Characterization of low-mass companion HD 142527 B

Abstract

Context. The circumstellar disk of the Herbig Fe star HD 142527 is host to several remarkable features including a warped inner disk, a 120 au-wide annular gap, a prominent dust trap and several spiral arms. A low-mass companion, HD 142527 B, was also found orbiting the primary star at ∼14 au. Aims. This study aims to better characterize this companion, which could help explain its impact on the peculiar geometry of the disk. Methods. We observed the source with VLT/SINFONI in H+K band in pupil-tracking mode. Data were post-processed with several algorithms based on angular differential imaging (ADI). Results. HD 142527 B is conspicuously re-detected in most spectral channels, which enables us to extract the first medium-resolution spectrum of a low-mass companion within 0 . 1 from its central star. Fitting our spectrum with both template and synthetic spectra suggests that the companion is a young M2.5±1.0 star with an effective temperature of 3500 ± 100 K, possibly surrounded with a hot (1700 K) circum-secondary environment. Pre-main sequence evolutionary tracks provide a mass estimate of 0.34 ± 0.06M , independent of the presence of a hot environment. However, the estimated stellar radius and age do depend on that assumption; we find a radius of 1.37 ± 0.05R (resp. 1.96 ± 0.10R ) and an age of 1.8 +1.2 −0.5 Myr (resp. 0.75 ± 0.25 Myr) in the case of the presence (resp. absence) of a hot environment contributing in H+K. Our new values for the mass and radius of the companion yield a mass accretion rate of 4.1-5.8 ×10 −9 M yr −1 (2-3% that of the primary). Conclusions. We have constrained the physical properties of HD 142527 B, thereby illustrating the potential for SINFONI+ADI to characterize faint close-in companions. The new spectral type makes HD 142527 B a twin of the well-known TW Hya T-Tauri star, and the revision of its mass to higher values further supports its role in shaping the disk.

Cm-wavelength observations of MWC 758: resolved dust trapping in a vortex

“…This model makes a robust predictions for the vortex aspect ratio χ = 13.8 +4.3 −1.7 and temperature T = 23.5 +2.8 −1.9 K. An elongated vortex is consistent with hydrodynamical simulations taylored to MWC 758 (Baruteau et al 2018, submitted). This result suggests that the very long arc seen in the ALMA Band 4 observations reported by Cazzoletti et al (2018) in HD 135344B also correspond to a very elongated vortex. The large optical depths required by such low temperatures and narrow aspect ratios, of order ∼ 1 even in cm-wavelengths, have also been predicted in the generic models of Sierra et al (2017), and could be tested with further multi-frequency observations of MWC 758.…”

“…Crescents with extreme contrasts such as in HD 142527 and IRS 48 are however rarely observed, these two sources being examples of the very brightest protoplanetary disks (and HD 142527 can be seen as a circumbinary disk, e.g. Biller et al 2012;Christiaens et al 2018). Large crescents with smaller contrast ratios are nonetheless common in the submm continuum from the outer rings of protoplanetary disks with large central cavities (i.e.…”

Separating extended disc features from the protoplanet in PDS 70 using VLT/SINFONI

“…Our adaptation of the NEGFC algorithm is summarized in Figure 7. We first attempted to extract the exact position and contrast as a function of wavelength of Feature b using NEGFC coupled with PCA-ADI applied to each spectral channel, as performed for HD 142527 B in Christiaens et al (2018). Taking advantage of the whitening of the noise by ADI, we binned (40 by 40) adjacent spectral channels after PCA-ADI processing (Figure 7a to d), and over the whole K-band wavelength range (Figure 7e).…”

Dusty clumps in circumbinary discs

“…However, a companion was later discovered inside the inner cavity by Biller et al (2012). The stellar masses in HD 142527 are 1.8 M (Gaia Collaboration et al 2016) and 0.4 M (Christiaens et al 2018), so it is an unequal-mass binary. Further studies focused on the companion's orbital motion (Lacour et al 2016;Claudi et al 2019) indicating that the binary is eccentric and likely inclined with respect with the disc.…”