowd, Matthew; Scarpa, Riccardo
We have studied the host galaxies of a sample of radio-loud active galactic nuclei (AGNs) spanning more than 4 decades in the energy output of the nucleus. The core sample includes 40 low-power sources (BL Lac objects) and 22 high-power sources (radio-loud quasars) spanning the redshift range 0.15<~z<~0.5, all imaged with the high spatial re…
Analysis of H2 Emission from Mira B in Ultraviolet Spectra from the Hubble Space Telescope
Wood, Brian E.; Raymond, John C.; Karovska, Margarita
We analyze Lyα fluoresced H2 lines observed in the UV spectrum of Mira B. We identify 13 different sequences fluoresced by 13 different H2 transitions within the Lyα line. The observed H2 line ratios within these sequences imply significant line opacity, so we use a Monte Carlo radiative transfer code to model the …
Very Large Telescope Spectra of Carbon Stars in the Large Magellanic Cloud and Their Metallicity Dependence
Waters, L. B. F. M.; van Loon, J. Th.; Yamamura, I. +4 more
Very Large Telescope (VLT) L-band spectra of six carbon stars in the Large Magellanic Cloud are presented. The stars show absorption bands at 3.1 µm (HCN and C2H2), and 3.8 µm, which is probably due to C2H2. Two LMC stars show strong 3.5 µm HCN absorption. The equivalent widths of the 3…
Polaris: Amplitude, Period Change, and Companions
Evans, Nancy Remage; Short, C. Ian; Sasselov, Dimitar D.
Polaris has presented us with the rare phenomenon of a Cepheid with a pulsation amplitude that has decreased over the last 50 yr. In this study we have used this property to see whether the amplitude decrease during the last 15 yr has had any effect on upper atmosphere heating. We obtained IUE high- and low-resolution spectra but found no change i…
Multiple Collimated Outflows in the Proto-Planetary Nebula GL 618
Trammell, Susan R.; Goodrich, Robert W.
We present narrowband Hα, [S II], and [O I] Hubble Space Telescope images of the young planetary nebula GL 618. This object is a compact, bipolar nebula that is currently undergoing the transition from asymptotic giant branch star to planetary nebula. Our images confirm the presence of at least three highly collimated outflows emanating from the c…
Detection of the Neupert Effect in the Corona of an RS Canum Venaticorum Binary System by XMM-Newton and the Very Large Array
Güdel, Manuel; Behar, Ehud; Audard, Marc +3 more
The RS CVn-type binary σ Geminorum was observed during a large, long-duration flare simultaneously with XMM-Newton and the Very Large Array. The light curves show a characteristic time dependence that is compatible with the Neupert effect observed in solar flares: the time derivative of the X-ray light curve resembles the radio light curve. This o…
A New Measurement of the Average Far-Ultraviolet Extinction Curve
Hurwitz, M.; Dixon, W. V.; Sasseen, T. P. +1 more
We have measured the extinction curve in the far-ultraviolet wavelength region of (900-1200 Å) using spectra obtained with the Berkeley EUV/FUV spectrometer during the ORFEUS I and the ORFEUS II (Orbiting and Retrievable Far and Extreme Ultraviolet Spectrometer) missions in 1993 and 1996. From the complete sample of early-type stars observed durin…
Isolating Clusters with Wolf-Rayet Stars in I Zw 18
Brown, Thomas M.; Hubeny, Ivan; Heap, Sara R. +2 more
We present UV images and spectra of the starburst galaxy I Zw 18, taken with the Space Telescope Imaging Spectrograph. The high spatial resolution of these data allows us to isolate clusters containing Wolf-Rayet stars of the subtype WC. Our far-UV spectra clearly show C IV λλ1548, 1551 and He II λ1640 emission of WC stars in two clusters: one wit…
Deep Radio, Optical, and Infrared Observations of SGR 1900+14
Frail, D. A.; Kulkarni, S. R.; van Kerkwijk, M. H. +1 more
We present Hubble Space Telescope/STIS, Keck J- and Ks-band, and VLA 332 and 1400 MHz images of the region around the soft γ-ray Repeater SGR 1900+14. No nonstellar sources were detected at the position of SGR 1900+14, giving 3 σ limits of S332MHz<6 mJy, S1.4GHz<1.5 mJy, m50CCD>~29.0 mag, J>~…