STANDARD STAR NEWSLETTER No 37 An electronic publication of the Working Group on Standard Stars(IAU Commissions 25, 29, 30, 45) No. 37 editor: Richard O. Gray October 2004 grayro@appstate.edu CONTENTS: Editorial ``The Cosmological Implications of Our Work'' p. 1 Note from the Working Group Chair, Chris Corbally p. 2 Notes and Abstracts: Hoeg, E., Skiff, B, Griffin, R.E. p. 2 Meetings: The A-star Puzzle Meeting Report p. 7 From the editor The Cosmological Implications of Our Work The Standard Star Newsletter is a publication of the Standard Stars Working Group, supported by a number of IAU commissions. Its goal is to keep the astronomical community up-to-date on issues related to standard stars for all purposes -- radial velocities, MK classification, photometry, polarization, elemental abundances, etc. This newsletter is also intended to serve as a forum for discussions about standard stars, and it is to this purpose that I direct your attention. This issue includes a note from Erik Hoeg on a very important topic -- the calibration of astronomical photometry for faint stars. While we are now blessed with linear (or near linear) electronic detectors, there are still significant problems in extending the magnitude system to very faint stars, 20th magnitude and fainter. Apparently we do not know the size of the systematic errors at the faint end of the magnitude scale. This uncertainty may have cosmological implications! What better forum than the SSN to address this problem? Please send in your ideas and comments. If there is sufficient interest, I will set up a web forum for this discussion so that we do not have to wait for the next issue of the SSN. I will publish or summarize the contributions from this discussion in the next issue. In addition to Erik's note, we have a long contribution from Brian Skiff on his new compilation of spectral types. Readers will be happy to hear that this compilation includes references to the literature for each spectral type! I have already accessed this catalog and have extracted information on a number of stars of interest. There is also a note from Elizabeth Griffin on ozone and Be II measurements (another topic with cosmological implications!), and an abstract of a report on the ``A-star Puzzle'' meeting, written by Mike Dworetsky---psst! more cosmological implications! I have provided links to this report on the SSN website. Please pick it up and read it; it is a wonderful report. A Note From the Chair International Astronomical Union Working Group on Standard Stars (WGSS) 'Tis the Season ... for preparing proposals for IAU meetings in 2006, mostly centered around the General Assembly in Prague, Czech Republic. As of 21 September, 24 proposals for symposia were in preparation, 7 colloquia, 10 joint discussions, and 3 special sessions. Obviously not all the 21 symposia proposed to coincide with the GA can be accepted, but it is clear from the titles of the proposed meetings that this GA will be one rich in presentation of research work and in discussions. Do make sure that this GA's dates, August, 14-25, 2006, are in your calendar, and I hope you can find the resources you need to be there. Of direct interest to the readers of this newsletter would be the symposium entitled, "The Future of Photometric, Spectrophotometric and Polarimetric Standardization", proposed by Chris Sterken and Arlo Landolt. Since I am involved with a proposal for a joint discussion, I am experiencing from the inside the kind of work behind their preparations so far, and I wish this proposal every success in becoming an actual IAU-sponsored symposium during the GA. I know that many of you will be asked to help improve and/or to evaluate one or more of these proposals. This is how we try to end up with the best meetings possible, best for our science of astronomy, best for our own participation in that science. I also know that, despite other demands on your valuable time, you will do what you can to help all the organizing committees. With my best wishes for your own researches, Chris Corbally corbally@as.arizona.edu The Calibration of Astronomical Photometry of Faint Stars A Note from Erik Hoeg The calibration of astronomical photometry is of general interest and we would like to see what role a well calibrated GAIA photometry could play. What is the present state of the art for bridging the gap from about 10th to 20th apparent magnitude, which is an interval where GAIA could contribute? GAIA is an approved ESA cornerstone mission designed for launch in 2011. The GAIA mission will provide unprecedented positional and radial velocity measurements with accuracies needed to produce a stereoscopic and kinematic census of about one billion stars in our Galaxy and the Local Group. Combined with astrophysical information for each star, provided by on-board multi-colour photometry, these data will have the precision necessary to quantify the early formation, and subsequent dynamical, chemical and star formation evolution of the Milky