-
T. Abu-Zayyad,
K. Belov,
D. J. Bird,
J. Boyer,
Z. Cao,
M. Catanese,
G. F. Chen,
R. W. Clay,
C. E. Covault,
H. Y. Dai, [......],
P. Sokolsky,
P. Sommers,
C. Song,
J. K. K. Tang,
S. B. Thomas, J. C. van der Velde,
L. R. Wiencke,
C. R. Wilkinson,
S. Yoshida,
and X. Z. Zhang
[show abstract]
[hide abstract]
ABSTRACT: We study the spectrum and average mass composition of cosmic rays with primary energies between 10^{17} and 10^{18} eV using a hybrid detector consisting of the High Resolution Fly's Eye (HiRes) prototype and the Michigan Muon Array (MIA). Measurements have been made of the change in the depth of shower maximum as a function of energy. A complete Monte Carlo simulation of the detector response and comparisons with shower simulations leads to the conclusion that the cosmic-ray intensity is changing from a heavier to a lighter composition in this energy range. The spectrum is consistent with earlier Fly's Eye measurements and supports the previously found steepening near 4 × 10^{17} eV.
The Astrophysical Journal 08/2001; 557(2):686. · 6.02 Impact Factor
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T. Abu-Zayyad,
K. Belov,
D. J. Bird,
J. Boyer,
Z Cao,
M. Catanese,
G. F. Chen,
R. W. Clay,
C. E. Covault,
J. W. Cronin, [......],
P. Sokolsky,
P. Sommers,
C Song,
J. K. K. Tang,
S. B. Thomas, J. C. van der Velde,
L. R. Wiencke,
C. R. Wilkinson,
S Yoshida,
X. Z. Zhang
[show abstract]
[hide abstract]
ABSTRACT: The average mass composition of cosmic rays with primary energies between $10^{17}$eV and $10^{18}$eV has been studied using a hybrid detector consisting of the High Resolution Fly's Eye (HiRes) prototype and the MIA muon array. Measurements have been made of the change in the depth of shower maximum, $X_{max}$, and in the change in the muon density at a fixed core location, $\rho_\mu(600m)$, as a function of energy. The composition has also been evaluated in terms of the combination of $X_{max}$ and $\rho_\mu(600m)$. The results show that the composition is changing from a heavy to lighter mix as the energy increases.
Astroparticle Physics 01/2001; 16(1):1. · 3.22 Impact Factor
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A. Borione,
M. A. Catanese,
M. C. Chantell,
C. E. Covault,
J. W. Cronin,
B. E. Fick,
L. F. Fortson,
J. Fowler,
M. A. K. Glasmacher,
K. D. Green,
D. B. Kieda,
J Matthews,
B. J. Newport,
D. Nitz,
R. A. Ong,
S. Oser,
D. Sinclair, J. C. van der Velde
[show abstract]
[hide abstract]
ABSTRACT: We describe a new search for diffuse ultrahigh energy gamma-ray emission associated with molecular clouds in the galactic disk. The Chicago Air Shower Array (CASA), operating in coincidence with the Michigan muon array (MIA), has recorded over 2.2 x 10^{9} air showers from April 4, 1990 to October 7, 1995. We search for gamma rays based upon the muon content of air showers arriving from the direction of the galactic plane. We find no significant evidence for diffuse gamma-ray emission, and we set an upper limit on the ratio of gamma rays to normal hadronic cosmic rays at less than 2.4 x 10^{-5} at 310 TeV (90% confidence limit) from the galactic plane region: (50 degrees < l < 200 degrees); -5 degrees < b < 5 degrees). This limit places a strong constraint on models for emission from molecular clouds in the galaxy. We rule out significant spectral hardening in the outer galaxy, and conclude that emission from the plane at these energies is likely to be dominated by the decay of neutral pions resulting from cosmic rays interactions with passive target gas molecules. Comment: Astrophysical Journal, submitted, 11 pages, AASTeX Latex, 3 Postscript figures
