J/A+A/706/A349 XMM X-ray spectra of Proxima Centauri (Damonte+, 2026)
Time-resolved X-ray spectra of Proxima Centauri as seen by XMM-Newton.
Damonte A., Pillitteri I., Maggio A., Garcia Munoz A., Micela G.
<Astron. Astrophys. 706, A349 (2026)>
=2026A&A...706A.349D 2026A&A...706A.349D (SIMBAD/NED BibCode)
ADC_Keywords: Stars, nearby ; X-ray sources ; Spectroscopy
Keywords: planets and satellites: atmospheres - stars: activity - stars: flare -
stars: late-type - stars: low-mass - planetary systems
Abstract:
Stellar soft X-ray ([1, 100]Å) and Extreme Ultraviolet (also EUV,
[100, 920]Å; jointly, XUV) radiation affects the evolution and
chemistry of exoplanet atmospheres. It is however uncertain to what
extent the radiation's short-term variability contributes to these
effects. The answer might indeed depend on the atmospheric composition
in ways that remain largely unexplored. We are interested in what this
variability might imply for planets around M dwarf stars, and focus on
Proxima Centauri (Prox Cen) for three reasons, namely: it is an active
M dwarf with high levels of variability; it hosts a likely terrestrial
exoplanet within its habitable zone (HZ) that will be a prime target
for future direct imaging; and its proximity has led to extensive
observations, yielding some of the best available X-ray data. We set
out to produce time-resolved XUV spectra of Prox Cen that will serve
as input to atmospheric models, and to characterize the intrinsic
variability of the star and its uncertainties in the inferred spectra.
We analyzed the entire dataset of archival XMM-Newton observations for
Prox Cen. To derive the time- resolved X-ray spectra, we implemented a
new pile-up correction, a new adaptive time-binning algorithm, and a
time-dependent plasma model selection. The estimated EUV spectrum is
based on a published template, that we scale with proposed
relationships between X-ray and EUV fluxes. We produced spectra of
Prox Cen from 1 to 920Å over ∼260ks of observations with
unprecedented time resolution. The instantaneous X-ray flux of Prox
Cen varies between about 20 times and one-fifth of the average value
over the available baseline, with significant differences between
wavelengths. We further quantify how variability affects the estimated
average flux when a limited number of snapshots (each typically of 30
ks exposure) are available, as is common in X-ray surveys. Future
investigations of the atmospheres of Prox Cen b should fold in the
time variability and uncertainties described here.
Description:
The data products consists in one FITS file for each reduced
observation. Each file contains time series of spectra with a time
resolution of 30s. We remind that this time resolution was obtained
by linear interpolation of overlapping larger time bins. Each file
contains two extension. The first extension contains the time series
of irradiance (over different wavelengths ranges) and spectral
irradiance, with the first column corresponding to the time. The
second extension contains the wavelength grid.
Each fits file contains time series of spectra of Proxima Centauri
obtained from each XMM-Newton observation analyzed in this work. The
name of the file corresponds to the observation id.
Each FITS file contains three HDUs:
HDU 0 : PRIMARY
HDU 1 : TIME_SERIES
HDU 2 : WAVELENGTHS
Times are expressed in seconds (TT) relative to MJDREF = 50814.0.
The nominal time resolution is 30 s.
HDU 0 : PRIMARY HEADER
This HDU contains no data array and provides global metadata through the
header keywords.
HDU 1 : TIME_SERIES
Time series of irradiance and spectral irradiance derived from
XMM-Newton observations of Proxima Centauri.
---------------------------------------------------------------------------
Column Name Format Unit Description
---------------------------------------------------------------------------
TIME D s Time since MJDREF
TIME_LO D s Lower edge of time bin
TIME_HI D s Upper edge of time bin
IRR D erg cm-2 s-1 Irradiance over
1-920 Angstrom
IRR_LO D erg cm-2 s-1 IRR lower bound
IRR_HI D erg cm-2 s-1 IRR upper bound
IRR_X D erg cm-2 s-1 Irradiance over
1-100 Angstrom
IRRXLO D erg cm-2 s-1 IRR_X lower bound
IRRXHI D erg cm-2 s-1 IRR_X upper bound
IRR_EUV D erg cm-2 s-1 Irradiance over
100-920 Angstrom
IRREUVLO D erg cm-2 s-1 IRR_EUV lower bound
IRREUVHI D erg cm-2 s-1 IRR_EUV upper bound
SPEC_IRR 18100D erg cm-2 s-1 Angstrom-1 Spectral irradiance
over 1-920 Angstrom
SPECIRRLO 18100D erg cm-2 s-1 Angstrom-1 SPEC_IRR lower bound
SPECIRRHI 18100D erg cm-2 s-1 Angstrom-1 SPEC_IRR upper bound
---------------------------------------------------------------------------
The spectral irradiance arrays are defined on the wavelength grid
provided in HDU 2.
HDU 2 : WAVELENGTHS
Wavelength grid associated with the spectral irradiance.
---------------------------------------------------------------------------
Column Name Format Unit Description
---------------------------------------------------------------------------
WAVE D Angstrom Wavelength bin center
WAVE_LO D Angstrom Lower edge of wavelength bin
WAVE_HI D Angstrom Upper edge of wavelength bin
WIDTH D Angstrom Wavelength bin width
---------------------------------------------------------------------------
Objects:
---------------------------------------------------------
RA (2000) DE Designation(s)
---------------------------------------------------------
14 29 42.94 -62 40 46.1 Proxima Centauri = GJ 551
---------------------------------------------------------
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
list.dat 56 8 List of fits files
fits/* . 8 Individual fits files
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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/A+A/626/A111 : Proxima Cen flare activity temporal changes (Pavlenko+, 2019)
J/A+A/638/A120 : SPHERE maps around Proxima Cen (Gratton+, 2020)
J/A+A/639/A77 : Proxima Cen RV, FWHM and fluxes (Suarez Mascareno+, 2020)
J/A+A/658/A115 : Proxima Cen ESPRESSO RV and FWHM (Faria+, 2022)
J/A+A/666/A196 : Proxima telluric-corrected ESPRESSO RV (Allart+, 2022)
J/A+A/700/A11 : Proxima spectroscopy and photometry (Suarez Mascareno+, 2025)
J/A+A/700/A177 : Proxima + Gl581 activity-sensitive lines
(Gomes da Silva+, 2025)
J/AJ/153/93 : MOST photometry of Proxima (Kipping+, 2017)
J/AJ/155/12 : Photometry of Proxima Centauri observed by BSST (Liu+, 2018)
J/AJ/157/226 : Photometry of Proxima Centauri from 2006 to 2017
(Feliz+, 2019)
Byte-by-byte Description of file: list.dat
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Bytes Format Units Label Explanations
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1- 6 I6 --- Nx Number of pixels along X-axis
8- 11 I4 --- Ny Number of pixels along Y-axis
13 I1 --- Nz Number of tables
15- 33 A19 "datime" Obs.date Observation date
35- 40 I6 Kibyte size Size of FITS file
42- 56 A15 --- FileName Name of FITS file, in subdirectory fits
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Acknowledgements:
Andrea Damonte, andrea.damonte(at)inaf.it
(End) Patricia Vannier [CDS] 22-Dec-2025