ESO 434-16 misidentified as NGC 2973

[NGC7702]

Hi All,

Just a brief query.

I was observing tonight working my way through a short list of NGC objects in Antlia and slewed the 'scope to NGC 2973 which, according to Steve Gottlieb's notes here:

http://www.astronomy-mall.com/Adventures.In.Deep.Space/NGC%202000-2999.html

was a double recorded by Herschel but is misidentified in most versions of the NGC as ESO 434-16. (As it is in Megastar and SIMBAD)

The misidentification or error is not the issue here.

As I was observing ESO 434-16, I noticed a couple of very faint stars superimposed that I couldn't see on the Realsky version of the DSS (due no doubt to the compression of the images). They are visible on the uncompressed DSS here:

http://stdatu.stsci.edu/cgi-bin/dss_search?v=poss2ukstu_red&r=09+37+59.6&d=-30+08+52&e=J2000&h=15.0&w=15.0&f=gif&c=none&fov=NONE&v3=

approximately 29" distant in PA 12, and 19" distant in PA 170 from the core embedded in the halo. I've been trying to find the magnitude of these stars (which initially rang alarm-bells as supernova candidates) without success.

Is there a better researcher out there than I that can find a magnitude for either (or both) of them?


Best,

Les D

[Jim Chandler]

Try posting your query on Amastro. Chances are good Brian Skiff will respond to your question.

[Steve Gottlieb]

I use VizierR (http://vizier.cfa.harvard.edu/viz-bin/VizieR) to look up stellar magnitudes across several catalogues. If you input 09 38 00.15 -30 08 32.1 (that's your northern star in PA 12°) into "Search by Position" and set the "Target dimension" to 0.04 arcminutes, you'll get several results, including Gaia DR1 and USNO -B1.0. In this case, though, there are no V magnitudes -- only Rmag and Gmag. It's possible a Vmag can be estimated from these, though from different sources I'm not sure that would be very accurate.

For the southern star input 09 37 59.944 -30 09 14.42 with a Target dimension of 0.06 arc minutes. USNO -B1.0 has a Bmag of 18.8, but again there are no Vmags listed. These are dim stars!

[NGC7702]

Hi Steve,


I use VizierR (http://vizier.cfa.harvard.edu/viz-bin/VizieR) to look up stellar magnitudes across several catalogues. If you input 09 38 00.15 -30 08 32.1 (that's your northern star in PA 12°) into "Search by Position" and set the "Target dimension" to 0.04 arcminutes, you'll get several results, including Gaia DR1 and USNO -B1.0. In this case, though, there are no V magnitudes -- only Rmag and Gmag. It's possible a Vmag can be estimated from these, though from different sources I'm not sure that would be very accurate.


For the southern star input 09 37 59.944 -30 09 14.42 with a Target dimension of 0.06 arc minutes. USNO -B1.0 has a Bmag of 18.8, but again there are no Vmags listed. These are dim stars!

Yes, apparently quite faint. I'd suggest from what I saw at x247, they were in the order of V mag 15.5-16 for the northern star, and mag 16 - 16.5 for the southern one. A little surprised I saw the 2nd one against the glow of the galaxy. That and the fact I couldn't see them on Realsky was what made the supernova candidate bells ring, but as usual it's the compression on Realsky that makes them disappear.

Best,

L.

P.S I just typed the observing note up from the voice recorded notes:

x185 27' TF, x247 20' TF

NGC 2973 (ESO 434-16) (PGC 27439) Galaxy *
RA: 09h 37m 59.6s Dec: -30° 08' 52"
Mag: 14.0 S.B.: --- B-V: --- Size: 1.3'x0.9' Class: Sa
P.A.: 36 Inclination: --- R.V.: --- Source: PGC *

This eg is very nearly pointed at from the N by 2 *s of mag 11.5 & 12 that are about 2' apart. Mod faint and mod to quite LSB. The eg is a further 2' S from the S most one*. The eg is slightly elong in about PA 30 and as I said almost pointed at by those two stars to its north. 50" x 30" in PA 30 with a weak central brightening

I can see two very faint embedded star-like points in the LSB halo, one is about PA 20. One is on the northern edge of the halo (NNW flank) (the brighter) and the other is S of the core by about 10-15".