AA Tau is a classical T Tauri star with a highly inclined, warped circumstellar disk. For decades, AA Tau exhibited photometric and spectroscopic variability that were successfully modelled as occultations of the primary star by circumstellar material. In 2011, AA Tau entered an extended faint state, presumably due to enhanced levels of circumstellar dust. We use two sets of contemporaneous optical-NIR spectra of AA Tau, obtained in December of 2008 and 2014, to directly measure the wavelength-dependent extinction associated with the dust enhancement driving AA Tau's 2011 optical fade. Taken alone, AA Tau's apparent optical-NIR increased extinction curve cannot be fit well with standard extinction laws. At optical wavelengths, AA Tau's dimming event is consistent with predictions of common extinction models for an increase of $A_V=2$, but no such model reproduces AA Tau's color-color excess at NIR wavelengths. We show that veiling emission accounts for the apparent anomalous NIR extinction: after including this veiling flux, AA Tau's dimming event is consistent with a standard $A_V=2$ extinction law across the full optical-NIR range. We also report an increase in AA Tau's mid-IR flux since its 2011 fade, and suggest that an increase in the height of AA Tau's inner disk is the most likely explanation for both the IR brightening and the additional extinction along the line of sight. In addition to informing our understanding of AA Tau, this analysis demonstrates that caution should be exercised when inferring extinction (and stellar parameters) from the NIR color-color excess of young stars with measurable NIR veiling fluxes.
We present the discovery of a plausible disk-eclipse system OGLE-BLG182.1.162852. The OGLE light curve for OGLE-BLG182.1.162852 shows three episodes of dimming by $I \simeq 2 - 3$ magnitudes, separated by 1277 days. The shape of the light curve during dimming events is very similar to that of known disk eclipse system OGLE-LMC-ECL-11893 (Dong et al. 2014). The event is presently undergoing a dimming event, predicted to end on December 30th, 2014. We encourage spectroscopic and multi-band photometric observations now. The next dimming episode for OGLE-BLG182.1.162852 is expected to occur in Mar…
We present optical spectrophotometry of the red supergiant Betelgeuse from 2020 February 15, during its recent unprecedented dimming episode. By comparing this spectrum to stellar atmosphere models for cool supergiants, as well as spectrophotometry of other Milky Way red supergiants, we conclude that Betelgeuse has a current effective temperature of 3600 +/- 25 K. While this is slightly cooler than previous measurements taken prior to Betelgeuse's recent lightcurve evolution, this drop in effective temperature is insufficient to explain Betelgeuse's recent optical dimming. We propose that epis…
AA Tau, a classical T Tauri star in the Taurus cloud, has been the subject of intensive photometric monitoring for more than two decades due to its quasi-cyclic variation in optical brightness. Beginning in 2011, AA Tau showed another peculiar variation -- its median optical though near-IR flux dimmed significantly, a drop consistent with a 4-mag increase in visual extinction. It has stayed in the faint state since.Here we present 4.7um CO rovibrational spectra of AA Tau over eight epochs, covering an eleven-year time span, that reveal enhanced 12CO and 13CO absorption features in the $J_{\rm …
Betelgeuse, one of the most studied red supergiant stars, dimmed in the optical by ~1.2 mag between late 2019 and early 2020, reaching an historical minimum called "the Great Dimming." Thanks to enormous observational effort to date, two hypotheses remain that can explain the Dimming: a decrease in the effective temperature and an enhancement of the extinction caused by newly produced circumstellar dust. However, the lack of multi-wavelength monitoring observations, especially in the mid infrared where emission from circumstellar dust can be detected, has prevented us from closely examining th…
AA Tau is a well studied young stellar object that presents many of the photometric characteristics of a Classical T Tauri star (CTTS), including short-timescale stochastic variability attributed to spots and/or accretion as well as long duration dimming events attributed to occultations by vertical features (e.g., warps) in its circumstellar disk. We present new photometric observations of AA Tau from the Kilodegree Extremely Little Telescope North (KELT-North) which reveal a deep, extended dimming event in 2011, which we show supports the interpretation by Bouvier et al. (2013) of an occulta…
