3 research outputs found
EI Eridani: a star under the influence -- The effect of magnetic activity in the short and long term
We use our photometric time series of more than forty years to analyze the
long-term behaviour of EI Eri. Flare activity is investigated using space-borne
photometric data obtained with TESS. The MUSICOS campaign aimed to achieve
high-resolution spectroscopic observations from many sites around the globe, so
that uninterrupted phase coverage of EI Eri became available. We use these data
to reconstruct successive surface temperature maps of the star in order to
study the changes of starspots on a very short timescale.
We use long-term, seasonal period analysis of our photometric time series to
study changes in the rotational period. Short-term Fourier-transform is also
applied to look for activity cycle-like changes. We also study the phase and
frequency distribution of hand-selected flares. We apply our multi-line Doppler
imaging code to reconstruct four consecutive Doppler images. These images are
also used to measure surface differential rotation by our cross-correlation
technique. In addition, we carry out tests to demonstrate how Doppler imaging
is affected by the fact that the data came from several different instruments
with different spectral resolutions.
Seasonal period analysis of the light curve reveals a smooth, significant
change in period, possibly indicating the evolution of active latitudes.
Temperature curves from and show slight differences, indicating the
activity of EI Eri is spot dominated. Short-term Fourier transform reveals
smoothly changing cycles between 4.5--5.5 and 8.9--11.6 years. The
time-resolved spotted surface of EI Eri from Doppler imaging enabled us to
follow the evolution of the different surface features. Cross-correlating the
consecutive Doppler maps reveal surface shear of . Our
tests validate our approach and show that the surface temperature distribution
is adequately reconstructed by our method.Comment: 14 pages, 13 figures, A&A accepte
The cycle of metals in the infalling elliptical galaxy NGC 1404
High Energy AstrophysicsGalaxie
The cycle of metals in the infalling elliptical galaxy NGC 1404
Hot atmospheres pervading galaxy clusters, groups, and early-type galaxies
are rich in metals, produced during epochs and diffused via processes that are
still to be determined. While this enrichment has been routinely investigated
in clusters, metals in lower mass systems are more challenging to probe with
standard X-ray exposures and spectroscopy. In this paper, we focus on very deep
XMM-Newton (350 ks) observations of NGC 1404, a massive elliptical galaxy
experiencing ram-pressure stripping of its hot atmosphere while infalling
toward the centre of the Fornax cluster, with the aim to derive abundances
through its hot gas extent. Importantly, we report the existence of a new
fitting bias - the "double Fe bias" - leading to an underestimate of the Fe
abundance when two thermal components cannot realistically model the complex
temperature structure present in the outer atmosphere of the galaxy.
Contrasting with the ''metal conundrum'' seen in clusters, the Fe and Mg masses
of NGC 1404 are measured 1-2 orders of magnitude below what stars and
supernovae could have reasonably produced and released. In addition, we note
the remarkable Solar abundance ratios of the galaxy's halo, different from its
stellar counterpart but similar to the chemical composition of the ICM of rich
clusters. Completing the clusters regime, all these findings provide additional
support toward a scenario of early enrichment, at play over two orders of
magnitude in mass. A few peculiar and intriguing features, such as a possible
double metal peak as well as an apparent ring of enhanced Si near the galaxy
core, are also discussed.Comment: 20 pages, 14 figures, accepted for publication in MNRA