03/1997;
-
A. Borione,
M. C. Chantell,
C. E. Covault,
J. W. Cronin,
B. E. Fick,
J. W. Fowler,
L. F. Fortson,
K. G. Gibbs,
K. D. Green,
B. J. Newport,
R. A. Ong,
S. Oser,
L. J Rosenberg,
M. A. Catanese,
M. A. K. Glasmacher,
J. Matthews,
D. F. Nitz,
D. Sinclair, J. C. van der Velde,
D. B. Kieda
[show abstract]
[hide abstract]
ABSTRACT: We have carried out a high statistics (2×109 events) search for ultrahigh energy γ-ray emission from the x-ray binary sources Cygnus X-3 and Hercules X-1. Using data taken with the CASA-MIA detector over a five year period (1990–1995), we find no evidence for steady emission from either source. The derived 90 % C.L. upper limit to the steady integral flux of γ rays from Cygnus X-3 is Φ(E>115TeV)<6.3×10-15 photons cm-2 sec-1, and from Hercules X-1 it is Φ(E>115TeV)<8.5×10-15 photons cm-2 sec-1. These limits are more than two orders of magnitude lower than earlier claimed detections and are better than recent experiments operating in the same energy range. We have also searched for transient emission on time periods of one day and 0.5 h and find no evidence for such emission from either source. The typical daily limit on the integral γ-ray flux from Cygnus X-3 or Hercules X-1 is Φdaily(E>115TeV)<2.0×10-13 photons cm-2 sec-1. For Cygnus X-3, we see no evidence for emission correlated with the 4.8 h x-ray periodicity or with the occurrence of large radio flares. Unless one postulates that these sources were very active earlier and are now dormant, the limits presented here put into question the earlier results, and highlight the difficulties that possible future experiments will have in detecting γ-ray signals at ultrahigh energies.
Phys. Rev. D. 02/1997; 55(4).
-
M. Catanese,
A. Borione,
C. E. Covault,
J. W. Cronin,
B. E. Fick,
L. F. Fortson,
K. G. Gibbs,
M. A. K. Glasmacher,
K. D. Green,
D. Kieda,
J. Matthews,
B. J. Newport,
D. Nitz,
R. A. Ong,
D. Sinclair, J. C. van der Velde
[show abstract]
[hide abstract]
ABSTRACT: Extensive air shower data collected using the CASA-MIA detector are
examined for evidence of gamma rays above 50 TeV from the directions of
32 active galactic nuclei. Gamma rays above 100 MeV from all of these
objects have been detected previously by the Energetic Gamma Ray
Experiment Telescope aboard the Compton Gamma Ray Observatory. One of
these, Markarian 421, has also been observed by the Whipple Observatory
Gamma Ray Telescope to emit TeV gamma rays. No evidence of continuous or
short-term emission is found for data collected between 1990 March and
1994 November. The flux limits calculated from these data indicate a
reduction in the signal extrapolated from the EGRET data, which is
consistent with microwave attenuation of the gamma-ray spectra.
The Astrophysical Journal 09/1996; 469:572. · 6.02 Impact Factor
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D. J. Bird,
A. Borione,
J. Boyer,
M. Catanese,
G. F. Chen,
R. W. Clay,
C. E. Covault,
J. W. Cronin,
H. Y. Dai,
B. R. Dawson, [......],
D. Sinclair,
J. D. Smith,
P. Sokolsky,
P. Sommers,
J. K. K. Tang,
S. B. Thomas, J. C. van der Velde,
L. R. Wiencke,
C. R. Wilkinson,
S. Yoshida
24th International Cosmic Ray Conference. 08/1995; 2:760.
