English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

The dynamic range of photon counting micro-channel-plate (MCP) intensifiedcharged-coupled device (CCD) instruments such as the Swift Ultraviolet/OpticalTelescope (UVOT) and the XMM-Newton Optical Monitor (XMM-OM) is limited at thebright end by coincidence loss, the superposition of multiple photons in theindividual frames recorded by the CCD. Photons which arrive during the briefperiod in which the image frame is transferred for read out of the CCD aredisplaced in the transfer direction in the recorded images. For sufficientlybright sources, these displaced counts form read-out streaks. Using UVOTobservations of Tycho-2 stars, we investigate the use of these read-out streaksto obtain photometry for sources which are too bright (and hence have too muchcoincidence loss) for normal aperture photometry to be reliable. Forread-out-streak photometry, the bright-source limiting factor is coincidenceloss within the MCPs rather than the CCD. We find that photometric measurementscan be obtained for stars up to 2.4 magnitudes brighter than the usualfull-frame coincidence-loss limit by using the read-out streaks. The resultingbright-limit Vega magnitudes in the UVOT passbands are UVW2=8.80, UVM2=8.27,UVW1=8.86, u=9.76, b=10.53, v=9.31 and White=11.71; these limits areindependent of the windowing mode of the camera. We find that a photometricprecision of 0.1 mag can be achieved through read-out streak measurements. Asuitable method for the measurement of read-out streaks is described and allnecessary calibration factors are given.

The use and calibration of read-out streaks to increase the dynamic range of the Swift Ultraviolet/Optical Telescope