[vsnet-newvar 1738] De-Reddening of MisV1147 V-I Photometry

[DWest61506@aol.com]

In this note I de-redden Arne Henden's V-I photometry for MisV1147 and determine an approximate spectral class.

Distance = 3.4 kpc per http://vsnet.kusastro.kyoto-u.ac.jp/vsnet/Mail/vsnet-newvar/msg01736.html.

Henden photometry:
No. HJD V B-V U-B V-R R-I
1 52288.61 13.365 0.814 0.087 0.558 0.628
2 52577.67 14.876 0.933 0.044 0.706 0.906

Av = 3.3 mag per Neckel and Klare 1980

E(B-V) = 0.323Av = (0.323)*(3.3) = 1.07

E(V-I) = 1.242 E(B-V) per Dean et al. 1978
E(V-I)= (1.243)*(1.07) = 1.33

For Henden observation #1 V-I = 1.186
(V-I)intrinsic = (V-I)observed - E(V-I)
(V-I)intrinsic = 1.186 - 1.33 = -0.14
This implies a spectral class of B4V or B2I per Bessell 1990.

For Henden observation #2 V-I = 1.621
(V-I)intrinsic = (V-I)observed - E(V-I)
(V-I)intrinsic = 1.621 - 1.33 = 0.29
This implies a spectral class of A7V or F0I per Bessell 1990.

The first observation is in agreement with my spectral class determination using UBV photometry http://vsnet.kusastro.kyoto-u.ac.jp/vsnet/Mail/vsnet-newvar/msg01714.html.  The spectral class for the second observation doesn't agree with prior estimates.  I am still a bit confused on the Av value.  The Neckel and Klare paper isn't very clear the Av value for an object at 3.4 kpc and galactic coordinates long = 108.3 and lat = -0.6 degree.  If anyone has any suggestion on improvement of the calculation and a better estimate of Av please let me know.

Regards,
Doug West
http://hometown.aol.com/dwest61506/index.html

References:

Th. Neckel and G. Klare, "The Spatial Distribution of the Interstellar Extinction", Astron. Astrophys. Suppl. Ser. 42:251-281, 1980.

J.F. Dean et al., Mon. Not. R. Astro. Soc., 183: 569-583, 1978.

M.S. Bessell, "UBVRI Passbands", PASP, 102:1181-1199, October 1990.

VSNET Home Page

Return to Daisaku Nogami

---

vsnet-adm@kusastro.kyoto-u.ac.jp