Publications of the Astronomical Society of the Pacific 106: 382-396, 1994 April

An Atlas of Southern MK Standards From 5800 to 10,200 A1

Anthony C. Danks Hughes STX/Goddard Space Flight Center, Code 683.0, Greenbelt, Maryland 20771 Michel Dennefeld Institut d'Astrophysique, 98bis Boulevard Arago, F-75014 Paris, France Received 1992 December 30; accepted 1994 February 2

ABSTRACT. An atlas of stellar spectra covering the wavelength range from 5800 to 10,200 A is presented of 126 southern MK standard stars, covering the luminosity classes I, III, and V. Some peculiar stars are included for comparison purposes. The spectra were obtained at a resolution of 4.3 A per pixel using a Cassegrain-mounted Boiler and Chivens spectrograph equipped with a Reticon detector. The quality and utility of the data are discussed and examples of the spectra are presented. The atlas is available in digital format through the NSSDC.

1. INTRODUCTION tion of 15 A which is lower than that used in this atlas, but overlaps nicely in wavelength. Mantegazza (1992) has be- Spectral synthesis of galaxies is one of the major driving forces for producing new stellar libraries covering as large gun the work of extending calibration to the Magellanic a spectral interval as possible. The "photographic" wave- clouds by observing 34 LMC and 15 SMC supergiants be- length region from 3800 to 4800 A, initially used for the tween AO and G5 in the wavelength range from 5600 to MK classification scheme, has been extended to shorter 9000 A, interestingly made with the same spectrograph as wavelengths through space technology. The UV range has this study. Origlia et al. (1993) have recently produced a been included in the classification schemes thanks to con- list of G, K, and M stars in the 1.5-1.7 μιη region for siderable efforts made by, e.g., Rountree and Sonneborn synthesis of NGC 1068. Our atlas bridges the gap between (1991), Massa (1989), Walbom and Nichols-Bohlin visible and IR nicely at a reasonable spectral resolution. A (1987), Walborn et al. (1985), Wu et al. (1983, 1991), detailed review of recent stellar spectral libraries can be and Heck (1982). found in Bica (1991). As spectral synthesis approaches improve, it has become Our intent in this paper is to augment the spectral li- clear that multiple stellar populations are needed, includ- braries available in the near infrared and provide as high a ing older and/or cooler stellar components, and this in spectral resolution possible without compromising flux turn is driving the need for red to near-infrared stellar considerations. The Cassegrain-mounted Boiler and Chiv- spectra. ens spectrograph with its high resolution-luminosity prod- With advances in detector technology (specially for sil- uct, equipped with a cooled Reticon diode array was an icon devices) observations can now routinely be made into ideal combination for this work. The observations were the near infrared, from the ground. The work of Jacoby et carried out at ESO, Chile. The initial intent was to select al. ( 1984) is an example of one of the first extensions into the wavelength range to start at 5000 A just longward of the red, with a library of 161 stellar spectra covering the the traditional MK spectral range and extend the spectral wavelength region 3150 to 7427 A at a spectral resolution coverage as far as possible into the red with one grating ~4.5 A. Similarly, Faber et al. (1985) studied 110 gi- Κ setting. However, by starting instead at 5800 A just short- ants and subgiants at a resolution of 9 A over the wave- ward of the Nai lines, we could take advantage of the length range 4000 to 6200 A. More recently, Silva and Cornell (1992) have studied stars from 3510 to 8930 A. Reticon red sensitivity out to 10,200 A. This combination For the near infrared, data available in the literature are gives approximately an additional 4000 A of spectrum to fragmentary and of varying quality, e.g., treating specific the usual visible range and should be particularly useful for spectral types, Fawley ( 1977), Barbieri et al. ( 1981 ), Jones stellar population synthesis studies of elliptical galaxies, et al. (1984), Alloin and Bica (1989), and Kirkpatrick et especially because their major constituents appear to be al. ( 1991, 1993). Many studies have been designed for flux late-type stars (O'Connell 1980). A first step was naturally calibration purposes and therefore of necessity low resolu- to obtain a set of standard stars to extend the spectral tion, e.g., O'Connell (1973), Breger (1976), Cochran classification to this region and to serve as a reference for (1981), Cochran and Barnes (1983), Gunn and Stryker comparison with other objects. The 126 stars presented in (1983). Recently, Torres-Dodgen and Weaver (1993) this paper were chosen from a master list of MK standards have published a digital near-IR atlas of 57 northern stars provided by the Stellar Data Center in Strasbourg. The in the wavelength region from 5700 to 8900 A at a resolu- number of MK standards in the Southern Hemisphere is limited, and our selection was made in consultation with C. ^ased on observations obtained at the European Southern Observatory, Jaschek. The complete list of stars, spectral type, luminos- La Silla, Chile. ities, magnitudes, and positions is given in Table 1. The

Table 1 Name, Spectral Type, Luminosity Class, Position, Magnitude, and Colors for the Stars Observed cu