-
D. J. Bird,
A. Borione,
J. Boyer,
M. Catanese,
G. F. Chen,
R. W. Clay,
C. E. Covault,
J. W. Cronin,
H. Y. Dai,
B. R. Dawson, [......],
D. Sinclair,
J. D. Smith,
P. Sokolsky,
P. Sommers,
J. K. K. Tang,
S. B. Thomas, J. C. van der Velde,
L. R. Wiencke,
C. R. Wilkinson,
S. Yoshida
24th International Cosmic Ray Conference, Rome, Italy; 08/1995
-
C. E. Covault,
A. Borione,
J. W. Cronin,
B. E. Fick,
L. F. Forston,
K. G. Gibbs,
T. A. McKay,
B. J. Newport,
R. A. Ong,
L. J. Rosenberg,
M. Catanese,
K. D. Green,
A. Kennedy,
J. Matthews,
D. Nitz,
D. Sinclair, J. C. van der Velde,
D. Kieda
[show abstract]
[hide abstract]
ABSTRACT: Diffuse gamma‐rays from molecular clouds are excellent tracers of cosmic rays in the galaxy over a wide range of energies. For example, diffuse emission detected by EGRET already places significant constraints on the spectrum and origin of galactic cosmic rays at GeV energies. Likewise, by measuring diffuse gamma rays with ground‐based air shower experiments, we can probe the galactic distribution of cosmic rays in the energy regime above 100 TeV.
AIP Conference Proceedings. 06/1994; 304(1):499-503.
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S. Sampson,
A. Borione,
C. E. Covault,
J. W. Cronin,
B. E. Fick,
L. F. Fortson,
K. G. Gibbs,
B. J. Newport,
T. A. McKay,
R. A. Ong,
L. J. Rosenberg,
M. Catanese,
K. D. Green,
A. Kennedy,
J. Matthews,
D. Nitz,
D. Sinclair, J. C. van der Velde,
D. B. Kieda
[show abstract]
[hide abstract]
ABSTRACT: CASA-MIA is a ground based array which detects the air-showers produced
by gamma-rays at 100 TeV and above. The array's ability to detect muons
allows much of the cosmic-ray background to be discarded. Data from 1990
to 1993 has been used to search for short duration gamma-ray bursts from
arbitrary direction. No evidence for 0.035s bursts has been found. This
result has been used to set a limit on the rate-density of evaporating
primordial black holes. Additional point source searches with longer
time windows of 1s, 10s and 100s are also investigated.
04/1994; 26:873.
-
A. Borione,
M. Catanese,
C. E. Covault,
J. W. Cronin,
B. E. Fick,
K. G. Gibbs,
K. D. Green,
S. Hauptfeld,
D. Kieda,
H. A. Krimm,
N. C. Mascarenhas,
J. Matthews,
T. A. McKay,
D. Müller,
B. J. Newport,
D. Nitz,
R. A. Ong,
L. J. Rosenberg,
D. Sinclair, J. C. van der Velde
[show abstract]
[hide abstract]
ABSTRACT: The Chicago Air Shower Array has imaged the shadows of the Moon and Sun and measured the angular diameter of the Moon with cosmic rays having energies above about 100 TeV. The shadow of the Sun shows effects attributed to the curvature of cosmic rays by the solar magnetic field. This study verifies that our direction reconstruction has no serious systematic errors, and provides a measure of the angular resolution of the array.
Phys. Rev. D. 01/1994; 49(3).
-
T. A. McKay,
A. Borione,
M. Catanese,
C. E. Covault,
J. W. Cronin,
B. E. Fick,
K. G. Gibbs,
K. D. Green,
S. Hauptfeld,
D. Kieda,
H. A. Krimm,
N. M. Mascarenhas,
J. Matthews,
B. J. Newport,
D. Nitz,
R. A. Ong,
L. J. Rosenberg,
D. Sinclair, J. C. van der Velde
[show abstract]
[hide abstract]
ABSTRACT: The CASA-MIA experiment is a very large extensive air shower detector
with good angular resolution. A part of this instrument has been used to
search the visible sky for astrophysical point sources of gamma rays
with energies ≥ too TeV. Approximately 90% of the charged cosmic-ray
background is rejected through measurement of the muon content of the
showers. Stringent limits are placed on the flux of 100 TeV gamma rays
from previously unknown point sources across a large fraction of the
northern sky. The complete instrument, with significantly greater
sensitivity, has been in operation for more than a year.
