UT Aug 13, 2023: Photometry of V347 Aur

Michael Richmond
Aug 13, 2023

On the night of Aug 12/13, 2023, under fair 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. Although some cirrus was present for most of the observations, the night was not bad.

V347 is a bit brighter this morning ...

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
• B and V filters, 20-second exposures
• images binned 4x4
• no guiding
• focus position:
  • in V: 0.353 yields FWHM 2.7 at T = 69/20
  I shifted the focus up by +0.020 units for B-band, and then back down by -0.020 units for a second set of V-band images at the end of the run.

Notes from the night:

• Opened after midnight. Broken clouds for the first few hours, but skies were mostly clear after 4 AM
• waning crescent Moon in the East -- pretty!
• no sign of animals
• I didn't see any Perseids, despite 10 or 15 minutes of lying down and looking up at the sky. The lights of Rochester to the northeast had a lot to do with that failure, I think; the limiting magnitude was only 2 or 3 at best.

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 91 x 20 sec for V-band and 85 x 20 sec for B-band. In the B-band median image, I could barely detect star "D", used for calibration; I had to set the threshold in stars to 1.5 sigma.

I reported the following to AAVSO:

    JD             filter          mag
---------------------------------------------------
  2460169.86        B         15.9  +/- 0.4 

  2460169.86        V         14.82 +/- 0.20

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

The variable has brightened again, relative to its value two nights ago.