Way Galaxy. Some astronomers have therefore been asked, what are the systematic errors of faint magnitudes obtained with e.g. the HST or VLT? This has implications for the accuracy of, e.g., the cosmic distance scale. It is generally agreed that the question is important, and one experienced photometrist, A.T. Young (2004, priv. comm.) would not be surprised if the systematic errors at the faintest end of the scale for HST exceed 0.1 mag. A paper by Heyer et al. (2002) considers the accuracy of WFPC2 photometric zeropoints and gives ``tentative" conclusions. The ``true uncertainty" of WFPC2 zeropoints is currently about 0.02-0.03 mag. The mean scatter between different studies using wide bands is between 0.016 mag for F555W and 0.043 mag for F336W. Since Poisson statistics for these studies would predict that 1% absolute accuracy should be attainable, the authors conclude that there are still systematic error sources which have not yet been identified. Readers of this Newsletter are encouraged to send their opinions to Erik Hoeg, erik@astro.ku.dk. Editor's Note: This newsletter is an ideal venue for a general discussion on this topic. If you have expertise in this area, please contribute a note for the next issue of the SSN (see Editorial, page 1). References: ESA 2000, GSR (the Gaia Study Report), GAIA: Composition, Formation and Evolution of the Galaxy, Technical Report ESA-SCI(2000)4 Photometric and imaging performance GAIA-CUO-091.pdf 2 Aug. 2001 E. Hoeg available on: http://www.astro.ku.dk/~erik/gaia/ The Accuracy of WFPC2 Photometric Zeropoints. I. Heyer et al. (2002) In: 2002 HST Calibration Workshop http://www.stsci.edu/largefiles/hst/HST_overview/documents/calworkshop/ workshop2002/CW2002_Papers/heyer.pdf A New Compilation of Spectral Classifications Brian A. Skiff Lowell Observatory, Flagstaff AZ Why a new, continued compilation? Spectral classifications, far from being a ``dead art", continue to accumulate at a rapid rate. Over 5000 classifications appear in the literature published in 2003. These frequently are not readily accessible in searches by object-name or coordinates in SIMBAD/ADS, and thus cannot be associated with objects detected at various wavelengths. Jaschek-Kennedy-Buscombe It is easy to dismiss Bill Buscombe's numerous compilations, starting in 1977, comprising nearly 300,000 entries. These sadly lacked any citations whatsoever apart from those cribbed from Kennedy, for which he was castigated in comments appearing, for instance, in successive triennial IAU commission reports. In addition, for tens of thousands of stars the complete spectral type was inferred or, worse, ``invented" from broadband colors and/or proper motion, for instance by assuming that faint IRAS-detected M-type stars are giants. Something more than half of the stars appearing in his last three catalogues (13th, 14th, and 15th from 1998, 1999, and 2001, respectively) were taken from lists prepared by me, and so are included in the present compilation with full details. Apparently unable to switch from an antiquated UPPER-CASE ONLY 80-column IBM card format, Buscombe's object-names and types are often bizarrely truncated, abbreviated, or simply omitted altogether. For faint objects coordinates are omitted. The resulting catalogues seem rather garbled. At the CDS catalogue service, only Buscombe's 3rd, 12th, 13th, and 14th catalogues are available, but other data centers have most of the remaining volumes (the 5th and 6th never seem to have been made available in machine-readable form). By comparison the classic MK catalogues by Mercedes and Carlos Jaschek (and their collaborators) and by Pam Kennedy suffer mainly by sins of omission. In their effort, one suspects, to get the job done in their own lifetimes, they generally omitted stars not contained in the HD catalogue or one of the Durchmusterungen. It was certainly also the case at the time that determining coordinates for fainter stars was non-trivial. Probably for this reason stars in open clusters and outside the Galaxy were omitted (viz. at the time, in the Clouds). Similarly, classifications from the many large objective-prism surveys were usually not included unless a complete MK type was given for an HD/DM star. Stars in these surveys were typically identified only on charts similar to the HDE charts and thus coordinates were not readily found. The Jascheks also omitted details of the classifications beyond the bare temperture type and luminosity class with no provision for comments. An example is the well-known survey of Am stars by Osawa (1959ApJ...130..159O), where all the metallic-line and Ap stars are given as only that, skipping all the details of the classifications as published in the notes to his tables. On the other hand, they also did not omit types that were merely copied from antecedent papers. A good example is the much-cited Hiltner OB photometric survey (1956ApJS....2..389H), where some 1200 types are duplicated almost entirely from the similarly-famous contemporaneous