The Astrophysical Journal 10/1993; 417:742. · 6.02 Impact Factor
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K. G. Gibbs,
A. Borione,
C. E. Covault,
J. W. Cronin,
B. E. Fick,
T. A. McKay,
B. J. Newport,
R. A. Ong,
L. J. Rosenberg,
M. Catanese,
K. D. Green,
J. Matthews,
D. Nitz,
D. Sinclair, J. C. van der Velde,
D. B. Kieda
[show abstract]
[hide abstract]
ABSTRACT: The Chicago Air Shower Array (CASA) is the world's largest experiment
for detecting extensive air showers from cosmic rays and gamma rays at
100 TeV energies. CASA operates in coincidence with a large area
underground muon detector (MIA), thus making possible a significant
degree of cosmic ray background rejection. CASA was designed to search
for point sources of gamma rays, such as Cygnus X-3 and Hercules X-1,
for which detections were claimed by a number of smaller experiments
during the early 80's. However, analysis of CASA-MIA data from February
1989 through April 1991 shows no evidence for point sources, and CASA
limits for continuous emission are significantly lower than have been
previously reported. While the search for galactic point sources
continues, we are pursuing several new classes of potential ultra-high
energy gamma ray sources. Recent work includes a search for diffuse
emission resulting from the interaction of galactic cosmic rays with
large molecular clouds, a search for coincident emission from gamma ray
bursts detected by the BATSE experiment, and a search for emission from
extragalactic sources (AGN) detected by the EGRET experiment. At least
one such source has been detected at TeV energies by the Whipple air
Cerenkov experiment. Observations of several AGN at 10-100 TeV might be
used to probe the time-evolution of the CMBR. We present preliminary
results for searches from all of these sources and summarize the
implications for cosmic ray origins and cosmology.
04/1993; 25:847.
-
C. E. Covault,
A. Borione,
J. W. Cronin,
B. E. Fick,
K. G. Gibbs,
T. A. McKay,
B. J. Newport,
R. A. Ong,
L. J. Rosenberg,
M. Catanese,
K. D. Green,
J. Matthews,
D. Nitz,
D. Sinclair, J. C. van der Velde,
D. B. Kieda
[show abstract]
[hide abstract]
ABSTRACT: The origin of cosmic rays with energies above 100 TeV remains a profound
astrophysical mystery. If such cosmic rays are accelerated by a handful
number of point sources, such as Cygnus X-3, then the gamma ray emission
from such sources should have already been detected by the current
generation of large area air shower experiments which have been
operating during the past few years. However, no continuous point source
emission has been detected. Therefore we consider the implications of a
new search for gamma ray emission from diffuse sources. The Chicago Air
Shower Array (CASA) which operates in coincidence with the Michigan muon
array (MIA) is the world's most sensitive experiment to gamma rays with
energies ~ great 100 TeV, and is well-suited for studies of diffuse
sources based upon the muon content of air showers. We describe a search
for diffuse gamma ray emission from molecular cloud regions observed by
CASA-MIA. Such emission would be indicated by an excess of muon-poor
showers from the direction of the source. If we conservatively assume
that the flux of cosmic rays is uniform in the galaxy, the we predict
that the diffuse emission should be detectable by CASA-MIA within the
lifetime of the experiment. However, if there are sources of cosmic rays
in close proximity to certain molecular clouds, then spectrum of gamma
rays from these clouds will be stronger and harder. By searching for
such enhancements in the diffuse emission, and by correlating the
CASA-MIA results with emission detected at lower energies by EGRET, we
may identify or constrain the nature of cosmic rays sources in both
energy regimes.
04/1993; 25:929.
