Discovery of SiO band emission from Galactic B[e] supergiants

Abstract

B[e] supergiants (B[e]SGs) are evolved massive stars in a short-lived transition phase. During this phase, these objects eject large amounts of material, which accumulates in a circumstellar disk-like structure. The expelled material is typically dense and cool, providing the cradle for molecule and dust condensation and for a rich, ongoing chemistry. Very little is known about the chemical composition of these disks, beyond the emission from dust and CO revolving around the star on Keplerian orbits. As massive stars preserve an oxygen-rich surface composition throughout their life, other oxygen-based molecules can be expected to form. As SiO is the second most stable oxygen compound, we initiated an observing campaign to search for first-overtone SiO emission bands. We obtained high-resolution near-infrared L-band spectra for a sample of Galactic B[e]SGs with reported CO band emission. We clearly detect emission from the SiO first-overtone bands in CPD-52 9243 and indications for faint emission in HD 62623, HD 327083, and CPD-57 2874. From model fits, we find that in all these stars the SiO bands are rotationally broadened with a velocity lower than observed in the CO band forming regions, suggesting that SiO forms at larger distances from the star. Hence, searching for and analyzing these bands is crucial for studying the structure and kinematics of circumstellar disks, because they trace complementary regions to the CO band formation zone. Moreover, since SiO molecules are the building blocks for silicate dust, their study might provide insight in the early stage of dust formation.

arXiv comment6 pages, 2 figures, 2 tables, accepted for publication in ApJ Letters

References in corpus (23)

• Validation of the new Hipparcos reduction
• Spitzer SAGE Infrared Photometry of Massive Stars in the Large Magellanic Cloud
• Spitzer SAGE-SMC Infrared Photometry of Massive Stars in the Small Magellanic Cloud
• ExoMol line lists II: The ro-vibrational spectrum of SiO
• ExoMol molecular line lists V: The ro-vibrational spectra of NaCl and KCl
• Imaging the spinning gas and dust in the disc around the supergiant A[e] star HD62623
• The pre- versus post-main sequence evolutionary phase of B[e] stars: Constraints from 13CO band emission
• And in the Darkness Bind Them: Equatorial Rings, B[e] Supergiants, and the Waists of Bipolar Nebulae
• Probing the ejecta of evolved massive stars in transition: A VLT/SINFONI K-band survey
• The supergiant B[e] star LHA 115-S 18 - binary and/or luminous blue variable?
• A new observational tracer for high-density disc-like structures around B[e] supergiants
• Neutral material around the B[e] supergiant star LHA 115-S 65: An outflowing disk or a detached Keplerian rotating disk?
• VLTI/AMBER and VLTI/MIDI spectro-interferometric observations of the B[e] supergiant CPD-57 2874
• Molecular emission from GG Car's circumbinary disk
• The ${}^{13}$Carbon footprint of B[e] supergiants
• AMBER and CRIRES observations of the binary sgB[e] star HD 327083: evidence of a gaseous disc traced by CO bandhead emission
• Discovery of the first B[e] supergiants in M 31
• Dusty Blue Supergiants: News from High-Angular Resolution Observations
• Evidence of the Evolved Nature of the B[e] Star MWC 137
• Discovery of Raman-scattered lines in the massive luminous emission-line star LHA 115-S 18
• The sudden appearance of CO emission in LHA 115-S 65
• High spectral resolution spectroscopy of the SiO fundamental lines in red giants and red supergiants with VLT/VISIR
• Fast ray-tracing algorithm for circumstellar structures (FRACS). II. Disc parameters of the B[e] supergiant CPD-57° 2874 from VLTI/MIDI data

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• The 2020 release of the ExoMol database: molecular line lists for exoplanet and other hot atmospheres
• Spectroscopic survey of emission-line stars. I. B[e] stars
• Resolving the kinematics of the disks around Galactic B[e] supergiants
• Inhomogeneous molecular ring around the B[e] supergiant LHA 120-S 73
• Red Supergiants in M31: The Humphreys-Davidson limit at high metallicity
• Resolving the circumstellar environment of the Galactic B[e] supergiant star MWC 137 from large to small scales
• On the evolutionary state of massive stars in transition phases in M33
• Properties of Galactic B[e] Supergiants: V. 3 Pup -- constraining the orbital parameters and modeling the circumstellar environments
• Evidence of an evolved nature of MWC 349A
• First detection of silicon-bearing molecules in $\eta$ Car
• Resolving the circumstellar environment of the Galactic B[e] supergiant star MWC 137. II. Nebular kinematics and stellar variability
• Dense Molecular Environments of B[e] Supergiants and Yellow Hypergiants
• The circumbinary rings of GG Carinae: indications of disc eccentricity growth in the B[e] supergiant's atomic emission lines
• Discovery of sulfur oxides in the ejecta of a B[e] supergiant
• New constraints on the binary system HD 327083 and its gaseous and dusty environments
• Gas chemistry in the dust depleted inner regions of protoplanetary disks. I. Near-IR spectra and overtones