NOAO: username: keflavich password: 123456 Title: Dust emission from P Cygni's Nebula Abstract: We propose to observe the circumstellar LBV nebula around P Cygni to search for emission from cool dust. Observations of the [Fe II] 1.64\um emission line using a coronagraph have revealed the the emission nebula is clumpy throughout. Other LBV nebulae with [Fe II] emission also tend to have warm dust, and a measurement of the dust in P Cygni's nebula will provide a direct constraint on the mass lost in the eruption event in 1600. Science Justification: Luminous Blue Variables (LBVs) represent a short stage in the evolution of the most massive stars. Their ejectae may be responsible for the shapes of the light curves of Type II supernovae (e.g. Smith and McCray 2007) and could be the explanation of the ring nebula around SN 1987A (Smith 2007). LBV shell ejection events are the most energetic events in a main sequence star's lifetime, sometimes involving energy expenditures just shy of supernovae (Smith 2006). Because P Cygni has no known binary companion, in contrast to Eta Carinae which has a very clear 5.54 year periodicity that implies the presence of a companion, it may provide a more pure laboratory for the study of LBV ejectae. Recent observations of P Cygni in the near-IR [Fe II] 1.64\um line have displayed an inner portion of the nebula in greater detail than has been possible in optical observations. They revealed a clumpy, asymmetric structure that, contrary to expectations from slit spectroscopy (Smith and Hartigan 2006), is not limb-brightened. The bright inner nebula has a spatial extent of $\sim$20" ($\sim$.12 pc, assuming a distance of 1.7 kpc). These observations imply that P Cygni's nebula is not a hollow shell but a clumpy, at least partly filled blob with only partial spherical symmetry. Smith and Hartigan measured a shell width of $\sim$.017pc under the assumption that the nebula is simply a hollow shell, which implies that clumps will be simimately that size. The dust we expect to observe is therefore constrained to small clumps or filaments, so it will be faint. Assuming a distance of $10^{17.3}$ cm from the star, the expected dust temperature is $\sim$70K, giving a blackbody peak around 40\um. QUESTION (as in, delete this paragraph from proposal): [What temperature do we REALLY expect? Cloudy suggests 68K before I put in any grains, but then gave me temperatures $\sim$180-250K with Orion grain abundances input. I can talk to John about this, though... it's a simple calculation, but I'm missing some piece of it] This [Fe II] emission line is a good tracer of shock-excited emission, and the line's strength suggests significant variations in density in a vaguely point-symmetric, concentric structure. In all other LBV nebulae with [Fe II] emission, warm dust emission is also seen (REF?). P Cygni, as the nearest unobscured LBV, has been the motivator for the current models of LBV evolution (Smith, Vink, and de Koter 2004), but dust emission has not yet been observed in its nebula. The measured gas mass of .1 solar masses (Smith and Hartigan, 2006) suggests a dust mass of .001 solar masses, which would be consistent with some known LBVs but is on the low end of the mass-loss spectrum (Clark 2003). A measurement of the dust emission from P Cygni's nebula will provide constraints on physical quantities, i.e. mass and kinetic energy, of the ejected shell that is presumed to have come from P Cygni's eruption in 1600. While previous optical observations of nebulosity around P Cygni reveal a rich ejection history from the star (Barlow et al 1994, Boumis et al 2006, Meaburn et al 2004, Meaburn et al 2000), they do not directly measure kinematic properties of these ejecta and therefore tell little about the processes involved in the ejection. They have also been mostly unable to image the ejected nebula from the 1600 event, which will likely be the most observable region in the 20\um images. Adaptive Optics observations of the innermost portion of P Cygni's nebula were limited by a 1" field of view (Chesneau et al 2000). Determinations of the circumstellar material's kinematic properties are necessary to constrain models of the ejection mechanism. In particular, Eta Carinae's eruption in the 1840s is proposed to have been from a hydrodynamic explosion (Smith and Townsend 2007). It is unclear whether P Cygni's multiple ejectae were ejected in similar hydrodynamic-driven expulsions or radiation-driven mass loss events. \begin{references} \par Barlow, M.J., Drew, J.E., Meaburn, J., Massey, R.M., 1994, MNRAS, 268, L29 \par Boumis, P., Meaburn, J., Redman, M.P., Mavromatakis, F., 2006, A\&A, 457, L13 \par Chesneau, O., Roche, M., Boccaletti, A., Abe, L., Moutou, C., Charbonnier, F., Aime, C., Lanteri, H., Vaklil, F., 2000, A\&A Supplement Series, 144, 523 \par Clark, J.S., Egan, M.P., Crowther, P.A., Mizuno, D.R., Larionov, V.M., Arkaharov, A., 2003, A\&A, 412, 185 \par Meaburn, J., Boumis, P., Redman, M.P., Lopez, J.A., Mavromatakis, F., 2004, A\&A, 422, 603 \par Meaburn, J., O'Connor, J.A., Lopez, J.A., Bryce, M., Redman, M.P., Noriega-Crespo, A. 2000, MNRAS, 318, 561 \par Smith, N., Hartigan, P., 2006, APJ, 638, 1045 \par Smith, N., 2001, ASP Conference Series, 233, 125S \end{references} Experimental Design: Images of P Cygni's nebula in the Qa (Q'?) filter are requested in order to observe cool thermal dust emission. Two separate observations, centered $\sim$5" from the central star and on opposite sides, will be required so that the 15" chop does not overlap with the nebula. Imaging in Qa (Q'?) has two significant advantages over other bands. First, the longer wavelength will sample the dust at a point closer to its blackbody peak. Second, the contribution of the stellar photosphere and free-free emission from its stellar wind both drop at longer wavelengths. PI Nathan Smith has attempted detections of dust in P Cygni's nebula using 3m telescopes at 10\um, but has not observed it. A larger aperture operating at longer wavelengths is needed to detect the thin, cold layer of dust that is expected. The resolution of an 8m telescope is also required because the dust is expected to be in thin, filamentary structures that are washed out in images from smaller telescopes. Technical Description: P Cygni's nebula will be observed with two separate pointings, offset 5" in RA from the star in opposite directions, in the Qa (Q'?) filter. In order to achieve a S/N ratio of $\sim$10, assuming a surface brightness of 10 mJy / sq arcsec, a 120 minute exposure with chop/nod (50% of time on source) will be required.