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152. Hubble Space TelescopeSTIS Observations of GRB 000301C: CCD Imaging and Near‐Ultraviolet MAMA Spectroscopy

Author

Smette, Alain, primary, Fruchter, Andrew S., additional, Gull, Theodore R., additional, Sahu, Kailash C., additional, Petro, Larry, additional, Ferguson, Henry, additional, Rhoads, James, additional, Lindler, Don J., additional, Gibbons, Rachel, additional, Hogg, David W., additional, Kouveliotou, Chryssa, additional, Livio, Mario, additional, Macchetto, Duccio, additional, Metzger, Mark R., additional, Pedersen, Holger, additional, Pian, Elena, additional, Thorsett, Stephen E., additional, Wijers, Ralph A. M. J., additional, Fynbo, Johan P. U., additional, Gorosabel, Javier, additional, Hjorth, Jens, additional, Jensen, Brian L., additional, Levine, Alan, additional, Smith, Donald A., additional, Cline, Tom, additional, Hurley, Kevin, additional, and Trombka, Jack, additional

Published
2001
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158. An Unusual Brightening Of Eta Carinae

Author

Davidson, Kris, primary, Gull, Theodore R., additional, Humphreys, Roberta M., additional, Ishibashi, Kazunori, additional, Whitelock, Patricia, additional, Berdnikov, Leonid, additional, McGregor, Peter J., additional, Metcalfe, Travis S., additional, Polomski, Elisha, additional, and Hamuy, Mario, additional

Published
1999
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159. [ITAL]Hubble Space Telescope[/ITAL] and Palomar Imaging of GRB 990123: Implications for the Nature of Gamma-Ray Bursts and Their Hosts

Author

Fruchter, Andrew S., primary, Thorsett, S. E., additional, Metzger, Mark R., additional, Sahu, Kailash C., additional, Petro, Larry, additional, Livio, Mario, additional, Ferguson, Henry, additional, Pian, Elena, additional, Hogg, David W., additional, Galama, Titus, additional, Gull, Theodore R., additional, Kouveliotou, Chryssa, additional, Macchetto, Duccio, additional, van Paradijs, Jan, additional, Pedersen, Holger, additional, and Smette, Alain, additional

Published
1999
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161. On-orbit performance of the space telescope imaging spectrograph

Author

Kimble, Randy A., primary, Woodgate, Bruce E., additional, Bowers, Charles W., additional, Kraemer, Steven B., additional, Kaiser, M. E., additional, Gull, Theodore R., additional, Heap, Sara R., additional, Danks, Anthony C., additional, Boggess, A., additional, Green, Richard F., additional, Hutchings, John B., additional, Jenkins, Edward B., additional, Joseph, Charles L., additional, Linsky, J. L., additional, Maran, S. P., additional, Moos, Henry W., additional, Roesler, Fred L., additional, Timothy, J. Gethyn, additional, Weistrop, D. E., additional, Grady, J. F., additional, Loiacono, Joan J., additional, Brumfield, Mark D., additional, Feinberg, Lee D., additional, Krebs, Carolyn A., additional, Meyer, Wallace W., additional, Hood, D. F., additional, Argabright, Vic S., additional, Hetlinger, J. C., additional, Stocker, Ralph B., additional, Woodruff, Robert A., additional, Baum, Stefi A., additional, Hartig, George F., additional, Bohlin, Ralph C., additional, Clampin, Mark, additional, Ferguson, Harry C., additional, Goudfrooij, Paul, additional, McGrath, Melissa, additional, Lindler, Don J., additional, Beck, Terrence L., additional, Feggans, Keith, additional, Plait, P. C., additional, Sandoval, Jennifer L., additional, Hill, Robert S., additional, Collins, Nicholas R., additional, Cornett, R. H., additional, Fowler, Walter B., additional, Hill, Robert J., additional, Landsman, Wayne, additional, Malumuth, Eliot M., additional, Crenshaw, D. M., additional, Robinson, R. D., additional, and Valenti, Jeff A., additional

Published
1998
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162. On-orbit optical performance of the Space Telescope Imaging Spectrograph

Author

Bowers, Charles W., primary, Woodgate, Bruce E., additional, Kimble, Randy A., additional, Kaiser, M. E., additional, Gull, Theodore R., additional, Kraemer, Steven B., additional, Hartig, George F., additional, Content, David A., additional, Ebbets, Dennis C., additional, Michika, David, additional, Sullivan, Joseph F., additional, Woodruff, Robert A., additional, Bottema, M., additional, Lindler, Don J., additional, Plait, P. C., additional, Standley, Clive, additional, Collins, Nicholas R., additional, Cornett, R. H., additional, Landsman, Wayne, additional, Malumuth, Eliot M., additional, and Robinson, R. D., additional

