STANDARD STAR} NEWSLETTER An electronic publication of the Working Group on Standard Stars IAU Commissions 25, 29, 30, 45) No. 30 editor: Richard O. Gray March 2001 grayro@appstate.edu CONTENTS: Editorial p. 1 Note from the Working Group Chair, Chris Corbally p. 2 Abstracts of Papers (Gray et al, Pasinetti Fracassini, Schuster & Parrao p. 3 Websites of Interest p. 4 Announcements of Meetings p. 5 From the editor In contrast to the last issue, this, the 30th issue of the Standard Star Newsletter is thin, but not without some interesting features. First, Chris Corbally, chair of the Standard Star Working Group brings us the good news that our working group has been given approval to continue operating as an official IAU entity for three more years. Second, we have three abstracts of papers which should prove to be of considerable interest. Next, is a feature new with this issue of the Standard Star Newsletter - a section drawing attention to websites of interest to many readers of this publication. The websites featured in this issue are concerned with the NStars (Nearby Stars) Project, and contain valuable and original data on stars in the immediate solar neighborhood. I encourage readers of this newsletter to send me notice of websites of particular relevance to the topic of Standard Stars. I will announce them in this newsletter, and pass them on to the SOFA (``Standard Objects for Astrononmy'') website, found at http://sofa.astro.utoledo.edu/SOFA and http://www.prl.ernet.in/$\sim$shashi/SOFA/index.html Lastly, I would like to draw the readership's attention to a special meeting that will occur slightly over a year from now in May 2002. Many of you know Robert F. Garrison, former chair of this working group and former president of IAU Commission #45. Bob will be retiring at the end of this academic year, and a group of his former students, colleagues and friends are organizing a scientific meeting to celebrate Bob's many contributions to the fields of stellar spectroscopy, galactic structure and the morphological classification of galaxies. See the last page for details of this meeting. Please note that the website of the Standard Star Newsletter and Working Group has been changed to: http://stellar.phys.appstate.edu/ssn/ This homepage will give you access to previous issues of this newsletter, links to other astronomical newsletters, as well as a description of the Standard Stars Working Group. With many thanks to our contributors, R.O.G. A Note From the Chair International Astronomical Union Working Group on Standard Stars (WGSS) Working Groups in the IAU are precisely that: when its work is done, the IAU rules say that the group terminates. The status of the working groups are reviewed by the IAU Executive Committee (EC) every three years, around the time of the General Assembly. We were asked to make the case for the WGSS's continuance, and this was based on what was written by our former Chair, Bob Garrison, in SSN #28 (March 2000). I am pleased to report that I received the following brief communication from the IAU General Secretary: Date: Fri, 09 Feb 2001 16:20:13 +0100 From: Hans Rickman To: corbally@as.arizona.edu Cc: iau@iap.fr, hans@astro.uu.se, tle@saao.ac.za Subject: WG approval Dear Christopher, With some unfortunate delay that I apologize for, I have been able to get the EC decisions on the Working Groups within the IAU, as prescribed by the IAU Working Rules. I'm happy to confirm that the WG on Standard Stars under your chairmanship is thus approved for the triennium 2000-2003, until GA25. Best regards, Hans Rickman (IAU GS) So, we are ``working" for another three years. In the words of Bob Garrison, our goals ``are to examine, organize, and co-ordinate the various sets of standards for fields in which they are used: radial velocities, spectral classification, photometry, astrometry, and others, as well as to provide a forum for discussion and education. Without a clearing house for co-ordination of standards, chaos soon develops." A major way of achieving this co-ordination in the time between IAU-GAs is through this newsletter. So, again I encourage you to use its pages, through the generous editing of Richard Gray, to let people know what you are doing in the realm of stellar standards and to react to what you learn of others' work. I wish you all productive research over the next six months until the next SSN issue is due. Chris Corbally ccorbally@as.arizona.edu Abstracts The Physical Basis of Luminosity Classification in the late-A, F and early G-type Stars. II. Basic Parameters of Program Stars and the Role of Microturbulence R. O. Gray, P. W. Graham and S. R. Hoyt Department of Physics and Astronomy, Appalachian State University, Boone, NC 28608 USA This is the second in a series of two papers that attempt to address the problem of the physical nature of luminosity classification in the late-A, F and early G-type stars. Recent precise parallaxes from the {\it Hipparcos} satellite have yielded absolute magnitudes that are often in remarkably poor agreement with stellar luminosity classes on the MK system, even when factors such as rotation, nonhomogeneities in classifications, etc. are taken into account (Jaschek & Gomez 1998). Jaschek & Gomez suggest, as a result, that ``it would seem advisable to eliminate some of the standards which cause problems.'' To address this question, we have, in Paper I of this series, carried out precise, homogeneous classifications for 372 late A, F and early G-type stars of all luminosity classes. In this paper, we use a multi-dimensional downhill simplex algorithm to derive the basic physical parameters (Teff, log g, [M/H] and xi_t, the microturbulent velocity) for all of the normal stars in this set by deriving fits of synthetic spectra and fluxes (based on Kurucz 1993 atlas9 models) to the observed spectra and fluxes from Stromgren $uvby$ photometry. The method yields errors of $\pm 80$K in the effective temperature, +/- 0.10$ in log g, +/- 0.10 in [M/H] and +/- 0.5km/s in the microturbulent velocities. A partial correlation analysis on the relationships between the luminosity class, the gravity