J/A+A/639/A77 Proxima Cen RV, FWHM and fluxes (Suarez Mascareno+, 2020)
Revisiting Proxima with ESPRESSO.
Suarez Mascareno A., Faria J.P., Figueira P., Lovis C., Damasso M.,
Gonzalez Hernandez J.I., Rebolo R., Cristiano S., Pepe F.,Santos N.C.,
Zapatero Osorio M.R., Adibekyan V., Hojjatpanah S., Sozzetti A.,
Murgas F., Abreu M., Affolter M., Alibert Y., Aliverti M., Allart R.,
Allende Prieto C., Alves D., Amate M., Avila G., Baldini V., Bandi T.,
Barros S.C.C., Bianco A., Benz W., Bouchy F., Broeng C., Cabral A.,
Calderone G., Cirami R., Coleho J., Conconi P., Coretti I., Cumani C.,
Cupani G., D Odorico V., Deiries S., Delabre B., Di Marcantonio P.,
Dumusque X., Ehrenreich D., Fragoso A., Genolet L., Genoni M.,
Genova Santos R., Hughes I., Iwert O., Kerber F., Knusdrtrup J.,
Landoni M., Lavie B., Lillo-Box J., Lizon J., Lo Curto G., Maire C.,
Manescau A., Martins C.J.A.P., Megevand D., Mehner A., Micela G.,
Modigliani A., Molaro P., Monteiro M.A., Monteiro M.J.P.F.G.,
Moschetti M., Mueller E., Nunes N.J., Oggioni L., Oliveira A., Palle E.,
Pariani G., Pasquini L., Poretti E., Rasilla J.L., Redaelli E., Riva M.,
Santana Tschudi S., Santin P., Santos P., Segovia A., Sosnowska D.,
Sousa S., Snano P., Tenegi F., Udry S., Zanutta A., Zerbi F.
<Astron. Astrophys. 639, A77 (2020)>
=2020A&A...639A..77S 2020A&A...639A..77S (SIMBAD/NED BibCode)
ADC_Keywords: Stars, double and multiple ; Stars, dwarfs ; Exoplanets ;
Radial velocities
Keywords: techniques: radial velocity -
planets and satellites: terrestrial planets - stars: activity -
stars: low-mass - stars: individual: Proxima
Abstract:
The discovery of Proxima b marked one of the most important milestones
in exoplanetary science in recent years. Yet the limited precision of
the available radial velocity data and the difficulty in modelling the
stellar activity calls for a confirmation of the Earth-mass planet. We
aimed 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 (Gl 551)
taken during 2019. We obtained radial velocity measurements with a
typical radial velocity photon noise of 26cm/s. We combined these
data with archival spectroscopic observations and newly obtained
photometric measurements to model the stellar activity signals and
disentangle them from planetary signals in the radial velocity (RV)
data. We ran a joint Markov chain Monte Carlo analysis on the time
series of the RV 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 the stellar
activity signals. We confirm the presence of Proxima b independently
in the ESPRESSO data and in the combined ESPRESSO+HARPS+UVES dataset.
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±0.13Me. In the
combined dataset we measure a period of 11.18427±0.00070 days with a
minimum mass of 1.173±0.086Me. We get a clear measurement of the
stellar rotation period (87±12d) and its induced RV signal, but 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 only
40cm/s. If caused by a planetary companion, it would correspond to a
minimum mass of 0.29±0.08Me. We find that for the case of Proxima,
the full width half maximum of the cross-correlation function can be
used as a proxy for the brightness changes and that its gradient with
time can be used to successfully detrend the RV data from part of the
influence of stellar activity. The activity-induced RV 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. This could be used to create differential RVs that are
activity dominated and can be used to disentangle activity-induced and
planetary-induced signals. The data collected excludes the presence of
extra companions with masses above 0.6Me at periods shorter than
50-days.
Description:
We obtained 67 individual spectra as part of the ESPRESSO GTO, as part
of programme ID 1102.C-744 (PI: F.Pepe). Measurements were taken in
ESPRESSO's 1UT high resolution (HR) mode with 15 minutes of
integration time. More information on the different observing modes
can be found on the ESO instrument page. ESPRESSO is equipped with its
own pipeline providing extracted and wavelength-calibrated spectra, as
well as RV measurements. The RV measurements are determined by a
Gaussian fit of the cross-correlation function (CCF) of the spectrum
with a binary mask computed from a stellar template. The mask was
created using an ESPRESSO spectrum of Proxima as a template. Lines
were identified through an automatic line-searching algorithm based on
the spectrum derivative. The pipeline, version 2.0.0, is fully
available to download from the ESO pipeline website.
