arXiv subjects

Gerd Weigelt

Publications and source records attributed to Gerd Weigelt.

At least 55 records · Page 3Linked to original sources

arXiv2019

Infrared interferometric three-dimensional diagnosis of the atmospheric dynamics of the AGB star R Dor with VLTI/AMBER

The mechanism of mass loss in late evolutionary stages of low- and intermediate-mass stars is not yet well understood. Therefore, it is crucial to study the dynamics of the region within a few stellar radii, where the wind acceleration is considered to take place. We present three-dimensional diagnosis of the atmospheric dynamics of the closest asymptotic giant branch (AGB) star R Dor from the low photospheric layers to the extended outer atmosphere--for the first time for a star other than the Sun. The images reconstructed with a spatial resolution of 6.8 mas--seven times finer than the star's angular diameter of 51.2 mas in the continuum--using the AMBER instrument at the Very Large Telescope Interferometer show a large, bright region over the surface of the star and an extended atmosphere. The velocity-field maps over the star's surface and atmosphere obtained from the Mg and H2O lines near 2.3 micron forming at atmospheric heights below ~1.5 stellar radii show little systematic motion beyond the measurement uncertainty of 1.7 km/s. In marked contrast, the velocity-field map obtained from the CO first overtone lines reveals systematic outward motion at 7--15 km/s in the extended outer atmosphere at a height of ~1.8 stellar radii. Given the detection of dust formation at ~1.5 stellar radii, the strong acceleration of material between ~1.5 and 1.8 stellar radii may be caused by the radiation pressure on dust grains. However, we cannot yet exclude the possibility that the outward motion may be intermittent, caused by ballistic motion due to convection and/or pulsation.

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arXiv2019

A compact gaseous accretion disk in Keplerian rotation around MWC147

The disks around some Herbig Be stars have been observed to be more compact than the expected dust sublimation radius for such objects, with highly refractory dust grains and optically thick gas emission having been proposed as possible explanations for this phenomenon. Our aim is to search for direct evidence for the presence of hot gas inside of the expected dust sublimation radius of MWC147. By combining VLTI/AMBER spectro-interferometry (R=12,000) with CRIRES spectroscopy (R=100,000) we can both spectrally and spatially resolve the Br-gamma line-emitting gas around MWC147. Our interferometric visibility modelling of MWC147 indicates the presence of a compact continuum disk with a close to face-on orientation. We model the continuum with an inclined Gaussian, as well as a ring with a radius of 0.60mas (0.39au) which is well within the expected dust sublimation radius of 1.52au. We detect no significant change in the measured visibilities across the Br-gamma line, indicating that the line-emitting gas is located in the same region as the continuum-emitting disk. We fit our AMBER spectro-interferometry data with a kinematic model of a disk in Keplerian rotation, with both the line-emitting and continuum-emitting components of the disk originating from the same compact region close to the central star. The presence of line-emitting gas in the same region as the K-band continuum supports the interpretation that the K-band continuum traces an optically-thick gas disk. Our spatially and spectrally resolved observations of MWC147 reveal that the K-band continuum and Br-gamma emission both originate from a similar compact region, with Br-gamma emitted from the accretion disk or disk wind region and exhibiting a rotational velocity profile. We conclude that we detect the presence of a compact, gaseous accretion disk in Keplerian rotation around MWC147.

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arXiv2018

Why Chromatic Imaging Matters

During the last two decades, the first generation of beam combiners at the Very Large Telescope Interferometer has proved the importance of optical interferometry for high-angular resolution astrophysical studies in the near- and mid-infrared. With the advent of 4-beam combiners at the VLTI, the u-v coverage per pointing increases significantly, providing an opportunity to use reconstructed images as powerful scientific tools. Therefore, interferometric imaging is already a key feature of the new generation of VLTI instruments, as well as for other interferometric facilities like CHARA and JWST. It is thus imperative to account for the current image reconstruction capabilities and their expected evolutions in the coming years. Here, we present a general overview of the current situation of optical interferometric image reconstruction with a focus on new wavelength-dependent information, highlighting its main advantages and limitations. As an Appendix we include several cookbooks describing the usage and installation of several state-of-the art image reconstruction packages. To illustrate the current capabilities of the software available to the community, we recovered chromatic images, from simulated MATISSE data, using the MCMC software SQUEEZE. With these images, we aim at showing the importance of selecting good regularization functions and their impact on the reconstruction.

