相关论文: Magnetospheric Accretion as a Source of H$\alpha$ …

Context. Protoplanetary discs are the birthplaces of planets. Recent studies highlight the role of stellar mass sampling in determining disc lifetimes from the observed fraction of stars with discs. Low-mass stars tend to host longer-lived…

Accretion among planets is a poorly understood phenomenon, due to lack of both observational and theoretical studies. Detection of emission lines from accreting gas giants facilitate detailed investigations into this process. This work…

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…

As part of a multi-faceted program to investigate the origin and early evolution of sub-stellar objects, we present high-resolution Keck optical spectra of 14 very low mass sources in the IC 348 young cluster and the Taurus star-forming…

The Paschen beta (1.2822 micron) emission line found in the near-infrared spectra of T-Tauri stars (TTSs) is believed to trace the accretion of material onto the central star. We present spectroscopic data which suggests that this may not…

The accretion/ejection processes in T-Tauri stars are fundamental to their physical evolution, while also impacting the properties and evolution of the circumstellar material at a time when planet formation takes place. To this date,…

Protoplanetary disks around young Sun-like stars are the cradles of the vast majority of detected exoplanets. Probing these disks at multiple spatial scales is key to uncovering how planets form. We aim to spatially and spectrally resolve…

High resolution (lambda / Delta-lambda = 50,000) K-band spectra of massive, embedded, young stellar objects are presented. The present sample consists of four massive young stars located in nascent clusters powering Galactic giant H II…

The accretion and ejection of mass in pre-main sequence (PMS) stars are key processes in stellar evolution as they shape the stellar angular momentum transport necessary for the stars' stability. Magnetospheric accretion onto classical T…

Studies of magnetospheric accretion and magnetic field topology in T Tauri stars have advanced over the years, but their applications to fully convective, very-low-mass T Tauri stars remain relatively unexplored. We aim to analyze the…

We present high-quality, medium resolution X-shooter/VLT spectra in the range 300-2500 nm for a sample of 12 very low-mass stars in the \sigma Orionis cluster. The sample includes stars with masses ranging from 0.08 to 0.3 M$_\odot$. The…

In this work, we introduce the use of H I Pfund-beta (4.6538 micron) as a tracer of mass accretion from protoplanetary disks onto young stars. Pf-beta was serendipitously observed in NIRSPEC and CRIRES surveys of CO fundamental emission,…

Magnetospheric accretion is an important process for a wide range of astrophysical systems, and may play a role in the formation of gas giant planets. Extending the formalism describing stellar magnetospheric accretion into the planetary…

Magnetothermal (MHD) winds and jets originate in a wide range of regions of protoplanetary disks (1-30 au) and are thought to be the primary mechanisms driving accretion onto the central star. One indirect signature of these processes is…

Accreting protoplanets enable the direct characterization of planet formation. As part of a high-contrast imaging search for accreting planets with the Hubble Space Telescope (HST) Wide Field Camera 3, we present H$\alpha$ images of AB…

As the number of planetary mass objects (PMOs, $\lessapprox$13 M$_{\rm{Jupiter}}$) at wider separation ($\gtrapprox$10 AU) grows, there is emerging evidence that they form differently from their higher-mass brown-dwarf (BD) counterparts.…

Accretion plays a central role in the physics that governs the evolution and dispersal of protoplanetary disks. The primary goal of this paper is to analyze the stability over time of the mass accretion rate onto TW Hya, the nearest…

We have discovered T Tauri stars which show startling spectral variability between observations seperated by 20 years. In spectra published by Bouvier & Appenzeller (1992) these objects showed very weak H-alpha emission, broad CaII…

Recent observations show a strong correlation between stellar mass and accretion rate in young stellar and sub-stellar objects, with the scaling $\dot{M}_{acc} \propto M_*^2$ holding over more than four orders of magnitude in accretion…

The accretion of material from protoplanetary disks onto their central stars is a fundamental process in the evolution of these systems and a key diagnostic in constraining the disk lifetime. We analyze the relationship between the stellar…