The peculiar B[e] star HD 45677

Abstract

Abstract. The photometric behaviour of the peculiar B[e] star HD 45677 over the last 25 years is investigated. We conclude that the photometric variations (V = 7.m 22−8. m 85) on such a time scale can be well explained by obscurations, possibly due to large (> 1 µm) circumstellar (CS) dust grains which were created after an explosive event around 1950. Intermediate time scale variations are also identified and can be well explained by infall of CS material.Evidence is also found for smaller, pulse-like, amplitude variations. The time scale of this "flickering" ranges from days down to hours and is explained by instabilities in accretion flows towards HD 45677. The accretion mechanisms can be the origin of the hypothesized existence of a bipolar flow.HD 45677, seen edge-on, shows evidence for the presence of a circumstellar disk. The significant accretion flows in this disk probably increased some time after the 1950 event, either due to a fall-back of part of the ejected material by a blow-out around 1950 or either due to the explosive dissociation of a large cometary-like body. Dynamic effects of such infalling and outflowing material close to the stellar surface are also detected by high resolution spectroscopy in the Hα and He i profiles. These short time scale variations are also seen in the cool material as detected by the variations in the violet part of the Na i D profiles, which are probably due to collisions of the outflowing material with the outer disk.The presence of a disk is often indicated and here by the emission of the sodium lines with a strong absorption component at the systemic velocity (about 20 km s −1 ). Most detected lines, except Hα, are well centered at this velocity. Apart from the red [Sii] lines, all other nebular lines as well as many other emission lines, including the Fe ii emission spectrum, were seen in spectra taken far Send offprint requests to: D. de Winter (dolf@astro1.ft.uam.es) Based on observations collected at the European Southern Observatory, La Silla, Chile, and on data collected in the longterm photometry of variables programme at ESO. before and after the 1950 event as well as in the latest spectra. So, the situation of the gaseous stellar environment seems to be stable in spite of the large photometric variations. The Fe ii emission lines are double peaked with a velocity separation of about 32 km s −1 . This could mean that the inner disk material, in which these lines are thought to be formed, rotates with about 16 km s −1 . In our 1992 data this rotation velocity seems to range up to 30 km s −1 , which could be due to material accelerated by the 1950 event.We discuss in this paper the evolutionary status of HD 45677. Because of its rather isolated position in the sky and because of the very fast evolution of a B2 type star, we think that HD 45677 could be young, but not in the sense of being a pre-main sequence object. Options like an evolved object such as a LBV or PN are not suitable because of the probable luminosity class III, IV or V and its rather cool c...

Analysis of the circumstellar environment of the B[ e] star HD 45677 (FS Canis Majoris)

“…2−5, in the higher resolution spectra of HD 45677, the strongest permitted lines present a double peaked emission. This feature has been in previous papers ascribed to emission from a rotating equatorial disk (de Winter et al 1997). But they can be as well attributed to absorption in the emitting medium or in a circumstellar shell according to Grady et al (1993) from their ultraviolet observations.…”

“…These last authors agreed on the presence, around the star, of an actively accreting circumstellar, protoplanetary disk, and the presence of low-velocity absorption profiles in Fe II lines, among other species, while optical spectroscopic measurements of strong absorption cores of a few lines are commented on by de Winter et al (1997). In the optical HD 45677 is characterised by a rich emission line spectrum, including the Balmer lines of hydrogen, and both permitted and forbidden lines of neutral and ionized metals (Mg I, Mg II, Na I, Cr II Israelian et al (1996) found a surface gravity of log g = 3.85 ± 0.05 (luminosity class V) from the photospheric wings of Hγ and Hδ, while examination of the He I absorption lines suggested a spectral class of B2 (T eff = 22 000 ± 1500 K).…”

“…Higher resolution spectra of HD 45677 were obtained from October 14, 19 and 20 in 1995 by Musaev with the Coudé Echelle Spectrometer at the 1-m telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences (Israelian & Musaev 1997), and kindly provided for us by Garik Israelian. For the purpose of our analysis of the emission lines we need the absolute values of the fluxes. To do this, we have normalized the individual spectra to the local continuum level and, following de Winter et al (1997), we multiplied the line fluxes by the energy distribution of the Kurucz (1979Kurucz ( , 1993 model of T eff = 22 500 K and log g = 4.0 with solar abundance, normalized to the visual magnitude of the star, V 0 = 6.6. The results are not dependent on the model choosen in the limit of the precision of the determination of the star's type by various authors (see Introduction).…”

“…HD 45677 (FS CMa) is generally recognized as an early type star, usually classified as B [e], or more precisely as showing the B[e] phenomenon, even if it is difficult to determine its exact evolutionary stage (de Winter et al 1997;Lamers et al 1998).…”

ISO Observations of Solid-State Features in Circumstellar Disks

“…The modelling presented in Figure 2 is -as for HD142527 in Figure 1 -the result of a radiative-transfer calculation with the MODUST programme (de Koter & Bouwman 2000). From the presence at 69 Mm of the longest-wavelength silicate feature, which is very sensitive to the Mg/Fe ratio, it follows that forsterite, i.e.…”