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arXiv2018

The LEECH Exoplanet Imaging Survey: Limits on Planet Occurrence Rates Under Conservative Assumptions

We present the results of the largest $L^{\prime}$ ($3.8~μ$m) direct imaging survey for exoplanets to date, the Large Binocular Telescope Interferometer (LBTI) Exozodi Exoplanet Common Hunt (LEECH). We observed 98 stars with spectral types from B to M. Cool planets emit a larger share of their flux in $L^{\prime}$ compared to shorter wavelengths, affording LEECH an advantage in detecting low-mass, old, and cold-start giant planets. We emphasize proximity over youth in our target selection, probing physical separations smaller than other direct imaging surveys. For FGK stars, LEECH outperforms many previous studies, placing tighter constraints on the hot-start planet occurrence frequency interior to $\sim20$ au. For less luminous, cold-start planets, LEECH provides the best constraints on giant-planet frequency interior to $\sim20$ au around FGK stars. Direct imaging survey results depend sensitively on both the choice of evolutionary model (e.g., hot- or cold-start) and assumptions (explicit or implicit) about the shape of the underlying planet distribution, in particular its radial extent. Artificially low limits on the planet occurrence frequency can be derived when the shape of the planet distribution is assumed to extend to very large separations, well beyond typical protoplanetary dust-disk radii ($\lesssim50$ au), and when hot-start models are used exclusively. We place a conservative upper limit on the planet occurrence frequency using cold-start models and planetary population distributions that do not extend beyond typical protoplanetary dust-disk radii. We find that $\lesssim90\%$ of FGK systems can host a 7 to 10 $M_{\mathrm{Jup}}$ planet from 5 to 50 au. This limit leaves open the possibility that planets in this range are common.

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arXiv2018

BRITE-Constellation reveals evidence for pulsations in the enigmatic binary $η$ Carinae

$η$ Car is a massive, eccentric binary with a rich observational history. We obtained the first high-cadence, high-precision light curves with the BRITE-Constellation nanosatellites over 6 months in 2016 and 6 months in 2017. The light curve is contaminated by several sources including the Homunculus nebula and neighboring stars, including the eclipsing binary CPD$-$59$^\circ$2628. However, we found two coherent oscillations in the light curve. These may represent pulsations that are not yet understood but we postulate that they are related to tidally excited oscillations of $η$ Car's primary star, and would be similar to those detected in lower-mass eccentric binaries. In particular, one frequency was previously detected by van Genderen et al. and Sterken et al. through the time period of 1974 to 1995 through timing measurements of photometric maxima. Thus, this frequency seems to have been detected for nearly four decades, indicating that it has been stable in frequency over this time span. These pulsations could help provide the first direct constraints on the fundamental parameters of the primary star if confirmed and refined with future observations.

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arXiv2017

Gas dynamics in the inner few AU around the Herbig B[e] star MWC297: Indications of a disk wind from kinematic modeling and velocity-resolved interferometric imaging

