Derived Spectra of Comet C/Hyakutake Data Set Overview ================= This dataset presents spectra of Comet C/Hyakutake taken in 1996 at four different offsets from the nucleus. The spectra were obtained at Kitt Peak National Observatory using the Echelle Spectrograph on the 4m Mayall Telescope. The echelle spectrograph had a resolving power of ~18000 and a sky-projected slit size of 0.87 x 7.4 arcsec. The spectral range was from 3000-5000 Ångstroms with deteriorating S/N beyond 4200 Ångstroms. Parameters ========== The data are presented as ASCII tables with two columns. The first column is the wavelength in Ångstrom. The second column is the corresponding flux density in erg per second per centimeter squared per Ångstrom. Processing ========== Bright quartz lamps were used to create a flat field for the data. Relative sensitivity functions for individual orders were derived after a color correction for the lamps was applied. Spectra of solar analog 16 Cyg B and 'sky flats' were used to remove the cometary dust continuum. Obvious emissions were flagged by hand. Over most of the spectral range, the wavelength was calibrated using exposures on a thorium-argon lamp, with careful matching in the overlap between orders of the echelon. At the shortest wavelengths there are not enough lines from the thorium-argon lamp, so the wavelength was calibrated using readily identified cometary emission lines of OH. The data were all obtained on the date of closest approach to Earth, so there is no significant Doppler shift in the cometary OH lines used to calibrate part of the spectrum. After this an automated correlation algorithm was used. This algorithm scanned iteratively for weaker lines and scaled and shifted the solar spectrum to the cometary continuum. After this an additional fitting parameter was used to correct for small DC offsets from scattered light. Finally, for this data set the exposures were combined, weighted by exposure time, and corrected for atmospheric extinction. The individual observations used to create the weighted spectra have not been submitted to PDS for archiving, but are available at Kitt Peak National Observatory (KPNO). Data ==== The data are presented as ASCII tables that give the wavelength and the corresponding flux density. Each file is at a different distance away from the photocenter. 1) offset_0_arcsec.dat: Table at 0 arcsec from photocenter 2) offset_2_arcsec.dat: Table at 2 arcsec from photocenter 3) offset_7_arcsec.dat: Table at 7 arcsec from photocenter 4) offset_10_arcsec.dat: Table at 10 arcsec from photocenter The aperture over which flux density is measured is ±3.7 arcsecond orthogonal to the offset direction and ±0.43 arcsec in the offset (sunward) direction. Apart from the 2 arcsec table, the offset tables are weighted averages of two or more exposures. The table of exposures presented in A'Hearn et al. (2015) as "Table 2" is reproduced below. Individual Exposures -------------------- Exp ID Mid-UTC Exp Time(s) AirMass Offset (arcsec) coo23 06:02:57 600 1.530 0 coo24 06:16:02 600 1.513 0 coo35 07:04:45 600 1.468 7 coo36 07:17:27 600 1.460 7 coo37 07:31:14 600 1.453 10 coo38 07:44:05 600 1.449 10 coo39 08:31:03 600 1.443 10 coo40 08:54:26 1800 1.445 10 coo41 09:27:58 1800 1.458 10 coo42 10:15:54 3600 1.489 2 coo43 11:04:23 1800 1.544 0 Start and stop times in the labels for offsets other than 2 arcseconds indicate the beginning of the first exposure and end of the last exposure. Total actual exposure time and number of exposures averaged is indicated in the comment section of the label "Observation_Area". A more detailed description of the observations is provided in Meier, et al. (1998). Ancillary Data ============== In addition to the spectral tables, this archive includes a 31-page PDF file, built from the original 20-foot display poster by breaking it into standard letter-size sections (text is repeated at the boundaries to enable a user to manually tile the printed pages, if desired), that shows flux density vs. wavelength at offsets of zero and ten arcseconds, at three different vertical (i.e., flux axis) zoom settings: 1x, 12x, and 60x. Two traces are shown in each panel: the one in orange is a spectral extract centered on the nucleus (i.e., a nucleus-centered extract), the one in green is arbitrarily offset vertically and by 1 Å in wavelength, and represents the spectrum extracted 10 arcseconds off the nucleus. The positions of many spectral lines are indicated. Those in purple are firm identifications, while those in blue are not - some match observed peaks and some do not. The lines labels "?A" and "?B" on pages 3-5 are now identified as prompt emission by OH in A'Hearn, et al. (2015). Data Coverage and Quality ========================= Spectral coverage is continuous between 3000-5000 Ångstroms. The Signal-to-Noise ratio deteriorates beyond 4200 Ångstroms. Additional Publications Related to These Data ============================================= Kim, S.J.; A'Hearn, M.F.; Wellnitz, D.D.; Lee, Y.S. 2003. The rotational structure of the B-X system of sulfer dimers in the spectra of Comet Hyakutake (C/1996 B2). Icarus, 166, 157-166. doi:10.1016/j.icarus.2003.07.003 A'Hearn, M.F.; Wellnitz, D.D.; Meier, R. 2014. Lambda 4430 Emission by Comet Hyakutake. The Diffuse Interstellar Bands, Proc. IAU Symp. 297, Ed. J. Cami and N. L. J. Cox (Cambridge Univ. Press, Cambridge) 216-218. doi:10.1017/S1743921313015883 References ========== Meier, R.; Wellnitz, D.D.; Kim, S.J.; A'Hearn, M.F. 1998. The NH and CH Bands of Comet C/1996 B2 (Hyakutake). Icarus, 136, 268-279. doi:10.1006/icar.1998.6022 A'Hearn, M.F, Krishna Swamy, K.S., Wellnitz, D.D., and Meier, R., Prompt Emission by OH in Comet Hyakutake, A.J., 150:5 (2015), doi:10.1088/0004-6256/150/1/5.