# Rise and fall of the dust shell of the classical nova V339 Delphini

Evans, A, Banerjee, DPK, Gehrz, RD, Joshi, V, Ashok, NM, Ribeiro, VARM, Darnley, MJ, Woodward, CE, Sand, D, Marion, GH, Diamond, TR, Eyres, SPS, Wagner, RM, Helton, LA, Starrfield, S, Shenoy, DP, Krautter, J, Vacca, WD and Rushton, MT (2017) Rise and fall of the dust shell of the classical nova V339 Delphini. Monthly Notices of the Royal Astronomical Society, 466 (4). pp. 4221-4238. ISSN 0035-8711

We present infrared spectroscopy of the classical nova V339 Delphini, obtained over a $\sim2$ year period. The infrared emission lines were initially symmetrical, with HWHM velocities of 525 km s$^{-1}$. In later ($t\gtrsim77$days, where $t$ is the time from outburst) spectra however, the lines displayed a distinct asymmetry, with a much stronger blue wing, possibly due to obscuration of the receding component by dust. Dust formation commenced at $\sim$ day 34.75 at a condensation temperature of $1480\pm20$K, consistent with graphitic carbon. Thereafter the dust temperature declined with time as $T_{\rm d}\propto{t}^{-0.346}$, also consistent with graphitic carbon. The mass of dust initally rose, as a result of an increase in grain size and/or number, peaked at $\sim$ day 100, and then declined precipitously. This decline was most likely caused by grain shattering due to electrostatic stress after the dust was exposed to X-radiation. An Appendix summarises Planck Means for carbon, and the determination of grain mass and radius for a carbon dust shell.