We present near-infrared AMBER (R = 12, 000) and CRIRES (R = 100, 000) observations of the Herbig B[e] star MWC297 in the hydrogen Br-gamma-line. Using the VLTI unit telescopes, we obtained a uv-coverage suitable for aperture synthesis imaging. We interpret our velocity-resolved images as well as the derived two-dimensional photocenter displacement vectors, and fit kinematic models to our visibility and phase data in order to constrain the gas velocity field on sub-AU scales. The measured continuum visibilities constrain the orientation of the near-infrared-emitting dust disk, where we determine that the disk major axis is oriented along a position angle of 99.6 +/- 4.8 degrees. The near-infrared continuum emission is 3.6 times more compact than the expected dust-sublimation radius, possibly indicating the presence of highly refractory dust grains or optically thick gas emission in the inner disk. Our velocity-resolved channel maps and moment maps reveal the motion of the Br-gamma-emitting gas in six velocity channels, marking the first time that kinematic effects in the sub-AU inner regions of a protoplanetary disk could be directly imaged. We find a rotation-dominated velocity field, where the blue- and red-shifted emissions are displaced along a position angle of 24 +/- 3 degrees and the approaching part of the disk is offset west of the star. The visibility drop in the line as well as the strong non-zero phase signals can be modeled reasonably well assuming a Keplerian velocity field, although this model is not able to explain the 3 sigma difference that we measure between the position angle of the line photocenters and the position angle of the dust disk. We find that the fit can be improved by adding an outflowing component to the velocity field, as inspired by a magneto-centrifugal disk-wind scenario.

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arXiv2016

A high-mass protobinary system with spatially resolved circumstellar accretion disks and circumbinary disk

High-mass multiples might form via fragmentation of self-gravitational disks or alternative scenarios such as disk-assisted capture. However, only few observational constraints exist on the architecture and disk structure of high-mass protobinaries and their accretion properties. Here we report the discovery of a close ($57.9\pm0.2$mas=170au) high-mass protobinary, IRAS17216-3801, where our VLTI/GRAVITY+AMBER near-infrared interferometry allows us to image the circumstellar disks around the individual components with 3 milliarcsecond resolution. We estimate the component masses to $\sim20$ and $\sim18 M_{\odot}$ and find that the radial intensity profiles can be reproduced with an irradiated disk model, where the inner regions are excavated of dust, likely tracing the dust sublimation region in these disks. The circumstellar disks are strongly misaligned with respect to the binary separation vector, which indicates that the tidal forces did not have time to realign the disks, pointing towards a young dynamical age of the system. We constrain the distribution of the Br$γ$ and CO-emitting gas using VLTI/GRAVITY spectro-interferometry and VLT/CRIRES spectro-astrometry and find that the secondary is accreting at a higher rate than the primary. VLT/NACO imaging shows $L'$-band emission on 3-4 times larger scales than the binary separation, matching the expected dynamical truncation radius for the circumbinary disk. The IRAS17216-3801 system is $\sim3\times$ more massive and $\sim5\times$ more compact than other high-mass multiplies imaged at infrared wavelengths and the first high-mass protobinary system where circumstellar and circumbinary dust disks could be spatially resolved. This opens exciting new opportunities for studying star-disk interactions and the role of multiplicity in high-mass star formation.

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arXiv2016

Clumpy dust clouds and extended atmosphere of the AGB star W Hya revealed with VLT/SPHERE-ZIMPOL and VLTI/AMBER II. Time variations between pre-maximum and minimum light

Our recent visible polarimetric images of the well-studied AGB star W Hya taken at pre-maximum light (phase 0.92) with VLT/SPHERE-ZIMPOL have revealed clumpy dust clouds close to the star at ~2 Rstar. We present second-epoch SPHERE-ZIMPOL observations of W Hya at minimum light (phase 0.54) in the continuum (645, 748, and 820 nm), in the Halpha line (656.3 nm), and in the TiO band (717 nm) as well as high-spectral resolution long-baseline interferometric observations in 2.3 micron CO lines with the AMBER instrument at the Very Large Telescope Interferometer (VLTI). The high-spatial resolution polarimetric images have allowed us to detect clear time variations in the clumpy dust clouds as close as 34--50~mas (1.4--2.0 Rstar) to the star. We detected the formation of a new dust cloud and the disappearance of one of the dust clouds detected at the first epoch. The Halpha and TiO emission extends to ~150 mas (~6 Rstar), and the Halpha images reveal time variations. The degree of linear polarization is higher at minimum light (13--18%) than that at pre-maximum light. The power-law-type limb-darkened disk fit to the AMBER data in the continuum results in a limb-darkened disk diameter of 49.1+/-1.5 mas and a limb-darkening parameter of 1.16+/-0.49, indicating that the atmosphere is more extended with weaker limb-darkening compared to pre-maximum light. Our Monte Carlo radiative transfer modeling suggests the predominance of small (0.1 micron) grains of Al2O3, Mg2SiO4, and MgSiO3 at minimum light, in marked contrast to the predominance of large (0.5 micron) grains at pre-maximum light. The variability phase dependence of the grain size implies that small grains might just have started to form at minimum light in the wake of a shock, while the pre-maximum light phase might have corresponded to the phase of efficient grain growth.

