NEAT SOUTHERN PLANETARIES : 27
He2-60 / Hf 48 in Carina

This section centres on the faint but unusual bipolar planetary, He2-60, which was discovered from Red Schmidt telescope plates produced in South Africa. Our ancillary story here also with the Annals of Harvard College Observatory, being a wonderful paper published by Hoffleit, D., “A Preliminary Survey of Nebulosities and Associated B-stars in Carina” in 1953. [See Ref. 4.] This is a good read for any visual observers or astroimagers who are interested in the deep survey of the area around the magnificent Eta Carinae.

He2-60 / Hf 48 / Sa2-71 / Wray 16-85 / ESO 128-29 / PK 290-0.1 / PN G290.1-0.4 (11039-6036) is an extraordinary looking Carina planetary nebula that we presently know very little about. It is a very tough object for amateur telescopes, with only its tight luminous central region being the only portion that is like visible to us. Available catalogued data says He2-60 is 15.0p magnitude and visually subtends about 19 arcsec across. In the V-V PNe classification it is oddly as III or 3 — irregular disk — even though it is clearly now not the case.

Discovered by Dorrie Hoffleit in August 1953 as Hf 48, it was then next observed and to be later catalogued by Henize (1967) as He2-60. Here I have preferred using the ‘He2-’ designation, as Hoffleit did find objects that are mixtures of only just sixty-nine nebulae rather than specific or dedicated PNe discoveries — although Hoffleit did call Hf 48 as a planetary! This, with other interesting nebulae, appears all in Hoffleit (1953), whose quite remarkable paper* investigates the much wider nebulous region in and around the famed environs of the grand NGC 3372 / Eta Carinae Nebula / η Car Nebula / Gum 33 / RCW 55 (10440-5930). This faint PN was discovered on the sixty minute 103a-E red plate image using the variable aperture 81/90cm. f/2.6 South African Schmidt telescope that was originally installed at its site near Bloemfontein during 1948. [See the short but quiet informative book by Marx (1992)].

Fig. 1. He2-60 Wide Field. CDS Aladin Colour Image about AAO Red (red), IR plates (blue), average (green) 11½′×11½′ in size.

Technical Information

Observationally, this remains a difficult object, but should respond to the O-III filter. This can be adjudged from the CGPN data [Ref.1 Acker, A., et al. (1992)], from the relative line intensity of the blue-green [O-III] (500.7nm.) of 1353, being usually compared to the similar bluish line of the “standard” Hβ line (486.1nm) set at 100.0. This is roughly average compared to the red Hα line (656.3nm.) of 1017, while [NII] (658.4nm.) easily exceeds the average PNe values of 6083. Redder [SII] lines (671.7nm. + 673.1nm.) are 207 and 206. This makes the more likely ratio for [OIII]/Hα at about 3:1., so we can conclude that any OIII filter may respond quite well. Any takers?

Comparing the energy output by the Hβ flux of NGC 3132 to He2-60, [log -10.45 mW.m^-2 against log -12.7 mW.m^-2], He2-60 is 180 times less luminous than NGC 3132.

Looking at the available Aladin images, clearly shows the commonly stated bipolar structure, with its bright waist with many outflows roughly diagonally across the image. Hoffleit (1953) first describes “Very small “dumb[b]ell.” Superimosed star not classified.”

Fig. 2. He2-60 Narrow Field. CDS Aladin Colour Images showing the nebulae in various wavelengths. Image scale is roughly 30″×30″ for each frame. The Short Red image shows evidence of the very faint PNN.

Pascoli (1990) [Paper I] describes Hf 48 as follows;

“The Hα map (Fig 6.) shows a minor-axis “I” shape. The dashed lines outline the ansae which delineate the edges of the bipolar lobes. These ansae clearly start from both the extremities of the central bar (a ring seen edge-on) as observed in [Carina’s brightest planetary,] NGC 2899.”

In Pascoli (1990) [Paper II], he gives the tentative classification for Hf 48 as “late butterfly”, Greig-Sabbandin bipolar classification of ‘B’ [From Sabbadin (1984, 1986)] whose angle between the major geometric axis and the line of sight is 80°. He does not give any true radius nor any equatorial expansion velocity, though Pascoli classes it as Type 5 in his published paper’s classification. I have reproduced it here to show the structural nature of this obvious bipolar planetary. This figure shows the various lines that have equal brightness or intensity, all just expressed not in units by as relative numbers. (See Fig. 3.)