Published
1998
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163. STIS on-orbit testing: limiting magnitudes, spectral sensitivity, thermal flexure, and MAMA time-tagging

Author

Gull, Theodore R., primary, Woodgate, Bruce E., additional, Kimble, Randy A., additional, Bowers, Charles W., additional, Kraemer, Steven B., additional, Kaiser, Mary Elizabeth, additional, Bohlin, Ralph C., additional, Hulbert, Steve J., additional, Shaw, Richard A., additional, Feggans, Keith, additional, Lindler, Don J., additional, Sandoval, Jennifer L., additional, Hill, Robert S., additional, Collins, Nicholas R., additional, Brown, Thomas M., additional, and Valenti, Jeff A., additional

Published
1998
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164. Space Telescope Imaging Spectrograph detectors and ultraviolet signal-to-noise capabilities

Author

Kaiser, Mary Elizabeth, primary, Woodgate, Bruce E., additional, Kimble, Randy A., additional, Bowers, Charles W., additional, Kraemer, Steven B., additional, Argabright, Vic S., additional, Driggers, Phillip A., additional, Lindler, Don J., additional, Bohlin, Ralph C., additional, Van Houten, Charles N., additional, Bybee, Richard L., additional, Delamere, Alan W., additional, Dorn, David A., additional, Danks, Anthony C., additional, Joseph, Charles L., additional, Timothy, J. Gethyn, additional, Gull, Theodore R., additional, Beck, Terrence L., additional, Blouke, Morley M., additional, Brown, Lawrence W., additional, Brumfield, Mark D., additional, Clampin, Mark, additional, Content, David A., additional, Feinberg, Lee D., additional, Fowler, Walter B., additional, Goudfrooij, Paul, additional, Hill, Robert J., additional, Reed, Richard, additional, Standley, Clive, additional, and Yagelowich, J. J., additional

Published
1998
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166. Imaging and Spectroscopy of Arcs around the Most Luminous X-Ray Cluster, RX J1347.5−1145

Author

Sahu, Kailash C., primary, Shaw, Richard A., additional, Kaiser, Mary Elizabeth, additional, Baum, Stefi A., additional, Ferguson, Henry C., additional, Hayes, Jeffrey J. E., additional, Gull, Theodore R., additional, Hill, Robert J., additional, Hutchings, John B., additional, Kimble, Randy A., additional, Plait, Philip, additional, and Woodgate, Bruce E., additional

Published
1998
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167. The STIS Parallel Survey: Introduction and First Results

Author

Gardner, Jonathan P., primary, Hill, Robert S., additional, Baum, Stefi A., additional, Collins, Nicholas R., additional, Ferguson, Henry C., additional, Fosbury, Robert A. E., additional, Gilliland, Ronald L., additional, Green, Richard F., additional, Gull, Theodore R., additional, Heap, Sara R., additional, Lindler, Don J., additional, Malumuth, Eliot M., additional, Micol, Alberto, additional, Pirzkal, Norbert, additional, Sandoval, Jennifer L., additional, Tolstoy, Eline, additional, Walsh, Jeremy R., additional, and Woodgate, Bruce E., additional

Published
1998
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168. Space Telescope Imaging Spectrograph Observations of the Interstellar Velocity Structure and Chemical Composition toward the Carina Nebula

Author

Walborn, Nolan R., primary, Danks, Anthony C., additional, Sembach, Kenneth R., additional, Bohlin, Ralph C., additional, Jenkins, Edward B., additional, Gull, Theodore R., additional, Lindler, Don J., additional, Feggans, J. Keith, additional, Hulbert, Stephen J., additional, Linsky, Jeffrey, additional, Hutchings, John B., additional, and Joseph, Charles L., additional

Published
1998
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169. Ultraviolet Imaging Telescope observations of the Crab Nebula

Author

Hennessy, Gregory S., primary, O'Connell, Robert W., additional, Cheng, Kwang P., additional, Bohlin, Ralph C., additional, Collins, Nicholas R., additional, Gull, Theodore R., additional, Hintzen, Paul, additional, Isensee, Joan E., additional, Landsman, Wayne B., additional, Roberts, Morton S., additional, Smith, Andrew M., additional, Smith, Eric P., additional, and Stecher, Theodore P., additional

Published
1992
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170. Space Telescope Imaging Spectrograph detectors and ultraviolet signal-to-noise capabilities.

