The late infrared development of Nova Serpentis 1970

Abstract

Broad-band infrared observations of FH Ser (Nova Ser 1970) covering the period 40 to 529 days after discovery are presented. Strong quantitative evidence for grain growth in the period 60–111 days is derived from the agreement between predictions of dust shell models and the observations. Between days 111 and 129 the grains undergo a significant reduction in size. The infrared luminosity is found to fall as t⁻³ for t ≳ 100. However, up until day 200 this is due to a continuing grain size reduction, while the bolometric luminosity remains approximately constant. After day 200 the bolometric luminosity falls off as ∼t⁻¹. At late times, an excess flux in the 1-3 µm region appears above the dominant cool dust emission component. This excess flux is probably due to increasing line emission in the J, H and K bandpasses as the ejected shell expands.

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