Spectral Type/L HD Number Spectral Type/L Real Name a (2000) 8 O-Type HD 200499 A5 V 22 CAP 21 0424.2 -1951 18 4.84 +.17 HD 66811 05 laf ζ PUP 08 03 35.0 -40 00 11 2.25 HD 187642 A7V 53 α AQL 19 50 46.9 +08 52 06 0.77 +.22 HD 37742 OS Ibe 50 ζ ORI 05 40 45.5 -01 56 34 2.05 -.21 HD 88824 A7 V 10 13 22.8 -51 13 59 5.28 +.25 HD 57061 091b 30 τ CMa 07 18 42.4 -24 57 15 4.40 -.15 F-Type HD 37043 09 III 44 ι ORI 05 35 25.9 -05 54 36 2.77 -.24 HD 36673 FOIb 05 32 43.7 -17 49 20 2.58 HD 47839 07 Ve 15 MON 06 40 58.6 +09 53 44 4.66 -.25 HD 90772 FOI 10 27 24.4 -57 38 20 4.66 HD 37468 09.5 V 48 σ ORI 05 38 44.7 -02 36 00 3.81 -.24 HD 161471 F2 la 17 47 35.0 -40 07 37 3.03 B-Type HD 61715 F4 lab 07 38 18.2 -48 36 04 5.68 HD 38771 BO.5 lav 53 κ ORI 05 47 45.3 -09 40 11 2.06 HD 54605 F8 la 25 δ CMA 07 08 23.4 -26 23 35 1.84 HD 53138 B3 la 24 o2 CMA 07 03 01.4 -23 50 00 3.02 HD 38558 FOUI 130 TAU 05 47 26.1 +17 43 45 5.49 +.30 HD 58350 31 η CMA 07 24 05.6 -29 18 11 2.45 HD 13174 F2 III 14 ARI 02 09 25.3 +25 56 24 4.98 +.33 HD 164353 67 ΟΡΗ 18 00 38.6 +02 55 53 3.97 HD 164584 F3 III 7 SGR 18 02 51.0 -24 16 56 5.34 +.52 HD 34085 81 19 β ORI 05 14 32.2 -08 12 06 0.12 HD 27290 F4 III γ DOR 04 1601.6 -51 29 12 4.25 +.30 HD 44743 B1 III 2 β CMA 06 22 41.9 -17 57 22 HD 48737 F5 III 31 ξ GEM 06 45 17.3 + 1253 44 3.36 HD 52089 B2 II 21 ε CMA 06 58 37.5 -28 50 20 HD 196524 F5 III 6 β DEL 20 37 32.9 + 14 35 43 3.63 HD 51309 B3 II 20 t CMA 06 56 08.1 -1703 15 4.37 HD 217096 F8 III-IV 22 58 34.9 -35 31 24 6.13 HD 53244 B8II 27 γ CMA 07 03 45.5 -15 38 00 4.12 HD 220657 F8 III 68 υ PEG 23 25 22.7 +23 24 15 4.40 HD 30836 B2III 3 π4 ORI 04 51 12.3 +05 36 18 3.69 HD 17094 F0IV 87 μ CET 02 44 56.5 + 10 06 51 4.27 HD 35468 B2 III 24 γ ORI 05 25 07.8 +06 20 59 1.64 HD 27397 F0IV 57 TAU 04 19 57.6 + 14 02 07 5.59 HD 34503 B5 III 20 τ ORI 05 17 36.3 -06 50 40 3.60 HD 182640 F3 IV 30 δ AQL 19 25 29.8 +03 06 53 3.36 HD 36822 B0 III 37 01 ORI 05 34 49.2 +09 29 22 4.41 -.16 HD 216385 F7IV 49 σ PEG 22 52 24.0 +09 50 09 5.16 HD 147165 B2 III + 09.5 V 20 σ SCO 1621 11.2 -25 35 34 2.89 +.13 HD 29992 FI V β CAE 04 42 3.4 -37 08 40 5.05 +.37 HD 886 B2 IV 88 γ PEG 00 13 14.1 +15 11 01 2.83 HD 26690 F2 V + F5 V 46 TAU 04 13 33.0 +07 42 58 5.29 +.36 HD 143018 B1 V + B2 V 6 π SCO 15 58 51.0 -26 06 51 2.89 HD 30652 F6V π3 ORI 04 49 50.3 +06 57 41 3.19 HD 16582 B2 IV 82 δ CET 02 39 28.9 +00 19 43 4.07 HD 173667 F6V 110 HER 18 45 39 +20 33 00 4.20 HD 23302 B6 IV 17 TAU 03 44 52.2 +24 06 48 3.70 HD 222368 F7V 17 ι PSC 23 39 57.0 +05 37 35 4.13 +.51 HD 23630 B7 IV 25 η TAU 03 47 29.0 +24 06 18 2.87 HD 1581 F9V ζ TUC 00 20 04.2 -64 52 30 4.23 +.58 HD 23850 B8 IV 27 TAU 03 49 09.7 +24 03 12 3.63 -.09 G-Type HD 35411 B0.5 V 28 η ORI 05 24 29 -02 23 00 3.35 -.19 HD 204867 GO Ib 22 β AQR 21 31 33.4 -05 34 16 2.91 HD 149438 B0V 23 τ SCO 16 35 53 -28 13 00 2.82 +.26 1 HD 52220 G1 Ib 06 58 56.3 -32 43 14 6.91 HD 144470 81 V 9 ω SCO 16 06 48 -20 40 00 3.95 -.04 HD 209750 G2 Ib 34 α AQR 22 05 46.9 -00 19 11 2.96 HD 74280 B3 V 7 η HYA 08 43 14 +03 23 00 4.30 -.20 HD 44362 G2 Ib 06 18 46.8 -50 21 33 7.04 +.83 HD 208057 B3 V 16 PEG 21 530 4 +25 55 00 5.07 HD 206859 G5 Ib 9 PEG 21 44 30.6 + 17 21 00 4.34 + 1.17 HD 219688 B5 V 93 Ψ AQR 23 17 54.1 -09 10 57 4.39 HD 48329 G8 Ib 27 ε GEM 06 43 55.9 +25 07 52 2.98 + 1.40 HD 58715 B8 V 3 β CMI 07 27 09.0 +08 17 21 2.90 HD 36079 G5 II 9 β LEP 05 28 14.7 -20 45 34 2.84 +.82 HD 214923 B8 V 42 ζ PEG 22 41 27.6 + 10 49 53 3.40 HD 185758 G1 III 5 α SEG 19 40 05.7 + 18 00 50 4.37 +.78 HD 218045 B9 V 54 α PEG 23 04 45.6 +15 12 19 2.49 HD 21120 G6 III 1 o TAU 03 24 48.7 +09 01 44 3.60 +.89 A-Type HD 33833 G7 III 05 12 48.1 -06 03 26 5.91 +.96 HD 46300 AO lb 06 32 54.2 +07 19 58 4.50 +.00 HD 10761 G8 III 110 o PSC 01 45 23.6 +09 09 28 4.26 +.96 HD 59612 A5 lb 08 29 51.4 -23 01 28 4.85 +.23 HD 3919 G8 III μ PHE 00 41 19.5 -46 05 06 4.59 +.97 HD 43836 AO II 6 19 22.7 23 16 37 7.03 HD 184492 G9 III 37 μ AQL 19 35 07.2 -10 33 38 5.12 + 1.13 HD 47306 A2 II 06 34 58.5 -52 58 32 4.39 -.02 HD 195564 G2 IV 20 32 23.6 -09 51 12 5.65 HD 73634 A6 II 08 37 38.6 -42 59 21 4.14 +.11 HD 188512 G8 IV 60 β AQL 19 55 18.7 +06 24 24 3.71 HD 216627 A2 III 76 δ AQR 22 54 38.9 -15 49 15 3.27 +.05 HD 39587 GO V 54 χ' ORI 05 54 22.9 +20 16 34 4.41 +.59 HD 33111 A3 III 67 β ERI 05 07 50.9 -05 05 11 2.79 +.13 2 HD 214850 G3 V 22 40 52.6 + 1432 58 5.71 +.90 HD 28319 A7 III 78 Θ TAU 04 28 39.7 + 15 52 15 3.40 +.18 HD 20630 G5 V 03 19 21.6 +03 22 13 4.83 +.68 HD 48843 A9 III 32 GEM 06 45 54.2 + 12 41 37 6.46 HD 69830 G7 V 08 18 24.9 -12 36 41 6.04 HD 47105 AO IV 24 γ GEM 06 37 42.7 + 16 23 57 1.93 +.00 K-Type HD 161868 AO V 62 γ ΟΡΗ 17 47 53.5 +02 42 26 3.75 +.04 HD 65699 K2 lab 12 PUP 07 59 5.7 -23 18 38.0 5.11 HD 71155 AO V 08 25 39.6 -03 54 23 3.90 -.02 HD 206778 K2 Ib 8 ε PEG 2144 11.1 +09 52 30 2.39 +1.53 HD 198001 Al V 20 47 40.5 -09 29 45 3.77 +.00 HD 185622 K4 Ib 19 39 25.3 +16 34 17 6.38 +2.07 HD 18331 Al V 02 56 37.4 -03 42 44 5.17 HD 52877 K7 Ib 07 01 43.1 -27 56 06 3.47 +1.73 HD 222095 A2 V 23 37 50.9 -45 29 33 4.74 HD 179870 KO II 19 1353.3 090115 8.35 HD 155125 A2V 35 η ΟΡΗ 17 10 22.6 -15 43 29 2.43 +.06 HD 31767 K2 II 10 π6 ORI 04 58 33 +1 43 60 4.46 + 1.39 HD 55179 A2 V 24 α PSA 22 57 39.0 -29 37 20 +.09 HD 167818 K3 II 18 18 03.1 -27 02 33 4.65 +1.66 HD 11636 A5 V 6 ι ARI 01 54 38.3 +20 48 29