Author

Kaiser, Mary Elizabeth, Woodgate, Bruce E., Kimble, Randy A., Bowers, Charles W., Kraemer, Steven B., Argabright, Vic S., Driggers, Phillip A., Lindler, Don J., Bohlin, Ralph C., Van Houten, Charles N., Bybee, Richard L., Delamere, Alan W., Dorn, David A., Danks, Anthony C., Joseph, Charles L., Timothy, J. Gethyn, Gull, Theodore R., Beck, Terrence L., Blouke, Morley M., and Brown, Lawrence W.

Published
1998
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171. On-orbit performance of the space telescope imaging spectrograph.

Author

Kimble, Randy A., Woodgate, Bruce E., Bowers, Charles W., Kraemer, Steven B., Kaiser, M. E., Gull, Theodore R., Heap, Sara R., Danks, Anthony C., Boggess, A., Green, Richard F., Hutchings, John B., Jenkins, Edward B., Joseph, Charles L., Linsky, J. L., Maran, S. P., Moos, Henry W., Roesler, Fred L., Timothy, J. Gethyn, Weistrop, D. E., and Grady, J. F.

Published
1998
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172. η Carinae: Testing a Binary Orbit Model with the Hubble Space Telescope/Space Telescope Imaging SpectrographBased on observations with the NASA/ESA Hubble Space Telescope. Our observations and data reduction were supported by grant number GO-7302 from the Space Telescope Science Institute and also by NASA funding to the STIS Science Team. The HST is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555.

Author

Davidson, Kris, Ishibashi, Kazunori, Gull, Theodore R., Humphreys, Roberta M., and Smith, Nathan

Published
2000
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173. Limits on the Optical Brightness of the Eridani Dust Ring

Author

Proffitt, Charles R., Sahu, Kailash, Livio, Mario, Krist, John, Calzetti, Daniela, Gilliland, Ron, Grady, Carol, Lindler, Don, Woodgate, Bruce, Heap, Sara, Clampin, Mark, Gull, Theodore R., and Lisse, Casey M.

Abstract

The STIS CCD camera on the Hubble Space Telescope (HST) was used to take deep optical images near the K2 V main-sequence star [?] Eridani in an attempt to find an optical counterpart of the dust ring previously imaged by submillimeter observations. Upper limits for the optical brightness of the dust ring are determined and discussed in the context of the scattered starlight expected from plausible dust models. We find that even if the dust is smoothly distributed in symmetrical rings, the optical surface brightness of the dust, as measured with the HST STIS CCD clear aperture at 55 AU from the star, cannot be brighter than about 25 STMAG arcsec-2. This upper limit excludes some solid-grain models for the dust ring that can fit the IR and submillimeter data. Magnitudes and positions for [?]59 discrete objects between 12.''5 and 58'' from [?] Eri are reported. Most if not all of these objects are likely to be background stars and galaxies.

Published
2004

174. Kinematics and Ultraviolet to Infrared Morphology of the Inner Homunculus of ? Carinae

Author

Smith, Nathan, Morse, Jon A., Gull, Theodore R., Hillier, John, Gehrz, Robert D., Walborn, Nolan R., Bautista, Manuel, Collins, Nicholas R., Corcoran, Michael F., Damineli, Augusto, Hamann, Fred, Hartman, Henrik, Johansson, Sveneric, Stahl, Otmar, and Weis, Kerstin

Abstract

We present the first ultraviolet and optical images of e Car and its circumstellar Homunculus nebula, obtained with the Advanced Camera for Surveys/High Resolution Camera (ACS/HRC) on board the Hubble Space Telescope (HST). Compared to those at visual wavelengths, UV images reveal excess emission 0.''1-0.''6 from the central source along the minor axis that may emanate from the outer parts of e Car's nonspherical stellar wind, which dominates the UV flux from e Car. The UV emission fills the cavity inside a dust torus measured from infrared (IR) data; within 0.''2 of the star the UV emission projects a morphology reminiscent of the IR torus, but it is a factor of 10 smaller. This "little torus" seen in the UV may be related to the "Little Homunculus" discovered recently, signifying recurrent mass ejections with the same geometry. Finally, we reexamine the kinematics of nebular condensations near the star (Weigelt objects C and D) in HST images and spectra obtained over the past decade. We measure heliocentric velocities slower than previous estimates, and from proper motions we derive an ejection date of 1908 +- 12 yr, assuming linear motion. However, because of radiative acceleration, these objects may have been ejected earlier--perhaps during the 1890 outburst of e Car.

