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# Program information file
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PROGRAM_ID           2023A037
PROGRAM_TITLE        Probing the evolution of Protostellar Photospheres and Accretion with SpeX
PROGRAM_INV1         Himanshu Tyagi
PROGRAM_INV2         Mayank Narang
PROGRAM_INV3         Manoj Puravankara
PROGRAM_INV4         Bihan Banerjee
PROGRAM_INV5         Prasanta Nayak
PROGRAM_SCICAT       stellar
PROGRAM_ABSTRACT_BEG
Protostars represent the earliest and perhaps the most important evolutionary phase in star formation: most of the stellar mass is accreted during this phase, and the initial assembly of protoplanetary disks also occurs during this phase. Protostellar evolution is shaped and regulated by the interplay between mass accretion and jets/outflows. However, several questions regarding the mass assembly and formation of the stars remain unanswered. When does the central star attain its final mass, and when is the stellar photosphere first formed? How does mass accretion-ejection evolve with time? What is the dominant mode of accretion in protostars? 
To answer these questions, spectroscopic observations of a protostellar sample spread uniformly over the evolutionary stages, are required because most of the near-IR spectroscopic studies have been carried out for Class I, and Flat spectrum sources. We have compiled a well-balanced sample of protostars, that contains 30% Class 0, 35% Class I, and 35% FS sources. Our sample consists of 55 protostars from the four nearby star-forming regions of the Serpens, Ophiuchus, Orion, and Cepheus, and spans a wide range in protostellar luminosity and evolutionary stages [a proxy for age].
We propose near-IR spectroscopic observations of this sample with SpeX on IRTF in SXD mode.
 From these observations, we will investigate the long-standing questions about the evolution of mass accretion rates, mass accretion-ejection relation, photospheric properties, and the mode of accretion [magnetospheric vs. boundary layer] in protostars. Our proposed study will provide answers to some of the fundamental questions about protostellar evolution and star formation.
PROGRAM_ABSTRACT_END