15 research outputs found
Revisiting Proxima with ESPRESSO
We aim to confirm the presence of Proxima b using independent measurements
obtained with the new ESPRESSO spectrograph, and refine the planetary
parameters taking advantage of its improved precision. We analysed 63
spectroscopic ESPRESSO observations of Proxima taken during 2019. We obtained
radial velocity measurements with a typical radial velocity photon noise of 26
cm/s. We ran a joint MCMC analysis on the time series of the radial velocity
and full-width half maximum of the cross-correlation function to model the
planetary and stellar signals present in the data, applying Gaussian process
regression to deal with stellar activity. We confirm the presence of Proxima b
independently in the ESPRESSO data. The ESPRESSO data on its own shows Proxima
b at a period of 11.218 0.029 days, with a minimum mass of 1.29
0.13 Me. In the combined dataset we measure a period of 11.18427 0.00070
days with a minimum mass of 1.173 0.086 Me. We find no evidence of
stellar activity as a potential cause for the 11.2 days signal. We find some
evidence for the presence of a second short-period signal, at 5.15 days with a
semi-amplitude of merely 40 cm/s. If caused by a planetary companion, it would
correspond to a minimum mass of 0.29 0.08 Me. We find that the FWHM of
the CCF can be used as a proxy for the brightness changes and that its gradient
with time can be used to successfully detrend the radial velocity data from
part of the influence of stellar activity. The activity-induced radial velocity
signal in the ESPRESSO data shows a trend in amplitude towards redder
wavelengths. Velocities measured using the red end of the spectrograph are less
affected by activity, suggesting that the stellar activity is spot-dominated.
The data collected excludes the presence of extra companions with masses above
0.6 Me at periods shorter than 50 days.Comment: 25 pages, 26 figure
A precise architecture characterization of the Men planetary system
The bright star Men was chosen as the first target for a radial
velocity follow-up to test the performance of ESPRESSO, the new high-resolution
spectrograph at the ESO's Very-Large Telescope (VLT). The star hosts a
multi-planet system (a transiting 4 M planet at 0.07 au, and a
sub-stellar companion on a 2100-day eccentric orbit) which is
particularly appealing for a precise multi-technique characterization. With the
new ESPRESSO observations, that cover a time span of 200 days, we aim to
improve the precision and accuracy of the planet parameters and search for
additional low-mass companions. We also take advantage of new photometric
transits of Men c observed by TESS over a time span that overlaps with
that of the ESPRESSO follow-up campaign. We analyse the enlarged spectroscopic
and photometric datasets and compare the results to those in the literature. We
further characterize the system by means of absolute astrometry with Hipparcos
and Gaia. We used the spectra of ESPRESSO for an independent determination of
the stellar fundamental parameters. We present a precise characterization of
the planetary system around Men. The ESPRESSO radial velocities alone
(with typical uncertainty of 10 cm/s) allow for a precise retrieval of the
Doppler signal induced by Men c. The residuals show an RMS of 1.2 m/s,
and we can exclude companions with a minimum mass less than 2 M
within the orbit of Men c). We improve the ephemeris of Men c using
18 additional TESS transits, and in combination with the astrometric
measurements, we determine the inclination of the orbital plane of Men b
with high precision ( deg). This leads to the precise
measurement of its absolute mass M, and
shows that the planetary orbital planes are highly misaligned.Comment: Accepted for publication on A&
ESPRESSO@VLT -- On-sky performance and first results
ESPRESSO is the new high-resolution spectrograph of ESO's Very-Large
Telescope (VLT). It was designed for ultra-high radial-velocity precision and
extreme spectral fidelity with the aim of performing exoplanet research and
fundamental astrophysical experiments with unprecedented precision and
accuracy. It is able to observe with any of the four Unit Telescopes (UT) of
the VLT at a spectral resolving power of 140,000 or 190,000 over the 378.2 to
788.7 nm wavelength range, or with all UTs together, turning the VLT into a
16-m diameter equivalent telescope in terms of collecting area, while still
providing a resolving power of 70,000. We provide a general description of the
ESPRESSO instrument, report on the actual on-sky performance, and present our
Guaranteed-Time Observation (GTO) program with its first results. ESPRESSO was
installed on the Paranal Observatory in fall 2017. Commissioning (on-sky
testing) was conducted between December 2017 and September 2018. The instrument
saw its official start of operations on October 1st, 2018, but improvements to
the instrument and re-commissioning runs were conducted until July 2019. The
measured overall optical throughput of ESPRESSO at 550 nm and a seeing of 0.65
arcsec exceeds the 10% mark under nominal astro-climatic conditions. We
demonstrate a radial-velocity precision of better than 25 cm/s during one night
and 50 cm/s over several months. These values being limited by photon noise and
stellar jitter show that the performanceis compatible with an instrumental
precision of 10 cm/s. No difference has been measured across the UTs neither in
throughput nor RV precision. The combination of the large collecting telescope
area with the efficiency and the exquisite spectral fidelity of ESPRESSO opens
a new parameter space in RV measurements, the study of planetary atmospheres,
fundamental constants, stellar characterisation and many other fields.Comment: 26 pages, 28 figure
ESPRESSO at VLT. On-sky performance and first results
Context. ESPRESSO is the new high-resolution spectrograph of ESO's Very Large Telescope (VLT). It was designed for ultra-high radial-velocity (RV) precision and extreme spectral fidelity with the aim of performing exoplanet research and fundamental astrophysical experiments with unprecedented precision and accuracy. It is able to observe with any of the four Unit Telescopes (UTs) of the VLT at a spectral resolving power of 140 000 or 190 000 over the 378.2 to 788.7 nm wavelength range; it can also observe with all four UTs together, turning the VLT into a 16 m diameter equivalent telescope in terms of collecting area while still providing a resolving power of 70 000. Aims: We provide a general description of the ESPRESSO instrument, report on its on-sky performance, and present our Guaranteed Time Observation (GTO) program along with its first results. Methods: ESPRESSO was installed on the Paranal Observatory in fall 2017. Commissioning (on-sky testing) was conducted between December 2017 and September 2018. The instrument saw its official start of operations on October 1, 2018, but improvements to the instrument and recommissioning runs were conducted until July 2019. Results: The measured overall optical throughput of ESPRESSO at 550 nm and a seeing of 0.65″ exceeds the 10% mark under nominal astroclimatic conditions. We demonstrate an RV precision of better than 25 cm s-1 during a single night and 50 cm s-1 over several months. These values being limited by photon noise and stellar jitter shows that the performance is compatible with an instrumental precision of 10 cm s-1. No difference has been measured across the UTs, neither in throughput nor RV precision. Conclusions: The combination of the large collecting telescope area with the efficiency and the exquisite spectral fidelity of ESPRESSO opens a new parameter space in RV measurements, the study of planetary atmospheres, fundamental constants, stellar characterization, and many other fields. Based on GTOs collected at the European Southern Observatory under ESO program(s) 1102.C-0744, 1102.C-0958 and 1104.C-0350 by the ESPRESSO Consortium