Table 1 at NASA/Goddard Space Flight Center, Code 933.4, (Continued) Greenbelt, Maryland 20771. CRUSO can also be reached HD Number Spectral Type/L Real Name α (2000) δ B-V electronically via Internet at REQUEST® NSSDC A. HD 8512 KO III 45 θ CET 012401.3 -08 1101 3.60 +1.06 GSFC.NASA.GOV or via DECnet at NSSDCA:RE- HD 39810 KO III λ MEN 05 47 48.9 -72 42 09 6.53 +1.12 QUEST, or by phone (301)-286-6695. HD 211416 K3 III α TUC 22 18 30.1 -60 15 35 2.86 + 1.39 HD 223719 K4 III 22 PSC 23 5158 +02 55 00 5.69 HD 23249 KO IV 23 δ ERI 03 43 14.8 -09 45 48 3.54 +.92 2. OBSERVATIONS HD 3651 KOV 54 PSC 00 39 21.7 +21 15 02 5.87 +.85 HD 22049 K2V 18 ε ERI 03 32 55.8 -09 27 30 3.73 The observations were carried out between 1979 and M-Type 1981 with the ESO Boller and Chivens spectrograph HD 36389 M2 lab-lb 119 TAU 05 32 12.7 + 18 35 39 4.38 +2.07 equipped with a Reticon photodiode array (Dennefeld et HD 200914 M0.5 III 24 CAP 21 07 07.6 -25 00 21 4.50 + 1.61 HD 216032 MO III 71 τ2 AQR 22 49 35.4 -13 35 33 4.01 + 1.57 al. 1979 and the ESO Users Manual, Danks 1981). The HD 219215 M 1.5 III 90 φ AQR 23 1419.3 -06 02 56 4.22 + 1.56 Reticon type used was a custom-made RL 1024C/17 with HD 198026 M3 III 3 AQR 20 47 44 -05 02 00 4.60 a double array of 1024 diodes separated by 2.44 mm, to HD 19285 M5 Illa 03 03 27.8 -58 55 37 allow simultaneous sky observations. Each diode was 450 HD 184313 M5 III 19 033 7.9 05 27 52 /xm high by 25.4 μηι wide with no dead spaces between HD 207076 M7 III 21 46 34.5 -02 12 18 diodes. The detector was mounted in a liquid-nitrogen- HD 202560 MOV 21 17 48.9 -38 49 55 cooled dewar. The Reticon sensitivity in the red is deter- HD 36395 Ml .5 V 05 31 16.9 -03 36 28 HD 217987 M3 V 23 04 55.7 -35 53 39 mined by the operating temperature, which was main- HD 180617 M3 V 19017 1.9 05 13 41 tained at 168 K, giving good response out to 10,200 A. Peculiar Stars Faint stars were observed with this system at the 3.6-m HD 68273 WC 8 + 07.5e γ VEL 08 09 31.5 -47 20 12 1.78 telescope but most stars were observed with the same de- HD 49798 06 p 06 47 0.0 -44 19 44 8.27 tector and a similar spectrograph at the ESO 1.5-m tele- HD 37490 B3 lile 47 ω ORI 05 39 11.1 04 07 17 4.57 scope. The dispersion used was 171 A mm-1, which gave HD 49333 87 Hin 12 CMA 06 47 11.1 •21 00 56 6.08 -.19 approximately 4400 A of spectrum, starting at —5800 A 00 58 36.3 4.31 -.16 HD 5737 07 Illp aSCL 29 21 28 and extending to 10,200 A. The slit was oriented east-west HD 315 88 IIIp Si 00 07 44 02 32 55 6.43 HD 12767 89.5 ρ Si ν FOR 02 04 29.4 29 17 49 4.69 -.17 and a 6 arcsec long decker was used to subtended 2X6 HD 92207 AO lae V370 CAR 10 37 26.8 58 44 00 5.45 +.50 arcsec on the sky, large enough to ensure little light was HD 62623 A2 labe 3 PUP 07 43 48.4 28 57 18 3.96 lost at the slit. The resolution was 4.3 A per pixel. HD 18557 A2 m 02 5 8 47.3 •09 43 35 6.14 +.22 The star was normally observed first in one aperture for HD 20320 A5 m 13 ζ ERI 03 15 49.9 -08 49 11 4.80 +.23 an exposure time of 5-20 min depending on its brightness HD 40372 A5 πιδ Del 59 ORI 05 58 23.8 +01 50 14 5.90 and spectral type, then moved to the other aperture and HD 67523 F6 ΙΙρδ Del 15 ρ PUP 08 07 32.6 -24 18 15 2.81 HD 189005 G6 III Ba 0.2 60 SGR 19 58 57.1 -26 11 44 4.83 observed for the same length of time. This procedure al- HD 223541 KO IV CN 23 50 27.0 -13 06 39 7.0 lows a clean sky subtraction before any further correction HD 223428 K2 III b Ca0.5 23 49 31.5 -1551 40 6.24 is introduced. Sky subtraction is important in this wave- HD 1157 K2 III CN 00 15 41.2 -46 14 39 7.7 length region as illustrated in Fig. 1, in order to eliminate HD 170975 K3 Ib-IICN 18 32 43.2 -1451 56 5.50 strong atmospheric emission bands. HD 46259 K2/K3 IIIp 06 30 26.0 -40 34 11 8.6 The data are corrected for atmospheric extinction and HD 216803 K4V 22 56 22.2 -31 33 48 6.32 instrument sensitivity using calibrated stars selected from HD 496 KO III ε PHE 00 09 23.2 -45 44 42 3.88 HD 60414 M2 Iabpe+ V KQ PUP 07 33 47.8 -1431 26 Breger (1976). Several star pairs of different spectral type HD 33894 M7e VS PIC 05 10 57.6 -48 30 43 were monitored during the night in order to correct for HD 24607 M6 Ille V μ HOR 03 52 46.3 -42 50 12 extinction. However, the near infrared proved to be rela- HD 42537 06 08 19.1 -52 32 03 8.9 tively insensitive to differential refraction. A He-Ar lamp HD 51208 06 54 26.5 -42 21 56 6.32 was regularly observed for wavelength calibration and a HD 7526 01 1434 -48 15 09 9.9 flat field was obtained for each night by observing a Quartz-Halogen lamp, mounted internally in the spectrograph. The individual stellar spectra were later divided by the flat field in order to remove the differences in sensitivity stars selected cover the normal range of spectral types, O to from pixel to pixel. The first integration before each obser- M and luminosity classes I, III, V. In addition a small vation was a 5-s dark exposure, which provided a measure number of peculiar stars have been included. Here we de- of the fixed-pattern noise to be subtracted from each inte- scribe the observations and reduction procedure and illus- gration, the dark current being negligible. For each stellar trate potential classification criteria available from this exposure, the corresponding sky exposure (taken with the data set. We should add as a cautionary note that compar- same aperture during the next half-integration) was sub- ison between spectra taken with different spectrograph and tracted. The cleaned spectra from the apertures A and Β detector combinations, and with varying spectral resolu- were then divided by the flat field, converted to wave- tions, can introduce classification errors. length, corrected for extinction, divided by the spectral The complete atlas can be obtained through the NSSDC response curve in order to obtain flux and averaged. The Coordinated Request and User Support Office (CRUSO), response curve was obtained by reducing the standard stars

