The Suzaku satellite has provided unique X-ray data from 0.2 to 300 keV with its combination of the X-ray Imaging Spectrometer (XIS) and Hard X-ray Detector (HXD) since its launch in July 2005. In the next observing cycle (AO-4) from April 2009 through March 2010, the Suzaku mission intends to initiate a program of Key Projects. Key Projects are defined as comprehensive observing programs sampling a number of objects of a particular class, or surveying a large region of the sky, in order to take maximal advantage of the unique attributes of Suzaku to address important astrophysical problems. Investigators are invited to propose Key Projects to NASA or JAXA. As these projects require a substantial investment of observing time, proposers are encouraged to include in their team US and Japanese collaborators.

The Suzaku project plans to reserve up to 2 Ms annually for the Key Projects, by drawing time from the US-J collaborative category and both US and Japanese national times. It is expected that at least 2 Key Projects will be underway at any time. If a Key Project requires more than the time available in a year it will be extended until complete.

Key Projects will be solicited annually. As existing Key Projects are completed, new ones will be initiated. Ongoing projects that take more than one year to complete will be reviewed annually to ensure they are being productive.

Proposals

Key Project proposals have the same components of ordinary guest observer proposals. They consist of a scientific justification, a feasibility demonstration of both observations and program, and a target list. The scientific justification must explain the scientific problem, how proposed observations address this problem, and how the proposed program makes use of the strengths of Suzaku. All proposals must be written in English. Those written in Japanese are automatically rejected without being sent to the refereeing process. Up to 8 pages are allowed for the science justification (text, figures, and tables).

Data rights

All Key Project data flow directly into the Suzaku public archive. This guarantees maximum exploitation of the data. The PI of a successful proposal will be expected to serve as the scientific lead for observation planning.

Time critical and TOO Key Projects

Operational constraints preclude the possibility that a Key Project consist entirely of time constrained observations or TOOs. It is possible to include in a Key Project a subset of constrained observations. As is the case for constrained observations during the regular proposal cycle, the imposition of a constraint or the need for a TOO must be well justified. 15% is the guideline of TC+ToO time for Key Projects and regular targets.

Proposal selection

For selection in AO-4, Key Project proposals will be solicited and submitted as part of the AO-4 call for GO proposals. The initial screening of these proposals will be by the respective national review panels. The final selection of Key Projects will be made at the Suzaku international merging committee meeting. Proposers with highly ranked proposals in the national programs will be invited to present and discuss their proposal with the merging committee.

Since key projects will be selected at the same time as targets for the general guest observer program, care will be exercised to minimize disruption of the general program. In particular, if a target proposed in a Key Project appears in a regular GO proposal with an equal or longer observing time and is ranked A or B, the target will be awarded to the PI of the regular proposal, with full one-year proprietary rights.

Selection of Key Projects in subsequent rounds might be performed through a separate solicitation from the general call for observing proposals.

Proposal Submission to Japan

Principal Investigators (PIs) affiliated with institutions outside the US should submit Key Project proposals to ISAS/JAXA for X-ray observations with the Suzaku observatory from April 2009 (PIs in the US must submit their proposals to NASA). It is forbidden for the same group to submit identical Key Project proposals both to ISAS/JAXA and to NASA. Key Project proposals that require more than 1 calendar year are allowed, unlike for the regular proposals. Key Project proposals to ISAS/JAXA are due at 12:00JST (3:00UT) on Friday, December 5, 2008, to be submitted electronically using the Remote Proposal-submission System (RPS), which can be followed from

http://www.astro.isas.jaxa.jp/suzaku/proposal/index.html.en

We also intend to update the Technical Description document, as well as planning tools, with latest information in early October, which will be found at

http://www.astro.isas.jaxa.jp/suzaku/doc/suzaku_td/

Existing versions should suffice for early planning of proposals, but may not give accurate results when detailed simulations are performed.

Appendix: Examples of potential Key Projects

The following are examples of potential Key Projects, listed by the Suzaku team in the 2008 proposal of the US Suzaku Project to the NASA Senior Review of operating missions. Observer may propose one or more of these projects, or any other they conceive.

• Survey of LMXB Lines to Constrain Neutron Star Parameters: With line detections possible in approximately 30 systems, Suzaku is poised to constrain stellar radii in a large number of sources. A large sample of such constraints is essential to finally characterizing the ultra-dense matter equation of state observationally.
• Solving the Mystery of the 30 keV X-ray Background: The 30 keV peak of the cosmic X-ray background discovered with HEAO-1 has been attributed to absorbed AGN. Swift and INTEGRAL have discovered numerous absorbed sources. Suzaku uniquely classifies these objects by simultaneous, sensitive observations of their soft and hard component. Suzaku will thereby determine the contribution of these objects to the 30 keV peak. This sensitive survey is instrumental to future missions such as NuSTAR or Fermi gamma-ray Space Telescope.
• Survey of Unidentified Extended Galactic TeV Sources: HESS has discovered numerous extended Galactic TeV sources, some of which have no apparent counterparts in other bands. Suzaku is the ideal followup observatory for a systematic survey of these enigmatic sources, with its sensitivity to low surface brightness and hard response. Many of these sources are unusual pulsar wind nebulae, and the relationship between the X-ray and TeV surface brightness and spectrum sheds light on the emission mechanism. A dozen of so of these objects are now known; each can be characterized using 1Ð3 brief (~ 50 ks) Suzaku exposures. VERITAS and MAGIC will undoubtedly add to the catalog of TeV sources suited for Suzaku followup.
• Investigating Dark Energy using Clusters: A carefully designed Suzaku Key Project would accurately measure w0, the Dark Energy equation of state parameter. Modest duration Suzaku observations will yield average temperatures for the 500 brightest clusters from the ROSAT All-Sky Survey (compared with the ~50 used for previous such X-ray studies). A total observation time of <2 Ms is required. The data analysis will derive the local cluster number density, N(kT). Suzaku's modest spatial resolution is not an impediment because only an average temperature is required. Five hundred clusters are enough to measure the relationship between cluster observables (e.g., flux) and mass. Based on previous X-ray measurements using smaller samples (Henry 2004) and simulations (Majumdar & Mohr 2004) we estimate improvements of a factor of 11.2 and 5.8 for Omega(matter) and w0 over existing measurements from any method. Both Henry (2004) and Majumdar & Mohr (2004) include systematic uncertainties in the mass-temperature calibration.
• Low Abundance Nucleosynthesis Products in SNRs: Different SN explosion models make very different predictions about the yields of the Fe group elements (Cr, Mn, Fe, Ni). Suzaku's combination of area and resolution make possible through deep observations the most sensitive searches for Cr, Mn and Ni in the growing number of known young (< 2000 yr) SNRs in the Galaxy and the Magellanic Clouds and mapping in some Galactic remnants.

September 8, 2008

Kazuhisa Mitsuda (Project Manager, ISAS/JAXA)
Tadayuki Takahashi (Project Sub-manager, ISAS/JAXA)
Hideyo Kunieda (Project Scientist, Nagoya University)