Object of the Week, October 15, 2017 – NGC 613, a gorgeous barred spiral

NGC 613 = ESO 413-011 = AM 0132-294 = MCG -05-04-044 = VV 824 = PGC 5849
RA: 01 34 18.2
DEC: -29° 25' 06"
Type: SB(rs)bc
Size: 5.5'x4.2'
P.A.: 120°
Mag: V = 10.1, B = 10.7

William Herschel discovered NGC 613 on 9 Dec 1798 and recorded "considerably bright, elongated north-preceding/south-following, 5 or 6' long, 1 1/2' broad, a nucleus in the middle. A pretty considerable star is about 3' north of it, and a little following." This bright barred-spiral is the 10th most southerly galaxy discovered by Herschel and is located 38' NW of mag 5.7 Tau Sculptor. Its been compared in structure to better known barred spirals NGC 7479 and NGC 1097, but yet this galaxy seems overlooked by amateurs.

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The galaxy hasn't been ignored by professionals -- NED has 332 references. NGC 613 lies at a distance of ~65 million light years, spans ~100,000 light years and contains an active Seyfert nucleus.

The 2004 paper "Double-barred galaxies" (A&A, 415, 941) writes, "Suggested as double-barred by Jungwiert et al. (1997), using their H-band image. Inspection of WFPC2 images reveals a pronounced and very elliptical nuclear ring with strong star formation, having the same size, ellipticity, and orientation as the suggested inner bar. A 1996 radio study concluded "NGC 613 is a barred spiral galaxy with an active hot spot nucleus, a radio jet and a circumnuclear radio ring; there is some evidence for an accelerated collimated outflow."

Finally, the 2002 study "Near-Infrared and Optical Morphology of Spiral Galaxies" (ApJS, 143, 73) writes "SB(r)bc: Bright nuclear point source. Nuclear bar aligned with elliptical bulge and large normal bar. Fairly highly inclined disk. Two bright arms emerge from the ends of the bar, with many bright knots near the bar ends. SE arm wraps loosely to the NE. NW arm wraps tightly to the SW and forms an inner disk ring. Several other, lower surface brightness arms emerge from the ring."

My first view was 36 years ago in 1981 using a C-8. My notes read, "faint, moderately large, diffuse, small bright core. *A mag 9 star lies 2.5' NE." The bar was first seen using my 17.5-inch in 1993, as well as the initial part of the southern spiral arm, which emerges at the southeast end of the bar.

As you would expect, the view improves with aperture as well as latitude, and from Australia NGC 613 was a superb showpiece in a 30-inch two years ago! These notes were taken at 303x.

"The bright central bar region is oriented NW-SE and extends ~2.5'x1' with the halo and arms stretching ~5'x3.6'. The central region is sharply concentrated with a very intense core that increases to a bright stellar nucleus. A prominent spiral arm is easily visible on the southeast end. It has a well defined edge and a high contrast as it emerges from the central region and unfurls east and north. The arm then dims but can be followed as it bends backwards on the east side towards the northwest! The arm dims out before reaching a mag 9.6 star 2.2' NE of center. A second bright, well-defined arm is attached on the northwest end and curls south on the west end of the halo."

GIVE IT A GO AND LET US KNOW!

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Hi Steve,
You’re right, NGC 613 does seem overlooked by amateurs. I was roaming around in Sculptor just the night before last. I wanted to observe the Sculptor Dwarf Galaxy under these great skies with my 16", look at some other obscure galaxies, and visit some bright old friends... and NGC 613 got completely overlooked in favour of the bright-and-glitzy old friends, and the extremely faint and not-glitzy new chaps! So I went back and observed it last night.

It’s a tremendous galaxy! At 100x it appears as a fairly bright, fairly large haze of delicate misty light, NW-SE oval-shaped, with a small bright core. It lies in a lovely star field peppered with bright stars, and with an attractive yellow 9th magnitude star 2.5' NE. At 230x, the central bar comes into view! Albeit not very distinct, it is a definite bar-shaped haze, punctuated by the bright intense core. No sign of a nucleus. Averted vision reveals a tiny portion of the southern spiral arm where it emerges from the southeastern end of the bar haze! It is just visible to the eye, but I can make out a small and faint eastward curve, that fades abruptly just as it begins to curve northwards. What a treat to see! The remainder of the arm, and the northern arm are invisible.

Steve,

I had a look at this one first three years ago with my 12.5-inch at Henry Coe State Park above the San Jose city lights while running through the H400 list (which includes this object). "100x Just visible direct vision, averted reveals some elongation but mostly roundish halo. Bright core pops with AV. No halo structure visible. Near a bright star to NE."

I looked at it again last night, this time with my 20-inch, albeit though much poorer seeing and some wildfire smoke haze from Pinnacles (SQML 21.3, 205x): "Bright elongated core and slightly brighter nucleus, well elongated and diffuse halo, 3:1 ENE-WSW. Some mottling and hint of structure in the halo. With some study I notice spur emerging from the core on its SE rim, the start of a spiral arm, noticed with averted vision but can hold direct"

Here my observation with my 20" from Spain:

At 320x I see a surprisingly nice galaxy, despite the low elevation above the horizon. I see a very long, elongated ellipse with a bright central region. Along the major axis I see a curved bar with some bright patches in it. Two on one side and one on the other.

Very nice object Steve.

Similar to you we Europeans also have travel to more southern latitudes to see all the beauty the galaxy can show.

sketch: 24", 300x, NELM 7m5+, Seeing IV (Hakos/Namibia)
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Just observed NGC 613 with my Tak FS128. From 35 degrees north it cleared the ridgeline to the south of my home by a few degrees. It took me a while to locate it, as the 9th magnitude star overwhelms it in only 5 inches of aperture, but at the end I detected it. By increasing magnification it appeared as a very faint oval patch of light with a slightly brighter center, that at magnifications of 80X or more could be held with direct vision...