WAVELENGTH (Â)

Fig. 1—A typical night sky spectrum is shown, taken at La Silla, covering the same wavelength region as the atlas and taken with the same spectrograph/detector combination. in a similar way, and comparing the resultant spectrum between plots to have an idea of which features are with the fluxes given in Breger (1976). The data for the strengthening or weakening. Some notable spectral differ- standard stars were binned every 20 A in order to deter- ences are immediately obvious by inspection. mine the response curve. All spectra obtained have a signal-to-noise ratio in excess of 100:1. 3.1 Hydrogen The seeing at La Silla is generally good, and consistently less than 2 arcsec and often subarcsec, but on occasions The effects of gravity are evident even at this resolution, when the seeing exceeded 1.5 arcsec not all the stellar flux the lines of Ha and the Paschen series being sharper and was recorded. The fluxes given then are not absolute but better defined in the supergiants. This results in a more relative. In order to convert to flux the intensity axis strongly defined Paschen limit in the supergiants, and the should be multiplied by 10-13 erg cm2 s-1 A-1. The data Paschen lines can be distinguished to higher «(« = 24 in are affected by seeing and transparency variations, but can supergiants). On the other hand the dwarf lines are always be converted from relative flux to absolute flux by broader and the lines blend together at high n, washing out comparison with existing photoelectric photometry. The the Paschen jump. relative fluxes are of the order of 10%-15% below the In the dwarfs Ha is prominent at 07 V, and develops absolute values. Some small features in the spectra have quickly in strength to AO V, and is still weakly present at been introduced by the instrumentation. The most notable MO V. However, Ha is extremely weak in the supergiants feature is a small emission peak close to the Na I 5896 A from 05 to B8 after which it manifests itself quickly at absorption line. This feature is an artifact of the flat ñeld AO I and remains reasonably strong up to G8, and contin- optics which could not entirely be eliminated due to its ues to be discernible to M2 I. This is shown graphically in strength and proximity to the Na I line. The reduction was Fig. 4 from which it is evident that the supergiants are carried out using the ESO-based system IHAP (Middel- easily distinguished from dwarfs and intermediate luminos- burg 1981). Using this system the equivalent widths of ity stars between AO and A7. This effect was demonstrated the spectral lines Na ι (5889, 5895 Α), Ηα, Ο I (7776 A), by Tinsley (1967) for H<5, Hy, and H/3, but she lacked Can (8500, 8544, 8664 A), and the unblended Paschen sufficient data to show a firm relationship for Ha. The lines (8600, 8756 were measured for all stars. These Paschen lines behave in a similar manner, as shown in Fig. values are given in Table 2. 5, where WÀ of Pn (which is unblended), is plotted against spectral type. The Paschen series is weakly present at 07 V, and de- 3. DISCUSSION velops systematically to a maximum strength at AO V, and Representative spectra from O to M for luminosity then weakens until it is just evident at F7 V. Similarly, for classes I and V are shown in Figs. 2 and 3, respectively. the supergiants the series is just discernible at 05 I and The ñgures are plotted scaled to the minimum of the at- grows quickly in strength to AO V. The Paschen decrement mospheric A band at 7200 A; as this band is variable, is most notable at F0 I and then decreases quickly to be relative intensities of spectral lines should be compared just visible at G2 I.

3.2 Ο ι 7776 Â 3.3 Ca II Triplet

This line was discussed by Parsons ( 1964) and shown to The behavior of the Ca π triplet is comparable to the Ο I be a luminosity indicator. By inspection it can be seen 7776 A line in that though present in dwarfs, it never weakly at B2 V, strengthening to approximately A5 V and reaches the strength exhibited in the supergiants. In the disappearing at GO V. In the case of the supergiants the dwarfs it first becomes evident at A2 V. Although blended line is present at B3 I, and develops quickly to great with the Paschen lines, its presence is clear from the inten- strength at F2 I and has disappeared at G2 lb. However, at sity modulation. The triplet grows in strength to MO V and no point in the dwarfs is the line comparable to the is still visible at M2 V. In the supergiants the triplet is strength manifest in the supergiants. This is demonstrated evident at AO I develops quickly to great strength at K3 I, graphically in Fig. 6 where it is possible to distinguish both and is still strongly evident at M2 I. The equivalent width supergiants and dwarfs, the maximum difference occurring of the Ca u 8662 A line is plotted in Fig. 7 against spectral at FO and falling off at B6 and GO. However, we have type. The Ca π lines from AO to approximately G2 are plotted in Fig. 6, }νλ versus spectral type, and it appears blended with the Paschen lines. The equivalent width given the effect is not as pronounced as plotting line depth versus in Table 2 for this line was obtained by linear interpolation spectral type as illustrated by Parsons (1964). between adjacent Paschen lines to estimate the strength of

