Collaboration Agreement: Chandra HETG Ultra-deep Gratings Spectroscopy of Sgr A* (CHUGSS), a.k.a., X-ray Visionary Program (XVP) of Sgr A*
1. Overview
Herein we describe the membership, publication and presentation policies, and data sharing rights of the team assembled to participate in the Chandra-High Energy Transmission Gratings Spectrometer (HETGS) X-ray Visionary Program (XVP) of Sgr A*. We recognize the long history of observations of Sgr A* at many different wavelengths that preceded and have been conducted independently of this campaign, but we also recognize that the XVP campaign has helped foster further opportunities for multi-wavelength observations of Sgr A*. We also recognize that the Chandra data is immediately public, such that any individual or group has the right to download and analyze it on their own. Conversely, much of the multi-wavelength data is not publicly available, and is associated with independent data rights agreements which must be honored.
We believe, however, that a dedicated group with a strong sense of cooperation and collaboration has the greatest opportunity to maximize the science that will come from these observations. Additionally, the analyses of the gratings data, and all associated multi-wavelength observations will be technically challenging. We plan to use this collaboration to share expert knowledge and best practices, as well as to provide expert-validated data products among members of the collaboration. We are providing a secure, password protected web site (www.sgra-star.com) for collaboration members to securely share data products, detailed schedules, and drafts of analyses and papers.
This document describes an organizational structure, consisting of a Science Steering Committee (SSC) and topical Working Groups (WG), and the policies and practices under which this collaboration will operate. It is meant to foster a sense of common purpose so that everybody who contributes to the program will be fairly represented, and that no one will receive an undue share of the credit by excluding other members of the collaboration. We cannot anticipate all possible circumstances, so we ask that all members of the collaboration abide by both the letter and spirit of this agreement.
2. Collaboration Organization
The collaboration consists of two levels. The top level is the Science Steering Committee (SSC), whose principle jobs will be to determine collaboration membership (defined essentially by compliance with this document), foster communication among all members of the group, and aid in resolution of any conflicts. At the next level are the Working Groups (WG), who will provide vetted data products to the collaboration as well as bring together individual collaboration members who share common research goals. Each WG will have coordinators responsible for setting the goals and agenda for that working group, as well as aid in determining publication priorities.
2.1 Science Steering Committee (SSC)
The Science Steering Committee will consist of the initial coordinators of the Chandra XVP proposal — Frederick Baganoff (MIT-Kavli), Michael Nowak (MIT-Kavli), and Sera Markoff (University of Amsterdam) — as well as Geoffrey Bower (UC Berkeley), Andrea Goldwurm (CEA-Saclay), and Charles Gammie (University of Illinois).
The SSC will determine collaboration membership and help implement the policies within this document.
2.2 Working Groups (WG)
The Working Groups (WG) are open to any interested member of the collaboration willing to actively contribute to the goals of each individual WG. However, each group has a set of coordinators who are responsible for setting the agenda of that WG and helping the group reach consensus about publication priorities. Our initial suggestions for the coordinators of the WGs are outlined below. Once we have established the coordinators of the WGs, other collaboration members will be able to join a given WG by contacting these coordinators.
* Chandra Data Products: Joey Neilsen (Boston University), John Davis (MIT-Kavli), John Houck (MIT-Kavli), Q. Daniel Wang (UMass Amherst)
This group will take the lead in creating spectra and response files for each individual Chandra observation that is further sub-divided into periods of quiescence and flare periods. They will be conducting studies into the best methods for creating background spectra for the gratings spectra, and eventually provide those data products. Longer term goals will be to provide zeroth order spectra for distinct spatial regions around Sgr A*, as well as create products for diffuse emission and other sources. Additionally, they will provide lightcurves and the times of flares.
