HD 204827, the C 2, C 3 rich sightline

HD 204827, the C2, C3 rich sightline

The C2 Diffuse Interstellar Bands Takeshi Oka Department of Astronomy and Astrophysics And Department of Chemistry The Enrico Fermi Institute, University of Chicago T. Oka, Thorburn, J. A., McCall, B. J., S. D. Friedman, L. M. Hobbs, P.Sonnentrucker, D. E. Welty, D. G. York ApJ 582, 823-829 (2003) J. A. Thorburn, L. M. Hobbs, T. Oka, D. E. Welty, D. G. York B. J. McCall, S. D. Friedman, P. Sonnentrucker, T. P. SnowApJ 584, 339-356 (2003) Carbon in space, Lago di Como, May 23, 2006

HD 204827, the C2, C3 rich sightline

William Huggins, Comet Tebbutt, 1881 Proc. R. Soc. London, A. 34, 148 (1881) 4050 Å 1942 1951 Alex Douglas C3 Cn 1966 IVR The Douglas effect 1975 HCCCCCN, 1977-8 HCCCCCCCN, HCCCCCCCCCN Origin of diffuse interstellar lines Nature, 269 130 (1977) Alex Douglas

Systematic observations of DIBs • J. A. Thorburn, L. M. Hobbs, T. Oka, D. E. Welty, D. G. York, B. J. McCall, S. D. Friedman, P. Sonnentrucker, T. P. Snow • Apache Point Observatory 3.5-meter • 3,800–10,000 Å ; / ~ 38,000 (8 km/s) • 53 stars, 0.11<E(B-V)<1.99, S/N > 800 at 5780 Å

C2 poor C2 rich HD 183143versus HD 204827 E(B-V)= 1.27 1.11 C2 C3 N(C2) < 6  1012 cm-2 = 440  1012 cm-2 High discrimination N(CH) = 50  1012 cm-2 = 80  1012 cm-2 Poor discrimination

Diffuse Interstellar Bands C2 DIBs C2 rich C2 poor Minority Weak and sharp

W(DIB) versus N(C2) C2 DIBs Non-C2 DIBs 5780.59 Å r = 0.305 4984.82 Å r = 0.857 6397.39 Å r = 0.416 5418.92 Å r = 0.905

C2 DIBs 21.3 cm-1 20.9 cm-1 20.4cm-1 15.0 cm-1 19.1 cm-1

Doublet Lines

The Doublets λ (Å) Δ Π Σ Is / Iw Tex 22 K 34 K 26 K Π←Σ 4963.99 4969.24 4979.64 4984.82 5170.57 5176.04 5541.87 5546.48 5762.76 5769.16 21.3 cm-1 4.0 3.8 3.8 2.4 1.8 2.2 3.1 2.8 1.6 1.0 1.1 1.0 1.5 2.0 1.3 20.9 cm-1 20.4 cm-1 A Π Π 15.0 cm-1 Or inverted 19.1 cm-1 3  106 s HC3 HC5 HC6 HC7 HC8 C3- C7- A (cm-1) 14.4 23.7 -15.1 26.2 -19.3 26.6 27.4 HD 204827 HD 147889 HD 172028

C2-rich HD 204827 Hot HD 34078 T = 301 K T = 40.6 K

C2 DIBs C2 rich C2 poor Minority Weak ans sharp

2.60 cm-1 B = 365 MHz for T = 100 K 182 MHz 200 K 122 MHx 300 K B = 564.00 MHz HC7N 290.52 MHz HC9N 169.06 MHz HC11N Keck Adamkovics, Blake and McCall

Summary DIBs which correlate well with C2 and C3 C2 DIB HD 204827, Minority, Weak and sharp Doublet structure suggests spin-orbit splitting Linear carbon chain molecule Relatively high density ? DIBs for high temperature medium HD 34078 Rotational structure  B n  8 – 12? Big question: C2, C3 C2 DIB or C2 DIB  C2, C3?

The high temperature sightline HD 34078 R head HD 34078 T = 301 K C3 HD 204827 T = 40.6 K Adamkovics, Blake, McCall RA 06

HD 204827, the C 2, C 3 rich sightline