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One of the largest uncertainties in the Point Source (PS) studies, at Fermi-LAT energies, is the uncertainty in the diffuse background. In general there are two approaches for PS analysis: background-dependent methods, that include modeling of the diffuse background, and background-independent methods. In this work we study PGWave, which is one of the background-independent methods, based on wavelet filtering to find significant clusters of gamma rays. PGWave is already used in the Fermi-LAT catalog pipeline for finding candidate sources. We test PGWave, not only for source detection, but especially to estimate the flux without the need of a background model. We use Monte Carlo (MC) simulation to study the accuracy of PS detection and estimation of the flux. We present preliminary results of these MC studies.
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Context: The eROSITA X-ray telescope onboard the Spectrum-Roentgen-Gamma (SRG) satellite has started to observe new X-ray sources over the full sky at an unprecedented rate. Understanding the selection function of the source detection is important to the subsequent scientific analysis of the eROSITA catalogs. Aims: Through simulations, we test and optimize the eROSITA source detection procedures, and characterize the detected catalog quantitatively. Methods: Taking the eROSITA Final Equatorial-Depth Survey (eFEDS) as an example, we run extensive photon event simulations using our best knowledge of the instrument characteristics, the background spectrum, and the population of astronomical X-ray sources. We analyze the source detection results based on the origin of each photon. Results. The source detection procedure is optimized according to the source detection efficiency. We choose a two-pronged strategy to build the eFEDS X-ray catalogs, creating a main catalog using only the most sensitive band (0.2-2.3 keV) and an independent hard-band selected catalog using multi-band detection in a range up to 5 keV. From the mock catalogs (available with this paper), we measure the catalog completeness and purity, which can be used in both choosing the sample selection thresholds and in further studies of AGN and cluster demography.
We present the 2SXPS (Swift-XRT Point Source) catalog, containing 206,335 point sources detected by the Swift X-ray Telescope (XRT) in the 0.3--10 keV energy range. This catalog represents a significant improvement over 1SXPS, with double the sky coverage (now 3,790 deg$^2$), and several significant developments in source detection and classification. In particular, we present for the first time techniques to model the effect of stray light -- significantly reducing the number of spurious sources detected. These techniques will be very important for future, large effective area X-ray mission such as the forthcoming Athena X-ray observatory. We also present a new model of the XRT point spread function, and a method for correctly localising and characterising piled up sources. We provide light curves -- in four energy bands, two hardness ratios and two binning timescales -- for every source, and from these deduce that over 80,000 of the sources in 2SXPS are variable in at least one band or hardness ratio. The catalog data can be queried or downloaded via a bespoke web interface at https://www.swift.ac.uk/2SXPS, via HEASARC, or in Vizier (IX/58).
We have obtained a deep 8-field XMM-Newton mosaic of M33 covering the galaxy out to the D$_{25}$ isophote and beyond to a limiting 0.2--4.5 keV unabsorbed flux of 5$times$10$^{-16}$ erg cm$^{-2}$ s$^{-1}$ (L${>}$4$times$10$^{34}$ erg s$^{-1}$ at the distance of M33). These data allow complete coverage of the galaxy with high sensitivity to soft sources such as diffuse hot gas and supernova remnants. Here we describe the methods we used to identify and characterize 1296 point sources in the 8 fields. We compare our resulting source catalog to the literature, note variable sources, construct hardness ratios, classify soft sources, analyze the source density profile, and measure the X-ray luminosity function. As a result of the large effective area of XMM-Newton below 1 keV, the survey contains many new soft X-ray sources. The radial source density profile and X-ray luminosity function for the sources suggests that only $sim$15% of the 391 bright sources with L${>}$3.6$times$10$^{35}$ erg s$^{-1}$ are likely to be associated with M33, and more than a third of these are known supernova remnants. The log(N)--log(S) distribution, when corrected for background contamination, is a relatively flat power-law with a differential index of 1.5, which suggests many of the other M33 sources may be high-mass X-ray binaries. Finally, we note the discovery of an interesting new transient X-ray source, which we are unable to classify.
This paper provides an overview of the PACS photometer flux calibration concept, in particular for the principal observation mode, the scan map. The absolute flux calibration is tied to the photospheric models of five fiducial stellar standards (alpha Boo, alpha Cet, alpha Tau, beta And, gamma Dra). The data processing steps to arrive at a consistent and homogeneous calibration are outlined. In the current state the relative photometric accuracy is around 2% in all bands. Starting from the present calibration status, the characterization and correction for instrumental effects affecting the relative calibration accuracy is described and an outlook for the final achievable calibration numbers is given. After including all the correction for the instrumental effects, the relative photometric calibration accuracy (repeatability) will be as good as 0.5% in the blue and green band and 2% in the red band. This excellent calibration starts to reveal possible inconsistencies between the models of the K-type and the M-type stellar calibrators. The absolute calibration accuracy is therefore mainly limited by the 5% uncertainty of the celestial standard models in all three bands. The PACS bolometer response was extremely stable over the entire Herschel mission and a single, time-independent response calibration file is sufficient for the processing and calibration of the science observations. The dedicated measurements of the internal calibration sources were needed only to characterize secondary effects. No aging effects of the bolometer or the filters have been found. Also, we found no signs of filter leaks. The PACS photometric system is very well characterized with a constant energy spectrum nu*Fnu = lambda*Flambda = const as a reference. Colour corrections for a wide range of sources SEDs are determined and tabulated.
The PAMELA satellite-borne experiment is providing first direct measurements of Solar Energetic Particles (SEPs) with energies from $sim$80 MeV to several GeV in near-Earth space. Its unique observational capabilities include the possibility of measuring the flux angular distribution and thus investigating possible anisotropies related to SEP events. This paper focuses on the analysis methods developed to estimate SEP energy spectra as a function of the particle pitch angle with respect to the Interplanetary Magnetic Field (IMF). The crucial ingredient is provided by an accurate simulation of the asymptotic exposition of the PAMELA apparatus, based on a realistic reconstruction of particle trajectories in the Earths magnetosphere. As case study, the results of the calculation for the May 17, 2012 event are reported.
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