STANDARD STAR NEWSLETTER No 33 An electronic publication of the Working Group on Standard Stars IAU Commissions 25, 29, 30, 45)} editor: Richard O. Gray October 2002 grayro@appstate.edu CONTENTS: Editorial p. 1 Note from the Working Group Chair, Chris Corbally p. 1 Abstracts of Papers (Hillenbrand et al., Knyazeva \& Kharitonov, TsujiX2 p. 2 Websites of Interest p. 5 Meeting Report p. 5 Announcements p. 6 From the editor It is remarkable how the subject of Standard Stars underlies the entire range of stellar astronomy, even at its cutting edge. The subjects touched on in this issue of the Standard Star Newsletter, which range from the definition of a new infrared photometric band, through the formation of dust in brown-dwarf atmospheres, to the discovery of O2 stars and the development of automated stellar classification only emphasize that fact. Long live Standard Stars! A Note From the Chair International Astronomical Union Working Group on Standard Stars (WGSS) You have probably also recently received the IAU Bulletin \#91 with information about the General Assembly next July in Sydney. I got fairly excited when looking at the preliminary details of the scientific programme. There is more than I expected around the theme of stars (see Symps 219, 211; JDs 04, 05, 09, 11, 12, 13 ,15, 20; SS 3 -- and I have probably left out your favorite). One you might overlook in this context is JD 08. It is on Future Giant Telescopes (FGTs) and the International Virtual Observatory. Two years ago at the Manchester General Assembly our Working Group talked briefly about the need for producing lists of faint enough standard stars, in all categories, for existing 6-m or greater class telescopes. These FGTs will just increase the problem. If you are working on this kind of thing, do let the rest of us know through the next Standard Stars Newsletter. We can then help you spread the good news in Sydney. Thinking of good news reminds me that my Note in the March 2002 SSN pointed out that last January's ApJ had two papers, each giving a slightly different approach to Near-IR classification of T-dwarfs. I am happy to report that Adam Burgasser told the participants at last June's Festschrift meeting for Bob Garrison that a working group, with both parties well represented, had been set up to define a joint classification scheme. It seems that ecumenism can operate in science as well as among religions. Well, may you find joy and success in your own researches, Chris Corbally ccorbally@as.arizona.edu Abstracts The Y-Band at 1.035 microns: Photometric Calibration and the Dwarf Stellar / Sub-stellar Color Sequence Lynne A. Hillenbrand(1) Jonathan B. Foster(1), S.E. Persson(2), K. Matthews(3) (1) California Institute of Technology; Dept. of Astronomy; MS 105-24; Pasadena, CA 91125 (2) Observatories of the Carnegie Institution of Washington; 813 Santa Barbara Street; Pasadena, CA 91101 (3) California Institute of Technology; Palomar Observatory; MS 320-47; Pasadena, CA 91125 We define and characterize a photometric bandpass (called ``Y") that is centered at 1.035 microns, in between the traditionally classified ``optical'' and ``infrared'' spectral regimes. We present Y magnitudes and Y-H and Y-K colors for a sample consisting mostly of photometric and spectral standards, spanning the spectral type range sdO to T5V. Deep molecular absorption features in the near-infrared spectra of extremely cool objects are such that the Y-H and Y-K colors grow rapidly with advancing spectral type especially from late M through mid L, substantially more rapidly than J-H or H-K which span a smaller total dynamic range. Consistent with other near-infrared colors, however, Y-H and Y-K colors turn blueward in the L6-L8 temperature range with later T-type objects having colors similar