We present the discovery of two extended $\sim$0.12 mag dimming events of the weak-lined T-Tauri star V1334. The start of the first event was missed but came to an end in late 2003, and the second began in February 2009, and continues as of November 2016. Since the egress of the current event has not yet been observed, it suggests a period of $>$13 years if this event is periodic. Spectroscopic observations suggest the presence of a small inner disk, although the spectral energy distribution shows no infrared excess. We explore the possibility that the dimming events are caused by an orbiting …
We present photometric observations of RW Aurigae, a Classical T Tauri system, that reveal two remarkable dimming events. These events are similar to that which we observed in 2010-2011, which was the first such deep dimming observed in RW Aur in a century's worth of photometric monitoring. We suggested the 2010-2011 dimming was the result of an occultation of the star by its tidally disrupted circumstellar disk. In 2012-2013, the RW Aur system dimmed by ~0.7 mag for ~40 days and in 2014/2015 the system dimmed by ~2 mag for >250 days. The ingress/egress duration measurements of the more recent…
Two recent short term dimmings of KIC 8462852 (Boyajian's Star) exhibit clear reddening in the B, r' and i' photometric passbands. We show that the intensity ratios of the three pass bands agree well with cooling of an approximately 6800 K black body by about 30K. This agreement, together with other recent findings on the timing and longer term dimmings of this star, support our previous argument that the star's photometric behavior is caused by internal storage of impeded convective flux, rather than by external sources of obscuration such the ISM or circumstellar material.
Context. RW Aur A is a classical T Tauri star (CTTS) with an unusually rich emission line spectrum. In 2014 the star faded by ~ 3 magnitudes in the V band and went into a long-lasting minimum. In 2010 the star suffered from a similar fading, although less deep. These events in RW Aur A are very unusual among the CTTS, and have been attributed to occultations by passing dust clouds. Aims. We want to find out if any spectral changes took place after the last fading of RW Aur A with the intention to gather more information on the occulting body and the cause of the phenomenon. Methods. We collect…
We report detection of quasi-periodic (1.5 day) dimming of HD 240779, the solar-mass primary in a 5" visual binary (also TIC 284730577), by the Transiting Exoplanet Survey Satellite. This dimming, as has been shown for other "dipper" stars, is likely due to occultation by circumstellar dust. The barycentric space motion, lithium abundance, rotation, and chromospheric emission of the stars in this system point to an age of ~125 Myr, and possible membership in the AB Doradus moving group. As such it occupies an important but poorly explored intermediate regime of stars with transient dimming bet…
The wind interaction with the dusty environment of the classical T Tauri star RY Tau has been investigated. During two seasons of 2013-2015 we carried out a spectroscopic and photometric (BVR) monitoring of the star. A correlation between the stellar brightness and the radial velocity of the wind determined from the H-alpha and Na D line profiles has been found for the first time. The irregular stellar brightness variations are shown to be caused by extinction in a dusty disk wind at a distance of about 0.2 AU from the star. We suppose, that variations of the circumstellar extinction results f…
In 2019 October Betelgeuse began a decline in V-band brightness that went beyond the minimum expected from its quasi-periodic ~420 day cycle, becoming the faintest in recorded photometric history. Observations obtained in 2019 December with VLT/SPHERE (Montarges 2020) have shown that the southern half of the star has become markedly fainter than in 2019 January indicating that a major change has occurred in, or near, the photosphere. We present SOFIA-EXES high spectral-resolution observations of [Fe II] 25.99 mic and [S I] 25.25 mic emission lines from Betelgeuse obtained during the unpreceden…
We report our analyses of the multi-epoch (2015-2017) ALMA archival data of the Class II binary system XZ Tau at Bands 3, 4 and 6. The millimeter dust continuum images show compact, unresolved (r <~ 15 au) circumstellar disks (CSDs) around the individual binary stars; XZ Tau A and B, with a projected separation of ~ 39 au. The 12CO (2-1) emission associated with those CSDs traces the Keplerian rotations, whose rotational axes are misaligned with each other (P.A. ~ -5 deg for XZ Tau A and ~ 130 deg for XZ Tau B). The similar systemic velocities of the two CSDs (VLSR ~ 6.0 km s-1) suggest that t…