Table 2 Measurements of the Equivalent Widths in mÂ of Selected Absorption Lines

O-Type Specoal 5889 5895.9 6563 7776 8500 8544 8664 8600 8756 A-Type Spectral 6563 7776 8500 8544 8664 Type/L Type/L HD 66811 05 laf HD 43836 AO II 1.063 4.311 0.949 3.262 3.875 5.337 4.162 4.718 HD 37742 09.5 Ibe 0.986 1,603 HD 47306 A2 II 0.939 6.003 0.85 3.113 4.196 6.039 4.788 5.916 HD 57061 09 1b 1.139 0.96 1.573 HD 73634 A61I 7.121 0.933 3.279 4.679 6.744 4.720 5.919 HD 37043 09 III 2.436 0.575 1.497 HD 216627 A2 III 10.658 0.77 1.408 2.655 5.772 3.237 7.026 HD 47839 07 Ve 2.691 0.688 1.027 HD 33111 A3 III 0.148 9.388 0.808 1.406 2.84 4.733 2.592 6.03 HD 37468 09_5 V 3.183 0.881 1.571 HD 28319 A7 III 0.244 9.472 0.814 1.612 2.752 4.854 2.193 4.505 B-Type HD 48843 A9 III 6.749 1.103 2.751 4.172 6.349 3.625 4.934 HD 38771 B0.5 la 1.167 0.947 1.191 HD 47105 AO IV 9.662 0.633 3.859 7.335 HD 53138 83 la 0.244 -0.425 0.75 2.191 2.258 HD 161868 AO V 13.073 0.640 2.533 6.399 HD 58350 85 la 0.495 1.049 2.322 1.886 HD 71155 AO V 11.821 0.625 2.554 6.908 HD 164353 85 la 2.198 0.957 2.311 3.044 HD 198001 A 1 V 10.843 0.805 3.844 8.741 HD 34085 88 I 1.335 1.419 2.111 2.201 HD 18331 Al V 11.239 0.690 3.035 6.132 HD 44743 81 III 3.096 0.247 0.944 2.759 HD 222095 A2 V 12.118 1.058 1.563 6.833 HD 52089 82 II 3.05 0.192 1.422 2.433 HD 155125 A2 V 12.737 0.626 3.320 6.309 HD 51309 83 II 2.036 0.732 2.276 3.522 HD 55179 A2 V 12.598 0.395 1.559 2.863 6,216 3.129 6.707 HD 53244 88 II 4,791 0.365 3,237 5.429 HD 216956 A3 V 0.426 13.034 0.704 0.86 1.787 4.715 2.42 5.825 HD 30836 82 III 3.396 0.297 1.622 3.838 HD 11636 A5 V 0.472 10.695 0.802 0.994 2.068 4.481 1.851 5.403 HD 35468 82 III 3.757 0.199 0.902 2.829 1.706 3.416 HD 2000499 A5 V 11.135 0.654 1.172 2.224 4.420 1.941 4.751 HD 34506 85 III 1.298 2.235 4.164 2,974 5.479 HD 187642 A7 V 9.016 0.644 1.137 2.468 5.622 1.862 3.965 HD 36822 80 ΙΠ+ HD 88824 A7 V 8.623 0.657 1.31 2.897 4.197 2.007 3.606 HD 147165 82 III+ 0.237 2.144 F-Type 09.5 V HD 36673 FO Ib 0.64 6.749 1.21 3.624 5.319 6.773 3.499 4.194 HD 886 3.758 0.148 HD 90772 FOI 1.164 0.701 2.476 2.777 3.272 3.085 2.340 2.212 HD 143018 BI 3.470 HD 161471 F2 la 0.293 1.647 3.514 V+82V 2.252 3.641 4.883 4.788 2.712 2.772 HD 61715 F4 la 0.628 1.483 3.875 0.885 2.512 4.875 5.517 1.639 2.201 HD 16582 3.816 0.285 1.937 3.418 HD 54605 F8 la 0.894 1.502 3.604 1.749 3.647 7.404 7.512 1.612 1.671 HD 23302 B6IV 3.604 0.599 3.1 17 5.794 HD 23630 87 Ve 4.303 3.204 4.781 HD 38558 F0 111 0.267 0.794 6.514 0.872 2.019 3.456 5.146 2.829 3.795 HD 23850 88 IV 5.180 0.494 3.837 6.166 HD 13174 F2 m 0.467 1.090 6.949 0.844 1.470 3.180 4.154 1.331 2.896 HD 35441 80.5 V 3.347 0.089 0.850 2.880 HD 164584 F3 111 0.339 0.895 5.365 0.834 2.216 3.69 5.057 1.81 2.996 HD 149438 BO V 2.698 0.622 1.450 HD 27290 F4I1I 0.338 1.195 7.558 0.596 1.199 2.503 3,294 1.098 2.821 HD 144470 81 V 3.398 0.154 0.622 2.407 HD 48737 F5 m 0.409 0.492 5.357 0.462 1,283 2.99 3,469 1.267 1.559 HD 74280 83 V 4.480 0.099 1.555 3.955 HD 196524 F5 111 0.355 0.98 5.605 0,542 1.18 2.852 3.524 0.954 1.977 HD 208057 83 V HD 217096 F8 III-1V 0.487 0.808 3.958 0.346 1,288 3.531 3.309 0.511 0.977 HD 219688 85 V 4.328 0.534 2.647 4.874 HD 220657 F8 III 0.423 0.828 3.315 0,465 1.408 3.456 3.493 0.663 0.965 HD 58715 BSV 4.328 0.534 2.647 4.874 HD 17094 F0 IV 0.354 0.695 7.505 0.690 1.201 2.275 3.826 1.199 2.592 HD 58715 88 V HD 27397 F0 IV 0.319 0.674 8,833 0.683 1.777 2.506 4.409 1.824 2.885 HD 182640 F3 IV 7,013 0.689 1.024 2.508 3.003 1.276 2.532 HD 214923 88 V 7.545 0.585 3.123 7.904 HD 216385 F5 IV 0.286 0.281 4.331 0.252 0.847 2.528 2.459 0.429 1.069 HD 218045 89 V 9.9 0.564 3.861 7.801 HD 2992 FI V 0.342 1.108 0.607 0.997 2.716 3.181 0.936 A-Typc HD 26690 F2V+F5 0.303 0.819 0.639 1.052 2,603 2.402 0.794 HD 46300 AG Ib 3.974 1.006 3.585 4.433 HD 59612 A5 Ib 5.213 1.549 3.427 6.03 3.717 3.96