to those of warmer M and L stars. Y-J colors remain constant at 1.0$\pm$0.15 mag from early-L through late-T dwarfs. The slope of the interstellar reddening vector within this filter is A_Y = 0.38 X A_V. Reddening moves stars nearly along the YHK dwarf color sequence making it more difficult to distinguish unambiguously very low mass candidate brown dwarf objects from higher mass stars seen, e.g. through the galactic plane or towards star-forming regions. Other diagrams involving the Y-band may be somewhat more discriminating. Appeared in PASP 114, 708 -- July 2002 For reprints, contact lah@astro.caltech.edu Observed and Calculated Normal Color Indices And Indices in Three Photometric Systems Knyazeva L.N. , Kharitonov A.V. Fessenkov Astrophysical Institute, Almaty,Kazakhstan We estimated the reliability of the previously derived intrinsic energy distributions for the 69 spectral subclasses by comparing the intrinsic calculated color indices with those derived from the photometric observations in three photometric systems (WBVR, Kornilov et al.,1991, uvby, Hauck and Merilliod, 1998 and UPXYZVS, Straizus and Kazlauskas,1993). Unfotunately the intrinsic color indices derived from photometric observations were available only in the UPXYZVS system. We derived the intrinsic color indices from photometric observations in the WBVR and uvby systems using the catalogues of Kornilov et al. (1991) and Hauck, Mermilliod (1998) respectively. The comparison of the inrtinsic calculated and observed color indices in the three photometric systems is given in the following table: The results of the comparison between the intrinsic calculated and observed color indices Sp d(U-V) d(P-V) d(X-V) d(Y-V) d(Z-V) d(V-S) d(W-V) d(B-V) d(b-y) d m_1 d c_1 B1V 0.015 0.047 0.045 0.026 0.013 -0.032 0.108 0.067 - - - B2V -0.068 -0.019 0.005 0.001 0.003 -0.033 0.066 0.045 - - - B3V -0.077 -0.040 -0.015 0.016 0.009 -0.025 -0.017 0.012 - - - B5V 0.011 0.014 0.008 0.022 0.009 -0.047 0.026 0.016 0.004 -0.002 0.030 B7V 0.031 0.012 0.022 0.032 0.022 -0.037 -0.022 0.005 0.017 -0.002 -0.037 B8V 0.030 0.037 0.029 0.017 0.007 -0.064 -0.001 0.008 -0.002 0.011 -0.034 B9V 0.179 0.150 0.061 0.031 0.021 -0.026 0.003 -0.002 0.000 0.011 0.054 B9.5V - - - - - - - - -0.002 0.004 0.006 A0V 0.024 0.043 0.010 0.014 0.007 -0.019 -0.018 -0.018 -0.019 0.011 -0.037 A1V 0.033 0.056 0.040 0.025 0.014 -0.030 -0.014 -0.009 -0.008 0.012 -0.022 A2V 0.011 0.039 0.042 0.020 0.009 -0.027 -0.018 -0.013 -0.017 0.026 -0.025 A3V 0.014 0.058 0.058 0.029 0.009 -0.038 0.017 0.004 -0.009 0.011 -0.019 A4V - - - - - - 0.037 0.013 0.010 0.003 -0.019 A5V 0.016 0.050 0.065 0.023 0.019 -0.051 0.017 0.012 -0.003 0.012 -0.005 A7V -0.053 0.039 0.061 0.021 0.012 -0.023 0.012 -0.013 -0.006 0.029 -0.072 F0V -0.049 0.001 0.038 0.023 0.008 -0.036 -0.013 -0.028 -0.018 0.017 0.003 F5V 0.009 0.021 0.037 0.016 0.000 -0.014 -0.003 -0.008 -0.005 0.016 -0.012 F6V - - - - - - 0.014 -0.033 -0.013 0.010 0.035 F7V - - - - - - 0.041 -0.011 -0.013 0.009 0.053 F8V 0.023 0.022 0.013 0.006 -0.002 -0.049 0.042 -0.014 -0.013 0.013 0.000 G0V 0.069 0.065 0.027 0.015 -0.005 -0.019 0.003 -0.021 -0.013 0.010 0.041 G2V -0.025 -0.029 -0.006 0.023 0.012 -0.029 0.003 -0.006 -0.006 -0.006 0.009 G5V -0.028 0.002 -0.006 0.002 -0.007 -0.018 - - -0.025 0.012 -0.033 G8V 0.057 0.061 -0.010 0.003 0.001 -0.034 -0.079 -0.047 -0.018 -0.022 0.014 B2IV 0.039 0.042 0.012 -0.002 0.009 -0.051 0.031 0.013 0.000 0.024 -0.007 B3IV -0.070 -0.060 -0.029 -0.018 -0.010 -0.067 -0.004 0.024 0.015 0.019 -0.049 B5IV 0.080 0.065 0.016 0.006 0.001 -0.036 0.028 0.024 0.015 0.012 -0.031 B9IV 0.224 0.133 0.048 0.021 0.012 -0.004 -0.101 -0.020 -0.011 0.012 -0.049 A3IV 0.039 0.020 0.012 0.011 0.003 -0.048 -0.015 -0.022 0.007 0.008 -0.010 A7IV 0.010 0.013 0.040 0.026 0.011 -0.010 0.002 -0.034 -0.014 0.014 -0.006 F0IV -0.024 0.015 0.078 0.051 0.018 -0.013 -0.045 0.014 0.005 0.010 -0.098 F2IV -0.018 0.015 0.021 0.017 0.005 -0.061 0.005 -0.009 0.000 0.014 -0.029 F5IV 0.066 0.048 0.069 0.037 0.013 -0.043 0.012 0.008 0.012 0.004 -0.002 B2III 0.041 0.040 0.053 0.020 0.025 -0.069 - - - - - B5III -0.107 -0.040 0.005 -0.005 0.001 -0.066 -0.065 0.002 0.002 0.041 -0.166 B6III -0.035 -0.041 -0.025 -0.022 -0.005 -0.052 0.026 -0.013 - - - B7III 0.095 0.067 0.021 0.014 0.015 -0.046 -0.002 0.015 0.016 0.001 -0.040 B8III 0.157 0.104 0.021 0.010 0.013 -0.033 -0.019 0.021 -0.003 0.048 -0.142 B9III 0.166 0.077 -0.003 0.007 0.007 -0.030 -0.038 -0.017 -0.010 0.008 -0.030 A0III 0.173 0.105 0.070 0.034 0.026 0.029 -0.016 0.003 0.002 0.016 -0.037 A3III 0.006 -0.002 -0.005 0.000 0.002 -0.029 0.011 -0.011 -0.005 0.025 -0.006 A5III 0.125 0.050 0.052 0.017 0.008 0.000 0.046 0.008 0.001 0.023 -0.021 A7III 0.064 0.044 0.072 0.036 0.021 -0.036 0.015 0.003 0.001 0.018 -0.037 F0III -0.057 -0.010 0.067 0.027 0.015 -0.023 -0.047 0.011 0.013 0.049 -0.269 G7III - - - - - - - 0.055 - - - G8III - 0.061 0.027 0.007 0.000 -0.025 - -0.017 - - - G9III - - - - - - - -0.029 - - - K0III - 0.122 0.058 0.024 0.010 -0.026 - 0.004 - - - K1III - 0.183 0.108 0.044 0.023 -0.014 - 0.002 - - - K2III - 0.100 0.049 0.026 0.009 -0.033 - -0.017 - - - K3III - 0.014 -0.028 -0.023 -0.014 -0.057 - -0.013 - - - K4III - -0.075 -0.072 -0.050 -0.015 -0.055 - -0.026 - - - K5III - 0.044 0.033 0.012 0.013 -0.063 - -0.016 - - - M0III - 0.068 0.049 0.017 0.017 -0.035 - -0.021 - - - M1III - 0.204 0.103 0.031 0.015 -0.023 - 0.005 - - - M2III - 0.220 0.076 0.030 0.022 -0.003 - -0.015 - - - M3III - 0.121 0.044 0.020 0.002 -0.007 - -0.005 - - - M4III - 0.071 -0.030 0.020 -0.015 -0.007 - -0.001 - - - M5III - 0.108 0.025 0.092 0.042 -0.022 - 0.013 - - - B1Iab -0.123 -0.045 0.011 -0.012 0.002 -0.039 - - - - - B2Iab -0.003 0.006 0.017 -0.000 -0.009 -0.062 - - - - - B5Iab 0.036 -0.004 0.022 0.008 -0.002 -0.049 - - - - - B9Iab 0.007 -0.013 0.029 0.025 0.005 -0.082 - - - - - G2Iab -0.150 -0.098 -0.068 -0.049 -0.015 -0.061 - - - - - This table presents the characteristics of our intrinsic energy distributions and enables one to estimate the reliability of the intrinsic color indices derived from the photometric observations in these systems. The full text of the article was published in Astronomy Report 2002,46,152. References Kornilov B.G. et al.Tr. Gos. Astron.Inst. Sternberg, Moscow,1991,63 Hauck B.& Mermilliod M. Astron. Astrophys.,Suppl. Ser 1998, 129,431 Straizus V.& Kazlauskas A. Balt.Astron 1993,2,1 For preprints, contactKhar@afi.academ.alma-ata.su Unified Cloudy Models of L and T Dwarfs - Physical Basis of the Spectral Classification in the Substellar Regime T. Tsuji Institute of Astronomy, School of Science, The University of Tokyo, Mitaka, Tokyo, 181-0015 Japan The spectral types from O to M (C, S) are directly related to the amount of ions, atoms, and molecules predicted by the ionization and dissociation theory. Beyond M dwarfs, dust may play a major role, but the new spectral types L and T appear to be not related directly to the amount of dust predicted by the thermochemical theory, since the warmer L dwarfs appear to be more dusty than the cooler T dwarfs. We propose a simple explanation on the L - T transition based on our unified cloudy models (ApJ 575, 264, 2002): In the photospheres of L and T dwarfs, dust forms at its condensation temperature (T_cond) but grows too large to be sustained in the photosphere at a slightly lower temperature which we refer to as the critical temperature (T_cr). For this reason, only small dust grains survive in the temperature range of T_cr < T < T_cond. This means a formation of a dust cloud whose temperature is fixed at rather high values (note that T_cond