J/A+A/709/A104 LBT spectra of 16 stars (Rouille+, 2026)
The abundance of interstellar C60 molecules toward BD+31 643 and other stars.
Rouille G., Gredel R.
<Astron. Astrophys. 709, A104 (2026)>
=2026A&A...709A.104R 2026A&A...709A.104R (SIMBAD/NED BibCode)
ADC_Keywords: YSOs ; Spectra, optical
Keywords: astrochemistry - ISM: abundances - ISM: lines and bands -
ISM: molecules
Abstract:
The diffuse interstellar bands (DIBs) at 9577 and 9632Å are
attributed to electronic transitions of the C60+ fullerene ion; thus,
its column density in molecular clouds may be inferred. A comparison
with the column density of the neutral C60 fullerene makes it possible
to determine local physical conditions in the clouds.
We aim to detect absorption lines of neutral C60 in the visible
spectra of stars toward interstellar clouds.
We searched for the γ0, A0, and A1 absorption bands of C60 near
6070Å, 4024Å, and 3980Å using the Potsdam Echelle
Polarimetric and Spectroscopic Instrument at the Large Binocular
Telescope. We measured spectra toward eight background stars including
BD+31 643.
None of the γ0, A0, and A1 absorption bands of C60 were detected
in our spectra. Toward BD+31 643, we determine an upper limit of
(14±11)x1012cm-2 for the column density of C60, and values in
the range of 1012-1014cm-2 toward other stars. Using literature
data for C60+, we derive upper limits of 0.8-3.8 for the C60:C60+
column density ratios.
The non-detection of the γ0 absorption band toward BD+31 643 is
in conflict with a measurement employing infrared (IR) emission bands
of C60. The discrepancy may indicate that free C60 molecules are not
the source of the observed IR emission bands toward the star and that
the IR emission arises from C60 molecules in dust grains instead.
Alternatively, the oscillator strength of the γ0 band may not be
well constrained from the laboratory measurements.
Description:
FITS files of stellar spectra consisting of normalized flux values
reduced in the barycentric standard of rest. Observations carried out
at the Large Binocular Telescope (LBT) with the Potsdam Echelle
Polarimetric and Spectroscopic Instrument (PEPSI), using the red and
blue arms. The table lists the targets and the corresponding files.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
stars.dat 110 8 List of studied stars
sp/* . 16 Individual fits spectra
--------------------------------------------------------------------------------
Byte-by-byte Description of file: stars.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 10 A10 --- Star Star name
12- 13 I2 h RAh Right ascension (J2000)
15- 16 I2 min RAm Right ascension (J2000)
18- 22 F5.2 s RAs Right ascension (J2000)
24 A1 --- DE- Declination sign (J2000)
25- 26 I2 deg DEd Declination (J2000)
28- 29 I2 arcmin DEm Declination (J2000)
31- 35 F5.2 arcsec DEs Declination (J2000)
37- 40 A4 --- Blue [Blue]
42- 73 A32 --- FileNameB Name of the blue arm spectrum file in
subdirectory sp
75- 77 A3 --- Red [Red]
79-110 A32 --- FileNameR Name of the red arm spectrum file in
subdirectory sp
--------------------------------------------------------------------------------
Acknowledgements:
Gael Rouille, gael.rouille(at)uni-jena.de
(End) Patricia Vannier [CDS] 25-Feb-2026