Abstract
KMOS (K-Band Multi Object Spectrograph) is a novel integral field
spectrograph installed in the Very Large Telescope's (VLT's) ANTU unit.
The instrument offers an ability to observe 24 2.8 arcsec × 2.8
arcsec subfields positionable within a 7.2 arcmin patrol field, each
subfield producing a spectrum with a 14 × 14-pixel spatial
resolution. The main science drivers for KMOS are the study of galaxies,
star formation, and molecular clouds, but its ability to simultaneously
measure spectra of multiple stars makes KMOS an interesting instrument
for exoplanet atmosphere characterization via transmission spectroscopy.
We set to test whether transmission spectroscopy is practical with KMOS,
and what are the conditions required to achieve the photometric
precision needed, based on observations of a partial transit of
WASP-19b, and full transits of GJ 1214b and HD 209458b. Our analysis
uses the simultaneously observed comparison stars to reduce the effects
from instrumental and atmospheric sources, and Gaussian processes to
model the residual systematics. We show that KMOS can, in theory,
deliver the photometric precision required for transmission
spectroscopy. However, this is shown to require (a) pre-imaging to
ensure accurate centring and (b) a very stable night with optimal
observing conditions (seeing ˜0.8 arcsec). Combining these two
factors with the need to observe several transits, each with a
sufficient out-of-transit baseline (and with the fact that similar or
better precision can be reached with telescopes and instruments with
smaller pressure), we conclude that transmission spectroscopy is not the
optimal science case to take advantage of the abilities offered by KMOS
and VLT.
Original language | English |
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Pages (from-to) | 3875-3885 |
Number of pages | 11 |
Journal | Monthly Notices of the Royal Astronomical Society |
Volume | 453 |
Issue number | 4 |
Early online date | 14 Sep 2015 |
DOIs | |
Publication status | Published - 11 Nov 2015 |
Externally published | Yes |
Keywords
- instrumentation: spectrographs
- techniques: photometric
- techniques: spectroscopic
- planets and satellites: atmospheres