219 research outputs found
A laboratory program to develop improved grazing incidence X-ray optics
Grazing incident double reflection X-ray telescop
Continuing data analysis of the AS/E grazing incidence X-ray telescope experiment on the OSO-4 satellite
The work to correct and extend the calculation of the theoretical solar X-ray spectrum produced during earlier OSO-4 data analysis is reported along with the work to formulate models of active regions, and compare these models with the experimental values. An atlas of solar X-ray photographs is included, and solar X-ray observations are correlated with the solar wind
Solar coronal differential rotation from XBPs in Hinode/XRT and Yohkoh/SXT images
Our aim is to identify and trace the X-ray Bright Points (XBPs) over the disk
and use them as tracers to determine the coronal rotation. This investigation
will help to clarify and understand several issues: whether (i) the corona
rotates differentially; (ii) the rotation depends on the sizes of the XBPs; and
(iii) dependence on phases of the solar magnetic cycle. We analysed the daily
full-disk soft X-ray images observed with (i) X-Ray Telescope (XRT) on-board
the Hinode mission during January, March and April, 2007 and (ii) Soft X-ray
Telescope (SXT) on-board the Yohkoh from 1992 to 2001 using SSW in IDL. We have
used the tracer method to trace the passage of XBPs over the solar disk with
the help of overlaying grids and derived the sidereal angular rotation velocity
and the coordinates (latitude and longitude) of the XBPs. We have determined
the position of a large number of XBPs both in Hinode/XRT and Yohkoh/SXT images
and followed them over the solar disk as a function of time. We derived the
coronal sidereal angular rotation velocity and compared it with heliocentric
latitude and as a function of solar activity cycle. In addition, we measured
the sizes of all the XBPs and related them with the coronal rotation. The
important results derived from these investigations are: (i) the solar corona
rotates differentially like the photosphere and chromosphere; (ii) the sidereal
angular rotation velocity is independent of the sizes of the XBPs; (iii) the
sidereal angular rotation velocity does not depend on phases of the solar
magnetic cycle; and (iv) the differential rotation of the corona is present
throughout the solar magnetic cycle.Comment: 9 pages, 4 figure
High resolution studies of the solar X-ray corona from Aerobee rockets
The research in high resolution solar X-ray astronomy is reported. The payload for the Aerobee 150 launch vehicle, which included a 23 cm diameter mirror whose polished surface was a nickel-phosphorus alloy is discussed along with the high resolution measurements, by Flight 13.028 CS, of the temperature and density structure of the lower corona. Flight 13.029 CS is also discussed
Coronal Temperature Diagnostic Capability of the Hinode/X-Ray Telescope Based on Self-Consistent Calibration
The X-Ray Telescope (XRT) onboard the Hinode satellite is an X-ray imager
that observes the solar corona with unprecedentedly high angular resolution
(consistent with its 1" pixel size). XRT has nine X-ray analysis filters with
different temperature responses. One of the most significant scientific
features of this telescope is its capability of diagnosing coronal temperatures
from less than 1 MK to more than 10 MK, which has never been accomplished
before. To make full use of this capability, accurate calibration of the
coronal temperature response of XRT is indispensable and is presented in this
article. The effect of on-orbit contamination is also taken into account in the
calibration. On the basis of our calibration results, we review the
coronal-temperature-diagnostic capability of XRT
Mechanical and Thermal Performance of Macro-Encapsulated Phase Change Materials for Pavement Application
Macro-encapsulated phase change material (PCM) lightweight aggregates (ME-LWA) were
produced and evaluated for their mechanical and thermal properties in road engineering applications.