paper by Morgan, Code, & Whitford (1955ApJS....2...41M). More surprising is that the Jaschek/Kennedy canvassing of the literature is far from complete. After noticing several lacunae among older papers that should have been listed (complete MK types from slit spectra of HD stars in mainstream journals) I made a test by indexing ``all" journals for the year 1962, nominally covered by the original 1964 La Plata catalogue, which claims to be complete through 1963. About one-third of the readily available papers were not indexed, skipping a variety of interesting stars. After 1963 the indexing becomes progressively less complete: in the 1978 compilation no papers at all are cited from the ApJ for 1975! Thus what might be considered a golden era of classification in the 70s and 80s---efficient (photographic) spectrographs on large telescopes in both hemispheres---is poorly represented in Kennedy's final (1983) catalogue. In general, they also list types shown only in tables: isolated items appearing in the notes to tables or in the text were overlooked. Many older papers do not have object-associations (i.e. object-wise indexing) in SIMBAD/ADS, and thus the results presented in them are invisible to on-line searches. Finally, Kennedy includes several hundred stars without coordinates, and also shows some types inferred from photometry, possibly inadvertently in error, since some of the indexed papers give types from spectra for the same stars. The three Jaschek and Kennedy catalogues are available from the CDS catalogue service and can be queried from VizieR as items III/18B (the original 1964 catalogue), III/42 (the 1978 `selected MK types' file by Mercedes Jaschek), and III/78 (the final Kennedy extension of 1983). What have I done? The new compilation is being made available through the CDS as item III/233A. The current version from May 2004 contains about 107,000 entries. I add a few thousand new entries per month. The recent literature has been canvassed through mid-2003 extending back to 2001, and the year 2000 is underway. A lot of old material has been added as well, mainly to fill gaps left by the Jascheks but also as interest in a particular list of stars strikes me. It is not obvious what the priorities should be. The main task is finding or determining coordinates for the stars. Even in recent work it is often the case that positions are not given or are erroneous when given. Most of the positions are drawn from precision astrometric catalouges on the J2000 ICRS system, specifically (at present) UCAC2, Tycho-2, or the all-sky 2MASS catalogue. Other lesser astrometry exists in the catalogue as well, the star-lists having been built in the years since 1995. In terms of sheer star-count, the bulk of my work has been directed toward building catalogues for large objective-prism surveys done at Case, Crimea, and Stockholm/Uppsala. I have explored some of the work done at Abastumani and elsewhere. All of McCuskey's northern Milky Way `LF' fields are complete, comprising some 20,000 stars. Francois Ochsenbein has kindly cobbled these together as a separate file at the CDS (II/221). Another list of 3600 stars at the Taurus/Gemini border by McCuskey (1967AJ.....72.1199M) has been larded into SIMBAD directly by Fabienne Woelfel at the CDS-Strasbourg. Another 30,000 stars from other surveys have also been worked over. Inter alia, probably some tens of thousands of identifications, corrections, and other links have been provided to SIMBAD for improvement of the database. Most of these corrections have been made by Gerard Jasniewicz. Another task was to make a list of standard 19-digit bibcodes for the references in the Kennedy catalogue, which again has been included and linked in the CDS file (III/78). Thus a query in the Kennedy catalogue produces not only the spectral type entry but also shows a Web link directly to the ADS for the paper cited. The format for my file is outlined byte-by-byte on the ReadMe page for the catalogue: http://cdsweb.u-strasbg.fr/viz-bin/Cat?III/233A Briefly, each entry includes the bibcode, a star name, coordinates, some magnitude except for variables, the type, and remarks. The star-name is either one given in the source paper (so that it can be recovered there) or a valid SIMBAD name. The maximum length is that of a complete 2MASS name. The source of the coordinates is shown by a letter code. The passband of the magnitude is similarly coded. The magnitude is mainly for identification and to give some indication of brightness. The spectral types as given in as complete a form as possible. The maximum length was set initially by the detailed types published by, um, the SSN editor, whose elaborate notation can extend not only the full length of the field allotted but also the full length of the space for remarks. The 20-line taster shown below gives a rough indication of what's included: faint, high-latitude white-dwarf and methane dwarfs from the Sloan survey; red variables observed at Harvard and Sonneberg; metallic-line stars; an entry from the excellent early survey by Petersson at the north celestial pole; other ordinary stars. 