← Fig. 3. He2-60 General Structure. (left) Structure according to gradient light intensity by Pascoli (1990), who classes it as his Type 5 (pg.189). The shape is slightly different from below, as the tilt of the line-of-sight is 80°.

Deeper images, like the study made by Hua et al. (1998) using various telescopes including the 2.3-metre ATT at Siding Spring, show the size extends to 25×20 arcsec in Hα, 28×80 in [NII] and 20×65 in [OIII]. These images appear in their Fig. 6 in this paper, and they look slight different from my Fig.2 presented here. Advanced readers might like to compare images of Hf 48 with other known PNe that they have investigated. Hua, et al. (1998) says;

“This planetary nebula is characterised by a quite strong reddening, since the Balmer decrement is rather high, and by a strong [NII] emission. The major part consists of a rectangular (10″×15″) core. The fuzzy (20″×25″) envelope is very faint.”

Central star or PNN is not listed at all in the literature, but it seems to be in the Short Red image (Fig. 2.), in the centre of three different nebulous parts of He2-60’s very narrow waist. Looking at Pascoli (1990) expectant shape or morphology (Fig. 3), shows the two bright or intense regions either side of the waist. Causing this region of intensity is a significant amount of luminous gas that the observer has to peer through. At the extreme edges we are looking through a thick region of gas. In the centre of the waist, the gas is at its thinnest, being more transparent to light, and so the bright central star can shine through it. This easily explains what we see.

In Fig. 3, if the observer was looking directly down from above (0° instead of the observed 80°), we would instead see a perfectly circular ring that would mimic PNe like the famous famous and huge apparent sized NGC 7293 / Helix Nebula (22297-2050) in Aquarius or Centaurus’ Lo 5 / Longmore 5 (11138-4806).

I could find only one estimate of distance for this planetary, being 2.0 kpc. by made Maciel (1984). Hua et al. (1998) estimates the nebula mass as at or below 0.1M⊙ and has the moderate electron nebula density (N_e) of about 1000 e^-.cm^-3 (electrons per cubic centimetre) — the energy fluorescing the nebulosity we see.

Other Morphologies for Hf 48

Hf 48 might not be spectacular in telescopes, but astrophysically, this is an interesting PNe, and is certainly another southern object worthy of much closer scrutiny. The closest paper published to date is by Soker & Rappaport (2000), which discusses the nature of some forty-three PNe with waists. Hf 48 in this paper is the only one with a totally blank listing of current knowledge! Advanced readers might like to read this paper for themselves, as they give a good summary of these kinds of planetaries, their morphology, and their complicated wind dynamics. These authors profess that the structure is formed by binary stars that have a red supergiant star on the top of asymptotic giant branch (AGB) with a white dwarf companion, whose orbital semi-major axis is between several AU and 200AU. They explain that the fast wind is made by collimating an accretion disk to form the observed bipolar structure. An interesting idea, in light that that the true cause of the phenomena still has not been explained even twelve years later.

Hopefully, and soon, perhaps a new dedicated investigation will come along and likely reveal more details about this unusual bipolar planetary.

Visual Observations

Visual observers with large apertures might like to attempt this objects, and possibly be the first to spot it. I could find no observation to present here, and even eagle-eyed Kent Wallace, has yet to record Hf 48 / He2-60.

References

1. Acker, A., et al., “Strasbourg-ESO Catalogue of Galactic Planetary Nebulae.”, ESOPN, (1992) (ISBN 3-923524-41-2) [Useful on-line version at; Strasbourg- ESO Catalogue of Galactic Planetary Nebulae.]
2. Corradi, R.L.M., Schwarz, H.E., “Morphological populations of planetary nebulae: which progenitors? I. Comparative properties of bipolar nebulae.”, A&A., 293, 871 (1995)
3. Henize, K.G., “Observations of southern planetary nebulae.”, AJ.Sup.Ser., 14, 125 (1967)
4. Hoffleit, D., “A Preliminary Survey of Nebulosities and Associated B-stars in Carina”, A.HCO., 119, 37 (1953) [Annals of Harvard College Observatory] ADS : Hoffleit (1953)
5. Hua, C.T., Dopita, M.A., Martinis, J., “Detection of new emission structures around planetary nebulae.”, A&A.Sup.Ser., 133, 361 (1998) [At ADS.]
6. Marx, S., “Astrophotography with the Schmidt Telescope.”, pg.32, Pub. Cambridge University Press (1992)
7. Pascoli, G., “Morphology of Bipolar Planetary Nebulae. I. The Two-dimensional Spectrophotometry.” A&A.Sup.Ser., 83, 27 (1990) [As Paper I.]
8. Pascoli, G., “Morphology of Bipolar Planetary Nebulae. II. The Three-dimensional Structures.” A&A., 232, 184 (1990) [As Paper II.]
9. Soker, N, Rappaport, S., “The Formation of Very Narrow Waist Bipolar Planetary Nebulae.”, AJ., 538, 241 (2000) [ADS: Soker & Rappaport (2000)
10. Westerlund, B.E., Henize, K.G., “Dimensions of Southern Planetary Nebulae”, AJ.Sup.Ser., 14, 154 (1967)

