The activities at Penn State University are described. During the period Oct. 1990 to Dec. 1991 work on HEAO-1 analysis of the Low Energy Detectors (LED) concentrated on using the improved detector spectral simulation model and fitting diffuse x-ray background spectral data. Spectral fitting results, x-ray point sources, and diffuse x-ray sources are described

Nousek, John A.

English

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NASA-CR-194087
THE PENNSYLVANIA STATE UNIVERSITY
DEPARTMENT OF ASTRONOMY AND ASTROPHYSICS
525 Davey Lab., University Park, PA 16802
Final Technical Report
For NASA Grant NAG-5-941
/?17o 
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k
John A. Nousek
March 3, 1992
This report describes the activities at Penn State University supported
by NASA Grant NAG-5-941. During the period 10/90 to 12/91 work on
HEAO- 1 analysis of the Low Energy Detectors (LED) concentrated on using
the improved detector spectral simulation model and fitting diffuse X-ray
background spectral data. M0st of thls Work was base_ on the work of
--I3r.-l_rlshna Apparao, Vi_slting Adjunct Professor, on leave from the Tata
Institute for Fundamental Research of Bombay, India, visiting Penn State
through 8/91. Collaboration with Dr. Denis Leahy of the University of
Calgary, Canada, lead to several joint publications.
More detailed descriptions of these activities are found in the following
sections.
1 Spectral Fitting Results
The original calibration models from the HEAO-1 ground tests were found
to give poor fits (reduced X2 > 10). Response matrices made from these cal-
ibrations gave temperature and emission measure spectra for selected areas
of the sky (North Ecliptic Pole, South Ecliptic Pole, and Crab supernova
remnant) that were not compatible with those found by other spacecraft.
This implied that additional work on counter fundamentals was necessary.
To test the effectiveness of these new calibrations the response matrix
generation program and spectra generation programs were upgraded to al-
low production of time weighted response matrices. These matrices compen-
sate for counter gain drift and allow better fits to sky spectra. These time
weighted response matrices were applied to selected sky areas of interest.
Another important result arising from the improved detector simulation
is the ability to completely reconcile the response of the front and back layers
(NASA-CR-194087) [HEAO-I ANALYSIS
OF LOW ENERGY DETECTORS (LED)]
Final Report, Oct. 1990 - Dec. 1991
(Pennsylvania State Univ.) 3 p
N94-12574
Unclas
G3/89 0181705
https://ntrs.nasa.gov/search.jsp?R=19940008102 2020-06-16T20:52:06+00:00Z
of the detector with the same spectral model parameters. This improvement
gives us much greater confidence in establishing the absolute normalization
level of the diffuse background, in particular the extra-galactic power law
component. We find that the diffuse background between 1 and 2 keV is
best described by a normalization of 10.44-0.5.
The final summary results of the HEAO-1 LED observations of the dif-
fuse soft X-ray background were presented by Garmire et al (1992). This
paper also includes the maps of the diffuse sky intensity in four bandpasses.
2 X-ray Point Sources
Dr. Apparan wrote several contributions on X-ray sources during his short
stay at Penn State (since July, 1990).
Apparao (1990a) has shown that six flares observed in EXO2030+375
with an average interval of about 4 h are due to l_ayleigh-Taylor instabilities
near the magnetospheric boundary of the neutron star when it reaches the
equilibrium period.
It is generally thought that the circumstellar gas er_velope around a Be
star results from accretion of gas. Apparao (1990b) has pointed out that
this is not tenable for Be star X-ray sources. The degenerate nature of the
X-ray emitting companion precludes contribution of matter to the Be star.
It is also shown that a triple system, where supposition is required to make
the accretion hypothesis tenable, is not possible by calculation of the period
of apsidal motion.
Apparao (1990c) discusses reasons for the non-detection of white dwarfs
in Be star binaries. Possible signatures of their presence are presented.
Apparao, Berthiaume and Nousek (1992) discuss the X-ray emitting
properties of two binary planetary nebulae.
3 Diffuse X-ray Sources
In similar work Leahy, Nousek and Garmire (1991) report diffuse X-ray emis-
sion which they interpret as being associated with the Gum Nebula, lending
support to the origin of this nebula as a result of a supernova explosion.
Leahy, Nousek and Hamilton (1991, 1992) apply the improved spectral
fitting results to more restrictively determine the characteristics of the su-
pernova remnants SN1006 and the Lupus Loop.
Burrowset al. (1992) uses maximum entropy enhanced spatial resolution
maps of the Eridanus X-ray enhancement to compare with radio and infrared
data from the region. Through a comparision of the detailed morphology
seen in various wavelengths they conclude the region most likely results from
stellar wind bubbles, possibly reheated by a later supernova explosion.
4 Publications
4.1 Refereed Journals
Apparao, K.M.V. (1990a), "Flares in the X-ray Source EXO2030%375", Ap.
J., submitted.
Apparao, K.M.V. (1990b), "White Dwarfs in Be Star Binary Systems",
Astr. Astrophys., submitted.
Apparao, K.M.V., Berthiaume, G.D., and Nousek, J.A. "X-ray Obser-
vations of Planetary Nebulae with Binary Nuclei", Ap.J. submitted (1991).
Burrows, D.N., Singh, K.P., Nousek, J.A., Garmire, G.P., and Good,
J. "A Multiwavelength Study of the Eridanus X-ray Enhancement", Ap.J.
submitted (1992).
Garmire, G.P., Nousek, J.A., Apparao, K.M.V., Burrows, D.N., Fink,
R.L., and Kraft, R.P. "The Soft X-ray Diffuse Background Measured by the
HEAO-1 Low Energy Detectors", Ap.J. submitted (1991).
Leahy, D.A., Nousek, J., and Hamilton, A.J.S. "HEAO-1 A2 LED X-ray
Spectra of the Lupus Loop and SN1006", Ap.J. 374, 218-226 (1991).
Leahy, D.A., Nousek, J., and Garmire, G. "Discovery of X-ray Emission
Associated with the Gum Nebula" Ap.J. accepted (1992).
4.2 Conference Proceedings and Unrefereed Journals
Apparao, K.M.V. (1990c), "Origin of the Be Star Circumstellar Envelope",
Be-star Newsletter (in press).
Leahy, D.A., Nousek, J., and Hamilton, A. "Non-equilibrium Ioniza-
tion Models for X-ray Emission from the Lupus Loop and from SN1006",
Frontiers o/X-Ray Astronomy ed. Y. Tanaka and K. Koyama, Universal
Academic Press, Inc., in press (1992).


HEAO-1 analysis of Low Energy Detectors (LED)

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