In combination with the ESPRESSO data we include the measurements
taken between 2003 and 2017 with the High Accuracy Radial velocity
Planet Searcher (HARPS) spectrograph. These data where obtained by the
Geneva/Grenoble survey and the RedDots project, under programmes
072.C-0488, 082.C-0718, 183.C-0437, 191.C-0505, 096.C-0082,
099.C-0205, and 099.C-0880. This dataset is comprised of 196
individual measurements that include two high cadence campaigns in
2016 and 2017. The RVs were calculated using the TERRA package and
have been obtained from. In 2015 HARPS was updated with new fibres,
which improved its stability but also caused an RV offset with respect
to previous measurements. For this reason we treat both HARPS datasets
independently. The majority of the data were obtained without
simultaneous calibration, which limits the stability of HARPS to a
level of 1m/s.
Along with the previous data we include the RVs taken with the
Ultraviolet and Visual Echelle Spectrograph (UVES) and analysed in
Dmasso et al. 2020. This dataset consists of 77 nightly binned UVES
RVs obtained between 2000 and 2007. The UVES data were obtained in one
of the early RV surveys for planets around M-dwarfs under ESO
programme IDs: 65.L-0428, 66.C-0446, 267.C-5700, 68.C-0415, 69.C-0722,
70.C-0044, 71.C-0498, 072.C-0495, 173.C-0606, and 078.C-0829 (PI: M.
Kuerster). The data reduction and RV measurement is described in
Butler et al., 2019AJ....158..251B 2019AJ....158..251B. Cat. J/AJ/158/251). The UVES data
do not include a measurement of the FWHM, as it is not easily
available due to calibration by the iodine gas absorption cell.
Objects:
--------------------------------------------
RA (2000) DE Designation(s)
--------------------------------------------
14 29 42.95 -62 40 46.2 Proxima = Gl 551
--------------------------------------------
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
tablea1.dat 28 334 Radial velocity data
tablea2.dat 29 257 FWHM data
tablea3.dat 39 297 LCO Photometry
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See also:
J/A+A/534/A133 : Proxima Cen chromospheric emission lines (Fuhrmeister+, 2011)
J/A+A/603/A58 : Full spectrum of Proxima Centauri (Ribas+, 2017)
J/AJ/153/93 : MOST photometry of Proxima (Kipping+, 2017)
J/AJ/155/12 : Proxima Centauri photometry observed by BSST (Liu+, 2018)
J/AJ/157/226 : Proxima Centauri photometry from 2006 to 2017 (Feliz+, 2019)
J/A+A/626/A111 : Proxima Cen flare activity temporal changes (Pavlenko+, 2019)
J/AJ/158/251 : New reduction of UVES data for 35 M dwarfs (Butler+, 2019)
Byte-by-byte Description of file: tablea1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
3- 10 F8.3 d BJD Barycentric Julian date (BJD-2450000)
13- 17 F5.2 m/s DRV Relative radial velocity
21- 24 F4.2 m/s e_DRV Relative radial velocity uncertainty
28 I1 --- Spec [0/4] Spectrograph (1)
--------------------------------------------------------------------------------
Note (1): Spectrograph as follows:
0 = UVES
1 = HARPS pre-upgrade
2 = HARPS post-upgrade
3 = ESPRESSO pre-upgrade
4 = ESPRESSO post-upgrade
--------------------------------------------------------------------------------
Byte-by-byte Description of file: tablea2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
3- 10 F8.3 d BJD Barycentric Julian date (BJD-2450000)
13- 18 F6.2 m/s DFWHM Relative FWHM
22- 25 F4.2 m/s e_DFWHM Relative FWHM uncertainty
29 I1 --- Spec [1/4] Spectrograph (1)
--------------------------------------------------------------------------------
Note (1): Spectrograph as follows:
1 = HARPS pre-upgrade
2 = HARPS post-upgrade
3 = ESPRESSO pre-upgrade
4 = ESPRESSO post-upgrade
--------------------------------------------------------------------------------
Byte-by-byte Description of file: tablea3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
3- 10 F8.3 d BJD Barycentric Julian date (BJD-2450000)
15- 21 F7.5 --- Flux Relative Flux
26- 32 F7.5 --- e_Flux Flux uncertainty
39 I1 --- Series [1/3] Data series (1)
--------------------------------------------------------------------------------
Note (1): Data series as follows:
1 = RedDots
2 = LCO 1-m data
3 = LCO 40-cm data
--------------------------------------------------------------------------------
Acknowledgements:
Alejandro Suarez Mascareno, asm(at)iac.es
(End) Patricia Vannier [CDS] 26-May-2020