Vallery Stanishev's chart, which is a "north up, east to the left" chart rotated counter-clockwise by about 110 degrees.
Here's some good evidence that SN 2005hk was caught well before maximum. This gives the instrumental B magnitudes vs. Julian Date. No color terms were applied. (Stanishev graph)
What follows is from imagery obtained by Kevin Krisciunas using the CTIO 0.9-m telescope on November 1 and November 27, 2005 (UT).
The standard stars were observed on two photometric nights. Here are the derived magnitudes on the two nights:
date * U B V R I 051101 1 14.507 0.002 14.406 0.001 13.744 0.001 13.348 0.001 12.983 0.001 051101 2 14.626 0.003 14.616 0.001 14.463 0.001 14.348 0.001 14.213 0.002 051101 3 17.721 0.033 17.241 0.006 16.235 0.004 15.666 0.003 15.128 0.004 051101 4 18.658 0.081 18.283 0.015 17.464 0.010 16.957 0.010 16.523 0.013 051101 5 15.250 0.005 14.970 0.001 14.230 0.001 13.797 0.001 13.405 0.001 051101 6 17.185 0.017 16.883 0.005 16.068 0.003 15.585 0.003 15.150 0.004 051101 7 19.177 0.083 17.717 0.008 16.373 0.004 15.559 0.003 14.876 0.003 051101 8 15.859 0.006 15.459 0.002 14.654 0.001 14.183 0.001 13.782 0.002 051101 9 -99 0 18.906 0.020 18.062 0.016 17.448 0.014 16.899 0.018 051101 10 19.126 0.078 18.212 0.011 17.185 0.007 16.552 0.006 16.060 0.008 051101 11 16.397 0.011 16.484 0.004 16.115 0.004 15.883 0.004 15.638 0.006 051101 12 18.414 0.058 18.057 0.011 17.281 0.008 16.778 0.008 16.310 0.011 051127 1 14.509 0.003 14.400 0.001 13.736 0.001 13.355 0.001 12.984 0.001 051127 2 14.629 0.005 14.612 0.002 14.459 0.002 14.352 0.002 14.219 0.003 051127 3 17.871 0.034 17.243 0.007 16.229 0.004 15.677 0.004 15.136 0.005 051127 4 18.669 0.072 18.313 0.015 17.431 0.010 16.972 0.011 16.524 0.015 051127 5 15.253 0.006 14.968 0.002 14.225 0.001 13.807 0.001 13.407 0.002 051127 6 17.218 0.021 16.882 0.005 16.071 0.004 15.600 0.004 15.161 0.005 051127 7 19.191 0.109 17.734 0.010 16.390 0.005 15.578 0.004 14.890 0.004 051127 8 15.894 0.008 15.459 0.003 14.654 0.002 14.204 0.002 13.797 0.002 051127 9 19.798 0.169 19.051 0.029 18.068 0.017 17.419 0.014 16.910 0.020 051127 10 18.918 0.083 18.236 0.015 17.179 0.008 16.565 0.008 16.044 0.009 051127 11 16.384 0.012 16.478 0.005 16.107 0.004 15.881 0.005 15.639 0.007 051127 12 18.388 0.059 18.066 0.013 17.268 0.009 16.789 0.009 16.304 0.012
The uncertainties given above should really be augmented by the RMS uncertainties of the UBVRI fits of the standard stars. For Nov 1 those values are +/- 0.036, 0.022, 0.016, 0.018, and 0.026 mag, respectively. For Nov 27 the RMS uncertainties are +/- 0.050, 0.019, 0.013, 0.017, and 0.023 mag for U, B, V, R, and I.
Here are the unweighted means:
* U B V R I 1 14.508 0.004 14.403 0.003 13.740 0.006 13.351 0.004 12.983 0.002 2 14.628 0.002 14.614 0.002 14.461 0.002 14.350 0.002 14.216 0.004 3 17.796 0.075 17.242 0.003 16.232 0.000 15.672 0.006 15.132 0.004 4 18.664 0.005 18.298 0.016 17.448 0.017 16.965 0.008 16.524 0.002 5 15.252 0.002 14.969 0.004 14.227 0.003 13.802 0.006 13.406 0.001 6 17.201 0.017 16.882 0.002 16.069 0.002 15.593 0.007 15.156 0.004 7 19.184 0.008 17.725 0.010 16.382 0.006 15.569 0.010 14.883 0.008 8 15.877 0.017 15.459 0.002 14.654 0.002 14.194 0.010 13.789 0.009 9 too faint 18.979 0.072 18.065 0.003 17.434 0.014 16.904 0.008 10 19.022 0.104 18.224 0.014 17.182 0.006 16.559 0.006 16.052 0.006 11 16.390 0.010 16.481 0.006 16.111 0.004 15.882 0.002 15.639 0.002 12 18.401 0.012 18.062 0.004 17.274 0.006 16.784 0.006 16.307 0.008 From aperture photometry with a radius of 10 px (or 4 arcsec), I obtain the following magnitudes for SN 2005hk: Julian Date U B V R I 2453675.59 16.049 0.009 16.813 0.006 16.870 0.009 16.762 0.011 16.754 0.020 2453701.55 18.298 0.060 17.667 0.014 16.405 0.006 15.880 0.006 15.583 0.008 The caveat for these measurements is that they also contain whatever host galaxy light is within 10 pixels of the SN.NED gives the heliocentric radial velocity of the host (UCG 272) to be 3912 km/sec. Using NED's velocity calculator to correct that to the frame of the CMB, the corrected velocity is 3565 km/sec. With a Hubble constant of 72, we get at distance modulus of 33.47 mag.
The Galactic reddening is E(B-V)_Gal = 0.022 from Schlegel et al. (1998).
The observed color on Nov 1 UT is B-V = -0.056, so the intrinsic color is B-V = -0.078 minus whatever the host galaxy reddening is. Given the blue color, this object was indeed caught early.
The absolute V-band magnitude on Nov 1B was -16.66 minus whatever the host galaxy V-band extinction is. As Weidong Li has pointed out, given how much fainter this is than a generic Type Ia supernova (M_Vmax ~ -19.2 or so), SN 2005hk could very well be like SN 2002cx, with 91T-like spectral features but underluminous for its redshift.
Below we show some consistency checks of the field star photometry from Nov 1st. The star marked by a green square in each panel is "star 9" of the sequence, which is the faintest star as measured in the V-band. One might expect it to be the most discrepant. In any case, the field star photometry seems quite self-consistent.
Kevin Krisciunas
Univ. of Notre Dame
[and Cerro Tololo Obs.]
Go back to Kevin Krisciunas home page by clicking here.