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Re: Nova V2540 Oph getting "bluer"? > On 08/19/2002 V-Rc=0.85 and currently V-Rc=0.67. V2540 Oph is getting > "bluer", I'm not sure what that means in terms of nova development. Maybe it > has entered the nebular phase? Possibly there is less dust surrounding the > nova and hence less reddening? I'm open to suggestions. It would be likely that the contribution from Halpha emssion line has reduced (the line can contribute to ~1.0 mag in Rc band for usual classical novae). This possibility could be easily tested by measuring a spectrum (measure equivalent width). It may be also possible different lines started more contributing to the V-band. In either cases, interpretation of broad-band colors of novae requires special attention. If one would use an intermediate-band filter such as Stoemgren y instead of V, and Ic instead of Rc (Ic contains less strong emission lines), the continuum color would be easier to assess. Regards, Taichi Kato
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