* Accretion Flow Quiescent Spectra (i.e., ADAF, Jet, and continuum modeling): Feng Yuan (SHAO), Chris Fragile (CofC), Heino Falcke (RU Nijmegen), Joey Neilsen (Boston University of), Sergei Nayakshin (University of Leicester)
This group would be concerned primarily with the Chandra zeroth order spectrum from within the Bondi radius (i.e., the “point source” spectra), and when available with a reliable background, the Chandra-HETGS spectra. These would be combined with multi-wavelength spectra, when available, to address issues concerning the accretion flow onto the black hole.
* Central Parsec Diffuse Spectra (i.e., plasma diagnostics): Q. Daniel Wang (UMass Amherst), Li Ji (Purple Mountain Observatory), Sergei Nayakshin (University of Leicester)
This group would be concerned with spatially resolved spectra from the Chandra zeroth order, and may be able to take advantage of line information from the Chandra-HETGS with a relatively less well-modeled background.
Given the uncertainty over the best theoretical models for the observed Fe line, there will be some overlap of interest with the Accretion Flow Quiescent Spectra working group. A diversity of approaches is of course welcome, and it will be up to the SSC to mediate any issues between these two WG.
* Flares, X-ray Properties: Jason Dexter (UC Berkeley), John Tomsick (UC Berkeley/SSL), Delphine Porquet (Observatoire de Strasbourg), Joey Neilsen (Boston University), Nathalie Degenaar (University of Michigan)
This group will be considering the spectral and temporal properties of the flares in the X-ray band. This would include averaged spectra for weaker flares, individual spectra for brighter flares, statistics concerning their fluences, peaks, and temporal distributions, etc. This will also include theoretical interpretation of the results.
* Flares, Multi-wavelength Properties: Mark Morris (UCLA), Stefan Gillessen (MPE), Daniel Marrone (University of Arizona), Daryl Haggard (Northwestern University), Karl Kosack (CEA-Saclay)
Not all Chandra-HETGS observations will have multi-wavelength observations associated with them, and even those that do will not necessarily show flare activity. Furthermore, there will likely be a number of different combinations of observatories for the different flaring periods. This group will specifically deal with any multi-wavelength observations of flares where the Chandra XVP data are part of the analysis. Work that does not include, nor refer to or rely upon previously unpublished results from the Chandra XVP data, are not the purview of this document.
* Flares, VLBI/EHT Observations/Constraints on Geometry: Sheperd Doeleman (MIT-Haystack), Vincent Fish (MIT-Haystack), Geoffrey Bower (UC Berkeley), Andreas Brunthaler (MPIfR)
This group focuses specifically on radio/mm interferometric observations attempting to constrain geometry and polarization changes associated with Sgr A* activity. This WG recognizes that VLBI observations are in some ways a separate category onto themselves, because changes in VLBI-observed properties from before to after a major flaring period, even if not including strictly simultaneous observations of flares with Chandra, could likely be an important avenue of study. As with the other Multi-wavelength Flare WGs, this WG will deal with any VLBI analyses where the Chandra XVP data are part of the analysis (used as constraints, etc). Work that does not include, nor refer to or rely upon previously unpublished results from the Chandra XVP data, are not the purview of this document.
* Non-Sgr A* Studies: Jon Miller (University of Michigan), Casey Law (UC Berkeley), Rudy Wijnands (University of Amsterdam)
This group primarily will deal with studies of point sources and extended emission from the Galactic Center, most likely utilizing the Chandra-HETG zeroth order, that is not associated with Sgr A* and its immediate environs.
* Theory: Charles Gammie (University of Illinois), Jason Dexter (UC Berkeley)
This group will focus on theories of accretion onto Sgr A*, including inflow/outflow solutions and jets, and Sgr A* flares. They will work with the other working groups to interpret the spectral, temporal and morphological properties of Sgr A* revealed by the data accumulated during this project.
2.3 Additional Working Groups
Based upon the suggestions of collaboration members, the SSC will establish additional WGs, and identify the core members of these new WGs, as necessary.
2.4 Inclusion of other individuals
Members of the various WGs may wish to enlist the aid, e.g., of grad students and/or postdocs working with them in order to assist with analysis and/or interpretation. Any such individuals need to be approved by the SSC, and they must agree to all the policies laid out in this document.
