J/ApJ/708/1628 Diffuse interstellar bands. IV. (McCall+, 2010) ================================================================================ Studies of the diffuse interstellar bands. IV. The nearly perfect correlation between {lambda}{lambda}6196.0 and 6613.6. McCall B.J., Drosback M.M., Thorburn J.A., York D.G., Friedman S.D., Hobbs L.M., Rachford B.L., Snow T.P., Sonnentrucker P., Welty D.E. =2010ApJ...708.1628M ================================================================================ ADC_Keywords: Interstellar medium ; Equivalent widths ; Spectroscopy ; Stars, early-type Keywords: ISM: lines and bands - ISM: molecules Abstract: In a sample of 114 diffuse cloud sightlines spanning a wide range of interstellar environments, we find the equivalent widths of the diffuse interstellar bands (DIBs) {lambda}6196.0 and {lambda}6613.6 to be extremely well correlated, with a correlation coefficient of 0.986. A maximum likelihood functional relationship analysis shows that the observations are consistent with a perfect correlation if the observational errors, which are dominated by continuum placement and other systematics such as interfering lines, have been underestimated by a factor of 2. The quality of this correlation far exceeds other previously studied correlations, such as that between the {lambda}5780.5 DIB and either the color excess or the atomic hydrogen column density. The unusually tight correlation between these two DIBs would seem to suggest that they might represent the first pair of DIBs known to be due to the same molecular carrier. However, further theoretical work will be required to determine whether the different linewidths and band shapes of these two DIBs can be consistent with a common carrier. If the two DIBs do not in fact share the same molecular carrier, their two carriers must be chemically very closely related. Description: The data used in this study were obtained using the Astrophysical Research Consortium Echelle Spectrograph (ARCES) at the 3.5m telescope at Apache Point Observatory between 1999 and 2003. The ARCES spectrograph has a resolving power of 38000 (corresponding to a velocity resolution of approximately 8km/s). File Summary: -------------------------------------------------------------------------------- FileName Lrecl Records Explanations -------------------------------------------------------------------------------- ReadMe 80 . This file table1.dat 74 114 Physical properties and equivalent width measurements for program stars -------------------------------------------------------------------------------- See also: II/135 : Suppl. to Diffuse Interstellar Band Measurements (Guarinos 1988) II/149 : Diffuse Interstellar Band Measurements (Snow+ 1977) J/ApJ/705/32 : Diffuse interstellar bands from HD 183143 (Hobbs+, 2009) J/MNRAS/358/563 : Diffuse Interstellar Bands in 49 stars (Megier+, 2005) J/A+A/414/949 : Interstellar bands and H2, CH, CO column densities (Weselak+ 2004) J/ApJS/93/211 : IUE survey of H I Ly{alpha} absorption. I. (Diplas+ 1994) Byte-by-byte Description of file: table1.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 10 A10 --- Star Star name 12- 20 A9 --- SpType MK spectral type 22- 25 F4.2 mag E(B-V) (B-V) color excess (1) 27 A1 --- l_logNH Limit flag on NH 28- 32 F5.2 [cm-2] logNH ? Log of Hydrogen column density 34- 37 F4.2 [cm-2] e_logNH ? NH uncertainty 39- 43 F5.2 [cm-2] logNH2 ? Log of H_2_ column density 45- 48 F4.2 [cm-2] e_logNH2 ? NH2 uncertainty 50 I1 --- r_logNH ? Reference for N(H) (2) 52- 53 I2 --- r_logNH2 ? Reference for N(H_2_) (2) 55- 59 F5.1 10-13m W6196 6196.0 equivalent width (in m{AA}) 61- 63 F3.1 10-13m e_W6196 W6196 uncertainty 65- 69 F5.1 10-13m W6613 6613.6 equivalent width (in m{AA}) 71- 74 F4.1 10-13m e_W6613 W6613 uncertainty ------------------------------------------------------------------------------- Note (1): The calculated E(B-V) values are based on the intrinsic colors from Johnson, H.L. (1963, Basic Astronomical Data, ed. K. A. Strand (Chicago, IL: Univ. Chicago Press), 214). Note (2): References as follows : 1 = Diplas & Savage 1994, Cat. J/ApJS/93/211, Table 1; 2 = Diplas & Savage 1994, Cat. J/ApJS/93/211, Table 2; 3 = Shull & van Steenberg 1985ApJ...294..599S, Table 1; 4 = Shull & van Steenberg 1985ApJ...294..599S, Table 2; 5 = Bohlin et al. 1978ApJ...224..132B; 6 = Savage, et al. 1977ApJ...216..291S; 7 = Spitzer et al. 1974ApJS...28..373S; 8 = Rachford et al. 2002ApJ...577..221R; 9 = B. L. Rachford, private communication; 10 = Rachford et al. 2009ApJS..180..125R. -------------------------------------------------------------------------------- History: From electronic version of the journal References: Thorburn et al. Paper I. 2003ApJ...584..339T Hobbs et al. Paper II. 2008ApJ...680.1256H Hobbs et al. Paper III. 2009ApJ...705...32H, Cat. J/ApJ/705/32 Friedman et al. Paper V. 2011ApJ...727...33F ================================================================================ (End) Emmanuelle Perret [CDS] 22-Feb-2012