The circumstellar environments of classical T Tauri stars are challenging to directly image because of their high star-to-disk contrast ratio. One method to overcome this is by using imaging polarimetry where scattered and consequently polarised starlight from the star's circumstellar disk can be separated from the unpolarised light of the central star. We present images of the circumstellar environment of SU Aur, a classical T Tauri star at the transition of T Tauri to Herbig stars. The images directly show that the disk extends out to ~500 au with an inclination angle of $\sim$ 50$^\circ$. U…
The aim of this paper is to study the molecular composition in the circumstellar envelope around the oxygen-rich star IK Tau. We observed IK Tau in several (sub)millimeter bands using the APEX telescope during three observing periods. To determine the spatial distribution of the $\mathrm{^{12}CO(3-2)}$ emission, mapping observations were performed. To constrain the physical conditions in the circumstellar envelope, multiple rotational CO emission lines were modeled using a non local thermodynamic equilibrium radiative transfer code. The rotational temperatures and the abundances of the other m…
RW Aur A is a classical T Tauri star, believed to have undergone a reconfiguration of its circumstellar environment as a consequence of a recent fly-by of its stellar companion, RW Aur B. This interaction stripped away part of the circumstellar disk of RW Aur A, leaving a tidally disrupted arm and a short truncated circumstellar disk. We present photometric observations of the RW Aur system from the Kilodegree Extremely Little Telescope (KELT) survey showing a long and deep dimming that occurred from September 2010 until March 2011. The dimming has a depth of ~2 magnitudes, a duration of ~180 …
Using time-series photometry from the Kilodegree Extremely Little Telescope (KELT) exoplanet survey, we are looking for eclipses of stars by their protoplanetary disks, specifically in young stellar associations. To date, we have discovered two previously unknown, large dimming events around the young stars RW Aurigae and V409 Tau. We attribute the dimming of RW Aurigae to an occultation by its tidally disrupted disk, with the disruption perhaps resulting from a recent flyby of its binary companion. Even with the dynamical environment of RW Aurigae, the distorted disk material remains very com…
The circumstellar ammonia (NH$_3$) chemistry in evolved stars is poorly understood. Previous observations and modelling showed that NH$_3$ abundance in oxygen-rich stars is several orders of magnitude above that predicted by equilibrium chemistry. In this article, we characterise the spatial distribution and excitation of NH$_3$ in the O-rich circumstellar envelopes (CSEs) of four diverse targets: IK Tau, VY CMa, OH 231.8+4.2, and IRC +10420 with multi-wavelength observations. We observed the 1.3-cm inversion line emission with the Very Large Array (VLA) and submillimetre rotational line emiss…
We present results of high-resolution imaging toward HL Tau by the Combined Array for Research in Millimeter-wave Astronomy (CARMA). We have obtained 1.3 and 2.7 mm dust continua with an angular resolution down to 0.13 arc second. Through model fitting to the two wavelength data simultaneously in Bayesian inference using a flared viscous accretion disk model, we estimate the physical properties of HL Tau, such as density distribution, dust opacity spectral index, disk mass, disk size, inclination angle, position angle, and disk thickness. HL Tau has a circumstellar disk mass of 0.13 solar mass…
Context. There are recent observational evidences that RY Tau may present two different outflow stages, a quiescent one and a more active one. We try to model that phenomenon. Aims. We have performed new 2.5D magneto-hydrodynamical simulations of the possible accretion-outflow environment of RY Tau based on analytical solutions to reduce the relaxation time. Methods. We used as initial conditions the analytical self-similar solution we used to model the RY Tau micro jet. In the closed field line region of the magnetosphere we have reversed the direction of the flow and increased the accretion …
