UT Sep 03, 2023: Photometry of V347 Aur

Michael Richmond
Sep 03, 2023

On the night of Sep 02/03, 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 night, but a full Moon made the background sky bright. I made measurements in both B and V.

The variable still continues to decline.

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, 60-second exposures
• images binned 4x4
• no guiding
• focus position (note changes from recent values due to use of high-speed camera last night)
  • in V: 0.962 yields FWHM 5.0 at T = 67/19
  • in B: 1.022 yields FWHM 4.5 at T = 66/19

Notes from the night:

• Opened after midnight. Pretty warm compared to other recent nights.
• place dome slit panel at bottom position at start of night, since target is pretty high in sky even at start
• waning gibbous Moon all night long in South
• no sign nor scent of animals
• the 60-second exposure times seem reasonable for V347 Aur

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 33 x 60 sec and 38 x 60 sec in V and B, respectively. The PSF was ugly in both cases, but that's due to the poor seeing, I think; I used photometric apertures of 7 pixels (8.4 arcsec) rather than the usual 5 pixels (6.0 arcsec) for tonight's measurements.

I reported the following to AAVSO:

    JD             filter          mag
---------------------------------------------------
  2460190.84        V         14.83 +/- 0.07

  2460190.87        B         16.77 +/- 0.20

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

Based on my measurements, the variable is still fading slowly. It's about 1 mag above the quiescent level.