scholarly journals AutoCal: A software application for calibrating photometric data

2016 ◽  
Vol Volume 112 (Number 3/4) ◽  
Author(s):  
Daniël J. Wium ◽  
Brian van Soelen ◽  
◽  
Keyword(s):  
Least Squares ◽  
Weighted Least Squares ◽  
Magellanic Cloud ◽  
Photometric Data ◽  
Field Of View ◽  
Small Magellanic Cloud ◽  
Outlier Removal ◽  
X Ray ◽  
Software Application ◽  
Least Squares Approach

Abstract We present a software application for the calibration of stellar magnitudes in the absence of standard stars. It uses an existing algorithm to match stars in the target’s field of view to catalogue entries and computes the average offset between the two sets of magnitudes using a weighted least-squares approach. This offset is used to calibrate the target’s instrumental magnitude. The software application was used to calibrate magnitudes for six Be/X-ray binary sources in the Small Magellanic Cloud and the results were compared with published results for these sources. Where comparisons were possible, our results agreed with those results within the uncertainties specified. Infrared variability was found for all six of the sources tested. The interactive outlier removal that was made possible by our software allowed for smaller uncertainties to be reported for our results.

Calibration in a closed system: the case of X-ray diffraction analysis

2007 ◽  
Vol 40 (4) ◽  
pp. 694-701
Author(s):  
Thaung Lwin
Keyword(s):  
Diffraction Analysis ◽  
Least Squares ◽  
Functional Relationship ◽  
Weighted Least Squares ◽  
Ordinary Least Squares ◽  
X Ray Diffraction ◽  
Unknown Parameters ◽  
X Ray ◽  
Relationship Model ◽  
Least Squares Approach

Knudsen [X-ray Spectrom.(1981),10, 54–561] proposed and demonstrated a least-squares approach to estimating the unknown parameters of a system of equations required for calibration in X-ray diffraction analysis. The approach is an ordinary least-squares approach which does not incorporate information on the errors of the measured intensities for a set of samples used as standards. The purpose of the present paper is to show that a functional relationship model can be applied to the problem to account for all the variation due to sampling and measurement error in the peak intensities. It is also shown that Knudsen's calibration estimator can be regarded as an approximation to a more general and potentially more efficient weighted least-squares estimator derived from the functional relationship model. The closeness of the approximation depends on the nature of the covariance structure of the intensity measurements.

scholarly journals Probing the nature of AX J0043−737: Not an 87 ms pulsar in the Small Magellanic Cloud

2018 ◽  
Vol 612 ◽  
pp. A87 ◽  
Author(s):  
C. Maitra ◽  
J. Ballet ◽  
P. Esposito ◽  
F. Haberl ◽  
A. Tiengo ◽  
...  
Keyword(s):  
Active Galactic Nucleus ◽  
Magellanic Cloud ◽  
Field Of View ◽  
Common Phenomenon ◽  
Small Magellanic Cloud ◽  
X Ray ◽  
Photon Index ◽  
Absorbed Power

Aims. AX J0043−737 is a source in the ASCA catalogue whose nature is uncertain. It is most commonly classified as a Crab-like pulsar in the Small Magellanic Cloud (SMC) following apparent detection of pulsations at ~87 ms from a single ASCA observation. A follow-up ASCA observation was not able to confirm this, and the X-ray detection of the source has not been reported since. Methods. We studied the nature of the source with a dedicated XMM-Newton observation. We ascertained the source position, searched for the most probable counterpart, and studied the X-ray spectrum. We also analysed other archival observations with the source in the field of view to study its long-term variability. Results. With the good position localisation capability of XMM-Newton, we identify the counterpart of the source as MQS J004241.66–734041.3, an active galactic nucleus (AGN) behind the SMC at a redshift of 0.95. The X-ray spectrum can be fitted with an absorbed power law with a photon-index of Γ = 1.7, which is consistent with that expected from AGNs. By comparing the current XMM-Newton observation with an archival XMM-Newton and two other ASCA observations of the source, we find signatures of long-term variability, another common phenomenon in AGNs. All of the above are consistent with AX J0043−737 being an AGN behind the SMC.

scholarly journals A new super-soft X-ray source in the Small Magellanic Cloud: Discovery of the first Be/white dwarf system in the SMC?

2012 ◽  
Vol 537 ◽  
pp. A76 ◽  
Author(s):  
R. Sturm ◽  
F. Haberl ◽  
W. Pietsch ◽  
M. J. Coe ◽  
S. Mereghetti ◽  
...  
Keyword(s):  
White Dwarf ◽  
Magellanic Cloud ◽  
Small Magellanic Cloud ◽  
X Ray
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