The ME-LWAs were first characterised in terms of their physical and geometrical properties. Then,
the ME-LWAs were investigated in detail by applying the European Standards of testing for the Bulk
Crushing Test and the Polished Stone Value (PSV) coefficient as well as Micro-Deval and laboratory
profilometry. In addition, the thermal performance for possible construction of smart pavements
with the inclusion of ME-LWAs for anti-ice purposes was determined. The crushing resistance of the
ME-LWAs was improved, while their resistance to polishing was reduced. Thermal analysis of the
encapsulated PCM determined it to possess excellent thermal stability and a heat storage capacity of
30.43 J/g. Based on the research findings, the inclusion of ME-LWAs in surface pavement layers could
be considered a viable solution for the control of surface temperatures in cold climates. Road safety
and maintenance could benefit in terms of reduced ice periods and reduced treatments with salts and
other anti-ice solutions.variou
Intensity oscillations in coronal XBPs from Hinode/XRT observations
Our aim is to investigate the intensity oscillations in coronal X-ray Bright
Points (XBPs). We analysed a 7-hours long time sequence of the soft X-ray
images obtained on April 14, 2007 with 2-min cadence using X-Ray Telescope
(XRT) on-board the Hinode mission. We use SSW in IDL to derive the time series
of 14 XBPs and 2 background regions. For the first time, we have tried to use
power spectrum analysis on XBPs data to determine the periods of intensity
oscillations. coronal X-ray Bright Points (XBPs). The power spectra of XBPs
show several significant peaks at different frequencies corresponding to a wide
variety of time scales which range from a few minutes to hours. The light
curves of all the XBPs give the impression that the XBPs can be grouped into
three classes depending on emission levels: (i) weak XBPs; (ii) bright XBPs;
and (iii) very strong XBPs. The periods of intensity oscillation are consistent
in all the XBPs and are independent of their brightness level, suggesting that
the heating mechanisms in all the three groups of XBPs are similar. The
different classes of XBPs may be related to the different strengths of the
magnetic field with which they have been associated.Comment: 7 pages, 3 figure
The structure and dynamics of a bright point as seen with Hinode, SoHO and TRACE
Our aim is to determine the plasma properties of a coronal bright point and
compare its magnetic topology extrapolated from magnetogram data with its
appearance in X-ray images. We analyse spectroscopic data obtained with
EIS/Hinode, Ca II H and G-band images from SOT/Hinode, UV images from TRACE,
X-ray images from XRT/Hinode and high-resolution/high-cadence magnetogram data
from MDI/SoHO. The BP comprises several coronal loops as seen in the X-ray
images, while the chromospheric structure consists of tens of small bright
points as seen in Ca II H. An excellent correlation exists between the Ca II
BPs and increases in the magnetic field, implying that the Ca II H passband is
a good indicator for the concentration of magnetic flux. Doppler velocities
between 6 and 15 km/s are derived from the Fe XII and Fe XIII lines for the BP
region, while for Fe XIV and Si VII they are in the range from -15 to +15 km/s.
The coronal electron density is 3.7x10^9 cm^-3. An excellent correlation is
found between the positive magnetic flux and the X-ray light-curves. The
remarkable agreement between the extrapolated magnetic field configuration and
some of the loops composing the BP as seen in the X-ray images suggests that a
large fraction of the magnetic field in the bright point is close to potential.
The close correlation between the positive magnetic flux and the X-ray emission
suggests that energy released by magnetic reconnection is stimulated by flux
emergence or cancellation.Comment: 10 pages with 11 figures. Accepted in Astronomy and Astrophysic
The VAST Survey - I. Companions and the unexpected X-ray detection of B6-A7 stars
With an adaptive optics imaging survey of 148 B6-A7 stars, we have tested the
hypothesis that unresolved lower-mass companions are the source of the
unexpected X-ray detections of stars in this spectral type range. The sample is
composed of 63 stars detected in X-rays within the ROSAT All-Sky Survey and 85
stars that form a control sample; both subsets have the same restricted
distribution of spectral type, age, X-ray sensitivity and separation coverage.
A total of 68 companion candidates are resolved with separations ranging from
0.3" to 26.2", with 23 new detections. The multiple star frequency of the X-ray
sample based on companions resolved within the ROSAT error ellipse is found to
be 43 (+6,-6)%. The corresponding control sample multiple star frequency is
three times lower at 12 (+4,-3)% -- a difference of 31\pm7%. These results are
presented in the first of a series of papers based on our Volume-limited A-Star
(VAST) survey -- a comprehensive study of the multiplicity of A-type stars.Comment: Accepted for publication in Monthly Notices of the Royal Astronomical
Societ
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