approx 2000K) independently of T_eff. Since T approx T_eff at tau_Ross approx 1, the dust cloud appears at the optically thin region (tau_Ross < 1) in L dwarfs whose T_eff's are relatively high and at the optically thick region (tau_Ross > 1) in T dwarfs whose T_eff's are lower. Then the dust will give direct observable effect in L dwarfs, which in fact appear to be dusty, and some spectral features (e.g. K I 1.2432microns) tend to be weaker at later L types where dust extinction is larger by the increased dust column density in the cloud than at earlier L types. On the other hand, the dust cloud is situated too deep to give significant observable effect in T dwarfs and the abundances of the volatile atoms (e.g. K) and molecules (e.g. H_2O, CH_4) above the cloud increase from early to late T dwarfs, as observed. The spectral types O, B, A, F, G, K, M, L, and T can be understood as a temperature sequence, but the formation of the dust cloud at different optical depths (although the temperatures are nearly constant at T approx T_cond) is essential in understanding the L - T spectral sequence. Accepted by Brown Dwarfs, IAU Symp.211, 2003, E. L. Martin, ed. For preprints, contact ttsuji@ioa.s.u-tokyo.ac.jp, also available as astro-ph/0208255} Water Observed in Red Giant and Supergiant Stars - Manifestation of a Novel Picture of the Stellar Atmosphere or else Evidence against the Classical Model Stellar Photosphere T. Tsuji Institute of Astronomy, School of Science, The University of Tokyo, Mitaka, Tokyo, 181-0015 Japan We detected the H2O 6.3 micron bands in more than 30 normal red giants stars from K5III to M8III as well as in some early M supergiants on the SWS spectra retrieved from the ISO Data Archive. This result, however, shows serious inconsistency with the present model photospheres which predict H2O only in the latest M (super)giant stars. Also H2O was once discovered in the early M (super)giant stars nearly 40 years ago with the balloon-borne telescope named Stratoscope II. This discovery was so unexpected at that time that it was not understood correctly and overlooked for a long time. Now, we reflect on our ignorance of this important discovery during the 40 years and should consider more seriously the meaning of the rediscovery of water in so many red (super)giant stars with ISO. In view of the detection of H2O in emission in the early M supergiant $\mu$ Cep as well as in late M giants with ISO, H2O should be in the outer atmosphere rather than in the photosphere. We propose that the absorption as well as emission of H2O should be originating in a new component, which we refer to as the molecular sphere. Since the extended atmospheres of red (super)giants radiate efficiently in the infrared, it is not surprising if the true structure of the atmospheres of these stars can first be revealed with the infrared observations especially from space. Our notion of ``standard stars'' will also be extended with the new infrared observations. Accepted by Proceedings of the Symposium Exploiting the ISO Data Archive - Infrared Astronomy in the Internet Age, ESA SP-511, 2003, C. Gry et al. eds. For preprints, contact ttsuji@ioa.s.u-tokyo.ac.jp, also available as astro-ph/0209495 Websites of Interest}}} I am certain that many of you have shared the experience with me of desperately needing photometry for a particular star, only to find that the required reference is missing from the dusty basement archives of the observatory, or is unavailable for some other reason. It was thus a pleasant experience to run across the on-line General Catalogue of Photometric Data (Mermilliod, Hauck & Mermilliod) at http://obswww.unige.ch/gcpd/gcpd.html. This database contains data from 80 different photometric systems. If you need information about the filter