Search Publications
Fragmentation Origin of Major Sungrazing Comets C/1970 K1, C/1880 C1, and C/1843 D1
Sekanina, Zdenek; Chodas, Paul W.
Following our recent successful modeling of the common origin of two of the brightest members of the Kreutz system of sungrazing comets, we now examine three other objects: C/1970 K1 (White-Ortiz-Bolelli), the most recent sungrazer discovered from Earth, C/1880 C1 (Great Southern Comet), and C/1843 D1 (Great March Comet). For White-Ortiz-Bolelli, …
Infrared Space Observatory Short Wavelength Spectrometer Observations of H II Regions in NGC 6822 and I Zwicky 36: Sulfur Abundances and Temperature Fluctuations
Skillman, Evan D.; Garnett, Donald R.; Dinerstein, Harriet L. +1 more
We report Infrared Space Observatory (ISO) Short Wavelength Spectrometer infrared spectroscopy of the H II region Hubble V in NGC 6822 and the blue compact dwarf galaxy I Zw 36. Observations of Brα, [S III] at 18.7 and 33.5 µm, and [S IV] at 10.5 µm are used to determine ionic sulfur abundances in these H II regions. There is relativel…
The Environment of FS Tauri Observed with Hubble Space Telescope Wide Field Planetary Camera 2 in Narrowband Emission Line Filters
Eislöffel, Jochen; Mundt, Reinhard; Ray, Thomas P. +1 more
We present the results of Hubble Space Telescope Wide Field Planetary Camera (WFPC2) observations of FS Tau and its environment obtained in the narrowband emission line filters Hα and [S II] λλ6716,6731 Å. Based on these data the morphology of line emission within this region can be studied on a size scale of 0.1" for the first time. Despite the f…
Hubble Space Telescope NICMOS Images of the HH 7/11 Outflow in NGC 1333
Noriega-Crespo, A.; Young, E.; Chen, H. +1 more
We present near-infrared images in H2 at 2.12 µm of the HH 7/11 outflow and its driving source SVS 13 taken with the Hubble Space Telescope NICMOS2 camera, as well as archival Hα and [S II] optical images obtained with the Wide Field Planetary Camera 2 (WFPC2). The Near-Infrared Camera and Multi-Object Spectrometer high angular re…
Interpreting the M22 Spike Events
Gaudi, B. Scott
Recently Sahu et al., using the Hubble Space Telescope to monitor stars in the direction of the old (~12 Gyr) globular cluster M22, detected six events in which otherwise constant stars brightened by ~50% during a time of <~1 day. They tentatively interpret these unresolved events as being caused by microlensing of background bulge stars by fre…
Boron in the Small Magellanic Cloud: A Novel Test of Light-Element Production
Lambert, D. L.; Cunha, K.; Venn, K. A. +3 more
Hubble Space Telescope Space Telescope Imaging Spectrograph (STIS) observations of the B III resonance line at λ2066 have been obtained and analyzed for two Small Magellanic Cloud (SMC) B-type stars. While boron is not detected in either star, upper limits to the boron abundance are set, with 12+log(B/H)<=1.6 for both AV 304 and NGC 346-637. Th…
Is Thermal Expansion Driving the Initial Gas Ejection in NGC 6251?
Melia, Fulvio; Liu, Siming; Fatuzzo, Marco
The relativistic jets in active galactic nuclei (AGNs) are probably driven by the action of supermassive, spinning black holes. There is very little direct evidence for this, however, since the nuclei of active galaxies are difficult to study. This is now changing with new, high-resolution multiwavelength observations of nearby sources such as Sgr…
Evidence of a Strong N V/C IV Correlation between Emission and Absorption Lines in Active Galactic Nuclei
Green, Paul J.; Kuraszkiewicz, Joanna K.
The narrow absorption lines (NALs) that are seen in the rest-frame ultraviolet near the systemic redshift of active galactic nuclei (AGNs) are not always intrinsic to the near-nuclear region but may originate in the host galaxy or in neighboring galaxies intervening along the line of sight. A variety of criteria have been sought-and several identi…
Ion Effective Temperatures in Polar Coronal Holes: Observations versus Ion-Cyclotron Resonance
Patsourakos, S.; Habbal, S. R.; Hu, Y. Q.
The resonant cyclotron interaction between ion-cyclotron waves and solar wind species is considered nowadays to be a strong candidate for heating and acceleration of protons, α-particles, and heavy ions. A crucial physical parameter for determining the amount and the location of significant heating and acceleration, which the different solar wind …
A Reexamination of the ``Planetary'' Lensing Events in M22
Anderson, Jay; Sahu, Kailash C.; King, Ivan R.
We have carried out a further analysis of the tentative, short-term brightenings reported by Sahu and coworkers, which were suggested to be possible lensing of Galactic bulge stars by free-floating planets in the globular cluster M22. Closer examination shows that-unlikely as it may seem-small, pointlike cosmic rays had hit very close to the same …