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Title: YSOVAR: MID-INFRARED VARIABILITY AMONG YSOs IN THE STAR FORMATION REGION GGD12-15

We present an IR-monitoring survey with the Spitzer Space Telescope of the star-forming region GGD 12-15. More than 1000 objects were monitored, including about 350 objects within the central 5′, which is found to be especially dense in cluster members. The monitoring took place over 38 days and is part of the Young Stellar Object VARiability project. The region was also the subject of a contemporaneous 67 ks Chandra observation. The field includes 119 previously identified pre-main sequence star candidates. X-rays are detected from 164 objects, 90 of which are identified with cluster members. Overall, we find that about half the objects in the central 5′ are young stellar objects (YSOs) based on a combination of their spectral energy distribution, IR variability, and X-ray emission. Most of the stars with IR excess relative to a photosphere show large amplitude (>0.1 mag) mid-infrared (mid-IR) variability. There are 39 periodic sources, and all but one is found to be a cluster member. Almost half of the periodic sources do not show IR excesses. Overall, more than 85% of the Class I, flat spectrum, and Class II sources are found to vary. The amplitude of the variability is larger in more embedded YSOs.more » Most of the Class I/II objects exhibit redder colors in a fainter state, which is compatible with time-variable extinction. A few become bluer when fainter, which can be explained with significant changes in the structure of the inner disk. A search for changes in the IR due to X-ray events is carried out, but the low number of flares prevented an analysis of the direct impact of X-ray flares on the IR light curves. However, we find that X-ray detected Class II sources have longer timescales for change in the MIR than a similar set of non-X-ray detected Class IIs.« less
Authors:
; ; ;  [1] ;  [2] ; ;  [3] ;  [4] ;  [5] ;  [6] ;  [7] ;  [8]
  1. Harvard–Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)
  2. NASA Ames Research Center, M/S 244-5 Moffett Field, CA 94035 (United States)
  3. Spitzer Science Center/Caltech, 1200 E. California Blvd., Pasadena, CA 91125 (United States)
  4. Department of Astronomy, University of Massachusetts, Amherst, MA 01003 (United States)
  5. Department of Astronomy, California Institute of Technology, Pasadena, CA 91125 (United States)
  6. Department of Physics Astronomy and Materials Science, Missouri State University, Springfield, MO 65897 (United States)
  7. Department of Physics and Astronomy, Western Washington Univ., Bellingham, WA 98225-9164 (United States)
  8. Physics and Astronomy Department, University of Georgia, Athens, GA 30602-2451 (United States)
Publication Date:
OSTI Identifier:
22520110
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astronomical Journal (Online); Journal Volume: 150; Journal Issue: 5; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ENERGY SPECTRA; INFRARED RADIATION; MAIN SEQUENCE STARS; MONITORING; PERIODICITY; PHOTOSPHERE; PROTOSTARS; SPACE; STAR EVOLUTION; TELESCOPES; VISIBLE RADIATION; X RADIATION