Nova V4444 Sagittarii 1999: Spectropolarimetric Evidence for a Preexisting Circumstellar Dust Cloud

We present the results of our optical spectropolarimetry of nova V4444 Sagittarii 1999 in its early stage. The observations were performed on four nights from 1999 April 29 ( t = 2 days) to 1999 May 7 ( t = 10 days). The polarization properties, including the absence of polarization difference across strong emission lines, have remained unchanged through the period. The observed polarization degree increases monotonically toward shorter wavelength. We separate the interstellar polarization component from the observed polarization by assuming that the component intrinsic to this nova has a power-law-type function of wavelength. The decomposed intrinsic polarization can be explained by scattering due to small grains. These results suggest the preexistence of the dust cloud in the vicinity of the nova, at least several dozens of AU from the central star.