-
C. E. Covault,
A. Borione,
J. W. Cronin,
B. E. Fick,
K. G. Gibbs,
S. Hauptfeld,
T. A. McKay,
D. Muller,
B. J. Newport,
R. A. Ong,
L. J. Rosenberg,
M. Catanese,
K. D. Green,
J. Matthews,
D. Nitz,
D. Sinclair, J. C. van der Velde,
D. B. Kieda
[show abstract]
[hide abstract]
ABSTRACT: Recently, the EGRET experiment aboard the Compton Gamma Ray Observatory
has reported the detection of strong episodic emission from over 15
extra-galactic sources, typically radio-loud quasars and BL Lac objects.
These sources are generally classified as ``blazars'', with significant
gamma-ray energy which may be beamed towards the observer. At least one
of these objects, Mrk 421, has also been detected at energies ~ 1 TeV by
the Whipple observatory. Depending on the details of intergalactic
absorption, it may be possible to detect such sources at energies above
50 TeV with large air shower arrays. We present a progress report on a
search for Ultra High Energy (UHE) gamma rays from extra-galactic
sources, such as the EGRET blazars, using the UMC air shower facility at
Dugway, Utah. The facility is comprised of the large-area Chicago Air
Shower Array (CASA) operating in coincidence with the underground
Michigan Muon array (MIA). We describe our analysis approach for Mrk 421
and other AGN which are under observation by CASA-MIA in the northern
hemisphere. We anticipate a sensitivity of ~ 3*E(-14) ph cm(-2) s(-1)
above 80 TeV to flux from Mrk 421 after one full year's observations.
11/1992; 24:1156.
-
C. E. Covault,
F. A. Aharonian,
A. Borione,
J. W. Cronin,
B. E. Fick,
K. G. Gibbs,
S. Hauptfeld,
T. A. McKay,
D. Müller,
B. J. Newport,
R. A. Ong,
L. J. Rosenberg,
M. Cantanese,
K. D. Green,
J. Matthews,
D. Nitz,
D. Sinclair, J. C. van der Velde
08/1991; 23:1471.
-
H. A. Krimm,
J. W. Cronin,
B. E. Fick,
K. G. Gibbs,
N. C. Mascarenhas,
T. A. McKay,
D. Müller,
B. J. Newport,
R. A. Ong,
L. J. Rosenberg,
K. D. Green,
J. Matthews,
D. Nitz,
D. Sinclair, J. C. van der Velde
07/1991; 1:432.
-
H. A. Krimm,
J. W. Cronin,
B. E. Fick,
K. G. Gibbs,
N. C. Mascarenhas,
T. A. McKay,
D. Müller,
B. J. Newport,
R. A. Ong,
L. J. Rosenberg,
K. D. Green,
J. Matthews,
D. Nitz,
D. Sinclair, J. C. van der Velde
07/1991; 1:269.
-
T. A. McKay,
A. Borione,
C. E. Covault,
J. W. Cronin,
B. E. Fick,
K. G. Gibbs,
H. A. Krimm,
N. C. Mascarenhas,
D. Müller,
B. J. Newport,
R. A. Ong,
L. J. Rosenberg,
M. Catanese,
K. D. Green,
J. Matthews,
D. Nitz,
D. Sinclair, J. C. van der Velde
07/1991; 1:230.
-
K. G. Gibbs,
A. Borione,
C. E. Covault,
J. W. Cronin,
B. E. Fick,
H. A. Krimm,
N. C. Mascarenhas,
T. A. McKay,
D. Müller,
B. J. Newport,
R. A. Ong,
L. J. Rosenberg,
M. Catanese,
K. D. Green,
J. Matthews,
D. Nitz,
D. Sinclair, J. C. van der Velde
07/1991; 1:208.
-
R. A. Ong,
A. Borione,
C. E. Covault,
J. W. Cronin,
B. E. Fick,
K. G. Gibbs,
H. A. Krimm,
N. C. Mascarenhas,
T. A. McKay,
D. Müller,
B. J. Newport,
L. J. Rosenberg,
M. Catanese,
K. D. Green,
J. Matthews,
D. Nitz,
D. Sinclair, J. C. van der Velde
07/1991; 1:273.
