Display, Thursday, January 13, 2000, 9:20am-6:30pm, Grand Hall

[Previous] | [Session 38] | [Next]

*K. Krisciunas, C. Stubbs (UW), A. Diercks (Caltech), E. Magnier (CFHT), B. Skiff (Lowell Obs.), K. Gloria, N. C. Hastings, R. McMillan (APO), A. Riess (STScI)*

We present optical photometry of seven Type Ia supernovae:
SNe 1998es, 1999aa, 1999cc, 1999cl, 1999cp, 1999da, and
1999dk. We also obtained near infrared photometry of three
of these. A more direct route to determining A_{V} (and
hence the correct distance to a host glaxy) is to use the
V-K color excess rather than E(B-V). One often assumes
that the unreddened B-V color of a Type Ia SN is 0.00 at
the time of B-band maximum, so the {\em observed} B-V
color at that time is taken as the color excess. This is not
true for all Type Ia SNe, especially the rapidly declining
ones. [The maximum brightness and rate of decline of Type Ia
SNe can be characterized by the parameter \Delta (Riess,
Press, & Kirshner 1996; Riess et al. 1998, Appendix). More
luminous (\Delta < 0) SNe are slow decliners. Less
luminous (\Delta > 0) SNe are faster decliners.] The B-V
color excess of Type Ia SNe can also be determined from the
photometry between 30 and 90 days {\em after} light maximum
(Phillips et al. 1999, astro-ph/9907052). We find that the
V-K color near light maximum for Type Ia SNe unreddened in
their host galaxies (SNe 1999cp, 1980N, 1981B, 1981D, and
1983R) implies a ``universal'' pair of linear relationships
that intersect at 6 days after maximum. If we let t be the
number of days since B-band maximum, for -10 \leq t \leq
+6, V-K = -0.68 - 0.055 \; t, while for +6 \leq t \leq
+25, V-K = -1.51 + 0.075 \; t. The RMS deviation of the
fits is ± 0.1 mag. This is based on SNe with -0.2 \leq
\Delta \leq 0.2 which have been corrected for small amounts
of reddening in {\em our} Galaxy (Schlegel, Finkbeiner, &
Davis 1998). Perhaps there are families of V-K curves as a
function of \Delta. Since A_{V} \approx 3.1 E(B-V)
scales any error in E(B-V) by a factor of three, while
A_{V} \approx 1.13 E(V-K), A_{V} might be more easily
determined from the V-band light curve of a Type Ia SN
(which can be easily interpolated) and a small amount of
K-band data obtained near maximum light.

If you would like more information about this abstract, please follow the link to http://www.astro.washington.edu/kevin/apo.html. This link was provided by the author. When you follow it, you will leave the Web site for this meeting; to return, you should use the Back comand on your browser.

The author(s) of this abstract have provided an email address for comments about the abstract: kevin@astro.washington.edu