1. Editorial

There has been much hard work and some major developments during the six months since the first MONS Newsletter. We now have an excellent idea of how the Rømer satellite will look. The next six months will see the end of the System Definition Phase and the start of detailed design work. Meanwhile, the astronomy teams have been busy discussing targets, constructing theoretical models and arranging workshops. Remember that the activities in the MONS Science Consortium have been organized around five groups: Solar-like Oscillations; B Stars; A and F Stars; Planets and Eclipsing Variables; and Ground-based Support Observations. Further details can be found at
http://astro.ifa.au.dk/MSC/#science_groups

The aim of this Newsletter is to keep the community informed of developments and opportunities in the project. We welcome articles, reports and comments - please e-mail them to the Editor:

Tim Bedding (bedding@physics.usyd.edu.au)

2. Update on the Rømer Mission

We are currently in the System Definition Phase (SDP), in which the design of the Rømer mission is to be defined. That will be followed by the Detailed Design Phase, whose name speaks for itself, and the Implementation Phase, in which the satellite will actually be built (subject to funding, of course). Here are the highlights of the past six months:

Fourth MONS Workshop:: This workshop (24-29 August 2000) was dedicated to selection and modelling of solar-like targets for the MONS Telescope. The outcome, described in Section 3 below, was a list of targets with assigned priorities and a plan for further work.
Mid-Term Review:: At this meeting (25-26 October 2000), an external panel assessed the status of the Rømer mission. They gave some valuable recommendations on all aspects of the project, and urged that a decision on the inclusion of the Ballerina X-ray telescope be taken soon.
Decision to cancel Ballerina:: On 20 November 2000, it was announced by the Danish Space Research Institute that it was too risky for the Danish Small Satellite Programme to pursue the combined mission, and that the study must therefore continue with a single-experiment mission based on the MONS proposal.
Extension of the System Definition Phase:: The decision to go with MONS alone required some changes to the design of the satellite. A new baseline design was chosen (see Section 2.1 below) and the System Definition Phase was extended by four months to allow the design to be properly defined. This phase is now scheduled for completion at the end of May 2001.

2.1 The New Baseline Design

The main features of interest to the astronomers who will use MONS are as follows:

MONS Telescope:

The telescope will perform simultaneous red and blue photometry on a highly defocused stellar image. The general design that has been developed during the System Definition Phase is not significantly affected by the removal of Ballerina. The aperture diameter has been reduced to 32cm to improve baffling. Without this change, southern targets such as $\alpha$ Cen and $\beta$ Hyi would suffer serious contamination from scattered Earth light falling on the primary mirror. The reduction in aperture will not affect noise levels for brighter targets, since noise for these stars is dominated by the stellar background (i.e., granulation). Fainter stars will be affected, but we expect the loss of photons to be mostly offset by improvements in the precision of the attitude control system that are made possible by the removal of Ballerina.

MONS Field Monitor:

There has always been a concern that photometry by the MONS Telescope would be affected by neighbouring stars, especially variables. The original proposal was to use ground-based images to characterize the field around each target, which should allow correction for any contaminating stars. Given the importance of this issue, it was decided to include an extra camera on the satellite, the MONS Field Monitor, which will obtain in-focus observations of the field simultaneously with the MONS Telescope. The Field Monitor will essentially be a copy of the Star Trackers, but with a longer focal length lens to give a field of view of about 1 degree. The need for intensive ground-based checkouts before launch is therefore greatly reduced.

Pointing restrictions:

In order to expose the solar panels to sunlight, the MONS Telescope must point close to 90 degrees from the Sun. Targets near the ecliptic plane can therefore only be observed during one of two windows, six months apart. Unfortunately, these windows are poorly placed for ground-based observations, being six months either side of the optimum date. Targets at higher ecliptic latitudes can be observed by MONS for greater fractions of the year.

Another restriction on the pointing of the MONS Telescope arises from the need to avoid pointing too close to the Earth and Moon. The Moon may interrupt observations of fields near the ecliptic plane for a few days a month. The Earth will affect observations of southern objects, since the satellite spends most of its orbit high over the northern hemisphere, and the exact region affected will precess during the two-year mission. The improved baffling (see above) will allow all high-priority targets to be observed.

Star Trackers:

The choice of two Star Trackers (STs), one forward- and one backward-facing, has now been finalized. This is to ensure that at least one should be unaffected by the Earth and Moon. The field of view of each ST is 11 degrees in radius, but the exclusion angle to the Earth is much greater (currently 50 degrees). Pointing closer than this to the limb of the Earth results in a high level of scattered light and prevents useful ST observations.

