[vsnet-alert 10198] Re: Variable in NGC 300
arne at aavso.org
Sun May 18 21:47:20 JST 2008
B Monard wrote:
> I was able to make some filtered observations of the transient just before dawn, incl a calibration sequence for V-I-R based on a calibrated field just South of the galaxy..
> Var in NGC 300 20080518.16 14.62 V
> Var in NGC 300 20080518.16 14.30 R
> Var in NGC 300 20080518.16 13.82 I
> These magnitudes tell that the transient is not as red as expected.
> For those that like to follow up with filtered photometry, a good reference star to use is at 00 55 06.47 -37 42 58.2 with V=13.71, R=13.40, I=13.10. The uncertainties are estimated to be around 0.03 for each.
> In view of the new sequence my earlier reported values of 14.2 (unfiltered CCD) would become 14.3 (as based on red zeropoint). Therefore no change in the (unfiltered CCD) brightness of the transient since May 14.16 .
There is a nice UBVRI sequence from Alcaino & Liller (1984AJ....89..814A),
which may be what you were using for your calibration.
Matt Templeton chose a subset for our VSP chart, so that you can get
easy identification of the comparison stars as well as precise coordinates
and UBVRI photometry.
The spectra do not indicate redness (V838 Mon did not become extremely
red until later in its outburst). The derived luminosity and emission
line structure are what make Bond et al. consider this a V838 Mon-like object.
More information about the vsnet-alert