To test alternative hypotheses for the behavior of KIC 8462852, we obtained measurements of the star over a wide wavelength range from the UV to the mid-infrared from October 2015 through December 2016, using Swift, Spitzer and at AstroLAB IRIS. The star faded in a manner similar to the long-term fading seen in Kepler data about 1400 days previously. The dimming rate for the entire period reported is 22.1 +\- 9.7 milli-mag/yr in the Swift wavebands, with amounts of 21.0 +\- 4.5 mmag in the groundbased B measurements, 14.0 +\- 4.5 mmag in V, and 13.0 +\- 4.5 in R, and a rate of 5.0 +\- 1.2 mmag…
We have conducted a survey of 17 wide (> 100 AU) young binary systems in Taurus with the Atacama Large Millimeter Array (ALMA) at two wavelengths. The observations were designed to measure the masses of circumstellar disks in these systems as an aid to understanding the role of multiplicity in star and planet formation. The ALMA observations had sufficient resolution to localize emission within the binary system. Disk emission was detected around all primaries and ten secondaries, with disk masses as low as $10^{-4} M_{\odot}$. We compare the properties of our sample to the population of known…
The binary system RW Aur consists of two classical T~Tauri stars (CTTSs). The primary recently underwent its second observed major dimming event ($ΔV\,\sim2\,$mag). We present new, resolved Chandra X-ray and UKIRT near-IR (NIR) data as well as unresolved optical photometry obtained in the dim state to study the gas and dust content of the absorber causing the dimming. The X-ray data show that the absorbing column density increased from $N_H<0.1\times10^{22}\,$cm$^{-2}$ during the bright state to $\approx2\times10^{22}\,$cm$^{-2}$ in the dim state. The brightness ratio between dim and bright st…
(Abridged) We present CARMA observations of the thermal dust emission from the circumstellar disks around the young stars RYTau and DGTau at wavelengths of 1.3mm and 2.8mm. The angular resolution of the maps is as high as 0.15arcsec, or 20AU at the distance of the Taurus cloud, which is a factor of 2 higher than has been achieved to date at these wavelengths. The unprecedented detail of the resulting disk images enables us to address three important questions related to the formation of planets. (1) What is the radial distribution of the circumstellar dust? (2) Does the dust emission show any …
We examine the long-term light curve, optical spectrum, spectral energy distribution, and Galactic location of V1117 Her in order to establish its nature. V1117 Her is most probably a young intermediate-mass star whose cyclic brightness dimmings are caused by changing circumstellar dust structures.
AA Tau has been monitored for more than 20 years since 1987, exhibiting a nearly constant brightness level of V=12.5 mag. We report here that in 2011 it suddenly faded away, becoming 2 magnitudes fainter in the V-band, and has remained in this deep state since then. We report new optical and near-IR photometry and spectroscopy obtained during the fading event. The system appears much redder and fainter than it was in the bright state. Also, the 8.2d photometric period continuously observed for more than 20 years is not seen during most of the deep state. The analysis of the system's brightness…
The immediate vicinity of T Tauri was observed with the new high-contrast imaging instrument SPHERE at the VLT to resolve remaining mysteries of the system, such as the putative small edge-on disk around T Tauri Sa, and the assignment of the complex outflow patterns to the individual stars. We used SPHERE IRDIS narrow-band classical imaging in Pa$β$, Br$γ$, and the $ν$ = 1-0 S(1) line of H$_2$, as well as in the nearby continua to obtain high spatial resolution and high contrast images over the NIR spectral range. Line maps were created by subtracting the nearby continuum. We also re--analyzed…
We conducted high-contrast polarimetry observations of T Tau in the H-band, using the HiCIAO instrument mounted on the Subaru Telescope, revealing structures as near as 0.$\arcsec$1 from the stars T Tau N and T Tau S. The whole T Tau system is found to be surrounded by nebula-like envelopes, and several outflow-related structures are detected in these envelopes. We analyzed the detailed polarization patterns of the circumstellar structures near each component of this triple young star system and determined constraints on the circumstellar disks and outflow structures. We suggest that the nearl…