2001A&A...375..366C HE 2357-3054 0 00 00.94 -30 37 36.4 U 16.7 V C 1927MeUpp..29....1P BD+82 746 0 00 04.61 +83 06 19.9 T 9.5 V M 2000AJ....119..241L PHL 615 0 00 05.18 -17 08 51.5 b 16.9 V sdO5: He4 1928AnHar..79..161T Z Peg 0 00 06.56 +25 53 11.2 U 10.5 V M6-7e 1979AbaOB..51....1B [B79] SA 2 +75 32 0 00 06.64 +75 28 59.8 T 10.2 V A7IV 2004ApJ...607..426K SDSS J000007.1-094339 0 00 07.16 -09 43 39.8 S 20.0 R DA 1961MitVS.529....1G DM Peg 0 00 07.29 +18 44 17.1 U 11.0 V A6 CaI 4227A present 2004ApJ...607..426K SDSS J000011.5-085008 0 00 11.57 -08 50 08.4 S 19.1 R DQ 2004AJ....127.3553K SDSS J000013.5+255418 0 00 13.54 +25 54 18.6 S 14.7 J T4.5 2004ApJ...607..426K SDSS J000022.5-105142 0 00 22.54 -10 51 42.2 S 18.8 R DA5 2004ApJ...607..426K SDSS J000022.8-000635 0 00 22.88 -00 06 35.7 S 18.5 R DA 1975A&AS...21...25F BD+46 4233 0 00 23.25 +47 22 25.9 T 9.4 V A3mF2 1988AbaOB..66...33R BD+63 2091 0 00 30.74 +64 36 35.1 T 10.4 V B 1984AJ.....89..379H GV Peg 0 00 35.59 +26 39 49.5 U 13.0 V hF3mA8: 1949AJ.....54..102H GSC 1732-0121 0 00 38.51 +27 16 00.5 U 11.0 V K: prob dwarf near K0 1979AbaOB..51....1B [B79] SA 2 +74 24 0 00 40.26 +74 41 56.1 T 10.3 V M3:III: 1988AbaOB..66...33R BD+60 2652 0 00 41.34 +61 29 42.0 T 10.0 V B9 1924AnHar..99.....C HD 224801 0 00 43.63 +45 15 12.0 T 6.4 V A0pSi 1951BHarO.920...38Z HD 224801 0 00 43.63 +45 15 12.0 T 6.3 V A0Si 1988AbaOB..66...33R BD+60 2654 0 00 47.70 +60 48 49.8 T 9.9 V B9 The Purity of Be II Measurements R. Elizabeth Griffin Department of Earth & Space Sciences and Engineering, York University, Toronto, Canada Guest Worker, Herzberg Institute for Astrophysics, Victoria, BC, Canada The detection and measurement of Be and Li, seen principally in F--G stars, is of prime importance for assessing the ages of stars. Both Be and Li form ground-state doublets, and all four lines are susceptible to blending, particularly the Be II lines which are near lambda 3130A. But that uv region is also affected by the Huggins bands of telluric ozone (O3) absorption, which extend from lambda 3000--3400A. The features are some 15--20A broad, and near lambda 3130A they are fairly shallow (~10%) with respect to the stellar continuum (see Fig.1). One O3 feature occurs close to the Be II doublet, yet interpretations of stellar Be II measurements seem generally to have ignored it. As Fig, 2a indicates, for objects with negative or small positive velocities the Be II lines are not noticeably blended with the nearby ozone feature. However, for objects with high positive velocities -- as in some globular cluster or Population II stars -- the stellar Be II lines are red-shifted onto its flanks to an extent that could be significant in accurate calculations of stellar Be abundances. Even if the magnitude of the effect is only a few percent, the very high quality of spectra that can routinely be obtained now on faint objects requires that the existence of telluric O3 be taken into account in such instances. Similar precautions should be followed for any spectroscopic study that makes use of this spectral region. figure 1 caption The observable uv region of the spectrum of Vega. The smooth line (displaced downwards for clarity) is an ``absorption" spectrum of \o3 derived from laboratory cross-sections. The broad dips in the stellar continuum can be identified unambiguously as telluric O3 figure 2 caption The location of the Be II doublet in relation to telluric O3. a: the spectrum of Vega, with zero RV. b: the same spectrum of Vega but red-shifted by 2A (~200 km/s). The arrows mark the stellar wavelengths of the Be II doublet. The smooth line in both plots is the laboratory spectrum of O3} Submitted to Astronomy & Astrophysics For preprints, contact Elizabeth.Griffin@hia-iha.nrc-cnrc.gc.ca Meetings IAU Symposium 224: The A-star Puzzle A report, written by Mike Dworetsky, summarizing this meeting is now available. Although Mike generously gave me permission to include this very interesting report in the Newsletter, the length of this issue makes that impossible. However, Mike has given me permission to distribute this report via links on the SSN website (http://stellar.phys.appstate.edu/ssn). Please pick up a copy of this very well-written report. The abstract of his report follows: Abstract: Some highlights of Symposium 224 on ``The A-Star Puzzle'' are reviewed and transcribed from the author's ad hoc oral presentation on the final day of the meeting. Articles referred to are all contained in this volume, hence there are no figures or references. Topics include theory and observations of normal A stars, HgMn, Am, and Ap stars, lambda Boo stars, magnetic fields, rotation, convection, pulsations, supergiant stars, and observational methods including polarimetry, spectroscopy, and photometry. Contributions to the next Newsletter, due out in March 2005, 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