Surrounding Objects of He2-60

There are so many objects around here that you could fill several issues of our Journaled “Universe”. Observers here might like to examine for themselves the open clusters of Cr 236, Bochum 12, NGC 3496 and NGC 3519 being all nearby and within 1½° of Hf 48 / He2-60.

1. Cr 236 / Bran 333 / C 1055-607 (10597-6058) is a 7.7b magnitude cluster that is 7′ across. It only contains about 20 stars, being place some 39′SW (PA 234°) from He2-60. Remarkably missed in the NGC, this weak scattering of stars have the poorly Trumpler classification of 3 2 p −. Distance is 800 pc, or about 2¼ times closer than the bright Eta Carinae nebula.

2. Bo 12 / Bochum 12 (10573-6144) is an open cluster that is fainter than Cr 238 at 9.7 magnitude that covers about 10′ across. It is populated by 20 stars, whose visual appearance is three groupings of three 11th magnitude stars among several other fainter stars. It is best seen in 15cm or 20cm. Location is 48′SSW (PA 200°) of Cr 238 or 1.4°SW (PA 215°) from He2-60. G. Lyngå classes Bo 12 as Trumpler class II 3 p −.

3. NGC 3496 / Cr 237 / h.3310 / C1057-600 (10597-6020) is an open cluster about 36′WNW (PA 295°) from He2-60. Containing about 60 stars, this 8.2v / 9.0b total magnitude cluster subtends about 9′. Most stars are of 12th magnitude, and all the stars are brighter by about two magnitudes than the foreground stars. The whole cluster is visible in 15cm. in good conditions, but 20cm would be better.

Discovered by John Herschel in 1834 during telescope sweep No. 435, who describes;

“Place of a small double star in the following part of a loose, rich, pretty large cluster of stars 13 m[ag], 8′ or 10′ diameter; a fine object; a very much condensed milky way group.”

Spectral observations do suggest the whole cluster is moving towards at −51.4 km.s^-1. Piskunov et al. (2008) finds the total mass for NGC 3496 is 198.6±1.9M⊙, whose linear radius is 7.9±1.7 pc. Age is about 417 Myr. and distance is a fairly close at 990pc.

4. NGC 3519 / h.3314 / Ru 93 (11041-6122) is the 7.7v magnitude small 4′ across cluster that lies 46′S (PA 179°) or 20′SSW (PA 200°) from the equal 7.7v magnitude double star Δ105 (11049-6103).

This open cluster was discovered by John Herschel in 1834 before his other discovery of NGC 3496. He reported seeing on declination sweep No.432;

“Chief star of a pretty rich cluster. Class VII.”

NGC 3519 contains about thirty stars, the cluster appears as a circular pattern of stars, with three stars forming a slightly elongated triangle. The very faint circular pattern did not appear obvious at first, but in 25cm could just make out several wavy lines of stars to the northeast, northwest and north. Brightest star is the alleged double, HJ 4400 AB (11041-6122), being of 9.7 and 12.8 arcsec. However, since 1924 no companion has since been seen. It was not visible in 30cm.

Open cluster diameter is estimated as 13.6±2.2 pc., age is 437 Myr. and whose total mass is 126 M⊙. Distance is 1.44 kpc.

Reference to NGC 3496 & NGC 3519

1. Piskunov, A.E., et al., “Tidal Radii and Masses of Open Clusters.”, A&A., 477, 165 (2008)

Last Update : 27th February 2012

Southern Astronomical Delights © (2012)

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