IAU Commission 30: Radial velocities Newsletter November 1999 Dear members and consultants of IAU Commission 30 This newsletter will be briefer than my last attempt to communicate with all members of the commission (in January 1998). However there are several points to raise. 1. Officers and organizing committee. I will repeat here the names of the current officers of the commission (president, vice-president and organizing committee of eight). They are: President: John Hearnshaw (that's me!) University of Canterbury, Christchurch, New Zealand Fax: +64 (3) 3642469 email: j.hearnshaw@phys.canterbury.ac.nz Vice-president: Andrei Tokovinin Sternberg State Astronomical Institute Moscow, Russia Fax: +7 095 939 16 61 email: toko@sai.msu.su but currently at Observatoire de Lyon CRAL/Observatoire de Lyon 9 avenue Charles Andre 69561 Saint-Genis-Laval France email: toko@obs.univ-lyon1.fr Fax: 33 4- 78 86 83 86 Organizing committee: a) serving until 2000 Bill Cochran Univ. Texas, Austin, USA Frank Fekel Tennessee State Univ., Nashville, TN, USA Birgitta Nordstrom Niels Bohr Institute for Astronomy, Copenhagen Bob Stefanik Center for Astrophysics, Cambridge, MA, USA b) serving until 2003 Tsevi Mazeh Wise Observatory, Israel Nidia Morrell Univ. Nacional de La Plata, Argentina Hernan Quintana Univ. Catolica de Chile, Santiago, Chile Stephane Udry Geneva Observ., Switzerland Among the functions of the OC is that of advising the president and vice-president and helping compile our triennial report (recently completed) as well as commenting on the requests for our commission's support in applications for IAU conferences. 2. Commission 30 procedures for the election of new officers I thought it would be useful to remind all members of our commission's procedures for electing new officers. These procedures don't formally get underway until early next year. However, there is some benefit in issuing them in this newsletter, so that members who wish to nominate or be nominated for vice-president or the organizing committee can now consider doing so with some lead time. The procedures were devised by our former president, Colin Scarfe, in 1996 and I thank him for placing the election of officers in Commission 30 on a transparent and democratic basis. 1. The terms of office of the president and vice-president will be three years. The normal expectation will be that the vice-president succeeds the president in that office, and an election for a president will be required only if the vice-president were unable or unwilling to do so. A new vice-president will be elected every three years, however. 2. In addition to the president and vice-president, the organizing committee will consist of eight members, four to be elected every three years. Thus the term of office will be six years, after which the retiring members will be ineligible for re-election to the committee for three years, but would be eligible for election to the vice-presidency. 3. Each triennial election will be conducted by a nominating committee, which will consist of the current president, his or her predecessor, and the vice-president if he or she is prepared to succeed the president. If not the other two members may, if they choose, co-opt a third member. 4. Six months before a General Assembly the nominating committee will a) ascertain whether the current vice-president is willing to succeed to the role of president, b) send to all members a list of the current composition of the organizing committee, indicating those who are completing their six-year terms, and c) solicit nominations for the position of vice-president and four new members of the organizing committee (and for a new president if necessary). Nominations may be made by any two members of the commission, and should be accompanied by an indication by the nominee that he or she is willing to serve. Nominations should be in the hands of the nominating committee three months before the General Assembly. 5. The nominating committee will then nominate further candidates to ensure a full slate, with a view to achieving as much of a balance as possible between geographic areas and fields of research for the full organizing committee, including the continuing members. 6. If a ballot is necessary it will be mailed two months prior to the general assembly, and all votes received before the commission's first business meeting will be valid. If no ballot is required, owing to the number of nominees being equal to that of the positions to be filled, the names of the new vice-president and members of the organizing committee will be announced prior to the General Assembly. 3. Membership and consultants Eleven new members have joined Commission 30 since the last General Assembly. They are: 1) Dr M. Al-Malki King Saud Univ., Riyadh, Saudi Arabia malmalki@ksu.edu.sa comms: none 2) Dr H.