Two UV serendipitous source catalogues are presented which were compiled based on the observations with two similar UV telescopes, one being on-board the ESA’s XMM Newton observatory and ...another—on-board the NASA’s Swift satellite. Both telescopes have similar optical and registration systems providing photometry in three ultraviolet and three visible bands. After processing a 10 years long series of observations from XMM and 5 years from Swift, we have compiled two source catalogues containing more than 4 million sources for XMM and 6 million sources for Swift. We describe the processing algorithms and present catalogue characteristics in comparison with each other.
Abstract
The XMM-Newton Serendipitous Ultraviolet Source Survey (XMM-SUSS) is a catalogue of ultraviolet (UV) sources detected serendipitously by the Optical Monitor (XMM-OM) on board the XMM-Newton ...observatory. The catalogue contains UV-detected sources collected from 2417 XMM-OM observations in one to six broad-band UV and optical filters, made between 2000 February 24 and 2007 March 29. The primary contents of the catalogue are source positions, magnitudes and fluxes in one to six passbands, and these are accompanied by profile diagnostics and variability statistics. XMM-SUSS is populated by 753 578 UV source detections above a 3σ signal-to-noise ratio threshold limit which relate to 624 049 unique objects. Taking account of substantial overlaps between observations, the net sky area covered is 29-54 deg2, depending on UV filter. The magnitude distributions peak at m
AB = 20.2, 20.9 and 21.2 in UVW2 (λeff = 2120 Å), UVM2 (λeff = 2310 Å) and UVW1 (λeff = 2910 Å), respectively. More than 10 per cent of the sources have been visited more than once using the same filter during XMM-Newton operation, and >20 per cent of sources are observed more than once per filter during an individual visit. Consequently, the scope for science based on temporal source variability on time-scales of hours to years is broad. By comparison with other astrophysical catalogues we test the accuracy of the source measurements and define the nature of the serendipitous UV XMM-OM source sample. The distributions of source colours in the UV and optical filters are shown together with the expected loci of stars and galaxies, and indicate that sources which are detected in multiple UV bands are predominantly star-forming galaxies and stars of type G or earlier.
ABSTRACT
It is possible to reduce the discrepancy between the local measurement of the cosmological parameter H0 and the value derived from the Planck measurements of the cosmic microwave background ...(CMB) by considering contamination of the CMB by emission from some medium around distant extragalactic sources, such as extremely cold coarse-grain dust. Though being distant, such a medium would still be in the foreground with respect to the CMB, and, as any other foreground, it would alter the CMB power spectrum. This could contribute to the dispersion of CMB temperature fluctuations. By generating a few random samples of CMB with different dispersions, we have checked that the increased dispersion leads to a smaller estimated value of H0, the rest of the cosmological model parameters remaining fixed. This might explain the reduced value of the Planck-derived parameter H0 with respect to the local measurements. The signature of the distant foreground in the CMB traced by supernovae (SNe) was previously reported by the authors of this paper – we found a correlation between the SN redshifts, zSN, and CMB temperature fluctuations at the SNe locations, TSN. Here we have used the slopes of the regression lines $T_{\rm SN}\, /\, z_{\rm SN}$ corresponding to different Planck wavebands in order to estimate the possible temperature of the distant extragalactic medium, which turns out to be very low, about 5 K. The most likely ingredient of this medium is coarse-grain (grey) dust, which is known to be almost undetectable, except for the effect of dimming remote extragalactic sources.
We present the calibration of the Swift Ultraviolet and Optical Telescope (UVOT ) grisms, of which there are two, providing low-resolution field spectroscopy in the ultraviolet and optical bands, ...respectively. The UV grism covers the range λ1700–5000 Å with a spectral resolution (λ/Δλ) of 75 at λ2600 Å for source magnitudes of u=10–16 mag, while the visible grism covers the range λ2850–6600 Å with a spectral resolution of 100 at λ4000 Å for source magnitudes of b=12–17 mag. This calibration extends over all detector positions, for all modes used during operations. The wavelength accuracy (1σ) is 9 Å in the UV grism clocked mode, 17 Å in the UV grism nominal mode and 22 Å in the visible grism. The range below λ2740 Å in the UV grism and λ5200 Å in the visible grism never suffers from overlapping by higher spectral orders. The flux calibration of the grisms includes a correction we developed for coincidence loss in the detector. The error in the coincidence loss correction is less than 20 per cent. The position of the spectrum on the detector only affects the effective area (sensitivity) by a few per cent in the nominal modes, but varies substantially in the clocked modes. The error in the effective area is from 9 per cent in the UV grism clocked mode to 15 per cent in the visible grism clocked mode.
