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Published November 2006 | Published
Journal Article Open

Spitzer Space Telescope Observations of Var Her 04: Possible Detection of Dust Formation in a Superoutbursting Tremendous Outburst Amplitude Dwarf Nova

Abstract

We present four MIPS (24 μm) and two IRAC (3.6, 4.5, 5.8, and 8.0 μm) Spitzer Space Telescope observations of the newly discovered tremendous outburst amplitude dwarf nova (TOAD) Var Her 04 during decline from superoutburst. The four MIPS observations span 271 days, and the two IRAC observations span 211 days. Along the line of sight to Var Her 04, there is a foreground M star within 1" of the variable; as a result, all of the Spitzer photometry presented in this paper is a blend of the foreground M star and Var Her 04. We estimate the quiescent level of the TOAD to be ΔV = 4-5 mag below that of the M star. Based on the spectral energy distribution and the Two Micron All Sky Survey colors, we find the M star to be an M3.5 V dwarf at a distance of 80-130 pc. Based on its outburst amplitude and quiescent apparent magnitude, we estimate the distance to Var Her 04 to be 200-400 pc, suggesting that the line-of-sight foreground star is physically unrelated to the cataclysmic variable. All of the Spitzer photometry is consistent with the photospheric emission of the line-of-sight M3.5 V star, except for one 24 μm observation obtained after the variable rebrightened. This 24 μm flux density is 75 μJy (4 σ) above the preceding and following MIPS observations. We tentatively suggest that the mid-infrared brightening of 75 μJy may be associated with a dust formation event in the superoutburst ejecta. Assuming a dust temperature of 100-400 K, we have estimated the amount of dust required. We find that 10^(-13) to 10^(-11) M_☉ of dust is needed, consistent with the amounts of mass ejection in TOADs expected during superoutburst and possibly making TOADs important contributors to the recycling of the interstellar medium.

Additional Information

© 2006 American Astronomical Society. Received 2006 June 2; accepted 2006 August 3. The authors would like to thank the Director of the Spitzer Science Center for granting our observing request through the Director's Discretionary Time. This work has been supported, in part, by NASA through the Spitzer Science Center and the Michelson Science Center at Caltech. We also extend a special thank you to Steve Schurr for his enthusiasm and red pen. We acknowledge with thanks the variable star observations from the AAVSO International Database contributed by observers worldwide and used in this research. This research has made use of the NASA/IPAC Infrared Science Archive, which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. This publication makes use of data products from the Two Micron All Sky Survey, which is a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center, California Institute of Technology, funded by the National Aeronautics and Space Administration and the National Science Foundation.

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Created:
August 22, 2023
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October 23, 2023