-H. Bernstein Astron. Rechen-Institut Heidelberg, Germany s03@ix.urz.uni-heidelberg.de comms: 8 3) Dr D. Dravins Lund Observatory Lund, Sweden dainis@astro.lu.se comms: 9, 12 , 29, 36 4) Prof. D. F. Gray Univ. of Western Ontario, London, Ontario, Canada dfgray@uwo.ca comms: 29, 36 5) Prof. G.R. Isaak Univ. of Birmingham, Birmingham, UK. gri@star.sr.bham.ac.uk comms: 35 6) Dr B. Khalesseh Ferdowsi Univ, Mashhad, Iran no email address, fax +98 51 838032 comms: 42 7) Dr D. Popper UCLA Los Angeles, USA popper@bonnie.astro.ucla.edu comms: 42 8) Dr D.J. Stickland Appleton-Rutherford Lab Berks, UK ds@astro1.bnsc.rl.ac.uk comms: none 9) Dr L. Szabados Konkoly Observatory, Budapest, Hungary. szabados@buda.konkoly.hu comms: 26, 27, 42 10) Dr G. Szecsenyi-Nagy ELTE University Budapest, Hungary. szena@ludens.elte.hu comms: 27, 36, 37, 46 11) Dr J. Vinko JATE University Szeged, Hungary vinko@physx.u-szeged.hu comms: none We warmly welcome all these new members to Commission 30. At the last General Assembly there were six new members and three consultants who joined Commission 30. The total membership is now 116 and the total number of consultants remains at 3. (Consultants are people active in the area of the commission's work but who are not members of the IAU. Being a consultant is seen as a temporary status conferred by the IAU Executive Committee to allow them to participate in Commission activities.) I have had no notifications of members leaving our commission since the last General Assembly. Overall, this is a fairly healthy growth in membership from three years ago, though I am sure that the actual number of astronomers world-wide with some interest in radial velocities may be double our current membership. Our membership is however just 1.4 per cent of the IAU total membership, indicating ours to be a very small commission. A full list of commission 30 members and consultants can be found on the Web at: http://www.phys.canterbury.ac.nz/~phys012/iau30/iau30.html (N.B.: this URL will change after August 2000.) 4. Recent radial-velocity conference Although many recent conferences have had some relevance to radial velocities, one in particular was organized by Commission 30. This was IAU Colloquium 170 `Precise stellar radial velocities' held at the University of Victoria, BC, Canada in June 1998. The conference proceedings were published in September 1999 and the following is a summary of the meeting: IAU Colloquium, Precise Stellar Radial Velocities Held at University of Victoria, BC, Canada, 21-26 June 1998 Published in ASP Conference Series vol 185 (1999) Editors J.B.Hearnshaw and C.D.Scarfe IAU Colloquium 170, on Precise Stellar Radial Velocities, was sponsored by IAU Commission 30 (Radial Velocities), with the support of Commissions 9, 26, 27, 29, 36 and 42; Division IX was the coordinating division. The scientific organizing committee was chaired by John Hearnshaw (New Zealand), with David Latham (U.S.A.) as deputy chairman, and included Gilbert Burki (Switzerland), Paul Butler (U.S.A. - Australia), William Cochran (U.S.A.), Dainis Dravins (Sweden), David Gray (Canada), Roger Griffin (U.K.), Alan Irwin (Canada), Michel Mayor (Switzerland), Tsevi Mazeh (Israel), Robert McMillan (U.S.A.), Larry Ramsey (U.S.A.), Colin Scarfe (Canada) and Robert Stefanik (U.S.A.) Fourteen years of rapid progress had elapsed since the last IAU meeting on stellar radial velocities (Colloquium 88), and hence this meeting was timely. In particular, the previous three years had seen the first detection of extrasolar planets, as a result of the substantially higher precision of radial velocities achieved by the use of CCDs. The scope of the Colloquium was deliberately broad, and included all effects on stellar spectral lines which involve the Doppler effect, and give rise to line broadening and line asymmetry, as well as a discussion of gravitational redshifts. Thus stellar rotation, stellar convection, binary star orbits, pulsating variable stars, spotted stars and asteroseismology were all discussed at Colloquium 170. The meeting took place between Sunday June 21 and Friday June 26, 1998, at Victoria, B.C., Canada. Its venue was Dunsmuir Lodge, a conference center of the University of Victoria, located on a wooded hillside some 20 km from the university campus, but overlooking the Victoria airport. Almost all the participants from outside Victoria were housed at the Lodge, which provided much opportunity for informal discussion away from sessions. Sixty-seven people from nineteen countries participated in the Colloquium. The local organizing committee was chaired by Colin Scarfe, with Alison Marchant, administrative officer of the university's Physics and Astronomy Department, as its treasurer. Other members were Russell Robb, Stephenson Yang and Alan Irwin from the university, and Murray Fletcher and Alan Batten from the Dominion Astrophysical Observatory (DAO), part of the Herzberg Institute of Astrophysics of the National Research Council of Canada. Lorraine Charron served briefly as the committee's secretary, and Ann Scarfe, assisted by Margaret Robb, organized a program of activities for the companions of participants. The meeting was structured around a series of about 20 invited talks, with contributed papers related to them presented either orally or as posters. It proved to be possible to allow each poster paper to be discussed briefly orally as well. The discussion proved often to be quite lively, but with controversial topics treated in a good-humoured fashion. The difficult task of summing things up was ably handled by Gordon Walker. Subsequent to the meeting, a few papers were published elsewhere, or were merged by agreement between their authors. Three of the invited talks, however, were not submitted to the editors for more than a year, despite repeated reminders and entreaties. They were ``Searching for Giant