2002IAUC.8005....2M

U. Munari and S. Desidera, Asiago Astrophysical Observatory; and A. Henden, Universities Space Research Association and U.S. Naval Observatory (USNO), communicate: "Photometry obtained with the USNO 1.0-m telescope shows the central star of V838 Mon to be constant in the blue around V = 16.05, U-B = -0.07, and B-V = +0.69 since September, while brightening by 0.012 and 0.020 mag/day in bands R and I, respectively (from R = 14.43 and I = 10.93 on Sept. 25.5 UT to R = 14.00 and I = 10.22 on Oct. 30.5). Spectroscopic observations (range 360-774 nm at 0.32 nm/pixel) of V838 Mon were obtained on Oct. 28 and 29 with the Asiago 1.82-m telescope (+ AFOSC). The hot companion star reported on IAUC 7982 (confirmation report on IAUC 7992) seems to resemble a normal B3 V star, suffering from a reddening of E(B-V) = +0.9 that is consistent with a law having R_V = A_V/E(B-V) = 3.1 (cf. Savage and Mathis 1979, ARAA 17, 73), in agreement with earlier estimates based on the intensity of Na I and K I interstellar lines (cf. IAUC 7812). However, if the companion is a genuine B3 V star, V838 Mon lies 10500 pc distant and just 200 pc above the galactic plane, for which such a low reddening is surprising, and the mass of the M- giant progenitor should have been larger than 7 solar masses. The fact that the B3 V star is about 1 mag fainter in B than V838 Mon in quiescence, and that the optical-infrared energy distribution of the latter closely matched an F0 star (luminosity class III-II for a distance of 10500 pc), suggests that the quiescent light could have been dominated by the progenitor of the outbursting companion or by circumstellar material in the form of a warm disk, or something else. The current spectrum of the cool component holds identical to the 'later-than-M10' classification of one month ago (cf. IAUC 7982)."