Sep 25, 2012 UT: A check on V1647 Ori (which is still bright)

Michael Richmond
Sep 25, 2012

On the night of Sep 24/25, 2012, I observed the object called V1647 Ori , but perhaps better known as McNeil's Nebula . My goal was to see if the object at the heart of this nebula was still in the "high" optical state, which it had during its discovery in 2004 and again in 2009-2011, or in the "low" state which occurred in late 2005.

The setup was:

Notes from the night

Below is a picture created from 39 individual 30-second I-band images, combined via a median technique. The field shifted during the observing run, leading to non-uniform exposure times for pixels near the edges. North is up, East to the left, and the field is about 14 by 10 arcminutes.

Compare this to an I-band image acquired on November 13, 2011, with the 0.9-m WIYN telescope. RIT image of Sep 2012 on left, WIYN image of Nov 2011 on right.

Pretty similar, aren't they? It seems clear that V1647 Ori hasn't changed much since Nov 2011.

I used the star labelled "C" in the charts on this page as a comparison. Arne Henden's measurements indicate that this star has magnitude I = 13.65. Using aperture photometry with a radius of 3 pixels = 5.6 arcsec (see note below), I measure a rough value of I = 14.6 +/- 0.2 for V1647 Ori on Sep 25, 2012 = JD 2456195.86.

Warning: The seeing was really bad in these images, so the light from the star is mixed up with light from the surrounding nebulosity. That will cause this measurement to be an overestimate of the true brightness of the star itself.

Nonetheless, when we compare the current value to its magnitude of approximate I = 18.5 during the low point of fall/winter 2005, we can conclude that the star is still in a "high" state in the optical.

Last modified 09/03/2012 by MWR.