Planets at the Haute Provence Observatory'', by Michel Mayor et al., ``Radial Velocities: Other Planetary Systems, Solar and Stellar Seismology'', by George Isaak, and ``Asteroseismology of Sun-like Stars with the Advanced Fiber Optic Echelle'', by Tim Brown. To avoid further delay, the editors have reluctantly decided to proceed without those contributions, although aware that this volume is the poorer as a result. The editors would like to thank all the other participants for providing their manuscripts, many of them promptly and a few somewhat more tardily. The organizers would like to thank the IAU Executive Committee for its support, as well as the University of Victoria administration, primarily Dean of Science John Weaver and Acting Associate Vice-President for Research Howard Brunt. Many members of the Physics and Astronomy Department, and several members of the staff of the DAO, in addition to those named above, provided material assistance with the arrangements. In particular, Russell Robb, Rob Cardinal and Chris Aikman set up and maintained the audio-visual equipment and recorded the discussion, Gerry Justice arranged Internet links to Dunsmuir Lodge, and Don Moffatt and Frank Younger conducted an evening tour of the DAO. The entire staff of Dunsmuir Lodge, led by its manager, Robin Cameron, and its conference officer, Leslie Solojuk, worked hard to ensure a pleasant and comfortable environment for the meeting. To all, we express our gratitude on behalf of all the participants. 5. Conference proposals supported by IAU Commission 30 Over the last 18 months or so the Commission's Organizing Committee has considered seven requests for the support of proposed conferences, be they IAU symposia, IAU colloquia or IAU Joint Discussions at the forthcoming General Assembly. The proposals to which we gave our Commission's support were as follows: a) Galactic astrophysics from Hipparcos to the future Proposed 30 April 1998 By Heiner Schwan and Elena Schilbach IAU Symposium, St Petersburg, June 99 Not supported by IAU Executive b) Sky surveys for the third millennium Proposed 6 May 1998 By Noah Brosch IAU Symposium, Aug.-Sept 99, Garching, Germany Not supported by the IAU Executive c) The Sun in astrophysics Proposed 25 Jan 1999 By Peter Foukal One day JD at GA, Manchester, Aug 2000 Not supported by the IAU Executive d) Designations of stellar companions Proposed 1 March 1999 By Helene Dickel JD at GA; later proposed as a multicommission meeting e) Formation of binary stars Proposed 27 Feb 1999 By Hans Zinnecker AIP Potsdam, spring 2000 Accepted as IAU Symp. 200 f) Extragalactic star clusters Proposed 24 Sept. 1999 By Eva Grebel and Doug Geisler IAU Symposium, Mar 2001, Concepcion, Chile 6. Commission 30 meetings at the General Assembly The IAU General Secretary has asked presidents of commissions to state what meetings commissions wish to hold at the General Assembly, in Manchester, England August 7-18 2000. We are being offered a 1.5 hour time slot for our business meeting, when working groups would also report to the commission. In addition we may hold a scientific meeting (up to half a day), and one such purpose for a scientific meeting might be to discuss a proposal by Dainis Dravins (Lund) for the precise definition of a radial velocity (see item 7 below). That meeting could be held jointly with other commissions. Are there any further suggestions, either for a topic or theme or resolution to bring to a scientific session of the commission, or for any matter to bring to the business meeting? IMPORTANT NOTE: Any request we make for time at the General Assembly must be lodged by December 1, 1999, which is very close! 7. Proposal for the precise definition of a radial velocity Dainis Dravins at Lund Observatory has recently drafted a proposal for the precise definition of radial velocity, taking into account various general relativistic effects. The full proposal is still in draft form; once it is finalised it will be placed on the Web and it will be an important matter for discussion at the forthcoming IAU General Assembly at Manchester, England in August 2000. It is possible that it will be a type C resolution handled by Commission 30 with support from other commissions. Meanwhile I thought it would be useful for members of Commission 30 to have some kind of preview of the proposal, so I am including the main part of Dainis' proposed definition here. I thank Dainis for the considerable amount of hard work and insight he has put into this matter. * * * * * On the definition of a spectroscopic "radial-velocity measure" Distributed to divisions I, IV, V, VI, VII, IX and X, and Commissions 8, 27, 29, 30, 31, 33, 34 and 40 of the International Astronomical Union Recognizing 1. That recently improved techniques for determining radial velocities in stars and other objects, reaching and exceeding precision levels of meters per second, require the definition of "radial velocity" to be examined; 2. That, due to relativistic effects, measurements being made inside gravitational fields, and alternative choices of coordinate frames, the naive concept of radial velocity being equal to the time derivative of distance, becomes ambiguous at accuracy levels around 100 m/s; Considering 1. That, although many effects may influence the precise shifts of spectroscopic wavelengths and frequencies, only