passbands, basic references or calibrations of a particular photometric system, it is all there. The same observatory (University of Geneva) hosts the extremely useful WEBDA database (by Jean Claude Mermilliod) of open clusters (http://obswww.unige.ch/webda/). Meeting Report Garrison Festschrift A meeting much advertised in these pages took place on 10-11 June in Tucson, AZ. This meeting was organized to honor Bob Garrison on the occasion of his retirement, but in addition, was in the tradition of the MK classification meetings held roughly every ten years. A group of about 25 colleagues and former students of Bob's gathered at the Arizona Inn for two days of talks, a Bobeque and a specially arranged solar eclipse. Highlights of the first day of the meeting included a talk by Adam Burgasser on the L and T-dwarfs, the announcement by Nolan Walborn of the discovery of O2 stars, a progress report by John Drilling on his classification scheme for subdwarf O and B-type stars, a summary by Chris Corbally of Bob Garrison's career in astronomy, a report on the NStars (Nearby Stars) project by Richard Gray and a talk, by Janet Rountree, on the extension of the MK system to other spectral domains, including taped comments by W.W. Morgan (never before published) on that subject. That evening, illuminated by the light of the setting, partially eclipsed sun, we held a barbecue in Bob's honor during which interesting and somewhat embarassing stories were told about his life and career. Highlights of the second day included papers on the role of small telescopes in cutting-edge astronomical research (Bruce Weaver), the remarkable characteristics of companions to interesting stars (David Turner), galaxy classification as inspired by the MK process (Omar Lopez-Cruz), an archive of data for normal stars and brown dwarfs (Babar Ali), near-infrared spectroscopy and young stellar populations (Mike Meyer) and automated stellar spectral classification (Ted von Hippel). The meeting was capped with a talk by Bob Garrison entitled ``The MK PROCESS: A Vision for the Future''. These talks will appear in proceedings to be published by L. Davis press. Richard Gray Announcements PDPP Newsletter No. 1 The IAU Task Force for the Preservation and Digitization of Photographic Plates (PDPP) has just issued its first Newsletter; it is available for downloading at http://stellar.phys.appstate.edu/ssn (editor's note - the website of the Working Group on Standard Stars is temporarily hosting this newsletter until it finds its permanent home - check for the link near the bottom of the webpage). The Newsletter contains reports of all the preservation and digitization activities which have come to the attention of the group. You are cordially invited to circulate the Newsletter to anyone who may be interested. Your attention is particularly directed to page 2, where it expresses the hope that membership of the Task Force will include a representative from every observatory or institute that harbours a photographic archive. Inevitably we will have missed some activities, and we would be grateful for relevant information and contact addresses. The Task Force is hosted by IAU Commission 5, and eventually the Newsletter will be available on Commission 5's Website. Elizabeth Griffin (Elizabeth.Griffin@hia.nrc.ca) Chair, PDPP Contributions to the next Newsletter}, due out in March 2003, will be welcomed at any time by grayro@appstate.edu. WHEN SUBMITTING AN ABSTRACT, PLEASE USE THE FOLLOWING TEMPLATE IF POSSIBLE: \begin{center}{\Large\bf{ Title }}\\{\bf{ A. Author$^1$ and B. Author$^2$ }}\\{\footnotesize $^1$ Institute One and Address \\ $^2$ Institute Two and Address }\end{center} \smallskip{ TEXT OF ABSTRACT }\\{\bf Accepted by} JOURNAL \\{\it For preprints, contact} YOUR ELECTRONIC ADDRESS