J/A+A/685/A124 Tomography of Betelgeuse (Jadlovsky+, 2024)
The Great Dimming of Betelgeuse:
The photosphere as revealed by tomography during the past 15 years.
Jadlovsky D., Granzer T., Weber M., Kravchenko K., Krticka J., Dupree A.K.,
Chiavassa A., Strassmeier K.G., Poppenhager, K.
<Astron. Astrophys. 685, A124 (2024)>
=2024A&A...685A.124J 2024A&A...685A.124J (SIMBAD/NED BibCode)
ADC_Keywords: Stars, supergiant ; Spectra, optical ; Radial velocities
Keywords: techniques: photometric - techniques: spectroscopic -
stars: late-type - stars: mass-loss - stars: winds, outflows
Abstract:
Betelgeuse, a red supergiant star of semi-regular variability,
underwent a historical minimum of brightness in February 2020, the
Great Dimming. Even though the brightness has returned to the values
prior to the Great Dimming by now, it continues to exhibit highly
unusual behavior.
Understanding the long-term atmospheric motions of Betelgeuse and its
variability could be a clue to the nature of the Great Dimming and the
mass-loss process in red supergiants. Our goal is to study long-term
dynamics of the photosphere, including during the Great Dimming.
We applied the tomographic method, which allows different layers in
the stellar atmosphere to be probed in order to reconstruct
depth-dependent velocity fields. The method is based on the
construction of spectral masks by grouping spectral lines from
specific optical depths. These masks are cross-correlated with the
observed spectra to recover the velocity field inside each atmospheric
layer.
We obtained about 2800 spectra during the past 15 years, observed with
the STELLA robotic telescope in Tenerife. We analyzed the variability
of 5 different layers of Betelgeuses photosphere. We found phase shift
between the layers, as well as between the variability of velocity and
photometry. The time variations of the widths of the cross-correlation
function reveal propagation of two shock waves during the Great
Dimming. For about 2 years after the Dimming, the time scale of
variability was different between the inner and outer photospheric
layers. By 2022, all the layers seemingly started to follow a similar
behavior as before the Dimming, but pulsating with higher frequency
corresponding with the first overtone.
Combination of the extensive high-resolution spectroscopic data set
with the tomographic method revealed the variable velocity fields in
the photosphere of Betelgeuse, for the first time in such detail. We
were also able to find new insights related to the Great Dimming event
and its aftermath, namely the discovery of another shock wave and the
subsequent rearrangement of the photosphere.
Description:
We present high-resolution echelle spectra of Betelgeuse taken with
STELLA echelle spectrograph (SES) operated by AIP. The extensive time
series consists of about 2800 spectra (6000 exposures in total)
obtained during the past 15 years. The data were reduced using the
IRAF-based pipeline SESDR in its version 4.0 (Weber et al. 2008,
2012). Tomographic method was used to create masks representing 5
distinct layers of photosphere. Radial velocities (RV) were determined
by cross-correlating the masks with the observed spectra.
Objects:
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RA (2000) DE Designation(s)
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05 55 10.31 +07 24 25.4 alpha Ori = Betelgeuse
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
rvmask1.dat 136 1679 RVs determined with mask 1
rvmask2.dat 136 2290 RVs determined with mask 2
rvmask3.dat 136 2309 RVs determined with mask 3
rvmask4.dat 136 2311 RVs determined with mask 4
rvmask5.dat 136 2312 RVs determined with mask 5
rvnomask.dat 136 2314 RVs determined with the original template
list.dat 132 2794 List of fits spectra
fits/* . 2794 Individual fits spectra
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See also:
J/ApJ/902/63 : SMEI photometry of Betelgeuse (Joyce+, 2020)
J/ApJ/905/34 : 2017-2020 photometry of Betelgeuse (Harper+, 2020)
J/A+A/650/L17 : HERMES spectra of Betelgeuse (Kravchenko+, 2021)
J/other/Nat/594.365 : Betelgeuse during its Great Dimming (Montarges+, 2021)
Byte-by-byte Description of file: rvmask?.dat dat rvnomask.dat
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Bytes Format Units Label Explanations
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1- 17 F17.9 d HJD Heliocentric Julian Day
19- 36 F18.15 km/s RV Radial velocity
38- 58 F21.19 km/s e_RV Uncertainty on radial velocity
60- 78 F19.16 km/s GFWHM Full width at half maximum
80- 98 F19.15 --- SNR Signal-to-noise ratio
100-136 A37 --- FileName Spectrum file name, in subdirectory fits
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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 Right Ascension (J2000)
4- 5 I2 min RAm Right Ascension (J2000)
7- 11 F5.2 s RAs Right Ascension (J2000)
12 A1 --- DE- Declination sign (J2000)
13- 14 I2 deg DEd Declination (J2000)
16- 17 I2 arcmin DEm Declination (J2000)
19- 22 F4.1 arcsec DEs Declination (J2000)
24- 27 I4 --- Nx Number of pixels along X-axis
29- 31 I3 --- Ny Number of pixels along Y-axis
33 I1 --- Nz Number of slices
35- 58 A24 "datime" Obs.date Observation date
60- 63 I4 Kibyte size Size of FITS file
65-101 A37 --- FileName Name of FITS file, in subdirectory fits
103-132 A30 --- Title Title of the FITS file
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Acknowledgements:
Daniel Jadlovsky, jadlovsky(at)mail.muni.cz
(End) Patricia Vannier [CDS] 20-Feb-2024