UT Sep 25, 2023: Photometry of V347 Aur

Michael Richmond
Sep 25, 2023

On the night of Sep 24/25, 2023, under awful conditions, I acquired images of V347 Aur as part of our optical monitoring program. All data was taken with the 12-inch telescope and ASI camera.

These measurements were taken through occasional breaks in the clouds, and are very uncertain. It appears the variable is starting to fall from its plateau.

V347 Aur

V347 Aur is a young stellar object (YSO) which undergoes semi-periodic outbursts. I'm part of a team of astronomers who have applied for (and received) time on the XMM-Newton X-ray telescope to study this object in the fall of 2023. We have organized an observing campaign with the AAVSO to monitor the object in the optical in order to determine when the outburst begins -- if it begins! Our prediction is some time in mid-August, 2023.

These observations involved:

• Meade 12-inch telescope
• no focal reducer, so working at f/10
• ASI 6200MM CMOS camera
• V and B filters, 60-second exposures
• images binned 4x4
• no guiding
• focus position
  • in V: 0.743 yields FWHM 2 at T = 52/15

Notes from the night:

• Opened after midnight. Chilly, no wind. Clouds when I arrived, and continued all morning with only occasional brief periods of broken clouds. On the edge of useless, really.
• no Moon at all, so skies dark.
• the heating in the house has stopped working; the furnace unit in the basement shows an error code. The temperature had dropped to 64 when I arrived. I submitted a work request to FMS -- I hope they fix it soon.

The position of the variable star is

   RA =  04:56:57.02   Dec = +51:30:50.9

At quiesence, it has magnitude V = 16-ish, but can rise to V = 12 in an outburst.

• chart of V347 Aur field from AAVSO

Here's a chart from the DSS2 Red plates, 0.6 degrees on a side.

The picture below, based on a stack of images taken on UT Jul 23, 2023, shows the area in the red box above. The variable is at its quiescent level in this image.

I've marked the location of several comparison stars.

  star       AAVSO ID            B          V         
------------------------------------------------------
   B            140              15.134    14.001                           

   C            127              13.617    12.660

   D            154              17.491    15.361
--------------------------------------------------------------------------

 

Here's a picture of the guider TV when pointed at the field (pointed slightly to the left of the variable, actually).

Tonight's stacks were formed from 17 x 60 sec in V band. I used a photometric aperture of 5 pixels (6.0 arcsec).

I reported the following to AAVSO. Note that the signal was so low that a change in the background sky value of just 1 count (from 3 counts per pixel to 4 counts per pixel) would cause the measurement to become fainter by 0.3 mag. Yikes!

    JD             filter          mag
---------------------------------------------------
  2460212.85        V         15.22 +/- 0.21

---------------------------------------------------

The variable has started to fade from its plateau.