Aims: By studying the photospheric abundances of 4 RV Tauri stars in the LMC, we test whether the depletion pattern of refractory elements, seen in similar Galactic sources, is also common for extragalactic sources. Since this depletion process probably only occurs through interaction with a stable disc, we investigate the circumstellar environment of these sources. Methods: A detailed photospheric abundance study was performed using high-resolution UVES optical spectra. To study the circumstellar environment we use photometric data to construct the spectral energy distributions of the stars, …
Dimming and pulsation shock of the coalesced star V838 Monocerotis
University of Minnesota（明尼苏达大学）；University of Tartu（塔尔图大学）；Nordic Optical Telescope（北欧光学望远镜）；Aarhus University（奥胡斯大学）；Leibniz-Institute for Astrophysics Potsdam (AIP)（波茨坦莱布尼茨天体物理研究所）；Nicolaus Copernicus Astronomical Center, Polish Academy of Sciences（波兰科学院尼古拉·哥白尼天文学中心）
We present H-band polarimetric imagery of UX Tau A taken with HiCIAO/AO188 on the Subaru Telescope. UX Tau A has been classified as a pre-transitional disk object, with a gap structure separating its inner and outer disks. Our imagery taken with the 0.15 (21 AU) radius coronagraphic mask has revealed a strongly polarized circumstellar disk surrounding UX Tau A which extends to 120 AU, at a spatial resolution of 0.1 (14 AU). It is inclined by 46 \pm 2 degree as the west side is nearest. Although SED modeling and sub-millimeter imagery suggested the presence of a gap in the disk, with the inner …
The study of spiral structures in protoplanetary disks is of great importance for understanding of processes in the disks, including planet formation. Bright spiral arms were detected in the disk of young star CQ Tau by Uyama et al. (2020) in H and L bands. The spiral arms are located inside the gap in millimeter size dust, recovered earlier using ALMA observations (Ubeira Gabellini et al. 2019). To explain the gap, Ubeira Gabellini et al. (2019) proposed the existence of a planet with the semimajor axis of 20 AU. We obtained multiepoch observations of a spiral feature in the circumstellar env…
We present the discovery of an exceptional dimming event in a cool supergiant star in the Local Volume spiral M51. The star, dubbed M51-DS1, was found as part of a Hubble Space Telescope (HST) search for failed supernovae (SNe). The supergiant, which is plausibly associated with a very young ($\lesssim6$ Myr) stellar population, showed clear variability (amplitude $ΔF814W\approx0.7$ mag) in numerous HST images obtained between 1995 and 2016, before suddenly dimming by $>$2 mag in $F814W$ sometime between late 2017 and mid-2019. In follow-up data from 2021, the star rebrightened, ruling out a f…
Aims. In this paper we model, in a self-consistent way, polarimetric, photometric, spectrophotometric and interferometric observations of the classical Be star $ζ$ Tauri. Our primary goal is to conduct a critical quantitative test of the global oscillation scenario. Methods. We have carried out detailed three-dimensional, NLTE radiative transfer calculations using the radiative transfer code HDUST. For the input for the code we have used the most up-to-date research on Be stars to include a physically realistic description for the central star and the circumstellar disc. We adopt a rotationall…
We report the results of optical spectroscopic monitoring observations of a T Tauri star, V409 Tau. A previous photometric study indicated that this star experienced dimming events due to the obscuration of light from the central star with a distorted circumstellar disk. We conducted medium-resolution (R ~10,000) spectroscopic observations with 2-m Nayuta telescope at Nishi-Harima Astronomical Observatory. Spectra were obtained in 18 nights between November 2015 and March 2016. Several absorption lines such as Ca I and Li, and the H alpha emission line were confirmed in the spectra. The Ic-ban…
To enhance our knowledge of the characteristics and distribution of the circumstellar dust associated with the individual components of the young hierarchical triple system T Tau, observations in the N-band with MIDI at the VLTI were performed. Our study is based on both the interferometric and the spectrophotometric measurements and is supplemented by new visual and infrared photometry. Also, the phases were investigated to determine the dominating mid-infrared source in the close southern binary. The data were fit with the help of a sophisticated physical disc model. This model utilises the …
