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Title: A RECENT ACCRETION BURST IN THE LOW-MASS PROTOSTAR IRAS 15398-3359: ALMA IMAGING OF ITS RELATED CHEMISTRY

Low-mass protostars have been suggested to show highly variable accretion rates throughout their evolution. Such changes in accretion, and related heating of their ambient envelopes, may trigger significant chemical variations on different spatial scales and from source-to-source. We present images of emission from C{sup 17}O, H{sup 13}CO{sup +}, CH{sub 3}OH, C{sup 34}S and C{sub 2}H toward the low-mass protostar IRAS 15398-3359 on 0.''5 (75 AU diameter) scales with the Atacama Large Millimeter/submillimeter Array at 340 GHz. The resolved images show that the emission from H{sup 13}CO{sup +} is only present in a ring-like structure with a radius of about 1-1.''5 (150-200 AU) whereas the CO and other high dipole moment molecules are centrally condensed toward the location of the central protostar. We propose that HCO{sup +} is destroyed by water vapor present on small scales. The origin of this water vapor is likely an accretion burst during the last 100-1000 yr increasing the luminosity of IRAS 15398-3359 by a factor of 100 above its current luminosity. Such a burst in luminosity can also explain the centrally condensed CH{sub 3}OH and extended warm carbon-chain chemistry observed in this source and furthermore be reflected in the relative faintness of its compact continuum emission compared to othermore » protostars.« less
Authors:
; ; ;  [1] ; ;  [2] ; ;  [3] ; ; ;  [4]
  1. Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, DK-2100 Copenhagen Ø. (Denmark)
  2. Department of Astronomy, University of Michigan, 500 Church Street, Ann Arbor, MI 48109-1042 (United States)
  3. Department of Physics, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan)
  4. Leiden Observatory, Leiden University, P.O. Box 9513, NL-2300 RA Leiden (Netherlands)
Publication Date:
OSTI Identifier:
22364082
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal Letters; Journal Volume: 779; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ASTRONOMY; ASTROPHYSICS; CARBON; CARBON MONOXIDE; COMPARATIVE EVALUATIONS; DIPOLE MOMENTS; GHZ RANGE; IMAGES; LUMINOSITY; MASS; METHANOL; MOLECULAR IONS; MOLECULES; PROTOSTARS; STAR ACCRETION; STARS; VARIATIONS; WATER VAPOR