Table 2 (Continued) cu F-Typc Spectral 5SS9 5896 6563 7776 8500 8544 8664 8600 M - Type Spectral 5896 6563 7776 8500 8544 8664 8600 Type/L Type/L HD 30652 F6V 0.301 0.812 4.965 0,420 1.001 2.754 2.643 HD 36389 M2 lab 7.319 3.562 2.736 5.386 6.472 HD 17366 F 6 V 0.284 0.848 4.737 0.459 1.524 3.12 2.655 0.589 HD 200914 MO.5 HI 1.276 4.556 2.887 1.690 4.932 4.992 HD 222368 F7V 0.187 0.982 4.635 0.309 0.815 2.363 2.362 HD 216032 MO III 0.834 4.179 2.535 1.711 4.394 4.233 HD 1581 F9 V 0.426 0.6S3 3.374 0.269 0.976 2.519 2.630 HD 219215 M 1.5 III 1.923 4.60 2.861 0.472 1.655 4.219 4.597 G-Type HD 198026 M3 III 1.883 3.965 3.755 HD 204867 GO lb 0.874 3.012 0.622 2.351 5.599 5.993 0.616 1.14 HD 19285 M5 lila 1.029 1.750 2.750 HD 52220 G1 Ib 0.81! 3.166 0.639 2.833 5.972 5.318 1,084 1.365 HD 184313 M5 III 1.658 3.737 4.381 HD 209750 G2 lb 0.913 2.917 0,425 2,404 5.743 5.367 HD 207076 M7 III HD 44362 G2 lb 0,809 3.267 0.568 2.123 5.012 4.868 HD 202560 MO V 9.598 1.102 2.732 2.286 HD 206859 G5 lb 0.853 2.349 2.79 5.816 5.788 HD 36395 M 1.5 V 17.805 0.884 2.370 2,210 HD 48329 G8 lb 1,328 2.591 2.94 6.215 7.332 HD 217897 M2 V 12.047 1.001 2.293 1.741 HD 36079 G5 H 0,681 2.28 1.843 4.017 3.125 HD 180617 M3 V 21.817 0.839 1.986 1.555 HD 185758 G1 HI 0,509 2.745 1.549 4.152 3.554 Peculiar Stars HD 21120 G6 III 0,561 2.078 1.350 3.717 2.979 HD 49798 06 ρ 3.29 HD 33833 G7 III 0.779 1.929 1.55 3.63 3.789 HD 37490 Β3 Ule 5.75 1.931 1.566 2.259 HD 10761 GS HI 0,856 2.113 1.472 3.799 3.398 HD 49333 Β7 Hin 5.4 0.311 3.657 1.814 4.807 HD 3919 G8 111 HD 5737 B7 IHp 4.457 0.326 1.383 2.565 4.706 3.419 4.943 HD 184492 G9 Ilia 0,555 2.047 2.172 - 1.503 3.816 3.374 HD 315 88 IllpSi 6.035 0.285 0.656 1.480 3.862 2.545 5.764 HD 195564 G2J IV 0.398 1.160 2.648 0.308 1.228 3.205 2.381 HD 12767 B9.5pSi 5.586 2.357 6.067 HD 188512 G8 IV 0.457 0.920 1.952 - 1.276 3.260 2.640 HD 92207 AO lae 0.325 0.945 -2.792 1.753 2.162 1.849 1.795 HD 39587 GO V 0.495 1.25 3.336 0.182 1.148 3.066 2.645 HD 62623 A2 labe 8.950 0.549 4.016 7.918 HD 214850 G3V+G8 0.283 1.529 2.411 - 0.758 2.641 2.442 HD 18557 A2 m 0.481 9.764 0.437 1.146 2.089 3.994 2.163 4.676 V HD 20320 A5 m 0.556 8.89 0.48 1.083 1.868 3.792 1.842 3.858 HD 26030 G5 V 0.531 1.111 3.071 1.043 3.24 2.844 HD 40372 A5 HD 69830 G7 V 0,631 2.374 2.512 1.236 3.329 2.819 móDcl (unbl) HD 67523 F6 II ρ 0.658 0.544 6,247 0.758 1.62 3.181 4.71 1.374 3.191 Κ - Type δ Del HD 65699 K2 lab G6H1 0.594 1.331 2.291 - 1.371 3.779 3,343 HD 206778 K2 Ib 1.101 3.952 2.338 2.398 5.806 6.737 Ba 0 .2 HD 185622 Κ4 Ib 0.827 5.160 3.277 2.283 6.319 6.135 HD 223541 HD 223428 K2 Illb 0.553 1.881 - 1.070 3.082 2.769 HD 52877 K7 Ib 1.693 6.824 3.Ô61 2.273 5.52 6.696 Ca 0.5 HD 179870 KO II 0.677 2.422 1.797 1.540 4.352 3.824 1.241 5.898 1.602 1.186 4.096 4.352 (0.71 HD 31767 K2 11 0.821 2.885 2.014 1.660 4.260 3.737 8} HD 167818 K3 II 0.872 3.692 2.547 2.201 5,681 4.546 HD 170975 K3 Ib-Il 1.479 5.132 2,934 2.279 6.335 6.373 CN HD 8512 KO III 0.776 1.861 1.857 1.582 3 597 3.204 HD 46259 KZ.KjIH 3.275 1.984 1.S18 5.158 5.141 HD 39810 KO III 0.652 2.132 1.905 1.26 3.622 3.643 Ρ HD 37192 K2 Illa 0.831 2.335 1.799 1.658 7.278 3.254 HD 216S03 K4V HD 211416 Κ3 III 0.744 3.984 2.138 1.572 4.499 5.193 HD 496 KO Hl HD 223428 Κ2 Illb 0.559 2.298 1.702 1.311 3.361 3.003 HD 223719 Κ4 111 0.872 3.686 2.161 1.523 4.476 4.455 HD 23249 KO IV 0.563 2.351 1.963 1.531 3.432 2.487 HD 3651 KO V 0.403 2,96 1.958 1.317 3.524 2.706 HD 22049 K2 V 0.525 2.841 1.896 1.136

the PXA line, which was then subtracted from the blended ence is probably due to the choice of the continuum level. feature to yield the strength of the Ca n 8662 A line. This A small difference could produce a large difference in the procedure was only necessary for stars earlier than G2, measured equivalent width. later the Paschen series is not present. As illustrated in Fig. Tinsley ( 1967) plotted the equivalent width of the Ca π 7, it is obvious that the Ca n lines are a luminosity indica- Κ line but did not see any luminosity effects, only a steady tor between supergiants and dwarfs between spectral types increase in }νλ from AO to K0. The behavior of Ca ι 4227 F4 and M2. A is similar. However this latter line was defined princi- The Ca π lines have been studied in detail by Jones et al. pally by dwarfs. (1984). We have six stars in common with them; these stars are shown in Table 3. The equivalent widths of the 3.4 Ha, Fe I 6495 A Ratio stars studied by Jones et al. are plotted against those of this study and are shown in Fig. 8. It can be seen that there is The Fe ι line is clearly present in supergiants at A5 and very good agreement for five of the six stars, while the grows in strength until it is roughly equal in strength to Ha G2 Ib star HD 204867 is slightly above the mean line. This at G8, and it continues to strengthen through to M2 I. star has the strongest Ca π lines, and we believe the differ- Similarly, Fe I is evident at A2 V in the dwarfs, and grows