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arXiv2016

TYC 8241 2652 1 and the case of the disappearing disk: no smoking gun yet

TYC 8241 2652 1 is a young star that showed a strong mid-infrared (mid-IR, 8-25 mu) excess in all observations before 2008 consistent with a dusty disk. Between 2008 and 2010 the mid-IR luminosity of this system dropped dramatically by at least a factor of 30 suggesting a loss of dust mass of an order of magnitude or more. We aim to constrain possible models including removal of disk material by stellar activity processes, the presence of a binary companion, or other explanations suggested in the literature. We present new X-ray observations, optical spectroscopy, near-IR interferometry, and mid-IR photometry of this system to constrain its parameters and further explore the cause of the dust mass loss. In X-rays TYC 8241 2652 1 has all properties expected from a young star: Its luminosity is in the saturation regime and the abundance pattern shows enhancement of O/Fe. The photospheric Ha line is filled with a weak emission feature, indicating chromospheric activity consistent with the observed level of coronal emission. Interferometry does not detect a companion and sets upper limits on the companion mass of 0.2, 0.35, 0.1 and 0.05 M_sun at projected physical separations of 0.1-4 AU,4-5 AU, 5-10 AU, and 10-30 AU, respectively (assuming a distance of 120.9 pc). Our mid-IR measurements, the first of the system since 2012, are consistent with the depleted dust level seen after 2009. The new data confirms that stellar activity is unlikely to destroy the dust in the disk and shows that scenarios where either TYC 8241 2652 1 heats the disk of a binary companion or a potential companion heats the disk of TYC 8241 2652 1 are unlikely.

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arXiv2016

The fossil wind structures of Eta Carinae: changes across on 5.54-year cycle

Eta Carinae, the closest, active, massive binary containing a highly unstable LBV, exhibits expanding, compressed wind shells, seen in emission, that are spatially and spectrally resolved by \hst/\stis. Starting in June 2009, these structures were mapped across its 5.54-year, highly elliptical, binary orbit to follow temporal changes in the light of [Fe~III] 4659Å and [Fe~II] 4815Å. The emissions trace portions of fossil wind-shells, that were formed by wind-wind interactions across each cycle. Over the high-ionization state, dense arcs, photo-ionized by far ultraviolet radiation from the hot secondary, are seen in [Fe~III]. Other arcs, ionized by mid-ultraviolet radiation from the primary star, are seen in [Fe II]. The [Fe III] structures tend to be interior to [Fe II] structures that trace extensive, less disturbed primary wind. During the brief periastron passage when the secondary plunges deep into the primary's extremely dense wind, on the far side of primary star, high-ionization [Fe III] structures fade and reappear in [Fe II]. Multiple fossil wind-structures were traced across the 5.7-year monitoring interval. The strong similarity of the expanding [Fe II] shells suggests that the wind and photo-ionization properties of the massive binary have not changed substantially from one orbit to the next over the past several orbital cycles. These observations trace structures that can be used to test three-dimensional hydrodynamical and radiative-transfer models of massive, interacting winds. They also provide a baseline for following future changes in Eta Carinae, especially of its winds and photoionization properties.

