J. Jeff Hester
Arizona State University
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Featured researches published by J. Jeff Hester.
Publications of the Astronomical Society of the Pacific | 1995
Jon A. Holtzman; Christopher J. Burrows; Stefano Casertano; J. Jeff Hester; John T. Trauger; Alan M. Watson; Guy Worthey
We discuss the photometric performance and calibration of the Wide Field Planetary Camera 2 (WFPC2) on the Hubble Space Telesopce (HST). The stability and accuracy of WFPC2 photometric measurements is discussed, with particular attention given to charge transfer efficiency (CTE) effects, contamination effects in the ultraviolet (UV), and flat field accuracy and normalization. Observational data are presented from both WFPC2 observations and ground observations using a system similar to that flown. WFPC2 photometric systems are defined both for the ground and flight systems. Transformations between these systems and the Landolt UBVRI system are presented. These transformations are sensitive to details in the spectra being transformed, and these sensitivities are quantified and discussed. On-orbit observations are used to revise the prelaunch estimates of response curves to best match synthetic photometry results with observations, and the accuracy of the resulting synthetic photometry is discussed. Synthetic photometry is used to determine zeropoints and transformations for all of the fight filters, and also to derive interstellar extinction values for the WFPC2 system. Using stellar interior and atmosphere models, isochrones in the WFPC2 system are calculated and compared with several observations.
Publications of the Astronomical Society of the Pacific | 1995
Jon A. Holtzman; J. Jeff Hester; Stefano Casertano; John T. Trauger; Alan M. Watson; G. E. Ballester; Christopher J. Burrows; John Clarke; David Crisp; Robin W. Evans; John S. Gallagher; Richard E. Griffiths; John G. Hoessel; L. D. Matthews; Jeremy R. Mould; Paul A. Scowen; Karl R. Stapelfeldt; James A. Westphal
The WFPC2 was installed in the Hubble Space Telescope (HST) in 1993 December. Since then, the instrument has been providing high-quality images. A significant amount of calibration data has been collected to aid in the understanding of the on-orbit performance of the instrument. Generally, the behavior of the camera is similar to its performance during the system-level thermal vacuum test at JPL in 1993 May. Surprises were a significant charge-transfer-efficiency (CTE) problem and a significant growth rate in hot pixels at the original operating temperature of the CCDs (-76 °C). The operating temperature of the WFPC2 CCDs was changed to -88 °C on 1994 April 23, and significant improvements in CTE and hot pixels are seen at this temperature. In this paper we describe the on-orbit performance of the WFPC2. We discuss the optical and thermal history, the instrument throughput and stability, the PSF, the effects of undersampling on photometry, the properties of cosmic rays observed on-orbit, and the geometric distortion in the camera. We present the best techniques for the reduction of WFPC2 data, and describe the construction of calibration products including superbiases, superdarks, and fiat fields.
The Astrophysical Journal | 2000
Martin C. Weisskopf; J. Jeff Hester; Allyn F. Tennant; Ronald F. Elsner; Norbert S. Schulz; Herman L. Marshall; Margarita Karovska; Joy S. Nichols; Douglas A. Swartz; Jeffery J. Kolodziejczak
The Chandra X-Ray Observatory observed the Crab Nebula and pulsar during orbital calibration. Zeroth-order images with the High-Energy Transmission Grating (HETG) readout by the Advanced CCD Imaging Spectrometer spectroscopy array (ACIS-S) show a striking richness of X-ray structure at a resolution comparable to that of the best ground-based visible-light observations. The HETG-ACIS-S images reveal, for the first time, an X-ray inner ring within the X-ray torus, the suggestion of a hollow-tube structure for the torus, and X-ray knots along the inner ring and (perhaps) along the inward extension of the X-ray jet. Although complicated by instrumental effects and the brightness of the Crab Nebula, the spectrometric analysis shows systematic variations of the X-ray spectrum throughout the nebula.