άΟΟΟ cu 3000 HD 209750 G21b 100 TMpvy, 80 HD 58134 G5I

10000 ^f|vi 8000 HD 68329 G8Ib 6000 A 10000 8000 HD 206778 K2Ib 6000 - 12001 Λ1 1000 800 yy 600 HD 170975 K3Ib

6000 7000 8000 9000 10000 6000 7000 8000 9000 10000

12000

j'HD 59612 A5 1 b

Γμ

6000 7000 8000 9000 10000

Κ, 20000 - i'hjiKx

10000 - HD 56605 F8 Ια 6000 7000 8000 9000 10000

FïG- 2—Representative Spectra of O to M supergiants. The plots are scaled to the minimum in the atmospheric A band.

Fig. 3—Representative Spectra of O to M main-sequence stars. e plots are scaled to the minimum in the atmospheric A band. in strength to KO V, but never reaches the strength seen in 3.5 He I 6678 A supergiants. It becomes only slightly stronger than Ha at MO V and is still weakly present at M2 V, before becoming This weak He I line is present in 07 dwarfs, and appears lost in the TiO bands. strongest at 09 V, before disappearing at B8 V. Similarly,

□ A · • o X 8.0 - 0 o o 7.0 - D ft Α ΑΑ □ □ kx Β Χ ο Χ χ Β ▲ο • o0 χ 4.0 - ο □ Δ^Ο φ ét 0 00 ^ \ 1 ^ 1 1 ^ 1 Δ 05 Β0 Β5 Α0 Α5 F0 F5 GO G5 KO δλ 2.0 - ' ^ Δ Spectral Type

Fig. 5—The equivalent width (mÀ) of the Paschen Pn is plotted vs. J _J_ I I I I spectral type, showing that the line is a luminosity indicator with a be- B5 AO A5 FO F5 KO K5 MO M5 havior similar to Ha, as shown in Fig. 4. Spectrat type - and later. The equivalent width of Na ι 5896 A line is Fig. 4—The equivalent width (mÂ) of Ηα is shown plotted against plotted against spectral type in Fig. 9, where the largest spectral type for luminosity classes from I to V. It is clear that supergiants values (for the MO V to M2 V) have been excluded to are easily distinguished from dwarfs and intermediate luminosity stars allow the scale to be expanded to show more details. The between AO and A7. curve is very similar to that shown by Tinsley ( 1967) and O'Connell ( 1973). The expected trend of metals increasing in the supergiants the line is present at OS I, strongest at with lower temperature is obvious in the figure, but two B0 5, and has completely disappeared at AO 1. points have to be noted. First, for the later types, the equivalent width is more difficult to measure as the sodium is 3.6 CN increasingly overtaken by TiO bands, which probably ex- The CN (1—0) 7872 A band head, is easily identified plains the displaced position of the few M m stars. Second, lying to the red of the O I 7776 A line in a relatively clean at the hot end, some Β stars show a larger than expected continuum region. Also easily recognizable is the CN WÀ which indicates that we are probably seeing interstellar (or circumstellar) sodium rather than photospheric. In- (1—0) 9140 A band head. These band sequences δη=2 deed, some of the stars plotted here were already known to and δη=1 are discernible in supergiants at F0 I and develop in strength to later spectral types. For the dwarfs the have interstellar Na ι lines. The star HD 43836 was ob- bands are first evident in our spectra at GO V. served by Merrill et al. ( 1937) who obtained a close to ours. Hobbs (1974), using an interferometer measured Nai in HD 35411, 53138, and 149438 and there are dif- 3.7 Na I 5889-5896 A ferences of up to a factor two with our results which we The Na I doublet first appears around AO in both lumi- believe can be accounted for by our poorer spectral reso- nosity classes I and V, and grows steadily in strength lution. However, he reported no detection of Na I in the through to M2. Our coverage of the late NTs is not detailed case of HD 53138 and the reported Wx for HD 35411 is enough to state precisely through which spectral types the five times lower. As these two stars are known to have Na I doublet can be detected against the growing TiO strong stellar winds, we tentatively suggest that the varia- bands in the luminosity classes I and V. However, for class tions seen are real and may correspond to a discontinuous III, the sodium is clearly seen at type M 1.5 but not at M3 ejection of matter. HD 35411 is a spectroscopic triple and

BO B5 AO A5 F0 F5 GO G5 KO Spectral Type ►

Fig. 6—The equivalent width (mÂ) of the OI (7776 Â) line is plotted against spectral type for luminosity classes I through V. It clearly shows that it is possible to distinguish between supergiants and dwarfs between B6 and GO, with the effect peaking at F0. there is the possibility of a small contribution to the Na ι observed are not always the most spectacular in their class. lines from the He ι 5876 A but, at the resolution of the Particular attention has been placed on finding possible atlas these lines should be separated. Extrapolating from spectral lines or bands of the species characteristic of the the above results, we believe that the sodium in HD 47306 peculiarity. The spectral type has been taken from the re- and possibly in HD 161471 is partly of interstellar or cir- vised version of the Bright Star Catalog (BSC), when in- cumstellar origin. Once the statistics on early stars have cluded, or from the Data Base of the Strasbourg Center de been improved, a diagram like the one shown in Fig. 9 will Données Stellaires when the star was too faint to be in- help to detect other anomalous cases. cluded in the BSC. Starting with hotter stars, we present the He-weak star 3.8 Peculiar Stars HD 49333, B7 Hin. The continuum compares well with To conclude and to illustrate some of the possibilities of HD 35468, B2 III Fig. 10, but the difference in strength of this spectral range, spectra have also been obtained of a He ι 6678 A and Paschen lines between the two stars is number of peculiar stars. As already noted above, one ad- striking. The He ι 5876 A is unfortunately affected by the vantage of the linear detector used in this survey is that the instrumental defect mentioned above. The hydrogen line shape of the continuum can be directly used as an estimate spectral type being definitely later than B5, this star would of the effective temperature. This is particularly valuable thus belong to the Scl group as defined by Jaschek and for the peculiar stars where the effective temperature is not Jaschek ( 1974). Another He-weak star, HD 5737, B7 IIIp, directly obtainable from the spectral features alone. We has a continuum shape which compares well with HD illustrate this below for a few "couples" where a peculiar 34503, B5 III Fig. 11, and the He ι 5876 A appears defi- star is displayed with the normal star of closest effective nitely weak. It seems therefore that He weak stars can be temperature. Due to the limited number of MK standards readily identified at low dispersion in this spectral range. observable in the south, the best possible star for compar- The subdwarf HD 49798 (sdO+sdB) as shown in Fig. ison was not always observed: we then have taken the clos- 12 is almost featureless, apart from the strong broad He ι est one available in our survey. The same limitation applies 5876 and 6678 A lines and Ha, but the Paschen lines are to the choice of the peculiar stars themselves; the ones absent.

