XMM-Newton and Swift observations of WZ Sge: spectral and timing analysis

WZ Sagittae is the prototype object of a subclass of dwarf novae, with rare and long (super)outbursts, in which a white dwarf primary accretes matter from a low mass companion. High-energy observations offer the possibility of a better understanding of the disk-accretion mechanism in WZ Sge-like binaries. We used archival XMM-Newton and Swift data to characterize the X-ray spectral and temporal properties of WZ Sge in quiescence. We performed a detailed timing analysis of the simultaneous X-ray and UV light curves obtained with the EPIC and OM instruments on board XMM-Newton in 2003. We employed several techniques in this study, including a correlation study between the two curves. We also performed an X-ray spectral analysis using the EPIC data, as well as Swift/XRT data obtained in 2011. We find that the X-ray intensity is clearly modulated at a period of about 28.96 s, confirming previously published preliminary results. We find that the X-ray spectral shape of WZ Sge remains practically unchanged between the XMM-Newton and Swift observations. However, after correcting for inter-stellar absorption, the intrinsic luminosity is estimated to be about 2.65X10^ 30 erg/s/cm^2 and 1.57X10^30 erg/s/cm^2 in 2003 and 2011, respectively. During the Swift/XRT observation, the observed flux is a factor of about 2 lower than that observed by XMM-Newton, but is similar to the quiescent levels observed various times before the 2001 outburst.Comment: Accepted for publication on A&A.10 pages, 9 figure

Affective stimulus properties influence size perception and the Ebbinghaus illusion

In the New Look literature of the 1950s, it has been suggested that size judgments are dependent on the affective content of stimuli. This suggestion, however, has been ‘discredited’ due to contradictory findings and methodological problems. In the present study, we revisited this forgotten issue in two experiments. The first experiment investigated the influence of affective content on size perception by examining judgments of the size of target circles with and without affectively loaded (i.e., positive, neutral, and negative) pictures. Circles with a picture were estimated to be smaller than circles without a picture, and circles with a negative picture were estimated to be larger than circles with a positive or a neutral picture confirming the suggestion from the 1950s that size perception is influenced by affective content, an effect notably confined to negatively loaded stimuli. In a second experiment, we examined whether affective content influenced the Ebbinghaus illusion. Participants judged the size of a target circle whereby target and flanker circles differed in affective loading. The results replicated the first experiment. Additionally, the Ebbinghaus illusion was shown to be weakest for a negatively loaded target with positively loaded and blank flankers. A plausible explanation for both sets of experimental findings is that negatively loaded stimuli are more attention demanding than positively loaded or neutral stimuli

Continuous-wave ultraviolet generation at 261.3 nm by intracavity frequency doubling of a laser diode pumped green emitting Pr:LiYF₄ laser

This paper report on cw UV generation by intracavity frequency doubling of a laser diode pumped Praseodymium (Pr)-doped:YLF laser operating at 523.6 nm. A lens of 50 mm focal length was used to focus the pump beam into the laser crystal. For the generation of UV radiation a beta-barium-borate (BBO)-crystal was placed in the beam waist of the cavity, located between mirrors.1 page(s

Combined treatments of modified atmosphere packaging with aminoethoxyvinylglycine maintained fruit quality in sweet cherry throughout cold storage and shelf life

The effects of combined aminoethoxyvinylglycine (AVG) and modified atmosphere packaging (MAP) treatments on quality attributes of ‘0900 Ziraat’ sweet cherry fruit during the cold storage and shelf life were investigated in this study. Significantly lower weight loss and decay ratios were observed in all treatments throughout the cold storage period as compared to the control. A similar case was also observed referring to the shelf life. MAP treatments were found to be more effective in retarding the weight loss and decay ratio. Higher hue angle values were measured from AVG-treated fruit at harvest. Similarly, hue angle of AVG and MAP-treated fruit were also higher than for the control in all periods of cold storage and on the 7th and 21st day of shelf life. AVG-treated fruit had higher firmness values than the control at harvest. However, higher firmness values were measured from MAP-treated fruit during the cold storage and shelf life. At the end of cold storage, lower SSC and higher titratable acidity values were observed in AVG and MAP-treated fruit than in the control. AVG + MAP treatments yielded significantly higher vitamin C, total phenolics and antioxidant activity values than the control. Contrarily, the control fruit had significantly higher total monomeric anthocyanin than the other treatments. Based on current findings, it was concluded that combined AVG + MAP treatments could be used as a beneficial tool to maintain the quality of sweet cherry fruit throughout the cold storage and shelf life