Tracing back the evolution of the candidate LBV HD168625

Abstract

Aims. We obtained Herschel/PACS imaging and spectroscopic observations of the nebula surrounding the candidate LBV HD168625. By combining these data with optical spectra of the star, we want to constrain the abundances in the nebula and in the star and compare them to trace back its evolution. Methods. We use CMFGEN to determine the fundamental parameters and the CNO abundances of the central star whilst the abundances of the nebula are derived from the emission lines present in the Herschel/PACS spectrum. Result. The FIR images show a nebula composed of an elliptical ring/torus of ejecta with a ESE-WNW axis and of a second perpendicular bipolar structure composed of empty caps/rings. We detect equatorial shells composed of dust and ionized material with different sizes when observed at different wavelengths, and bipolar caps more of less separated from the central star in H$\alpha$ and mid-IR images. This complex global structure seems to show 2 different inclinations: 40° for the equatorial torus and 60° for the bipolar ejections. From the Herschel/PACS spectrum, we determine nebular abundances of $N/H=4.1\pm 0.8\times 10^{-4}$ and $C/H\sim 1.6_{-0.35}^{+1.16}\times 10^{-4}$, as well as a mass of ionized gas of $0.17\pm 0.04$M${}_{\odot }$ and a neutral hydrogen mass of about $1.0\pm 0.3$M${}_{\odot }$ which dominates. Analysis of the central star reveals Teff = 14000K, log g = 1.74 and log (L/L${}_{\odot }$) = 5.58. We derive stellar abundances of about $N/H=5.0\pm 1.5\times 10^{-4}$, $C/H=1.4\pm 0.5\times 10^{-4}$ and $O/H=3.5\pm 1.0\times 10^{-4}$. All these measurements taken together are compatible with the evolutionary tracks of a star with an initial mass between $28$ and $33$M${}_{\odot }$ and with a crit. rotational rate between 0.3 and 0.4 that has lost its material during or just after the BSG phase.

arXiv comment14 pages, 16 figures, A&A, in press

References in corpus (33)

• The Wide-field Infrared Survey Explorer (WISE): Mission Description and Initial On-orbit Performance
• The Infrared Array Camera (IRAC) for the Spitzer Space Telescope
• Herschel Space Observatory - An ESA facility for far-infrared and submillimetre astronomy
• The Photodetector Array Camera and Spectrometer (PACS) on the Herschel Space Observatory
• Grids of stellar models with rotation - I. Models from 0.8 to 120 Msun at solar metallicity (Z = 0.014)
• Far Infrared and Submillimeter Emission from Galactic and Extragalactic Photo-Dissociation Regions
• Far Infrared Spectroscopy of Normal Galaxies: Physical Conditions in the Interstellar Medium
• UBVJHK synthetic photometry of Galactic O stars
• Scanamorphos: a map-making software for Herschel and similar scanning bolometer arrays
• Fourier method in the determination of rotational velocities in OB stars
• MESS (Mass-loss of Evolved StarS), a Herschel Key Program
• Discovery of a nearby twin of SN1987A's nebula around the luminous blue variable HD168625: Was Sk--69 202 an LBV?
• Galactic Twins of the Ring Nebula Around SN1987A and a Possible LBV-like Phase for Sk-69 202
• B fields in OB stars (BOB): low-resolution FORS2 spectropolarimetry of the first sample of 50 massive stars
• The MiMeS Survey of Magnetism in Massive Stars: CNO surface abundances of Galactic O stars
• The Multiplicity of Massive Stars: A High Angular Resolution Survey with the HST Fine Guidance Sensor
• Multiple ring nebulae around blue supergiants
• Abundances and density structure of the inner circumstellar ring around SN 1987A
• The first X-ray survey of Galactic Luminous Blue Variables
• The evolutionary status of Sher25 - implications for blue supergiants and the progenitor of SN1987A
• Constraints on gamma-ray burst and supernova progenitors through circumstellar absorption lines. (II): Post-LBV Wolf-Rayet stars
• The Ring Nebula Around the Blue Supergiant SBW1: Pre-Explosion Snapshot of a SN 1987A Twin
• Herschel/PACS observations of the 69 $\mu m$ band of crystalline olivine around evolved stars
• The blue supergiant Sher 25 and its intriguing hourglass nebula
• Modelling the asymmetric wind of the luminous blue variable binary MWC 314
• Multiple shells around G79.29+0.46 revealed from near-IR to millimeter data
• Herschel imaging and spectroscopy of the nebula around the luminous blue variable star WRAY 15-751
• Multi-wavelength study of the nebula associated with the galactic LBV candidate HD 168625
• The Herschel view of the nebula around the luminous blue variable star AG Carinae
• Luminous blue variables: An imaging perspective on their binarity and near environment
• Sher 25: pulsating but apparently alone
• Herschel observations of the nebula M1-67 around the Wolf-Rayet star WR 124
• Binarity of the LBV HR Car

Cited by in corpus (10)

• Multiplicity of Galactic Luminous Blue Variable stars
• Optical spectroscopy of the blue supergiant Sk-69 279 and its circumstellar shell with SALT
• On the bipolarity of Wolf-Rayet nebulae
• Modeling of extended atmospheres with temperatures below 40000K
• Binarity at LOw Metallicity (BLOeM): Multiplicity of early B-type supergiants in the Small Magellanic Cloud
• Modeling spectra of MN112
• SOFIA/FORCAST Observations of the Luminous Blue Variable Candidates MN 90 and HD 168625
• Two circumstellar nebulae discovered with the Wide-field Infrared Survey Explorer and their massive central stars
• HD 93795: a late-B supergiant star with a square circumstellar nebula
• Millimetre continuum from LBV stars and their environs. NIKA2 observations and Virtual Observatory data