Note that limits to on-board computer power mean that only one ST will be in operation at a time, even if both are clear of the Earth and Moon. Given the orbit, the ST that happens to be pointing south will often be affected by the Earth. Those interested in parallel science with the STs should therefore assume, to a first approximation, that the more northerly of the two ST fields will be observed for most of the time. For some stars near the equator, we will be able to choose which ST field to observe, but for many there will not be a choice. In those cases, it is not possible to say which ST will be free of Earth interference until the date of the observations is fixed.

The fraction of stars in each ST field for which photometry can be obtained is not yet clear, since it depends on the rate at which the ST is required to give updates to the Attitude Control System. We aim to have at least one hundred stars per field.

3. The Fourth MONS Workshop: Selection and modelling of solar-like targets

This workshop was held 24-29 August 2000 at Aarhus University, Denmark. Local participants were: Jørgen Christensen-Dalsgaard, Søren Frandsen, Frank Grundahl, Hans Kjeldsen, Frank Pijpers, Dennis Stello, Teresa Teixeira, Lars Peter Rasmussen and Maria Pia Di Mauro. International participants were: Tim Bedding (Australia), Wojtek Dziembowski (Poland), Douglas Gough (UK), Günter Houdek (UK), Jaymie Matthews (Canada), Mario Monteiro (Portugal), Mike Thompson (UK) and Mutlu Yildiz (Turkey).

The aim was to assign priorities to solar-like targets for the MONS Telescope. We considered the expected signal-to-noise and the desire to cover an interesting range in stellar parameters. The outcome of the Workshop is summarized in Table 1, with stars grouped according to the following priorities:

1.: Very high priority. Should definitely be observed.
2.: High priority. Should be observed.
2b.: High priority but may not be feasible. Should be observed if feasible.
3.: Excellent target. A small subset of this group will be observed
3b.: Excellent target but may not be feasible. Should be added to Priority 3 list if feasible.

The 2b and 3b groups were created for stars which are very interesting, but which may not show solar-like oscillations because of S/N limitations, or because they are too hot. We suggest that these stars could be checked out for one or two orbits to determine feasibility. There are also plans to have some fraction of the MONS Telescope time devoted to targets chosen from the other Science Groups.

The next tasks are to obtain detailed information on all these targets (from publications and, where necessary, new observations), and to construct theoretical models. Progress can be followed at the Web site of the Solar-Like Oscillations Group, accessible via
http://astro.ifa.au.dk/MSC/#science_groups
In particular, see the simulated time series of $\alpha$ Cen A and B. Follow the links or go directly to:
http://astro.ifa.au.dk/~hans/mons/SDP/simulations
You are encouraged to analyse the simulated data and try to extract the frequencies!

$\begin{center}\vbox{\input{mons-news-2000-dec-table.tex} }\end{center}$

4. The First COROT/MONS Workshop on Ground-Based Support Observations

In order to prepare the target selection, a photometric and spectroscopic survey is planned of bright main target candidates as well as fainter targets. The data obtained from different sites will be used for an automatic classification to derive effective temperature, gravity, and metallicity of stars. The spectra will also be used to derive detailed element abundances, rotational velocities, and to detect spectral peculiarities, using specific software to analyse the line profiles.

The first COROT/MONS Workshop on ground-support observations for the astereoseismologic space missions will take place on January 11 and 12 in the city of Ghent, Belgium. Details are given on http://www.vub.ac.be/STER/MONS/wscorotmons.html.

During this two-day workshop we shall discuss which existing tools must be applied for these tasks, and which tools should be adapted and further developed to give the maximal support to the space missions through groundbased support. At the same time we shall discuss operational aspects of the groundsupport activities. Please indicate your intended participation to Chris Sterken (csterken@vub.ac.be).

5. Other news

5.1 Related space missions

Integration of the MOST Instrument (http://www.astro.ubc.ca/MOST/) is scheduled to start in early-February 2001, and environmental testing will take place in (northern) spring and summer 2001. The Project is still on schedule to deliver a payload for launch by early 2002.
The funding for COROT is now secure and work is proceeding. For more on COROT, see:
http://www.astrsp-mrs.fr/projets/corot/pagecorot.html.
Eddington was proposed to ESA and has been listed as a reserve mission. The 1st Eddington Workshop on ``Stellar-structure and habitable planet finding'' will be held at Cordoba (Spain), 11-15 June 2001. For details, see:
http://astro.esa.int/SA-general/Projects/Eddington/
The star tracker on the WIRE satellite (http://www.ipac.caltech.edu/wire/), having produced some very nice results, has now ceased science operation.

5.2 Recent papers on solar-like oscillations

Is your paper missing from the following list? Please let the Editor know whenever you publish a paper on solar-like oscillations, so that future issues of this Newsletter can be as complete as possible.

