摘要：Context. Extended circumstellar emission has been detected within a few
100 milli-arcsec around ≳10%
of nearby main sequence stars using near-infrared interferometry. Follow-up observations
using other techniques, should they yield similar results or non-detections, can provide
strong constraints on the origin of the emission. They can also reveal the variability of
the phenomenon.
Aims. We aim to demonstrate the persistence of the phenomenon over the
timescale of a few years and to search for variability of our previously detected
excesses.
Methods. Using Very Large Telescope Interferometer (VLTI)/Precision
Integrated Optics Near Infrared ExpeRiment (PIONIER) in H band we have carried out
multi-epoch observations of the stars for which a near-infrared excess was previously
detected using the same observation technique and instrument. The detection rates and
distribution of the excesses from our original survey and the follow-up observations are
compared statistically. A search for variability of the excesses in our time series is
carried out based on the level of the broadband excesses.
Results. In 12 of 16 follow-up observations, an excess is re-detected
with a significance of >
2σ, and in 7 of 16 follow-up observations significant
excess (>
3σ) is re-detected. We statistically demonstrate with
very high confidence that the phenomenon persists for the majority of the systems. We also
present the first detection of potential variability in two sources.
Conclusions. We conclude that the phenomenon responsible for the
excesses persists over the timescale of a few years for the majority of the systems.
However, we also find that variability intrinsic to a target can cause it to have no
significant excess at the time of a specific observation.
