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

Recent improvements on the sensitivity and spectral resolution of X-rayobservations have led to a better understanding of the properties of matter inthe vicinity of High Mass X-ray Binaries hosting a supergiant star and acompact object. However the geometry and physical properties of theirenvironment at larger scales are currently only predicted by simulations. Weaim at exploring the environment of Vela X-1 at a few stellar radii of thesupergiant using spatially resolved observations in the near-infrared and atstudying its dynamical evolution along the 9-day orbital period of the system.We observed Vela X-1 in 2010 and 2012 using long baseline interferometry atVLTI, respectively with the AMBER instrument in the K band and the PIONIERinstrument in the H band. The PIONIER observations span through one orbitalperiod to monitor possible evolutions in the geometry of the system. Weresolved a structure of $8\pm3~R_\star$ from the AMBER data and$2.0\,_{-1.2}^{+0.7}~R_\star$ from the PIONIER data. From the closure phase wefound that the environment of Vela X-1 is symmetrical. We observed comparablemeasurements between the continuum and the spectral lines in the K band,meaning that both emissions originate from the same forming region. From themonitoring of the system over one period in 2012, we found the signal to beconstant with the orbital phase within the error bars. We propose threescenarios for the discrepancy between the two measurements: either there is astrong temperature gradient in the supergiant wind leading to a hot componentmuch more compact than the cool part of the wind observed in the K band, or weobserved a diffuse shell in 2010 possibly triggered by an off-state in theaccretion rate of the pulsar that was dissolved in the interstellar medium in2012, or the structure observed in the H band was the stellar photosphereinstead of the supergiant wind.

astronomy and astrophysics

The close environment of high-mass X-ray binaries at high angular  resolution I. VLTI/AMBER and VLTI/PIONIER near-infrared interferometric  observations of Vela X-1