and the microturbulent velocity yields the remarkable result that the microturbulent velocity is as important as, or even more important than, the gravity in the determination of the MK luminosity class. This result clearly has important implications for the interpretation of MK luminosity classification and its use in the method of spectroscopic parallax. However, it implies that the problem will not be solved by eliminating ``some of the standards which cause problems.'' References Jaschek, C. & Gomez, A.E. 1998, A & A 330, 619 Accepted by The Astronomical Journal For preprints, contact grayro@appstate.edu News on the CADARS Laura E. Pasinetti Fracassini Dipartimento di Fisica, Universita\'a degli Studi, Via G. Celoria 16, 20133 Milano, Italia The Third Edition of the "Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS)" by Pasinetti Fracassini L.E., Pastori L., Covino S., Pozzi A., was sent to the CDS of Strasbourg and installed as cat.II/224. This Edition consists of 13573 records concerning the results obtained from different methods for 7778 stars, reported in the literature. A brief description of the Catalogue with Comments and Statistics will appear in A&A 2001, 367, 521 The Atmospheric Extinction of San Pedro Martir W. J. Schuster (1) and L. Parrao (2) (1) Observatorio Astron\'omico Nacional, UNAM, Ensenada, Baja California, M\'exico (2) Instituto de Astronom\'{\i}a, UNAM, Mexico City, D.F., M\'exico The atmospheric extinction of SPM is analyzed using 13-color determinations from 294 nights of observations over the years 1973-1983, plus the extinction measures from 272 nights of $uvby$ observations over the years 1984-1999. The general behavior of the normal extinction at SPM is given and analyzed as a function of wavelength and as a function of time; mean and minimum atmospheric extinction values for SPM are given. A simple 3-component model for the extinction above SPM is derived and presented; this model includes Rayleigh-Cabannes and aerosol scatterings plus ozone absorption and fits the observed extinction curve well over 3370-6500A. The normal, average, non-volcanic aerosols above SPM are well fit by $k_{\rm p}(\lambda) = 0.0254\lambda^{-0.866}$. The extinction determinations for the periods following the volcanoes El Chichon and Pinatubo are given: 13-color data show the effects of El Chichon and uvby for Pinatubo. The extinction curves and their variations are analyzed to study the volcanic aerosols and their evolution with time; possible masking of the usual extinction components by the volcanic aerosols is discussed. The April/May 1998 observing run, when large non-volcanic extinction variations occurred, is also studied, and deductions drawn concerning these unusual aerosols and the climatological conditions required. Submitted to RevMex A&A For preprints, contact schuster@astrosen.unam.mx Large Websites of Interest The NStars Database The mission of the NStars Database is to be the most current, complete and accurate source of scientific data about all stellar objects within the current study radius of 25 parsecs. At present this includes approximately 2600 stars. The website contains detailed information on the NASA NStars research project. The database contains the following information (still incomplete) about each star within 25 parsecs: identifiers, including information on binary and multiple systems, astrometry (positions, proper motions and parallaxes), photometry from the optical to the far infrared, spectral types, flare status, radial velocity and rotation, as well as derived quantities such as mass, radius, age, effective temperature, etc. The website can be found at: http://nstars.arc.nasa.gov/ The Nearby Stars Project Homepage, Appalachian State University As part of the NStars / Space Interferometry Mission Preparatory Science Program, R.O. Gray (P.I., Appalachian State University) and Co.I's C.J. Corbally (Vatican Observatory Research Group) and R.F. Garrison, (David Dunlap Observatory) are carrying out spectroscopic studies of the dwarf and giant stars earlier than M0 within 40 parsecs of the sun. This project involves supplying homogeneous, precision MK spectral types of the 3600 stars in the sample, and deriving the basic physical parameters for these stars. Spectroscopic data, as soon as it is reduced, is placed on the website of the project: http://stellar.phys.appstate.edu. So far, over 1000 stars have been observed, and most of their spectra are available publically. The site also includes spectra of many MK Standards. Meetings MK Process 2003: A Festschrift for R.F. Garrison on his 66th Birthday Dates: May 9-10, 2002 (tentative) Location: Tucson, Arizona As mentioned in the Editor's Notes on page 1, Robert Garrison will retire at the end of this academic year. A number of his former students, colleagues and friends are organizing a scientific meeting to honor him on his retirement. Bob has been a colleague, a friend, a mentor and/or a teacher to many of us who work in the area of Standard Stars, and his views and philosophy have had an important influence on our work. During his career, Bob worked in the fields of stellar spectroscopy, the morphological classification of galaxies and galactic structure, directed the University of Toronto Southern Observatory for nearly 25 years and guided legions of MSc and PhD students through their projects. But Bob is best known for his work in MK Spectral Classification, and hence the title of this meeting. This meeting will be in the tradition of meetings on the MK System and Process held every ten years. The two most recent were ``The MK Process and Stellar Classification'' held in Toronto in 1983, and ``The MK Process at 50 years. A Powerful Tool for Astrophysical Insight'' held in Tucson in 1993. Those who are interested in attending or contributing to the scientific content of this meeting are invited to contact Richard Gray (grayro@appstate.edu). As the title of the meeting implies, we plan to publish the proceedings. Contributions to the next Newsletter}, due out in October 2001, 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 \end{verbatim} \end{document}