We present the discovery of a cold massive dust disk around the T Tauri star V1094 Sco in the Lupus molecular cloud from the 1.1 millimeter continuum observations with AzTEC on ASTE. A compact ($r\lesssim$320 AU) continuum emission coincides with the stellar position having a flux density of 272 mJy which is largest among T Tauri stars in Lupus. We also present the detection of molecular gas associated with the star in the five-point observations in $^{12}$CO J=3--2 and $^{13}$CO J=3--2. Since our $^{12}$CO and $^{13}$CO observations did not show any signature of a large-scale outflow or a mas…
Context. With its high complexity, large size, and close distance, the ringworld around GG Tau A is an appealing case to study the formation and evolution of protoplanetary disks around multiple star systems. However, investigations with radiative transfer models are usually neglecting the influence of the circumstellar dust around the individual stars. Aims. We investigate how circumstellar disks around the stars of GG Tau A are influencing the emission that is scattered at the circumbinary disk and if constraints on these circumstellar disks can be derived. Methods. We perform radiative tran…
Aims: We investigate the structure of the circumstellar disk of the T Tauri star S CrA N and test whether the observations agree with the standard picture proposed for Herbig Ae stars. Methods: Our observations were carried out with the VLTI/AMBER instrument in the H and K bands with the low spectral resolution mode. For the interpretation of our near-infrared AMBER and archival mid-infrared MIDI visibilities, we employed both geometric and temperature-gradient models. Results: To characterize the disk size, we first fitted geometric models consisting of a stellar point source, a ring-shaped d…
Classical T Tauri stars (CTTSs) are young low-mass stellar objects accreting mass from their circumstellar disks. They are characterized by high levels of coronal activity as revealed by X-ray observations. This activity may affect the disk stability and the circumstellar environment. Here we investigate if an intense coronal activity due to flares occurring close to the accretion disk may perturb the inner disk stability, disrupt the inner part of the disk and, possibly, trigger accretion phenomena with rates comparable with those observed. We model a magnetized protostar surrounded by an acc…
(abridged) We present 2-dimensional hydrodynamic simulations using the Smoothed Particle Hydrodynamic (SPH) code, VINE, to model a self-gravitating binary system similar to the GG Tau A system. We simulate systems configured with semi-major axes of either $a=62$~AU (`wide') or $a=32$~AU (`close'), and with eccentricity of either $e=0$ or $e=0.3$. Strong spiral structures are generated with large material streams extending inwards. A small fraction accretes onto the circumstellar disks, with most returning to the torus. Structures also propagate outwards, generating net outwards mass flow and e…
We derived upper limits of the circumstellar gas disk masses around the T Tauri stars St 34 and RX J0432.8+1735 in order to place constraints on theories of planet formation and to explore the evolution of the gas-to-dust ratio during the epoch of disk dissipation around young sun-like stars. Since sub-millimeter lines of ^{12}CO trace of the cold, outer regions of circumstellar disks, we observed ^{12}CO J=2-1 emission with the 10 m Sub-Millimeter Telescope (SMT) for two carefully chosen targets. St 34 is a rare classical T Tauri star with an age of 8\pm3 Myr, and RX J0432.8+1735 is a rare we…
As part of the "Dust, Ice, and Gas In Time (DIGIT)" Herschel Open Time Key Program, we present Herschel photometry (at 70, 160, 250, 350 and 500 micron) of 31 Weak-Line T Tauri star (WTTS) candidates in order to investigate the evolutionary status of their circumstellar disks. Thirteen stars in our sample had circumstellar disks previously known from infrared observations at shorter wavelengths, while eighteen of them had no previous evidence for a disk. We detect a total of 15 disks as all previously known disks are detected at one or more Herschel wavelengths and two additional disks are ide…
Molecular line polarization is a unique source of information about the magnetic fields and anisotropies in the circumstellar envelopes of evolved stars. Here we present the first detection of thermal CO(J=2-1) and SiO(J=5-4, v=0) polarization, in the envelope of the asymptotic giant branch star IK Tau. The observed polarization direction does not match predictions for circumstellar envelope polarization induced only by an anisotropic radiation field. Assuming that the polarization is purely due to the Goldreich-Kylafis effect, the linear polarization direction is defined by the magnetic field…
