UT Aug 28, 2023: Photometry of V347 Aur

Michael Richmond
Aug 28, 2023

On the night of Aug 27/28, 2023, under good 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. The sky was clear all morning, but I suspect some dew may have formed on the front lens of our telescope toward the end of the run.

The variable was slightly brighter than it was two nights ago.

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: 0.260 yields FWHM 2.1 at T = 57/14
  • in V: 0.238 yields FWHM 2.0 at T = 54/12
  • in B: 0.279 yields FWHM 2.0 at T = 55/13

Notes from the night:

• Opened after midnight. Cool, but very humid: fog in the fields below the observatory.
• waxing gibbous Moon setting when I arrived at the Observatory
• no sign of animals
• at the end of the night, the target was rising higher in the sky, yet the ensemble adjustment factor _also_ rose. That's a sign of less starlight entering the camera, so it's unusual. Perhaps some condensation formed on the front lens of the Schmidt-Cassegrain 12-inch telescope?
• Spent 10 minutes looking for M31 when it was near zenith. Could eventually find it with averted vision, but it was basically a point source. Stupid bright skies.

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 50 x 20 sec, 61 x 20 sec, and 54 x 20 sec for V-band; and from 57 x 20 sec for B-band.

I reported the following to AAVSO:

    JD             filter          mag
---------------------------------------------------
  2460184.81        V         13.79 +/- 0.10
  2460184.85        V         13.89 +/- 0.09
  2460184.89        V         13.84 +/- 0.09

  2460184.83        B         14.80 +/- 0.25

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

Based on my measurements, the variable is just a bit brighter than it was two nights ago, but still below the peak.