Observations indicate that massive stars in the Galaxy form in regions of very high surface density, Σ ∼ 1 g cm−2. Clusters containing massive stars and globular clusters have a column density comparable to this. The gas pressure in clouds of such a column density is P/k ∼ 108 − 109 K cm−3, far greater than that in the diffuse interstellar medium or the average in giant molecular clouds. Observ...

We report on the identification of 54 embedded clusters around 217 massive protostellar candidates of which 34 clusters are new detections. The embedded clusters are identified as stellar surface density enhancements in the 2 µm All Sky Survey (2MASS) data. Because the clusters are all associated with massive stars in their earliest evolutionary stage, the clusters should also be in an early st...

With ASCA, we have detected three X-ray flares from the Class I protostar YLW15. The flares occurred every ∼20 hours and showed an exponential decay with time constant 30–60 ks. The X-ray spectra are explained by a thin thermal plasma emission. The plasma temperature shows a fast-rise and slow-decay for each flare with kTpeak ∼ 4–6 keV. The emission measure of the plasma shows this time profile...

In this paper, I present background knowledge for high energy processes in Young Stellar Objects(YSO), including observation results, theoretical model. In addition, I also summarize the recent development in the field of high energy processes in YSO, especially the relationship between X-ray luminosity and rotational period. 1. Young Stellar Objects(YSO) Pierre-Simon Laplace in his Expositiond...

Protostellar jets have a fundamental role at the earliest evolution of protostars all masses. In case low-mass (<8 Msun) protostars, strong observational evidence exists that launching and collimation is due to X- and/or disk-wind mechanisms. these models, it protostar/disk system creates necessary conditions launch collimate near protostar via magnetic fields. The origin from more massive has ...

We estimate the levels of turbulence in the envelopes of Class 0 and I protostars using a model based on measurements of the peak separation of double-peaked asymmetric line profiles. We use observations of 20 protostars of both Class 0 & I taken in the HCO(J=3→2) line that show the classic double-peaked profile. We find that some Class 0 sources show high levels of turbulence whilst others dem...

We present new high resolution (R ≃ 18, 000) near-infrared spectroscopic observations of a sample of classical FU Orionis stars (FUors) and other young stars with FUor characteristics that are sources of Herbig-Haro flows. Spectra are presented for the region λ = 2.203 – 2.236 μm which is rich in absorption lines sensitive to both effective temperatures and surface gravities of stars. Both FUor...

High-resolution (R ≈ 90, 000) spectra of 34 nearby, young Sun-like stars were analyzed using stellar atmosphere models to estimate effective photosphere temperatures, surface gravities, and the abundance of certain heavy elements (C, Na, Mg, Si, S, Ca, Ti, Fe, and Ni). The effective temperatures derived from spectroscopy were compared with temperatures estimated using optical and near-infrared ...

Abstract We present an overview of the Large Program, “Early Planet Formation in Embedded Disks (eDisk),” conducted with Atacama Millimeter/submillimeter Array (ALMA). The ubiquitous detections substructures, particularly rings and gaps, protoplanetary disks around T Tauri stars raise possibility that at least some planet formation may have already started during embedded stages star formation....