2.5 Requests from Outside Individuals
It is likely that members of this collaboration will receive requests from other individuals for data products, information about unpublished results, or assistance in performing their own analyses of the publicly available Chandra XVP data. Collaboration members will refer these requests to the SSC for consideration on a case by case basis.
It is understood that normally the WGs will have the first opportunity to publish the XVP data. In some cases, however, unpublished XVP data could play a secondary role in an analysis by external collaborators (e.g., providing upper limits during a multi-wavelength observation). The SSC, in coordination with the relevant WG, will determine the policies for any collaboration with outside members, in adherence with the spirit of this document.
3. Data Access
We have created a password protected web site, www.sgra-star.com. Members of the collaboration (i.e., those who agree to this document) will be able to register at the web site and then be granted access to the non-public web pages. This will be a secure site where we will place reduced data products.
Registered users who request Publishing access to the web site (by separately e-mailing Michael Nowak) will also be able to securely place data products from the XVP campaign, as well as from any other relevant multi-wavelength observations, on these pages. It is understood that members of this collaboration will not give access to the non-public pages of this web site to any other individuals.
We will also use the web site to maintain a list of papers, conference proceedings, talks, and press releases associated with the Chandra XVP. This will aid collaboration members in submitting project reports to the appropriate funding agencies.
4. Publication Policy
Any works that explicitly include analysis of the Chandra XVP data, or rely upon or are strongly informed by unpublished results of the Chandra XVP data (such as MW observations which referred to the Chandra XVP in the proposal or used Chandra scheduling constraints for XVP observations) are subject to the publication policies of this document.
WGs are given the first opportunity to publish the XVP data. WGs will come to an agreement among themselves as to which members of the WG will lead the Chandra analyses. The WG will inform the SSC of works in progress, and in turn the SSC will ensure that various WG are not competing against one another. The SSC will resolve any conflicts between separate WGs, or any conflict that the WG itself cannot resolve.
4.1 Refereed Papers
The author list of any refereed paper should include all the actively participating members of the WG, as well as the members of the Chandra Data Products WG if the paper has made use of the provided data products (if even just for preliminary analysis).
For papers originating within a WG, the lead authors are to be determined by the WG. The authors should circulate a draft of the paper at least two weeks prior to submission to all the members of the WG and to the SSC. The SSC members are to be included in the authorship only if they have contributed actively to the coordination of the observations, the analyses presented, or the writing of the paper.
Papers that involve multi-wavelength data are also subject to any existing restrictions and agreements associated with the facilities used to procure those data. Especially in cases where the paper is being driven by data from outside of the XVP collaboration, the SSC together with the relevant WG, will help establish the order of authorship.
All XVP related papers will credit the entire collaboration in the acknowledgments section with reference to the URL listing the collaboration members (https://www.sgra-star.com/collaboration-members).
4.2 Conference Proceedings and Talks
Members are encouraged to present and disseminate published results within talks and conference proceedings; however, any dissemination of Chandra XVP data and analysis that has not been published must be approved by the SSC prior at least one week prior to abstract submission in the case of a conference, and at least one week prior to presentation for more general talks (e.g., a departmental colloquium). Collaboration members should share with the relevant WG members and the SSC any plans to present even published Chandra XVP data, at least one week prior to abstract submission for a conference. This is to ensure that multiple collaboration members do not submit significantly overlapping abstracts to the same conference.
As for refereed papers, conference proceedings that involve multi-wavelength data are also subject to any existing restrictions and agreements associated with the facilities used to procure those data.
As for refereed papers, the full collaboration membership should be acknowledged via reference to the membership list maintained at the web site.
4.3 Press Releases
For any press releases that involve data or analyses from the Chandra XVP, whether or not they are the primary focus of the press release, the Chandra Press Office should be offered the opportunity to participate in these press releases. Appropriate reference to the XVP collaboration should be made by citing the collaboration web site. Collaboration members should contact the SSC if there is any question of whether the Chandra Press Office should be involved in any given press release.