UT Sep 05, 2023: Photometry of V347 Aur

Michael Richmond
Sep 05, 2023

On the night of Sep 04/05, 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, but the moonlight rendered the B-band values too uncertain.

The variable paused for a bit in its 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
  • in V: 1.039 yields FWHM 4.2 at T = 72/22
  • in V: 1.044 yields FWHM 5.7 at T = 72/22

Notes from the night:

• Opened after midnight. Warm and humid.
• place dome slit panel at bottom position at start of night, since target is pretty high in sky even at start
• waning gibbous Moon was bright again
• the only animals to visit were mosquitoes
• I noticed (for the second night in a row) that the PSF suffered from some asymmetry: it went from squished one way to squished the other way as one moved through the best focus position. I also noticed a slight tiltability in the electric focuser: I could gently move the unit back and forth by a very small amount. At the end of the night, I discovered a loose set screw holding the focuser to the telescope back. I tightened it with a 3/32 hex wrench and the connection now no longer moves. Let's hope that this brings the PSF back to its usual symmetric appearance.

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 20 x 60 sec and 20 x 60 sec in V band. 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
---------------------------------------------------
  2460192.82        V         14.84 +/- 0.08

  2460192.85        V         14.76 +/- 0.08

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

Based on my measurements, the variable has paused for the past two days.