Publications

Spectral Evolution and Radial Dust Transport in the Prototype Young Eruptive System EX Lup

EX Lup is the prototype of a class of pre-main-sequence eruptive stars defined by their repetitive outbursts lasting several months. In 2008 January─September EX Lup underwent its historically largest outburst, brightening by about 4 mag in visual light. In previous studies we discovered ongoing silicate crystal formation in the inner disk during the outburst, but also noticed that the measured crystallinity fraction started decreasing after the source returned to the quiescent phase. Here we present new observations of the 10 μm silicate feature, obtained with the MIDI and VISIR instruments at Paranal Observatory. The observations demonstrate that within five years … Read more »

An ALMA Study of the FU Ori-type Object V900 Mon: Implications for the Progenitor

We present ALMA observations of 12CO, 13CO, and C18O J = 2-1 lines and the 230 GHz continuum for the FU Ori-type object (FUor) V900 Mon (d ̃ 1.5 kpc), for which the accretion burst was triggered between 1953 and 2009. We identified CO emission associated with a molecular bipolar outflow extending up to an ̃104 au scale and a rotating molecular envelope extending over >104 au. The interaction with the hot energetic FUor wind, which was observed using optical spectroscopy, appears limited to a region within ̃400 au of the star. The envelope mass and collimation of the extended CO outflow suggest that … Read more »

Diagnosing 0.1-10 au Scale Morphology of the FU Ori Disk Using ALMA and VLTI/GRAVITY

We report new Atacama Large Millimeter/submillimeter Array Band 3 (86-100 GHz; ̃80 mas angular resolution) and Band 4 (146-160 GHz; ̃50 mas angular resolution) observations of the dust continuum emission toward the archetypal and ongoing accretion burst young stellar object FU Ori, which simultaneously covered its companion, FU Ori S. In addition, we present near-infrared (2-2.45 μm) observations of FU Ori taken with the General Relativity Analysis via VLT InTerferometrY (GRAVITY; ̃1 mas angular resolution) instrument on the Very Large Telescope Interferometer (VLTI). We find that the emission in both FU Ori and FU Ori S at (sub)millimeter and near-infrared … Read more »

Resolved ALMA Continuum Image of the Circumbinary Ring and Circumstellar Disks in the L1551 IRS 5 System

L1551 IRS 5 is a FUor-like object located in the Taurus star-forming region. We present Atacama Large Millimeter/submillimeter Array (ALMA) 1.3 mm continuum observations using a wide range of baselines. The observations recovered the two circumstellar disks comprising the system and, for the first time, resolved the circumbinary ring. We determined the geometry and estimated lower mass limits for the circumstellar disks using simple models. We calculated lower limits for the total mass of both circumstellar disks. After subtracting the two circumstellar disk models from the image, the residuals show a clearly resolved circumbinary ring. Using a radiative transfer model, … Read more »

Dynamical Gaseous Rings in Global Simulations of Protoplanetary Disk Formation

Global numerical simulations of protoplanetary disk formation and evolution were conducted in the thin-disk limit, where the model included a magnetically layered disk structure, a self-consistent treatment for the infall from cloud core, and the smallest possible inner computational boundary. We compared the evolution of a layered disk with a fully magnetically active disk. We also studied how the evolution depends on the parameters of the layered disk model—the MRI triggering temperature and active layer thickness—as well as the mass of the prestellar cloud core. With the canonical values of parameters a dead zone formed within the inner ≈15 au … Read more »

Identification of Young Stellar Object candidates in the Gaia DR2 x AllWISE catalogue with machine learning methods

The second Gaia Data Release (DR2) contains astrometric and photometric data for more than 1.6 billion objects with mean Gaia G magnitude <20.7, including many Young Stellar Objects (YSOs) in different evolutionary stages. In order to explore the YSO population of the Milky Way, we combined the Gaia DR2 data base with Wide-field Infrared Survey Explorer (WISE) and Planck measurements and made an all-sky probabilistic catalogue of YSOs using machine learning techniques, such as Support Vector Machines, Random Forests, or Neural Networks. Our input catalogue contains 103 million objects from the DR2xAllWISE cross-match table. We classified each object into four … Read more »

Dust evolution in the circumstellar disc of the unclassified B[e] star HD 50138

We studied the disc of the unclassified B[e] star HD 50138 in order to explore its structure and to find indications for the evolutionary status of this system, whether it is a young Herbig Be or a post-main-sequence star. Using high spatial resolution interferometric measurements from MIDI instrument (N-band) on the Very Large Telescope Interferometer, we analysed the disc size, the time-variability of the disc’s thermal emission, and the spectral shape of the 10 μm silicate feature. By fitting simple disc models, we determined the inclination and the mid-infrared size of the disc, confirming earlier results based on a lower … Read more »

Protoplanetary Disk Science Enabled by Extremely Large Telescopes

We discuss how a spectroscopic and imaging survey of protoplanetary disks with Extremely Large Telescopes will enhance our understanding of planet formation by (1) measuring the physical and chemical conditions in disks using infrared spectroscopy and (2) studying planet-disk interactions using imaging and spectro-astrometry.

APEX Observations of the CO Envelope around the Young FUor-type Star V883 Ori

The accretion-driven outbursts of young FU Orionis-type stars may be a common stage of pre-main-sequence evolution and can have a significant impact on the circumstellar environment as it pertains to the growth of solids and eventually planets. This episodic accretion is thought to be sustained by additional gas infalling from the circumstellar envelope and disk. We present APEX observations of the CO gas in the envelope around V883 Orionis, a young outbursting star. The observations mapped the 12CO(4-3), 12CO(3-2), and 13CO(3-2) lines with the FLASH+ instrument and the 12CO(6-5) line with the SEPIA instrument. We detected high signal-to-noise emission extending out to radii >10,000 au … Read more »

The Weakening Outburst of the Young Eruptive Star V582 Aur

V582 Aur is a pre-main-sequence FU Orionis type eruptive star, which entered a brightness minimum in 2016 March due to changes in the line-of-sight extinction. Here, we present and analyze new optical B, V, R C , and I C band multiepoch observations and new near-infrared J, H, and K S band photometric measurements from 2018 January-2019 February, as well as publicly available midinfrared Wide-field Infrared Survey Explorer (WISE) data. We found that the source shows a significant optical-near-infrared variability, and the current brightness minimum has not completely finished yet. If the present dimming originates from the same orbiting dust clump that caused a similar brightness … Read more »