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arXiv2016

Planet Formation Imager (PFI): science vision and key requirements

The Planet Formation Imager (PFI) project aims to provide a strong scientific vision for ground-based optical astronomy beyond the upcoming generation of Extremely Large Telescopes. We make the case that a breakthrough in angular resolution imaging capabilities is required in order to unravel the processes involved in planet formation. PFI will be optimised to provide a complete census of the protoplanet population at all stellocentric radii and over the age range from 0.1 to about 100 Myr. Within this age period, planetary systems undergo dramatic changes and the final architecture of planetary systems is determined. Our goal is to study the planetary birth on the natural spatial scale where the material is assembled, which is the "Hill Sphere" of the forming planet, and to characterise the protoplanetary cores by measuring their masses and physical properties. Our science working group has investigated the observational characteristics of these young protoplanets as well as the migration mechanisms that might alter the system architecture. We simulated the imprints that the planets leave in the disk and study how PFI could revolutionise areas ranging from exoplanet to extragalactic science. In this contribution we outline the key science drivers of PFI and discuss the requirements that will guide the technology choices, the site selection, and potential science/technology tradeoffs.

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arXiv2016

V346 Normae: First post-outburst observations of an FU Orionis star

During their formation phase stars gain most of their mass in violent episodic accretion events, such as observed in FU Orionis (FUor) and EXor stars. V346 Normae is a well-studied FUor that underwent a strong outburst beginning in $\sim1980$. Here, we report photometric and spectroscopic observations which show that the visual/near-infrared brightness has decreased dramatically between the 1990s and 2010 ($ΔR\approx10.9^{\rm m}$, $ΔJ\approx7.8^{\rm m}$, $ΔK\approx5.8^{\rm m}$). The spectral properties of this fading event cannot be explained with variable extinction alone, but indicate a drop in accretion rate by 2-3 orders of magnitude, marking the first time that a member of the FUor class has been observed to switch to a very low accretion phase. Remarkably, in the last few years (2011-2015) V346 Nor has brightened again at all near-infrared wavelengths, indicating the onset of a new outburst event. The observed behaviour might be consistent with the clustered luminosity bursts that have been predicted by recent gravitational instability and fragmentation models for the early stages of protostellar evolution. Given V346 Nor's unique characteristics (concerning outburst duration, repetition frequency, and spectroscopic diagnostics), our results also highlight the need for revisiting the FUor/EXor classification scheme.

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arXiv2016

Clumpy dust clouds and extended atmosphere of the AGB star W Hya revealed with VLT/SPHERE-ZIMPOL and VLTI/AMBER

We present visible polarimetric imaging observations of the well-studied AGB star W Hya taken with VLT/SPHERE-ZIMPOL as well as high spectral resolution long-baseline interferometric observations with the AMBER instrument of the Very Large Telescope Interferometer (VLTI). We observed W Hya with VLT/SPHERE-ZIMPOL at three wavelengths in the continuum (645, 748, and 820 nm), in the Halpha line at 656.3 nm, and in the TiO band at 717 nm. The VLTI/AMBER observations were carried out in the wavelength region of the CO first overtone lines near 2.3 micron with a spectral resolution of 12000. Taking advantage of the polarimetric imaging capability of SPHERE-ZIMPOL combined with the superb adaptive optics performance, we have succeeded in spatially resolving three clumpy dust clouds located at ~50 mas (~2 Rstar) from the central star, revealing dust formation very close to the star. The AMBER data in the individual CO lines suggest a molecular outer atmosphere extending to ~3 Rstar. Furthermore, the SPHERE-ZIMPOL image taken over the Halpha line shows emission with a radius of up to ~160 mas (~7 Rstar). We found that dust, molecular gas, and Halpha-emitting hot gas are coexisting within 2--3 Rstar. Our modeling suggests that the observed polarized intensity maps can reasonably be explained by large (0.4--0.5 micron) grains of Al2O3 or Mg2SiO4 or MgSiO3 in an optically thin shell with an inner boundary radius of 1.9--2.0 Rstar. The observed clumpy structure can be reproduced by a density enhancement by a factor of 4 +/- 1. The grain size derived from our polarimetric images is consistent with the prediction of the hydrodynamical models for the mass loss driven by the scattering due to micron-sized grains. The detection of the clumpy dust clouds close to the star lends support to the dust formation induced by pulsation and large convective cells as predicted by the 3-D simulations for AGB stars.