Journal articles:

Seismic study of stellar convective regions: the base of the convective envelope in low-mass stars
M.J.P.F.G. Monteiro, J. Christensen-Dalsgaard and M. J. Thompson
MNRAS, 316, 165 (2000)
$\alpha$ Centauri AB
Guenther, D. B. and Demarque, P.
ApJ, 531, 503 (2000)
The detection of multimodal oscillations on $\alpha$ Ursae Majoris
Buzasi, D., Catanzarite, J., Laher, R. et al.,
ApJ, 532, L133 (2000)
Evolutionary model and oscillation frequencies for $\alpha$ Ursae Majoris: a comparison with observations
Guenther, D. B., Demarque, P., Buzasi, D., et al.,
ApJ, 530, L45 (2000)
Calibrations of $\alpha$ Cen A & B
P. Morel, J. Provost, Y. Lebreton, F. Thévenin and G. Berthomieu
A&A (accepted; http://arXiv.org/abs/astro-ph/0010180)
Evidence for solar-like oscillations in $\beta$ Hyi
T. R. Bedding. R. P. Butler, H. Kjeldsen et al.
ApJ Letters (accepted; http://arXiv.org/abs/astro-ph/0012417).

Conferences and workshops:

Helio- and Asteroseismology at the Dawn of the Millenium,
SOHO 10/GONG 2000 Workshop, October 2-6, 2000, Santa Cruz de Tenerife, Spain.
Proceedings to be published as ESA SP-464.
Talks:
- Current status of asteroseismology
  H. Kjeldsen and T. R. Bedding
  (http://arXiv.org/abs/astro-ph/0011354)
- Convective overshooting in the evolution and seismology of $\eta$ Bootis
  M. P. Di Mauro and J. Christensen-Dalsgaard
- Asteroseismology of subgiants
  D. B. Guenther
- Ultra precise photometry from space: exploring pulsation with the "Humble Space Telescope"
  J. Matthews
- Observations of p-modes in $\alpha$ Cen
  J. Schou and D. L. Buzasi
- Asteroseismology with the space mission COROT
  A. Baglin
Posters:
- Seismology of solar-type stars
  S. Basu, J. Christensen-Dalsgaard, M.J.P.F.G. Monteiro and M. J. Thompson
- Structure and rotation of solar-like stars seen by COROT
  G. Berthomieu, T. Toutain, T. Corbard, et al.
- The effect of turbulent pressure on the p-mode frequencies in stellar models
  P. Demarque, L. H. Li, F. J. Robinson, et al.
  (http://arXiv.org/abs/astro-ph/0011064)
- COROT instrument: Constraints and solutions
  G. Epstein, M. Auvergne, A. Baglin and the COROT team
- Asteroseismology results from MUSICOS multi-site campaigns
  B. H. Foing et al. (MUSICOS collaboration)
- Observing solar-like oscillations with ELODIE spectrograph
  M. Martic, J. C. Lebrun, J. Schmitt, T. Appourchaux
- Seismic detection of chemical gradients below the base of the convective envelope
  M.J.P.F.G. Monteiro
- $\alpha$ Centauri binary system: calibration and oscillations
  P. Morel, J. Provost, Y. Lebreton, F. Thévenin and G. Berthomieu
- Lithium in young suns
  L. Piau and S. Turck-Chieze
- Scanning the HR diagram: oscillation power as a test of stellar turbulence
  S. Reza, M.-J. Goupil, Y. Lebreton and A. Baglin
- Radiative hydrodynamics in the highly super-adiabatic layers of stellar evolution models
  F. J. Robinson, P. Demarque, S. Sofia et al.
  (http://arXiv.org/abs/astro-ph/0011065)
- A method to extract p-mode frequencies from solar-like stars acoustic spectra with S/N>1/100
  T. Roca Cortés, C. Régulo and R. Alonso
Recent Insights into the Physics of the Sun and Heliosphere: Highlights from SOHO and other Space Missions, IAU Symposium 203, 7-11 August 2000, Manchester, UK.
Proceedings to be edited by P. Brekke, B. Fleck, and J. B. Gurman (ASP Conf. Series)
Talk:
- Recent Progress in Asteroseismology
  Christensen-Dalsgaard, J.
Posters:
- Structure and dynamics of Procyon A by a seismological approach
  M. P. Di Mauro et al.
- Generalization of a mixing-length model for nonradially pulsating stars
  G. Houdek and D. O. Gough
- Search for p-mode frequencies on Procyon A from 1997, 1998 and 1999 velocity observations
  M. Martic et al.
Hipparcos and the Luminosity Calibration of the Nearer Stars,
IAU GA Joint Discussion 13 August 2000, Manchester, UK.
To appear in Highlights of Astronomy Vol. 12 (APS Conf. Series)
Talk:
- Hipparcos luminosities and asteroseismology
  T. R. Bedding (http://arXiv.org/abs/astro-ph/0010623)

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Tim Bedding
2000-12-21