A mid-IR study of the circumstellar environment of Herbig Be stars

Abstract

Context. The study of the formation of massive stars is complicated because of the short times scales, large distances, and obscuring natal clouds. There are observational and theoretical indications that the circumstellar environment of Herbig Be (HBe) stars is substantially different from that of their lower mass counterparts, the T Tauri and Herbig Ae stars. Aims. We map the spatial distribution and mineralogy of the warm circumstellar dust of a sample of HBe stars. We compare our results to a sample of less massive Herbig Ae stars. Methods. We used literature photometry to obtain optical extinctions and stellar parameters of the targets. We obtained N-band imaging and long-slit spectroscopic data with the VISIR instrument at the VLT and we analyzed these data. We performed photometry of the images and extracted spatial information. We corrected the spectra for extinction and performed mineralogical fits. We fitted Gaussian profiles to characterize the spatial extent of the spectra along the VISIR slit. Results. We find that the mid-infrared (IR) emission of the HBe stars is typically characterized by a circumstellar disk that efficiently reprocesses a substantial portion of the stellar flux. The mid-IR flux levels, the spatial compactness, and the dust composition are quite similar to those of the Herbig Ae stars. We find upper limits to the full-width-at-half-maximum (FWHM) size of the mid-IR emission of ∼500 AU. The main differences with the lower mass stars are the lower overall IR excess with a greater variety in shapes, the weaker PAH reprocessing power, and the lack of a silica-forsterite relation. The discrepancies between VISIR and IRAS photometry, the far-IR contributions and the large PAH sizes of HBe stars are attributed to natal clouds. Conclusions. Our results suggest that the Herbig Be disks are flatter than those around lower mass stars and they are likely truncated from the outside by photoevaporation.

Polycyclic Aromatic Hydrocarbons in Protoplanetary Disks around Herbig Ae/Be and T Tauri Stars

“…V596 Car, Hen 3-331) is a Herbig Be star (B7-8Ve: Juhász et al 2010) located at 1.5 ± 0.5 kpc (Verhoeff et al 2012). The existence of a close binary companion interacting with the circumstellar disk of HD 85567 was proposed (Miroshnichenko et al 2001), and the binary companion with a separation of 0.…”

“…To explain the observed IR emission, Acke et al (2008) adopted a geometric model consisting of three Gaussian disks, which can account for the IR emission but underestimates the observed submm/mm emission. Verhoeff et al (2012) have marginally resolved the PAH emission in the narrow-band peaking at 11.88 µm with VLT/VISIR, constraining a spatial extension of ∼ 110 AU in diameter. The mm observations obtained with the VLA and the IRAM Plateau de Bure interferometers (Alonso-Albi et al 2009) also showed that the MWC 297 disk is small, with an outer radius of ∼ 28 AU.…”

“…-(1) Alecian et al (2013), (2) Rigliaco et al (2015), (9) Sturm et al (2013), (10) Seok & Li (2015), (11) Maaskant et al (2014), (12) Juhász et al (2010), (13) Fairlamb et al (2015), (14) Mariñas et al (2011), (15) Verhoeff et al (2012), (16) van Boekel et al (2005), (17) Siebenmorgen et al (2000), (18) Hubrig et al (2009), (19) Folsom et al (2012, (20) Fukagawa et al (2010), (21) Seok & Li (2016), (22) Keller et al (2008), (23) Merín et al (2010), (24) Harvey et al (1984), (25) Kóspál et al(2012), (26) Boersma et al (2009), (27) Brown et al (2008), (28) Borges Fernandes et al (2007, (29) Schütz et al (2009), (30) Prato et al (2003), (31) Jeffers et al (2013), (32) Huélamo et al (2011), (33) Casey et al (1998), (34) Pinilla et al (2014), (35) Magazzu et al (1991), (36) Liu et al (2011), (37) …”

Identifying gaps in flaring Herbig Ae/Be disks using spatially resolved mid-infrared imaging

“…The observing conditions were good for HD 169142 and HD 135344 in which the airmass was in between 1.0-1.1 and the optical seeing ∼0.6 and ∼0.8 respectively, and poor for HD 97048 in which the airmass was in between 1.6-1.7 and the optical seeing ∼1.3 . The spatial FWHM of the spectra and their PSF was extracted with the method described in Verhoeff et al (2012). VLT/VISIR data of Oph IRS 48 is taken from Geers et al (2007b).…”

TOWARD UNDERSTANDING THE B[e] PHENOMENON. VI. NATURE AND SPECTRAL VARIATIONS OF HD 85567∗

“…First, we review a suggestion that HD 85567 might be a HAeBe star initially proposed by Thé et al (1994) and carried on in a number of later papers (e.g., Verhoeff et al 2012;Wheelwright et al 2013). This requires a comparison of the observed properties of HD 85567 with those of bona fide HAeBe stars.…”