By using the Planck map of the cosmic microwave background (CMB) radiation, we have checked and confirmed the existence of a correlation between supernova (SN) redshifts, z
SN, and CMB temperature ...fluctuations at the SNe locations, T
SN, which we previously reported for the Wilkinson Microwave Anisotropy Probe data. The Pearson correlation coefficient for the Planck data is r = +0.38 ± 0.08, which indicates that the correlation is statistically significant (the signal is about 5σ above the noise level). The correlation becomes even stronger for the Type Ia subsample of SNe, r
Ia = +0.45 ± 0.09, whereas for the rest of the SNe it is vanishing. By checking the slopes of the regression lines T
SN/z
SN for Planck's different frequency bands, we have also excluded the possibility of this anomaly being caused by the Sunyaev–Zeldovich effect. The remaining possibility is some, unaccounted for, contribution to the CMB from distant (z > 0.3) foreground through either the integrated Sachs–Wolfe effect or thermal emission from intergalactic matter.
The Ultraviolet/Optical Telescope (UVOT) is one of three instruments onboard the Swift observatory. The photometric calibration has been published, and this paper follows up with details on other ...aspects of the calibration including a measurement of the point spread function with an assessment of the orbital variation and the effect on photometry. A correction for large-scale variations in sensitivity over the field of view is described, as well as a model of the coincidence loss which is used to assess the coincidence correction in extended regions. We have provided a correction for the detector distortion and measured the resulting internal astrometric accuracy of the UVOT, also giving the absolute accuracy with respect to the International Celestial Reference System. We have compiled statistics on the background count rates, and discuss the sources of the background, including instrumental scattered light. In each case, we describe any impact on UVOT measurements, whether any correction is applied in the standard pipeline data processing or whether further steps are recommended.
We report here on the outburst onset and evolution of the new soft gamma-ray repeater SGR 0501+4516. We monitored the new SGR with XMM–Newton starting on 2008 August 23, 1 day after the source became ...burst active, and continuing with four more observations in the following month, with the last one on 2008 September 30. Combining the data with the Swift X-ray telescope (Swift–XRT) and Suzaku data, we modelled the outburst decay over a 3-month period, and we found that the source flux decreased exponentially with a time-scale of tc= 23.8 d. In the first XMM–Newton observation, a large number of short X-ray bursts were observed, the rate of which decayed drastically in the following observations. We found large changes in the spectral and timing behaviour of the source during the first month of the outburst decay, with softening emission as the flux decayed, and the non-thermal soft X-ray spectral component fading faster than the thermal one. Almost simultaneously to our second and fourth XMM–Newton observations (on 2008 August 29 and September 2), we observed the source in the hard X-ray range with INTEGRAL, which clearly detected the source up to ∼100 keV in the first pointing, while giving only upper limits during the second pointing, discovering a variable hard X-ray component fading in less than 10 days after the bursting activation. We performed a phase-coherent X-ray timing analysis over about 160 days starting with the burst activation and found evidence of a strong second derivative period component . Thanks to the phase connection, we were able to study the phase-resolved spectral evolution of SGR 0501+4516 in great detail. We also report on the ROSAT quiescent source data, taken back in 1992 when the source exhibits a flux ∼80 times lower than that measured during the outburst, and a rather soft, thermal spectrum.
Redshifts of supernova (SN) and gamma-ray burst (GRB) samples are compared with the pixel temperatures of the Wilkinson Microwave Anisotropy Probe (WMAP) seven-year data, the pixel locations ...corresponding to the SN and GRB sky coordinates. We have found a statistically significant correlation of the SN redshifts with the WMAP data, the average temperature deviation being
for redshifts z ranging from 0.5 to 1.0 and
for z∈ (0.0, 0.4). The latter value accords with the theoretical estimates for the distortion of the cosmic microwave background due to the integrated Sachs-Wolfe effect, whereas the larger anomaly for higher redshifts should be studied in more detail in the future.
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