local ones (i.e. arising within the solar system) can be reliably calculated. These local effects depend on the gravitational potential of the observer and the observer's position and motion relative to the solar-system barycenter; 2. That, although the wavelength displacement (or frequency shift) corrected for such local effects can thus be derived from spectroscopic measurements, the resulting quantity cannot unambiguously be interpreted as a radial motion of the object; Therefore recommend That, whenever radial velocities are considered to a high accuracy, the spectroscopic result from a measurement of shifts in wavelength or frequency is given as the [barycentric] "radial-velocity measure" cz, after correcting for gravitational effects caused by solar-system objects, and effects by the observer's displacement and motion relative to the solar-system barycenter. Here, c equals the conventional speed of light = 299,792.458 km/s, and z = (lambda - lambda0)/lambda0, where lambda0 is the rest-frame wavelength and lambda the wavelength observed by a hypothetical observer at zero gravitational potential, located at, and being at rest with respect to, the solar-system barycenter. The radial-velocity measure cz is expressed in velocity units: to first order in z it coincides with the classical concept of "radial velocity", while avoiding the implicit interpretation as physical motion. The solar-system barycenter is defined by Resolution A4 adopted at the IAU XXI:th General Assembly in 1991, and supplemented by Resolution B6 at the IAU XXIII:th General Assembly in 1997. 8. IUE radial velocities The following email from Myron Smith, Space telescope Science Inst., was received in March 1998 and may be of interest to Commission 30 members. I am writing you as President of IAU C30 to ask you who among its members might be interested in establishing RV standards for for UV spectra and whether such standards already exist. In turn, I'd like to communicate to them the following information on RV's I've determined from UV spectra. In connection with recent work in evaluating the IUE "NEWSIPS" (the modern processing system of IUE data for its final archiving) data products, I've been looking into various systematics of radial velocities in various high dispersion IUE spectra. One of the more interesting findings in my study so far has been a wavelength-dependent difference of apparent radial velocity between the NEWSIPS-processed IUE images and the older "IUESIPS"-processings of the same images, a difference which spans about 4--5 km/s in along the wavelength (SWP) camera range. I believe that I have traced this particular systematic to systematic differences in the NIST laboratory wavelengths which were used to calibrate the wavelengths the IUESIPS and NEWSIPS processing systems, that is wavelengths determined in the 1970's and 1990's for emission lines in the platinum-neon calibration lamps. There was a hint of a recognition of this problem in the original calibration of the Copernicus wavelength system for the Tau Sco atlas, see comments in Rogerson & Upson, ApJ, 35, p. 38). These authors used the "old'" and probably erroneous, PtNe lab values for their reference wavelength system instead of values they derived from a modeling of the optical system of the Copernicus spectrograph. The sense of the discrepancy they found is the same as I have found, but the magnitude they quote is apparently twice as large. The wavelength system problem of course may extend to other satellites apart from the IUE, and would be particularly insidious if the systems of contemporaneous satellites were tied uncritically to the system of an early- era mission. I am writing both to let you know about this potential problem and to find out what the history is for establishing RV standards in the UV. I am aware that the conventional procedure is to tie RV's measured from UV lines (e.g., ISM) in the optical region. Yet, if there is a danger of the determined RVs in particular narrow wavelength ranges being established from calibration errors from lab sources, it may be that this procedure should be modified or at least brought up to date. I have been having some difficulty finding someone who admits to being an expert in the area RV standards in the UV. Thus, I am hoping that you as C27 President can forward this message to anyone who might be able to speak more authoritatively to the issue of RV standards in the UV. Thank you for your attention and interest. Best wishes -- Myron Smith 9. Commission 30 triennial report The triennial report of Commission 30 has just be sent to the IAU General Secretary and will appear in the volume Reports on Astronomy 1999 (Trans. IAU XXIV A). There are sections by most members of the Comm. 30 Organizing Committee on the following topics: Radial velocities of galaxies Hernan Quintana The Milky Way Frank Fekel Star clusters Nidia Morrell Spectroscopic binaries Tsevi Mazeh Pulsating stars Andrei Tokovinin Extrasolar planets William Cochran Standard radial velocity stars Robert Stefanik and Stephane Udry Bibliography of stellar radial velocities Hugo Levato as well as miscellaneous information on conferences and radial-velocity websites. Since the report is rather long, I have placed it on the Web and not in this newsletter. You can find it at: http://www.phys.canterbury.ac.nz/~phys012/iau30/iau30rep