ﻻ يوجد ملخص باللغة العربية
A classical paradox in high-mass star formation is that powerful radiation pressure can halt accretion, preventing further growth of a central star. Disk accretion has been proposed to solve this problem, but the disks and the accretion process in high-mass star formation are poorly understood. We executed high-resolution ($R$=35,000-70,000) iSHELL spectroscopy in $K$-band for eleven high-mass protostars. Br-$gamma$ emission was observed toward eight sources, and the line profiles for most of these sources are similar to those of low-mass PMS stars. Using an empirical relationship between the Br-$gamma$ and accretion luminosities, we tentatively estimate disk accretion rates ranging from $lesssim$10$^{-8}$ and $sim$10$^{-4}$ $M_odot$ yr$^{-1}$. These low-mass-accretion rates suggest that high-mass protostars gain more mass via episodic accretion as proposed for low-mass protostars. Given the detection limits, CO overtone emission ($v$=2-0 and 3-1), likely associated with the inner disk region ($r ll 100$ au), was found towards two sources. This low-detection rate compared with Br-$gamma$ emission is consistent with previous observations. Ten out of the eleven sources show absorption at the $v$=0-2 ${rm R(7)-R(14)}$ CO R-branch. Most of them are either blueshifted or redshifted, indicating that the absorption is associated with an outflow or an inflow with a velocity of up to $sim50$ km s$^{-1}$. Our analysis indicates that the absorption layer is well thermalized (and therefore $n_{mathrm H_2} gtrsim 10^6$ cm$^{-3}$) at a single temperature of typically 100-200 K, and located within 200-600 au of the star.
We present full spectral scans from 200-670$mu$m of 26 Class 0+I protostellar sources, obtained with $Herschel$-SPIRE, as part of the COPS-SPIRE Open Time program, complementary to the DIGIT and WISH Key programs. Based on our nearly continuous, line
We present high resolution (R=25,000-35,000) K-band spectroscopy of two young stars, MWC 480 and V1331 Cyg. Earlier spectrally dispersed (R=230) interferometric observations of MWC 480 indicated the presence of an excess continuum emission interior t
We present moderate-resolution ($Rsim4000$) $K$ band spectra of the super-Jupiter, $kappa$ Andromedae b. The data were taken with the OSIRIS integral field spectrograph at Keck Observatory. The spectra reveal resolved molecular lines from H$_{2}$O an
We present multi-wavelength images observed with SOFIA-FORCAST from $sim$10 to 40 $mu$m of seven high luminosity massive protostars, as part of the SOFIA Massive (SOMA) Star Formation Survey. Source morphologies at these wavelengths appear to be infl
Sensitive 5-38 um Spitzer Space Telescope (SST) and ground based 3-5 um spectra of the embedded low mass protostars B5 IRS1 and HH46 IRS show deep ice absorption bands superposed on steeply rising mid-infrared continua. The ices likely originate in t