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Published February 2012 | Published
Journal Article Open

Optical TiO and VO Band Emission in Two Embedded Protostars: IRAS 04369+2539 and IRAS 05451+0037


Archival spectra from the Sloan Digital Sky Survey of two optically faint flat-spectrum protostars, IRAS 04369+2539 and IRAS 05451+0037, show strong emission-line features including—notably—clear and broad emission across several molecular bands of TiO and VO. The molecular emission is indicative of dense, warm circumstellar gas and has been seen previously in only one object: the flat-spectrum protostar IRAS 20496+4354 during a strong optical outburst (PTF 10nvg). The presence of broad molecular emission features in two additional objects having similar mid-infrared properties (but not known to be undergoing outbursts) could provide new insight into phases of rapid accretion/outflow at early stages of the protoplanetary disk. At present, the relevant geometry and the formation or heating mechanisms responsible for the observed TiO/VO cooling emission remain unexplained.

Additional Information

© 2012 The American Astronomical Society. Received 2011 August 14; accepted 2011 November 18; published 2012 January 5. We thank Ted Bergin and Colette Salyk for very helpful discussions concerning the origins of hot dense molecular emission in protostellar environments, Russel White for revisiting old observations, and Kunal Mooley for a thorough literature search. John Carpenter, Gregory Herczeg, Joan Najita, and an anonymous referee provided thought-provoking comments on the manuscript. Kevin Covey contributed the Appendix material, free of charge. This research made use of three indispensable databases: SIMBAD, operated at CDS, Strasbourg, France; NASA's Astrophysics Data System at the Center for Astrophysics, Harvard University; and NASA's Infrared Science Archive at the Infrared Processing and Analysis Center, California Institute of Technology.

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