[vsnet-campaign-v838mon 226] V838 Mon UBVRI polarimetry and photometry

["Efimov Yu.S." <efimov@crao.crimea.ua>]

                                                V838 Mon Polarimetry

UBVRI (central wavelengths 0.36, 0.44, 0.53, 0.69 and 0.83 mcm) linear polarimetry of V838 Mon has been performed on February 11,15,16 and 18, 2002 with the 125 cm reflector at the Crimean
astrophysical observatory. The difference between polarization data observed in these nights are in general within the errors of observations. It allows to combine the data and calculate the weighted average of wavelength dependence of polarization Pobs(%) which is very well fit by the curve of interstellar
polarization Pfit(%) applying the Serkowski' low with Pmax = 2.512 +-0.037 (%) at Lambda(max) = 0.554+/-0.002mcm. The data are given in the Table 1, where Pobs and PA are observed degree and position angle of polarization in equatorial frame with their rms errors, Pfit is the polarization fitted by the Serkowski' low, dp is the difference between observed and fitted data, and N is the number of
observations used to calculate the weighted average in each band. It is seen that the difference dp does not exeed 0.1%. The position angles of polarization of V838 Mon are very close to the position angle
of interstellar polarization of stars in the vicinity of the object.

                                                                                             Table 1.
     NOVA V838 MON, polarimetry in 2002, February 11-18
                Pmax(%)    Lambda(max)
           2.512+-0.037   0.554+-0.002
 Band  1/Lambda     Pobs    sP      PA     sPA    Pfit      dp    N
  U      2.78      2.073   0.106   147.4   1.5   2.027    0.046   52
  B      2.27      2.453   0.031   148.7   0.4   2.362    0.091   53
  V      1.89      2.449   0.025   150.3   0.3   2.506   -0.057   55
  R      1.45      2.337   0.017   152.4   0.2   2.377   -0.040   54
   I      1.20      2.118   0.016   152.5   0.2   2.083    0.035   53

The photometric data for two nights are given in the Table 2.

                                                                                            Table 2.
 Date, 2002             JD            U         B         V        R          I
Febr. 15/16   2452321.3935   10.006   9.402   7.946   6.746   5.739
Febr. 16/17   2452322.3419   10.209   9.448   7.921   6.667   5.593

The calibration star was HD 52533= SAO 134061 (O9V, V=7.702) from the
list of UBVRI photometric standards by A.U.Landolt (1983,  AJ,  88,  439).

Yuri Efimov.

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