WR stars in M33 HII regions (NGC 588/592/595/604)

[Uwe Glahn]

After inspiring NGC 604 during the last years I used very steady seeing conditions last new moon to detect as many individual stars as possible in NGC 588, NGC 592 and 595.
Interesting that Drissen et al. (astro-ph pdf, html link) published a work in which the detected WR stars are labeled.

First NGC 604. First "star peaks" could be detected in 8"+ instruments. I used a exceptional night to resolve some details.
27", 837x, Seeing I, NELM 7m+
NGC604.jpg
Seems like I got WR 2, WR 4 and WR 13.

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Second NGC 588. Small but most nebulous region with only 3 peaks within the nebula.
27", 837x, Seeing II-III, NELM 7m+
NGC588.jpg
The conglomerate of star MC3 was visible. Also star UIT 008.

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Third NGC 592. Largest and perhaps next to NGC 604 most interesting region with the most reserves for even better conditions or bigger aperture.
27", 837x-977x, Seeing II, NELM 7m+
NGC592.jpg
WR 1 and WR 2 were at the limit of detection.

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Last NGC 595. Similar small than NGC 588. Only a few peaks could be detected.
27", 837x-977x, Seeing II, NELM 7m+
NGC595.jpg
Only WR 4 could be detected. WR 2b seems to bright enough but could not separated from the southern (foreground?) star.

[Ivan Maly]

Excellent observations. What's your estimate of the magnitude of the brightest of these stars/clumps? Vm 17 perhaps?

[Daniel_Sp]

Hi Uwe,
these objects show the high quality of your mirror! I had the pleasure to observe NGC 604 a few years ago in the 44"-Nowton in the Melle-observatory. But we (Peter and myself) only observed at about 360x

best regards + CS
Daniel

[Steve Gottlieb]

Thanks for posting these excellent results, Uwe!

For an easier target, the brightest individual star in M33 (perhaps excluding LBVs at their maximum) is thought to be B324 (V = 15.2), a highly luminous hypergiant at the north edge of IC 142.

[Uwe Glahn]

@Ivan

What's your estimate of the magnitude of the brightest of these stars/clumps? Vm 17 perhaps?

I guess much brighter. Perhaps around 16vmag or 15,5vmag. A quick and dirty search gave me something around 16,5bmag.
The brightest stellar peaks (not sure if it was individual stars or clumps of stars) were barely visible with 8". Mathias Sawo recently posted a sketch with 10" with the two brightest spots at astrotreff.de

@Daniel

But we (Peter and myself) only observed at about 360x

360x with 44"? Be honest, you guys jam up the searching eyepiece, right? 360x was exactly the magnification I used with my 8" grab and go.

@Steve

the brightest individual star in M33 (perhaps excluding LBVs at their maximum) is thought to be B324 (V = 15.2)

Ok, thanks for the info. I have to check this out (and to return to observe some globs and individual stars).
I thought so far that VHK 83 (16,1bmag) is the brightest individual star in M 33. I observed this guy together with some brighter globs a few years ago with my 16".

[Ivan Maly]

Hubble's long-period varC (http://adsabs.harvard.edu/abs/1953ApJ...118..353H) was Vm 15.5-15.6 at the end of 2013 when I observed it, and it was already dimming then. Hubble's photographic maximum was 15.3. Visibility-wise, varC has the advantage of the essentially empty galactic background. Need to check these out now.

[Steve Gottlieb]

Here are the last several observations (magnitude) of M33 Var C from the AAVSO site.