X la ® Ib 7 - • II ▲ III • · □ IV ο V 6-

·· 5 -

U 4 -

1 3- Α ·Α À Á o Aqo 0α tf D 0 ÁD 2- A ΧX D A O a O D Ο #0 a 1 - # oo

Ί Γ Ί Γ 05 BO B5 AO A5 F0 F5 GO G5 KO K51 MOΓ Spectral Type

Fig. 7—The equivalent width (mÂ) of the Ca π 8662 A line is plotted against spectral type, and can be seen to be a luminosity indicator for supergiants and dwarfs between F4 and M2.

HD 92207 in Fig. 13 is classified AO leab, and can be pointed out earlier, similarly the Paschen lines are narrow contrasted with HD 62623 an A3 Hep Fig. 14. The He line and well defined to high There is also an indication of 6678 A is only weakly present in HD 92207 and the pres- the Can triplet in absorption blended with the Paschen ence and strength of the interstellar feature at 6284 A lines. The spectrum of HD 62623 also demonstrates weak points to the He ι 5876 A being blended with interstellar Na I. Also easily identifiable are the Si π lines at 6347 and 6371 A. Ha is seen in emission and the line appears broad in comparison with the absorption features. The strength of the Ο ι line at 7776 A is indicative of a supergiant as Table 3 The stellar names, effective temperature, log g, and measurements of the equivalent widths (mÂ of the three Ca π triplet lines ♦under the columns 1, 2, and 3), are given for the stars in common with the work of Jones et al. The equivalent widths measured by Jones et al. are given in brackets. The results are plotted in Fig. 7. Name SpT 0cff logg 0.97 2.44 2.05 HD 202560 (1.102) (2.732) (2.286) HD 204867 2.67 5.80 4.25 (2.351) (5.599) (5.993) 2.62 5.80 4.24 HD 209750 (2.404) (5.743) (5.367) 1.49 3.40 2.73 HD 3651 (1.317) (3.524) (2.706) HD 23249 1.31 2.94 2.30 (1.531) (3.432) (2.487) Fig. 8—The equivalent widths (mÂ) of the individual lines of the Ca π HD 30652 1.31 2.71 2.61 triplet are plotted for six stars we have in common with the work of Jones (1.001) (2.754) (2.643) et al. (1984). Details of the stars are given in Table 3.

7.0 6.5 6.0 5.5 5.0 4.5 4.0 3.5 Fig. 11—Spectrum of HD 34503 B5 III compared with the He weak star 3.0 HD 5737 B7 IIIp. 2.5 2.0 1.5 HD 49798 0E 5 AB 1.0 0.5 0.1 BO B5 AO A5 F0 F5 GO G5 KO K5 M5 Spectral type ^

Fig. 9—The equivalent widths (mÂ) of the Na i lines are plotted against spectral type for luminosity classes I through V. Note that the scatter increases to the blue, probably due to some ISM or circumstellar contribution. The largest values (MO V stars and redwards) fall off scale.

Fig. 12—Spectrum of the subdwarf HD 49798 (sdO+sdB); it shows strong He ι lines and Ha, but no Paschen lines are visible.

HD 92207 Λ0ΙΕ ΛΒ

Fig. 10—Spectrum of the He weak star HD 49333 B7 Hin, compared with that of HD 35468 B2 III. Differences in the strengths of the He ι Fig. 13—Spectrum of the AO leab star HD 92207. Note the He ι features, 5876 and 6678 À lines are noticeable. Ha in emission and the strong Ο ι at 7776 A.

Cool stars

Fig. 14—Spectrum of the A3 Hep star HD 62623. It has strong emission lines indicative of an extended shell or surrounding nebula.

Nai and the interstellar 6284 A lines, but has much weaker Si π features. By contrast the Ha emission is much narrower, and several other features are also seen in emission, notably the Ca π triplet and [Ο π] doublet at 7375 and 7319 A. The emission-line spectrum is more indicative of nebulosity or an extended shell, the ΟI 7776 A line is weaker, and the Paschen lines broader, in keeping with its WAVELENGTH (A) luminosity type. In Fig. 15 three emission-line stars are illustrated, S Coronae Australis, GG Carinae, and χ Oph- Fig. 16—The difference between three late-type stars, M5 III, C, and S is iuchi which exhibit a range of emission features. Can, illustrated. He π, Ο ι, and the Paschen series. The strong Ca π triplet in emission is characteristic of Τ Tauri stars, but is also eluded the spectra of two extreme emission stars (not in- seen in shock-excited nebulae (Dennefeld 1986). In Fig. 16 cluded in the NSSDC file), the Wolf-Rayet star we illustrate the easily discernible differences between very HD 50896 (HR 2583), Fig. 17, and SS 433, Fig. 18, which cool stars, here M5 III, C, and S stars. We have also in- serve to illustrate the advantages of using a linear detector with a large dynamic range. The emission lines are identi- Emission-line stars fied in the figures and the detector response out to 1.1 μπα. is clearly evident. The characteristics of WR stars, observed with the same equipment, have been discussed in details by Vreux et al. (1983). In the case of SS 433, the shape of the continuum is illustrative of a heavily reddened object. More generally, access to this spectral range can help to reveal the presence of cold companions otherwise not detectable in the visible. This is illustrated (among other features of this spectral range) in Dennefeld (1987)

ι I I 1 6,000 7,000 8,000 9,000 10,000 11,000 WAVELENGTH Κ WAVELENGTH (A) Fig. 17—The advantages of a large dynamic range and spectral sensitivity Fig. 15—Three emission-line stars are shown, illustrating the differences are illustrated here with the rich emission-line spectrum of HD 50896 between Τ Tau, Be, and Oe stars. (HR 2583) a Wolf-Rayet WN5 star.

WAVELENGTH (Â)

Fig. 18—The large dynamical range is again illustrated with this spectrum of SS 433, which also illustrates the detector response out to 1.1 μηι.

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