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arXiv2015

The LEECH Exoplanet Imaging Survey: Characterization of the Coldest Directly Imaged Exoplanet, GJ 504 b, and Evidence for Super-Stellar Metallicity

As gas giant planets and brown dwarfs radiate away the residual heat from their formation, they cool through a spectral type transition from L to T, which encompasses the dissipation of cloud opacity and the appearance of strong methane absorption. While there are hundreds of known T-type brown dwarfs, the first generation of directly-imaged exoplanets were all L-type. Recently, Kuzuhara et al. (2013) announced the discovery of GJ 504 b, the first T dwarf exoplanet. GJ 504 b provides a unique opportunity to study the atmosphere of a new type of exoplanet with a ~500 K temperature that bridges the gap between the first directly imaged planets (~1000 K) and our own Solar System's Jupiter (~130 K). We observed GJ 504 b in three narrow L-band filters (3.71, 3.88, and 4.00 microns), spanning the red end of the broad methane fundamental absorption feature (3.3 microns) as part of the LEECH exoplanet imaging survey. By comparing our new photometry and literature photometry to a grid of custom model atmospheres, we were able to fit GJ 504 b's unusual spectral energy distribution for the first time. We find that GJ 504 b is well-fit by models with the following parameters: T_eff=544+/-10 K, g<600 m/s^2, [M/H]=0.60+/-0.12, cloud opacity parameter of f_sed=2-5, R=0.96+/-0.07 R_Jup, and log(L)=-6.13+/-0.03 L_Sun, implying a hot start mass of 3-30 M_jup for a conservative age range of 0.1-6.5 Gyr. Of particular interest, our model fits suggest that GJ 504 b has a super-stellar metallicity. Since planet formation can create objects with non-stellar metallicities, while binary star formation cannot, this result suggests that GJ 504 b formed like a planet, not like a binary companion.

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arXiv2015

Investigating the origin and spectroscopic variability of the near-infrared HI lines in the Herbig star VV Ser

The origin of the near-infrared (NIR) HI emission lines in young stellar objects are not yet understood. To probe it, we present multi-epoch LBT-LUCIFER spectroscopic observations of the Paδ, Paβ, and Brγ lines observed in the Herbig star VVSer, along with VLTI-AMBER Brγ spectro-interferometric observations at medium resolution. Our spectroscopic observations show line profile variability in all the HI lines. The strongest variability is observed in the redshifted part of the line profiles. The Brγ spectro-interferometric observations indicate that the Brγ line emitting region is smaller than the continuum emitting region. To interpret our results, we employed radiative transfer models with three different flow configurations: magnetospheric accretion, a magneto-centrifugally driven disc wind, and a schematic bipolar outflow. Our models suggest that the HI line emission in VVSer is dominated by the contribution of an extended wind, perhaps a bipolar outflow. Although the exact physical process for producing such outflow is not known, this model is capable of reproducing the averaged single-peaked line profiles of the HI lines. Additionally, the observed visibilities, differential and closure phases are best reproduced when a wind is considered. Nevertheless, the complex line profiles and variability could be explained by changes in the relative contribution of the magnetosphere and/or winds to the line emission. This might indicate that the NIR HI lines are formed in a complex inner disc region where inflow and outflow components might coexist. Furthermore, the contribution of each of these mechanisms to the line appears time variable, suggesting a non-steady accretion/ejection flow.

