Search Publications
Proper Motion of the Irradiated Jet HH 399 in the Trifid Nebula
Yusef-Zadeh, F.; Wardle, M.; Biretta, J.
HH 399 is one of the first Herbig-Haro flows recognized to be irradiated by the UV radiation of the massive O7.5 star in the Trifid Nebula. We present the proper motion of the first irradiated jet, based on two epochs of Hubble Space Telescope (HST) observations of HH 399 separated by nearly 5 yr, using Hα and [S II] line filters. High proper moti…
X-Ray and Infrared Observations of Embedded Young Stars in NGC 2264
Simon, Theodore; Dahm, S. E.
Images of the NGC 2264 star-forming region, which we have acquired with the XMM-Newton spacecraft, reveal strong X-ray emission from three deeply embedded (AV>=10 mag) young stellar objects in the vicinity of Allen's infrared source (AFGL 989 = IRS 1) and Castelaz & Grasdalen's infrared source (RNO-EW = IRS 2). Thermal plasma mod…
UV/Optical Nuclear Activity in the gE Galaxy NGC 1399
Crane, Jeffrey D.; O'Connell, Robert W.; Burstein, David +5 more
Using HST STIS, we have detected far-ultraviolet nuclear activity in the giant elliptical galaxy NGC 1399, the central and brightest galaxy in the Fornax I cluster. The source reached a maximum observed far-UV luminosity of ~1.2×1039 ergs s-1 in 1999 January. It was detectable in earlier HST archival images in 1996 (B band) b…
Swift, INTEGRAL, RXTE, and Spitzer Reveal IGR J16283-4838
Gehrels, N.; Rodriguez, J.; Mowlavi, N. +9 more
We present the first combined study of the recently discovered source IGR J16283-4838 with Swift, INTEGRAL, and RXTE. The source, discovered by INTEGRAL on 2005 April 7, shows a highly absorbed [variable NH=(0.4-1.7)×1023 cm-2] and flat (Γ~1) spectrum in the Swift XRT and RXTE PCA data. No optical counterpart is de…
A Study of the Near-Ultraviolet Spectrum of Vega
Hubeny, Ivan; Allende Prieto, Carlos; García López, Ramón J. +1 more
UV, optical, and near-IR spectra of Vega have been combined to test our understanding of stellar atmospheric opacities and to examine the possibility of constraining chemical abundances from low-resolution UV fluxes. We have carried out a detailed analysis assuming local thermodynamic equilibrium (LTE) to identify the most important contributors t…
Faint Blue Objects in the Hubble Deep Field-South Revealed: White Dwarfs, Subdwarfs, and Quasars
Winget, D. E.; Kilic, Mukremin; von Hippel, Ted +1 more
We explore the nature of the faint blue objects in the Hubble Deep Field-South. We have derived proper motions for the point sources in the Hubble Deep Field-South using a 3 yr baseline. Combining our proper-motion measurements with spectral energy distribution fitting enabled us to identify four quasars and 42 stars, including three white dwarf c…
Properties of a Sunspot Plume Observed With the Coronal Diagnostic Spectrometer Aboard the Solar and Heliospheric Observatory
Landi, Enrico; Brosius, Jeffrey W.
We used three instruments (CDS, EIT, MDI) aboard the Solar and Heliospheric Observatory spacecraft to observe the large sunspot in NOAA Active Region 8539 on 1999 May 9 and 13. The spot contained a bright plume, most easily seen in EUV emission lines formed at 5.2<~logT<~5.7 (where T is the temperature in K), in its umbra on both dates. The …
Thermal and Nonthermal Nature of the Soft Excess Emission from Sérsic 159-03 Observed with XMM-Newton
Kaastra, Jelle S.; Bonamente, Massimiliano; Lieu, Richard +2 more
Several nearby clusters exhibit an excess of soft X-ray radiation that cannot be attributed to the hot virialized intracluster medium. There is no consensus to date on the origin of the excess emission: it could be either of thermal origin or due to an inverse Compton scattering of the cosmic microwave background. Using high-resolution XMM-Newton …
Young Stars and Dust in AFGL 437: Hubble Space Telescope NICMOS Polarimetric Imaging of an Outflow Source
Hines, Dean C.; Meakin, Casey A.; Thompson, Roger I.
We present near-infrared broadband and polarimetric images of the compact star-forming cluster AFGL 437 obtained with the NICMOS instrument on board HST. Our high-resolution images reveal a well-collimated bipolar reflection nebulosity in the cluster and allow us to identify WK 34 as the illuminating source. The scattered light in the bipolar nebu…
Magnetic Twist of an Extreme-Ultraviolet Coronal Loop Inferred from Plasma Constriction
Moon, Yong-Jae; Chae, Jongchul
Magnetic twist is a very likely way of constricting coronal plasma into loops. An attempt is made to determine the magnetic twist that can explain the constriction of coronal loops indirectly from observations. We decompose the coronal magnetic field into a large-scale magnetic field and a small-scale magnetic field. The large-scale field is assum…