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Young stars and planetary systems form in molecular clouds. For classical T Tauri stars (CTTS, F-K type precursors) the accretion disk does not reach down to the central star, but it is truncated near the co-rotation radius. The inner edge…

Solar and Stellar Astrophysics · Physics 2015-06-11 Hans Moritz Günther

We have investigated the mass accretion rate implied by published surface abundances of Si and C in the white dwarf component of the 3.62 hr period pre-cataclysmic binary and planet host candidate QS Vir (DA+M2-4). Diffusion timescales for…

Solar and Stellar Astrophysics · Physics 2014-01-30 Jeremy J. Drake , Cecilia Garraffo , Dai Takei , Boris Gaensicke

Over two hundred protoplanetary disk systems have been resolved by ALMA, and the vast majority suggest the presence of planets. The dust gaps in transition disks are considered evidence of giant planets sculpting gas and dust under…

Earth and Planetary Astrophysics · Physics 2024-06-05 Yinhao Wu

It has been found that some quasars are undergoing quasi-periodic variations (most of them with damped amplitudes) in optical bands from long-term monitoring campaigns, but how to explain the origin of such light curve variations still…

High Energy Astrophysical Phenomena · Physics 2024-12-25 Yue-Chang Peng , Jian-Min Wang , Pu Du , Shuo Zhai , Yan-Rong Li

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…

Solar and Stellar Astrophysics · Physics 2015-05-27 Ke Zhang , Nathan Crockett , Colette Salyk , Klaus Pontoppidan , Neal J. Turner , John M. Carpenter , Geoffrey A. Blake

RW Aur is a young binary system showing strong signatures of a recent tidal encounter between the circumprimary disk and the secondary star. The primary star has recently undergone two major dimming events ($\Delta$mag $\approx$ 2 in…

Solar and Stellar Astrophysics · Physics 2016-11-30 S. Facchini , C. F. Manara , P. C. Schneider , C. J. Clarke , J. Bouvier , G. Rosotti , R. Booth , T. J. Haworth

T Cha is a nearby (d = 100 pc) transition disk known to have an optically thin gap separating optically thick inner and outer disk components. Huelamo et al. (2011) recently reported the presence of a low-mass object candidate within the…

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…

The transition between massive Class II circumstellar disks and Class III debris disks, with dust residuals, has not yet been clearly understood. Disks are expected to dissipate with time, and dust clearing in the inner regions can be the…

Using the Infrared Spectrograph aboard the Spitzer Space Telescope, we observed multiple epochs of 11 actively accreting T Tauri stars in the nearby Taurus-Auriga star forming region. In total, 88 low-resolution mid-infrared spectra were…

Solar and Stellar Astrophysics · Physics 2014-11-20 Jeffrey S. Bary , Jarron M. Leisenring , Michael F. Skrutskie

The Kepler spacecraft observed a total of only four AM Herculis cataclysmic variable stars during its lifetime. We analyze the short-cadence K2 light curve of one of those systems, Tau 4 (RX J0502.8+1624), which underwent a serendipitous…

Solar and Stellar Astrophysics · Physics 2020-04-21 Colin Littlefield , Peter Garnavich , Paula Szkody , Gavin Ramsay , Steve Howell , Isabel Lima , Mark Kennedy , Lewis Cook

We present a comprehensive analysis of the HL Tau dust disk by modeling its intensity profiles across six wavelengths (0.45 to 7.9 mm) with a resolution of 0.05 arcsec ($\sim7$ au). Using a Markov Chain Monte Carlo (MCMC) approach, we…

Observations from Spitzer and ground-based infrared spectroscopy reveal significant diversity in the molecular emission from the inner few AU of T Tauri disks. We explore theoretically the possible origin of this diversity by expanding on…

Solar and Stellar Astrophysics · Physics 2015-05-30 Joan R. Najita , Mate Adamkovics , Alfred E. Glassgold

RW Aur A is a CTTS that has suddenly undergone three major dimming events since 2010. We aim to understand the dimming properties, examine accretion variability, and derive the physical properties of the inner disc traced by the CO…

Solar and Stellar Astrophysics · Physics 2019-05-08 M. Koutoulaki , S. Facchini , C. F. Manara , A. Natta , R. Garcia Lopez , R. Fedriani , A. Caratti o Garatti , D. Coffey , T. P. Ray

Theoretical models of grain growth predict dust properties to change as a function of protoplanetary disk radius, mass, age and other physical conditions. We lay down the methodology for a multi-wavelength analysis of (sub-)mm and cm…

We present the collection of all the mid- and far-IR observations (3-170 um) of the young eruptive variable PV Cep available so far in the literature. These data allow us to confirm that flux variability is a prominent feature at mid-IR…

Episodic accretion is one of the competing models to explain the observed luminosity spread in young stellar clusters. These short-lived high accretion events could also have a strong impact on planet formation. Observations of…

Solar and Stellar Astrophysics · Physics 2024-01-29 Carlos Contreras Peña , Philip W. Lucas , Zhen Guo , Leigh Smith

We present an optical/near-IR survey of 11 variable young stars (EXors and EXor candidates) aimed at deriving and monitoring their accretion properties. About 30 optical and near-infrared spectra ($\Re$ $\sim$ 1500-2000) were collected…

Solar and Stellar Astrophysics · Physics 2022-04-27 T. Giannini , A. Giunta , M. Gangi , R. Carini , D. Lorenzetti , S. Antoniucci , A. Caratti o Garatti , L. Cassarà , B. Nisini , A. Rossi , V. Testa , F. Vitali

Quasars emission is highly variable, and this variability gives us clues to understand the accretion process onto supermassive black holes. We can expect variability properties to correlate with the main physical properties of the accreting…

While the data analysis of $\gamma$-ray telescopes has now become more robust, some signals may be misinterpretations of a time-variable foreground emission from the Solar System, induced by low-energy cosmic-ray interactions with…

High Energy Astrophysical Phenomena · Physics 2023-10-13 Thomas Siegert