Published
2004

176. Latitude-dependent Effects in the Stellar Wind of ? Carinae

Author

Smith, Nathan, Davidson, Kris, Gull, Theodore R., Ishibashi, Kazunori, and Hillier, John

Abstract

The Homunculus reflection nebula around e Carinae provides a rare opportunity to observe the spectrum of a star from more than one direction. In the case of e Car, the nebula's geometry is known well enough to infer how line profiles vary with latitude. We present Space Telescope Imaging Spectrograph (STIS) spectra of several positions in the Homunculus, showing directly that e Car has an aspherical stellar wind. P Cygni absorption in Balmer lines depends on latitude, with relatively high velocities and strong absorption near the polar axis. Stronger absorption at high latitudes is surprising, and it suggests higher mass flux toward the poles, perhaps resulting from radiative driving with equatorial gravity darkening on a rotating star. Reflected profiles of He I lines are more puzzling, offering clues to the wind geometry and ionization structure. During e Car's high-excitation state in 2000 March, the wind was fast and dense at the poles, with higher ionization at low latitudes. Older STIS data obtained since 1998 reveal that this global stellar wind geometry changes during e Car's 5.5 yr cycle and may suggest that this star's spectroscopic events are shell ejections. Whether or not a companion star triggers these outbursts remains ambiguous. The most dramatic changes in the wind occur at low latitudes, while the dense polar wind remains relatively undisturbed during an event. The apparent stability of the polar wind also supports the inferred bipolar geometry. The wind geometry and its variability have critical implications for understanding the 5.5 yr cycle and long-term variability but do not provide a clear alternative to the binary hypothesis for generating e Car's X-rays.

Published
2003

177. Letters.

Author

Attas, E. Michael, Babaian, E. Michael, Gull, Theodore R., and Reid, Ted W.

Subjects
*STELLAR dynamics, *ELECTROMAGNETIC waves, *CATHODE ray tubes, *STELLAR winds, *GAS dynamics
Abstract

This document is a collection of letters to the editors of American Scientist. The first letter discusses the contrasting approaches to science presented in two articles, one emphasizing evidence and the other highlighting visualization and artistic creativity. The second letter shares the author's personal experiences with observing nebular structures and collaborating with other astronomers. The third letter expresses appreciation for an article on J. Willard Gibbs and shares an anecdote about him. The document also includes information on how to write to American Scientist. [Extracted from the article]

Published
2024

183. SUZAKU MONITORING OF HARD X-RAY EMISSION FROM η CARINAE OVER A SINGLE BINARY ORBITAL CYCLE.

Author

Hamaguchi, Kenji, Corcoran, Michael F., Takahashi, Hiromitsu, Yuasa, Takayuki, Ishida, Manabu, Gull, Theodore R., Pittard, Julian M., Russell, Christopher M. P., and Madura, Thomas I.

Subjects
BINARY stars, MULTIPLE stars, STELLAR atmospheres, SOLAR atmosphere, STELLAR chromospheres
Abstract

The Suzaku X-ray observatory monitored the supermassive binary system η Carinae 10 times during the whole 5.5 yr orbital cycle between 2005 and 2011. This series of observations presents the first long-term monitoring of this enigmatic system in the extremely hard X-ray band between 15 and 40 keV. During most of the orbit, the 15-25 keV emission varied similarly to the 2-10 keV emission, indicating an origin in the hard energy tail of the kT ∼ 4 keV wind-wind collision (WWC) plasma. However, the 15-25 keV emission declined only by a factor of three around periastron when the 2-10 keV emission dropped by two orders of magnitude due probably to an eclipse of the WWC plasma. The observed minimum in the 15-25 keV emission occurred after the 2-10 keV flux had already recovered by a factor of ∼3. This may mean that the WWC activity was strong, but hidden behind the thick primary stellar wind during the eclipse. The 25-40 keV flux was rather constant through the orbital cycle, at the level measured with INTEGRAL in 2004. This result may suggest a connection of this flux component to the γ-ray source detected in this field. The helium-like Fe Kα line complex at ∼6.7 keV became strongly distorted toward periastron as seen in the previous cycle. The 5-9 keV spectra can be reproduced well with a two-component spectral model, which includes plasma in collision equilibrium and a plasma in non-equilibrium ionization (NEI) with τ ∼ 1011 cm–3 s–1. The NEI plasma increases in importance toward periastron. [ABSTRACT FROM AUTHOR]

Published
2014
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185. Discovery of a Little Homunculus within the Homunculus Nebula of η Carinae.

