The study of planetary nebulae has been the focus of my research. Particular interests have been construction of photoionization models, radiative transfer problems, dust and thermal infrared emission in planetaries, and observations of these nebulae with a variety of instruments, including the Hubble Space Telescope and ISO.
The third conference in a series on asymmetric planetary nebulae was held at Mt. Rainier, WA, during the summer of of 2003 (APN3). I presented one of the summary talks; just a sampling of current research: Emerging Directions and Critical Research.
We have a paper on the expansion and distance of the nebula BD+30 3639, which appeared in the Astronomical Journal (v. 123, p. 2676) in May 2002. You can find it on astro-ph or here (in .pdf format). Here are the figures: Fig. 1, Fig. 2, Fig. 3, Fig. 4, Fig. 5, Fig. 6, Fig. 7, Fig. 8, Fig. 9.
Another interest is hydrogen deficient planetary nebulae. I wrote a short review of these objects "Observations and models of H-deficient planetary nebulae", which is in "Hydrogen- Deficient Stars", ed. C.S. Jeffery and U. Heber (PASP Conf. Ser. 96).
Here is an image of the protoplanetary He3-1475. This HST image shows, in unprecedented detail, jets producing a series of point-symmetric condensations. This color image was produced by combining our (Borkowski & Harrington) image obtained through the F658N [N II] filter of the HST WFPC2 (red) with a broad-band image taken by Matt Bobrowsky (Orbital Sciences Corp.) through the F555W filter (green). Our paper (K.J. Borkowski, J. Blondin and J.P. Harrington, Ap.J. Letters, 10 June 1997) discusses the production of these features by oblique shocks.
We have a paper (Ap.J., 550, 778) on the kinematics of the jets: Link to astro-ph
In addition to He 3-1475, three other nebulae have so far been imaged as part of our Cycle 6 snapshot program to search for jets in planetary nebulae. The target list has been drawn from nebulae with point symmetric morphologies and from objects with spectroscopic indications of high velocity flows. We presented images of them at the 190th AAS Meeting [Borkowski, K.J., Blondin, J.M., & Harrington, J.P. (1997) BAAS, 29, 786 -- abstract 7.05]. North is up and east to the left in these images.
NGC 6210. This is an HST WF2 Image in [N II]. While the bright parts of this nebula are chaotic and very asymmetrically placed with respect to the central star, there is also a fainter, symmetric, two-lobed bubble. Along the axis of this bubble 17" to the northeast of the star, is an elongated "bullet". This bullet is actually the brightest part of one of the pair of point symmetric "arms" that can be seen in a deep CCD image by Balick et al. (1992).
Hu 2-1 in H-alpha and in [N II]. The innermost ring seen in H-alpha, with a major axis of 0.7", was observed with the HST PC by Bobrowski (1996). The [N II] image, on the other hand, seems to show a cylindrical cavity which opens into a bi-lobal structure. In our deeper images, one can see how the axis of the nebular structure twists counterclockwise as we progress outward.
Hb 4, also in H-alpha and [N II]. We targeted this nebula because of the two outlying radial segments seen in the CCD images of Schwarz, Corradi & Melnick (1992). The HST images show how complex these features really are. The [N II] image of the northern segment, in particular, shows a distinct "corkscrew" structure. The southern segment may have a similar structure, but it is harder to trace. Also note that in the H-alpha image, the southern segment is in line with the "nipple" in the faint arc of nebulosity outside the bright core. A paper by Lopez, Steffen & Meaburn (1997) finds that the corkscrew segments have velocities of +/- 150 km/sec. A new study has just appeared in preprint "High velocity string of knots in the outburst of the Planetary Nebula Hb4" by Derlopa, S. Akras, P. Boumis, and W. Steffen (arXiv:1901.05767).
Balick, B., Gonzalez, G., Frank, A., & Jacoby, G. 1992. Ap.J., 392, 582.
Bobrowsky, M. 1996. in ``Science with the Hubble Space Telescope - II", P. Benvenuti, F.D. Macchetto, & E.J. Schreier eds., p 410.
Lopez, J.A., Steffen, W., & Meaburn, J. 1997. Ap.J., 485, 697.
Schwarz, H.E., Corradi, R.L.M., & Melnick, J. 1992. A&AS, 96, 23.
Here is a paper on the whole jet survey: Link to astro-ph
One of the most charming of all the old towns is
Schassburg (Sighisoara in Romanian), which is crowned by the great
clock tower. A few steps beyond the tower is the house where Vlad Tepes
(AKA Dracula) was born. I found a restaurant on the second floor;
we had a very pleasant lunch there.
(Compare the tower with this 19th century print.)
The quintessential Saxon city was Hermannstadt (Sibiu). The dormer windows in the roofs seem to regard you with sleepy eyes, while the arched openings turn buildings into Bosch-like creatures.
Most characteristic are the "Kirchenburgen", the fortified churches, which were a place of refuge in troubled times. This church is located near Kronstadt (Brasov). The name is Tartlau.
In the wall surrounding the church at Mediasch (Medias), I found this wonderful old door. More art deco than medieval, it nevertheless carries an aura of mystery.
"Time, Apollo and the Seasons" by Claude Lorrain
"The Beech-Tree" by Charles E. Burchfield (1919)
Zinc plate etching, 5 1/8 x 8 1/4 in. This heavily-inked impression is titled "The Beech-tree"
at the lower left, although the title is usually given as "Beech Tree and the Valley
of the Little Beaver". Between July and September, 1919, Burchfield completed this and
at least ten other etchings. Only trial proofs of the plates were pulled by Frank Wilcox,
who had encouraged him to try this medium. In 1953 an edition of ten impressions was
printed from this plate, in connection with an exhibition of Burchfield's drawings.
This is Burchfield's only published etching. The fact that the impression shown here
is titled but not numbered suggests that this is a proof pulled in 1919. Many of the
proofs were titled. The Burchfield-Penney Art Center in Buffalo NY holds one of the 1953
impressions; it is not titled, but is numbered in the lower right corner.
In addition to this etching, there are a small number of other prints by Burchfield.
Here are most of them:
prints by Charles Burchfield.
Since it is hard to "erase" a mark on an etching plate, Burchfield first did a series of drawings in violet indelible pencil as a sort of discipline for the etching process. Here are two of these drawings: "Under the Apple Tree" and "Evening in the Alley". (Did you notice the moon peeking through the trees in "Evening"?)
I gave a talk last year (8 Apr 2018) in Salem, Ohio to the Burchfield Homestead Society. While it was not recorded live, I've reproduced my talk for the record here: