This page presents examples of spectra collected with ESPaDOnS, either on the sky or during
Zeeman signatures of magnetic stars
ESPaDOnS was designed to be very efficient at detecting Zeeman signatures
induced by stellar magnetic fields (see science drivers).
These signatures mostly show up as circular and linear polarisation features
in line profiles. The figures below present such signatures in the particular case
of the chemically peculiar star β CrB, both in circular polarisation (Stokes V,
expanded by 5 and shown in red) and linear polarisation (Stokes Q and U, expanded by
10 and shown in red and blue respectively), within two selected wavelength domain.
The following two plots show the same information
in the case of another chemically peculiar star 78 Vir. Note in particular that
no linear polarisation signatures are detected in conjunction of the 614.9 FeII line
(despite the strong circular polarisation signatures that are present), as expected
if there is no crosstalk between polarisation states within the instrument. Click
on either plots to enlarge. Note that these
Stokes spectra are not produced with the cross-correlation type tool 'Least-Squares
Deconvolution' (LSD), conversely to what the plot titles say.
The last plot on the right provides an example of Zeeman signatures in a cool
active star, the giant primary star of the RS CVn system II Peg. Zeeman signatures
are now computed using the cross-correlation tool Least-Squares Deconvolution
(linear polarisation Zeeman signatures in the spectrum of cool stars are far
too small to be detected in individual spectral lines). Note that Zeeman signatures
are now expanded by factors of as much as 20 (for Stokes V) and 200 (for Stokes Q
These plots demonstrate very clearly that ESPaDOnS is very efficient at detecting
Zeeman signatures (in both circular and linear polarisation) in line profiles.
More on the interpretation and modelling of these signatures can be found in
the page presenting the most recent results obtained with
Solar spectrum, Balmer lines
The full optical spectrum of the Sun was also recorded and processed with Libre-ESpRIT,
to demonstrate that the spectroscopic properties of ESPaDOnS are nominal.
A few portions of the reduced solar spectrum are presented below, starting with Balmer
lines. Among the first five of the series (from Halpha to Hepsilon) present in the
ESPaDOnS spectra, only the first two are included here for illustration purposes:
Solar spectrum @ Halpha
Solar spectrum @ Hbeta
Note that in both cases, the lines appear in the overlap regions of two consecutive
orders. Rather than being concatenated, the orders are displayed on top of each other
(the straight crossing segment being due to the plotting routines going back to the
first wavelength of the following order). This illustrates in particular how well the two
consecutive orders match throughout their overlap region, both in intensity and wavelength.
Solar spectrum, selected regions
Here, we show two close-up views of selected line profiles in the solar spectrum:
the first graph shows a
spectrum portion very well known to solar physicists working on solar magnetism,
including 2 close-by FeI lines with different magnetic sensitivities. ESPaDOnS
observations (full line) are found to match perfectly with the reference Kitt Peak
solar spectrum (dotted line) once the latter is broadened to a spectral resolution of
69,000 (dashed line). Only the two time variable telluric lines (@ 630.20 and 630.28nm) show
(as expected) a significant difference with respect to the Kitt Peak spectrum;
the second graph shows
a spectrum region in the near infrared (@ 760nm) heavily crowded with strong telluric bands
having null core relative intensities; one can notice from this data that diffused light
within the spectrograph is small and well corrected out by the reduction routines.