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arXiv2015

The LEECH Exoplanet Imaging Survey: Orbit and Component Masses of the Intermediate Age, Late-Type Binary NO UMa

We present high-resolution Large Binocular Telescope LBTI/LMIRcam images of the spectroscopic and astrometric binary NO UMa obtained as part of the LBTI Exozodi Exoplanet Common Hunt (LEECH) exoplanet imaging survey. Our H, K$_s$, and L'-band observations resolve the system at angular separations <0.09". The components exhibit significant orbital motion over a span of ~7 months. We combine our imaging data with archival images, published speckle interferometry measurements, and existing spectroscopic velocity data to solve the full orbital solution and estimate component masses. The masses of the K2.0$\pm$0.5 primary and K6.5$\pm$0.5 secondary are 0.83$\pm$0.02 M$_{\odot}$ and 0.64$\pm$0.02 M$_{\odot}$, respectively. We also derive a system distance of d = 25.87$\pm$0.02 pc and revise the Galactic kinematics of NO UMa. Our revised Galactic kinematics confirm NO UMa as a nuclear member of the ~500 Myr old Ursa Major moving group and it is thus a mass and age benchmark. We compare the masses of the NO UMa binary components to those predicted by five sets of stellar evolution models at the age of the Ursa Major group. We find excellent agreement between our measured masses and model predictions with little systematic scatter between the models. NO UMa joins the short list of nearby, bright, late-type binaries having known ages and fully characterized orbits.

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arXiv2015

AMBER-NACO aperture-synthesis imaging of the half-obscured central star and the edge-on disk of the red giant L2 Pup

The red giant L2 Pup started a dimming event in 1994, which is considered to be caused by the ejection of dust clouds. We present near-IR aperture-synthesis imaging of L2 Pup achieved by combining data from VLT/NACO speckle observations and long-baseline interferometric observations with the AMBER instrument of the Very Large Telescope Interferometer (VLTI). We also extracted an 8.7 micron image from the mid-IR VLTI instrument MIDI. Our aim is to spatially resolve the innermost region of the circumstellar environment. The diffraction-limited image at 2.27 micron obtained by bispectrum speckle interferometry with NACO with a spatial resolution of 57 mas shows an elongated component. The aperture-synthesis imaging combining the NACO speckle data and AMBER data (2.2--2.29 micron) with a spatial resolution of 5.6x7.3 mas further resolves not only this elongated component, but also the central star. The reconstructed image reveals that the elongated component is a nearly edge-on disk with a size of ~180x50 mas lying in the E-W direction, and furthermore, that the southern hemisphere of the central star is severely obscured by the equatorial dust lane of the disk. The angular size of the disk is consistent with the distance that the dust clouds that were ejected at the onset of the dimming event should have traveled by the time of our observations, if we assume that the dust clouds moved radially. This implies that the formation of the disk may be responsible for the dimming event. The 8.7 micron image with a spatial resolution of 220 mas extracted from the MIDI data taken in 2004 (seven years before the AMBER and NACO observations) shows an approximately spherical envelope without a signature of the disk. This suggests that the mass loss before the dimming event may have been spherical.

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arXiv2015

Investigating 2MASS J06593158-0405277: a FUor burst in a triple system?

FUor outbursts in young stellar objects (YSOs) are the most dramatic events among episodic accretion phenomena. The origin of these bursts is not clear: disk instabilities and/or disk perturbations by an external body being the most viable hypotheses. Here, we report our VLT/SINFONI high angular resolution AO-assisted observations of 2MASS J06593158-0405277, which is undergoing a recently discovered FUor outburst. Our observations reveal the presence of an extended disc-like structure around the FUor, a very low-mass companion (2MASS J06593158-0405277B) at ~100 au in projection, and, possibly, a third closer companion at ~11 au. These sources appear to be young, displaying accretion signatures. Assuming the components are physically linked, 2MASS J06593158-0405277 would then be one of the very few triple systems observed in FUors.

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