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 Fermi Large Area Telescope (LAT) has made the first definitive GeVdetections of the binaries LS I +61^{\circ}303 and LS5039 in the first yearafter its launch in August 2008. These detections were unambiguous because,apart from a reduced positional uncertainty, the gamma-ray emission in eachcase was orbitally modulated with the corresponding orbital period. The LATresults posed new questions about the nature of these objects, after theunexpected observation of an exponential cutoff in the GeV gamma-ray spectra ofboth LS I +61^{\circ}303 and LS5039, at least along part of their orbitalmotion. We present here the analysis of new data from the LAT, comprising 2.5years of observations through which LS I +61^{\circ}303 continues to providesome surprises. We find an increase in flux in March 2009 and a steady decreasein the flux fraction modulation. The LAT now detects emission up to 30 GeV,where prior datasets led to upper limits only. At the same time,contemporaneous TeV observations either no longer detected the source, or foundit -at least in some orbits- close to periastron, far from the usual phases inwhich the source usually appeared at TeV energies. The on-source exposure of LS5039 has also drastically increased along the last years, and whilst ouranalysis shows no new behavior in comparison with our earlier report, thehigher statistics of the current dataset allows for a deeper investigation ofits orbital and spectral evolution.

Results from the binaries LS I +61{\deg}303 and LS 5039 after 2.5 years of Fermi monitoring