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

We report on the first detection of hard X-ray photons (E>2.5 keV) in theX-ray transient Narrow-Line Seyfert 1 galaxy WPVS 007 which was the AGN withthe softest X-ray spectrum during the ROSAT All-Sky Survey. The AGN is clearlydetected at a level of about 2 x 10^{-17} W m^{-2} in the observed 0.3-10.0 keVband by Swift in a 50 ks observation in 2007 September. For the first timesince the ROSAT All-Sky Survey observation in 1990 it was possible to derive anX-ray photon distribution by adding together all Swift observations that havebeen performed so far (85.5 ks in total). This photon distribution isconsistent with an X-ray spectrum of an AGN with a partial covering absorberwith a column density in the order of ~ 1 x 10^{23} cm^{-2} and a coveringfraction of about 90%. A comparison with the 2002 Chandra data suggests thatWPVS 007 has become brighter by a factor of about 4. The Swift data alsosuggest that the absorber which is causing the current low-state may havestarted to disappear. This disappearance is indicated by a significant changein the hardness ratio from a very soft X-ray state during the 2005 October to2007 January observations to a rather hard X-ray state in the 2007 Septemberobservations. In the UV, WPVS 007 seems to become fainter by up to 0.5 mag overthe last two years. The optical to X-ray spectral slope derived from thespectral energy distribution is alpha-ox=2.5 which classifies WPVS 007 as anX-ray weak AGN. After correcting for reddening and X-ray absorption, alpha-oxbecomes 1.9 and the luminosity in the Big-Blue-Bump is log LBBB=37.7 [W], whichtranslates into an Eddington ratio  L/LEdd ~ 1.0.

the astronomical journal

First detection of hard X-ray photons in the soft X-ray transient  Narrow-Line Seyfert 1 galaxy WPVS 007: The X-ray photon distribution observed  by Swift