We report on a pilot imaging line survey (36.0 - 37.0 GHz, with ~1 km/s spectral channels) with the Expanded Very Large Array for two asymptotic giant branch stars, RW LMi (= CIT6, which has a carbon-rich circumstellar envelope) and IK Tau (= NML Tau, with an oxygen-rich circumstellar envelope). Radio continuum emission consistent with photospheric emission was detected from both stars. From RW LMi we imaged the HC3N (J = 4 -> 3) emission. The images show several partial rings of emission; these multiple shells trace the evolution of the CSE from 400 to 1200 years. SiS (J = 2 -> 1) emission wa…
Our general understanding of multiple star and planet formation is primarily based on observations of young multiple systems in low density regions like Tau-Aur and Oph. Since many, if not most, of the stars are born in clusters, observational constraints from young binaries in those environments are fundamental for understanding both the formation of multiple systems and planets in multiple systems throughout the Galaxy. We build upon the largest survey for young binaries in the Orion Nebula Cluster (ONC) which is based on Hubble Space Telescope observations to derive both stellar and circums…
We present results from a survey searching for spatially resolved near-infrared line emission from molecular hydrogen gas in the circumstellar environments of nine young stars: AA Tau, AB Aur, DoAr 21, GG Tau, GM Aur, LkCa 15, LkH$α$ 264, UY Aur, and V773 Tau. Prior high-resolution spectra of these stars showed the presence of ro-vibrational H$_2$ line emission at 2.12$μ$m with characteristics more typical of gas located in proto-planetary disks rather than outflows. In this study, we spatially resolve the H$_2$ emission in the eight stars where it is detected. LkCa 15 is the only target that …
The nature of ASASSN-24fw's occultation: modelling the event as dimming by optically thick rings around a sub-stellar companion
Nicolaus Copernicus Astronomical Center, Polish Academy of Sciences（波兰科学院尼古拉·哥白尼天文学中心）；Inter-University Centre for Astronomy and Astrophysics（大学天文与天体物理联合中心）；Institute of Astronomy and Astrophysics, Academia Sinica（中央研究院天文及天文物理学研究所）；Instituto de Astrofísica de Canarias（加那利群岛天体物理学研究所）；Departamento de Astrofísica, Universidad de La Laguna（拉帕鲁纳大学天体物理学系）；European Space Agency (ESA)（欧洲空间局）；Division of Physics, Mathematics and Astronomy, California Institute of Technology（加州理工学院物理、数学与天文学部）
Circumstellar molecular composition of the oxygen-rich AGB star IK~Tau: II. In-depth non-LTE chemical abundance analysis
K.U.Leuven（荷语鲁汶大学）；University of Amsterdam（阿姆斯特丹大学）；Harvard-Smithsonian Center for Astrophysics（哈佛-史密森天体物理中心）；Universität zu Köln（科隆大学）；Max-Planck Institut für Radioastronomie（马克斯·普朗克射电天文研究所）；MPI für Gravitationsphysik（引力物理学马普研究所）；Jet Propulsion Laboratory, California Institute of Technology（加州理工学院喷气推进实验室）
Protoplanetary disks are a byproduct of the star formation process. In the dense mid-plane of these disks, planetesimals and planets are expected to form. The first step in planet formation is the growth of dust particles from submicrometer-sized grains to macroscopic mm-sized aggregates. The grain growth is accompanied by radial drift and vertical segregation of the particles within the disk. To understand this essential evolutionary step, spatially resolved multi-wavelength observations as well as photometric data are necessary which reflect the properties of both disk and dust. We present t…
We present ALMA 880 micron continuum observations of 20 K and M-type stars in the Upper Scorpius OB association that are surrounded by protoplanetary disks. These data are used to measure the dust content in disks around low mass stars (0.1-1.6 Msun) at a stellar age of 5-11 Myr. Thirteen sources were detected in the 880 micron dust continuum at >3 sigma with inferred dust masses between 0.3 and 52 Mearth. The dust masses tend to be higher around the more massive stars, but the significance is marginal in that the probability of no correlation is p ~ 0.03. The evolution in the dust content in …
By performing non-masked polarization imaging with Subaru/HiCIAO, polarized scattered light from the inner region of the disk around the GG Tau A system was successfully detected in the $H$ band with a spatial resolution of approximately 0.07$\arcsec$, revealing the complicated inner disk structures around this young binary. This paper reports the observation of an arc-like structure to the north of GG Tau Ab and part of a circumstellar structure that is noticeable around GG Tau Aa extending to a distance of approximately 28 AU from the primary star. The speckle noise around GG Tau Ab constrai…