Author

Ishibashi, Kazunori, Gull, Theodore R., Davidson, Kris, Smith, Nathan, Lanz, Thierry, Lindler, Don, Feggans, Keith, Verner, Ekaterina, Woodgate, Bruce E., Kimble, Randy A., Bowers, Charles W., Kraemer, Steven, Heap, Sarah R., Danks, Anthony C., Maran, Stephen P., Joseph, Charles L., Kaiser, Mary Elizabeth, Linsky, Jeffrey L., Roesler, Fred, and Weistrop, Donna

Published
2003
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189. η CARINAE'S DUSTY HOMUNCULUS NEBULA FROM NEAR-INFRARED TO SUBMILLIMETER WAVELENGTHS: MASS, COMPOSITION, AND EVIDENCE FOR FADING OPACITY.

Author

Morris PW, Gull TR, Hillier DJ, Barlow MJ, Royer P, Nielsen K, Black J, and Swinyard B

Abstract

Infrared observations of the dusty, massive Homunculus Nebula around the luminous blue variable η Carinae are crucial to characterize the mass-loss history and help constrain the mechanisms leading to the Great Eruption. We present the 2.4 - 670 μ m spectral energy distribution, constructed from legacy ISO observations and new spectroscopy obtained with the Herschel Space Observatory. Using radiative transfer modeling, we find that the two best-fit dust models yield compositions which are consistent with CNO-processed material, with iron, pyroxene and other metal-rich silicates, corundum, and magnesium-iron sulfide in common. Spherical corundum grains are supported by the good match to a narrow 20.2 μ m feature. Our preferred model contains nitrides AlN and Si 3 N 4 in low abundances. Dust masses range from 0.25 to 0.44 M ʘ but M tot ≥ 45 M ʘ in both cases due to an expected high Fe gas-to-dust ratio. The bulk of dust is within a 5″ × 7″ central region. An additional compact feature is detected at 390 μ m. We obtain L IR = 2.96 × 10 6 L ʘ , a 25% decline from an average of mid-IR photometric levels observed in 1971-1977. This indicates a reduction in circumstellar extinction in conjunction with an increase in visual brightness, allowing 25-40% of optical and UV radiation to escape from the central source. We also present an analysis of 12 CO and 13 CO J = 5 - 4 through 9 - 8 lines, showing that the abundances are consistent with expectations for CNO-processed material. The [ 12 C II] line is detected in absorption, which we suspect originates in foreground material at very low excitation temperatures.

Published
2017
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190. Eta Carinae's Thermal X-ray Tail Measured with XMM-Newton and NuSTAR .

Author

Hamaguchi K, Corcoran MF, Gull TR, Takahashi H, Grefenstette B, Yuasa T, Stuhlinger M, Russell C, Moffat AFJ, Madura T, Richardson ND, Groh J, Pittard J, and Owocki S

Abstract

The evolved, massive highly eccentric binary system, η Car, underwent a periastron passage in the summer of 2014. We obtained two coordinated X-ray observations with XMM-Newton and NuSTAR during the elevated X-ray flux state and just before the X-ray minimum flux state around this passage. These NuSTAR observations clearly detected X-ray emission associated with η Car extending up to ~50 keV for the first time. The NuSTAR spectrum above 10 keV can be fit with the bremsstrahlung tail from a kT ~6 keV plasma. This temperature is Δ kT ~2 keV higher than those measured from the iron K emission line complex, if the shocked gas is in collisional ionization equilibrium. This result may suggest that the companion star's pre-shock wind velocity is underestimated. The NuSTAR observation near the X-ray minimum state showed a gradual decline in the X-ray emission by 40% at energies above 5 keV in a day, the largest rate of change of the X-ray flux yet observed in individual η Car observations. The column density to the hardest emission component, N H ~10 24 H cm -2 , marked one of the highest values ever observed for η Car, strongly suggesting the increased obscuration of the wind-wind colliding X-ray emission by the thick primary stellar wind prior to superior conjunction. Neither observation detected the power-law component in the extremely hard band that INTEGRAL and Suzaku observed prior to 2011. The power-law source might have faded before these observations.

Published
2016
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