The Astronomical Journal | 1992
Jon A. Holtzman; S. M. Faber; Edward J. Shaya; Tod R. Lauer; Edward J. Groth; Deidre A. Hunter; William A. Baum; S. P. Ewald; J. Jeff Hester; Robert M. Light; C. Roger Lynds; Earl J. O'Neill; James A. Westphal
We have discovered a population of bright blue pointlike sources within 5 kpc of the nucleus of NGC 1275 using HST Planetary Camera observations. The typical object has M_v~- 12 to - 14 (H_0 = 75 km s^(-1) Mpc^(-1); the brightest has M_v~-16. They are all blue, with V- R≾0.3. The color distribution and lack of excess Ha emission are consistent with nearly all being continuum sources. Many of the sources are unresolved even with the HST and consequently have sizes of ≾ 15 pc. We suggest that these are young star clusters that will evolve to look like globular clusters. They are bluer than any clusters seen in the Milky Way or M87, and brighter than the blue clusters seen in the LMC. We derive ages of several hundred million years or less and corresponding masses of 10^5-10^8 M_☉. The existence of these young clusters may be connected with a current or previous interaction with another galaxy, with the cooling flow in NGC 1275, or with some combination. Structure is detected in the underlying galaxy light that is suggestive of a merge between NGC 1275 and a second galaxy some 10^8 yr ago. If this merger triggered star formation, it would naturally account for the observed uniformity of cluster colors. Steady-state star formation in the x-ray cooling flow would imply a wider range in cluster age and color than is seen, unless the clusters disrupt. An interaction with the projected high-velocity, infalling system cannot explain the observations because this system has not yet reached the center of NGC 1275 where the clusters are concentrated, and because it has a total interaction time that is far too short for either the observed cluster lifetimes or the dynamical lifetime of structure in the galaxy. If the presence of recently formed protoglobulars around NGC 1275 is related to a previous merger, this would remove an important objection to the merger hypothesis for elliptical galaxy origins, provided that adequate gas is available in the merger for their formation.
Science | 1996
John Clarke; G. E. Ballester; John T. Trauger; Robin W. Evans; J. E. P. Connerney; Karl R. Stapelfeldt; David Crisp; Paul D. Feldman; Christopher J. Burrows; Stefano Casertano; John S. Gallagher; Richard E. Griffiths; J. Jeff Hester; John G. Hoessel; Jon A. Holtzman; John E. Krist; Vikki Meadows; Jeremy R. Mould; Paul A. Scowen; Alan M. Watson; James A. Westphal
Far-ultraviolet images of Jupiter from the Hubble Space Telescope Wide Field Planetary Camera 2 reveal polar auroral emissions at 300 kilometer resolution and three times higher sensitivity than previously achieved. Persistent features include a main oval containing most of the emission and magnetically connected to the middle magnetosphere, diffuse and variable emissions poleward of the main oval, and discrete emission from Ios magnetic footprint equatorward of the oval. The auroral emissions are variable, exhibit magnetic conjugacy, and are visible above the planet limb. All emissions approximately co-rotate with Jupiter except the Io “footprint,” which is fixed along Ios magnetic flux tube.
The Astronomical Journal | 1996
Xiaohui Fan; David Burstein; Jian Sheng Chen; Jin Zhu; Zhaoji Jiang; Hong Wu; Haojing Yan; Zhongyuan Zheng; Xu Zhou; Li Zhi Fang; Fuzhen Chen; Z. G. Deng; Yao-Quan Chu; J. Jeff Hester; Rogier A. Windhorst; Yong Li; Phillip K. Lu; Wei-Hsin Sun; W. P. Chen; Wean Shun Tsay; Tzihong Chiueh; Chih Kang Chou; Chung Ming Ko; Ting Chang Lin; Hui Jean Guo; Yong Ik Byun
We present nine color CCD intermediate-band spectrophotometry of a two square degree field centered on the old open cluster M67, from 3890
The Astrophysical Journal | 1995
Christopher J. Burrows; John E. Krist; J. Jeff Hester; Raghvendra Sahai; John T. Trauger; Karl R. Stapelfeldt; John S. Gallagher; G. E. Ballester; Stefano Casertano; John Clarke; David Crisp; Robin W. Evans; Richard E. Griffiths; John G. Hoessel; Jon A. Holtzman; Jeremy R. Mould; Paul A. Scowen; Alan M. Watson; James A. Westphal
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The Astrophysical Journal | 2007
Nicholas T. Ouellette; Steven Joseph Desch; J. Jeff Hester
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The Astrophysical Journal | 1988
J. C. Raymond; J. Jeff Hester; Donald P. Cox; William P. Blair; Robert A. Fesen; Theodore R. Gull
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The Astrophysical Journal | 1996
Roberto Soria; Jeremy R. Mould; Alan M. Watson; John S. Gallagher; G. E. Ballester; Christopher J. Burrows; Stefano Casertano; John Clarke; David Crisp; Richard E. Griffiths; J. Jeff Hester; John G. Hoessel; Jon A. Holtzman; Paul A. Scowen; Karl R. Stapelfeldt; John T. Trauger; James A. Westphal
. These observations are taken as a part of the BATC (Beijing-Arizona-Taipei-Connecticut) Color Survey of the Sky, for both scientific and calibration reasons. With these data we show that the BATC survey can reach its goal of obtaining spectrophotometry to a zero point accuracy of 0.01 mag, and down to V = 21 with 0.3 mag random error. We fit the color-magnitude diagrams (CMDs) with Wortheys theoretical models. The net result is the excellent fit of the 4.0 Gyr, [Fe/H] =