J/A+A/700/A239 Exocomets of beta Pictoris HARPS spectra (Hoeijmakers+, 2025)
Exocomets of beta Pictoris. I: Exocomet destruction, sodium absorption and disk
line variability in 17 years of HARPS observations.
Hoeijmakers H.J., Jaworska K.P., Prinoth B.
<Astron. Astrophys. 700, A239 (2025)>
=2025A&A...700A.239H 2025A&A...700A.239H (SIMBAD/NED BibCode)
ADC_Keywords: Stars, A-type ; Spectroscopy ; Comets
Keywords: techniques: spectroscopic - comets: general - protoplanetary disks
Abstract:
The young beta Pictoris system has been monitored with high-resolution
optical spectrographs for decades. These observations have revealed
strongly variable, stochastic absorption in the CaII H&K lines
attributed to in-falling cometary bodies. Since 2003, over 9000 HARPS
observations of beta Pictoris have been taken and many of these have
not yet been used for exocomet studies. We aim to search these spectra
for new exocomet phenomenology enabled by the long time coverage and
large volume of this dataset. We systematically carry out telluric
correction of the HARPS spectra using molecfit, compare multi-year
observations at the wavelengths of the CaII and NaI lines and use a
Bayesian fitting algorithm to extract exocomet line parameters. We
explore the usage of an unbiased reference spectrum with which to
calibrate the continuum, and investigate Keplerian orbital solutions
to observed exocomet acceleration. We find a general absence of
exocometary sodium line absorption, with only two instances of clear
∼2% deep exocometary sodium out of 198 nights of observation, as well
as a weaker ∼1% feature that persists over 13 nights in 2004. We find
that these events occur during times of exceptionally deep CaII
absorption, at the same red-shift, implying that strongly
CaII-evaporating exocomets also exhibit detectable levels of Na I, in
spite of the vast majority of NaI being rapidly photo-ionised in
close proximity to the star. We find long-lived CaII absorption in
2017 and 2018 that persists on a timescale of a year, which may be
difficult to explain with the classical exocomet model. Finally, we
investigate two strongly accelerating, blue-shifted exocomet features
observed in 2019 that show strong and sudden departures from Keplerian
motion, suggesting rapid changes to the dynamics of the exocomet
cloud. We hypothesize that this is caused by the destruction of the
comet nuclei shortly after their periastron passages.
Description:
This archive contains telluric corrected spectra obtained by HARPS at
the wavelength range of the sodium doublet (order number 56). The
first extension of each FITS file preserves the original header of the
corresponding e2ds file that the order was extracted out of.
Objects:
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RA (2000) DE Designation(s)
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05 47 17.08 -51 03 59.4 beta Pic = HR 2020
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
list.dat 96 9114 List of fits telluric-corrected spectra
fits/* . 9114 Indivifual fits telluric-corrected spectra
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See also:
J/A+A/299/557 : Light variations on Beta Pic (Lecavelier des Etangs+, 1995)
J/A+A/542/A18 : beta Pic Harps radial velocity data (Lagrange+, 2012)
J/ApJ/823/108 : A dust model for bet Pic from 0.58 to 870um (Ballering+, 2016)
J/A+A/607/A25 : beta Pic HARPS spectrum (Vidal-Madjar+, 2017)
J/A+A/627/A28 : beta Pic BRITE, bRing, SMEI light curves (Zwintz+, 2019)
J/AJ/161/179 : Predicted positions of beta Pictoris b and c (Brandt+, 2021)
Byte-by-byte Description of file: list.dat
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Bytes Format Units Label Explanations
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1- 2 I2 h RAh Simbad right ascension of center (J2000)
4- 5 I2 min RAm Simbad right ascension of center (J2000)
7- 11 F5.2 s RAs Simbad right ascension of center (J2000)
12 A1 --- DE- Simbad declination sign of center (J2000)
13- 14 I2 deg DEd Simbad declination of center (J2000)
16- 17 I2 arcmin DEm Simbad declination of center (J2000)
19- 22 F4.1 arcsec DEs Simbad declination of center (J2000)
24- 46 A23 "datime" Obs.date Observation date
48- 50 I3 Kibyte size Size of FITS file
52- 96 A45 --- FileName Name of FITS file, in subdirectory fits
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History:
From Jens Hoeijmakers, jens.hoeijmakers(at)fysik.lu.se
Acknowledgements:
This work was supported by grants from eSSENCE (grant number
eSSENCE@LU 9:3), the Swedish National Research Council (project number
2023-05307), The Crafoord foundation and the Royal Physiographic
Society of Lund, through The Fund of the Walter Gyllenberg Foundation.
We are grateful to Brett Morris for useful discussions regarding the
inference method used extensively in this work, and the attendees of
the 2024 ISSI workshop on Exocomets in Bern, Switzerland, for
important discussions regarding the telluric Na I lines. We are also
grateful by the insightful comments and advice provided by an
anonymous referee, who is to be credited for remarking the existence
of the blended component in the second night of the 2019 observations.
Based on data obtained from the ESO Science Archive Facility with
DOI(s): https://doi.org/10.18727/archive/33.
(End) Jens Hoeijmakers [Lund Univ., Sweden], Patricia Vannier [CDS] 12-Jun-2025