Science Analysis Group
Broad-Band X-ray Observatory
The Broad-Band X-ray (BBX) Science Analysis Group (SAG) will focus on identifying the scientific opportunities that require coverage beyond the typical capabilities of focusing soft X-ray facilities like Chandra, XMM-Newton, and Swift/XRT. Membership, including volunteers from the PhysPAG and broader astrophysics and technology communities, is open.
About BBX SAG
Astrophysics Will Critically Need a High Angular Resolution Broad-Band X-ray Mission
Possibilities to be explored include a flagship-class mission with multiple instruments, or multiple missions operating in tandem.
This SAG’s mission is primarily focused on the science case available to different configurations.
Subscribe to the BBX SAG Email List about Astrophysics Will Critically Need a High Angular Resolution Broad-Band X-ray Mission
Nicknamed the "Hand of God," this object is called a pulsar wind nebula. It's powered by the leftover, dense core of a star that blew up in a supernova explosion. The stellar corpse, called PSR B1509-58, or B1509 for short, is a pulsar: it rapidly spins around, seven times per second, firing out a particle wind into the material around it -- material that was ejected in the star's explosion. These particles are interacting with magnetic fields around the material, causing it to glow with X-rays. The result is a cloud that, in previous images, looked like an open hand. The pulsar itself can't be seen in this picture, but is located near the bright white spot.
One of the big mysteries of this object is whether the pulsar particles are interacting with the material in a specific way to make it look like a hand, or if the material is in fact shaped like a hand.
NuSTAR's view is providing new clues to the puzzle. The hand actually shrinks in the NuSTAR image, looking more like a fist, as indicated by the blue color. The northern region, where the fingers are located, shrinks more than the southern part, where a jet lies, implying the two areas are physically different.
The red cloud at the end of the finger region is a different structure, called RCW 89. Astronomers think the pulsar's wind is heating the cloud, causing it to glow with lower-energy X-ray light.
In this image, X-ray light seen by Chandra with energy ranges of 0.5 to 2 kiloelectron volts (keV) and 2 to 4 keV is shown in red and green, respectively, while X-ray light detected by NuSTAR in the higher-energy range of 7 to 25 keV is blue.
Much of the progress to our understanding of high-energy astrophysical phenomena made over the past decade was driven by coordinated observations between multiple X-ray missions. Observations covering a wide range of energy enabled the simultaneous study of thermal and non-thermal physical processes in extreme environments such as shock waves, jets, accretion discs, and X-ray coronae. Many of these vary on short time scales. However, current high-energy broad-band observations are still limited by the lack of high angular resolution capabilities at energy ranges beyond Chandra's bandpass. Moreover, new multi-messenger facilities, both on the ground and in space, will increase the number of variable and transient objects by orders of magnitude in the upcoming decade. A high angular resolution broad-band X-ray mission will be critically needed by the astrophysics community to investigate the nature of these sources.
The Broad-Band-X-ray (BBX) Science Analysis Group (SAG) will focus on identifying the scientific opportunities that require coverage beyond the typical ~0.2 to ~10 keV capabilities of focusing soft X-ray facilities like Chandra, XMM-Newton, and Swift/XRT. Examples include:
- Directly detecting and understanding the obscured X-ray population that constitutes the bulk of the cosmic X-ray background at its peak (20-30 keV).
- Understanding physics in extreme environments through simultaneous broad-band observations from soft X-rays up to 100 keV or more.
- Resolving faint extended emission in sites of particle acceleration, such as AGN jets and shock waves in supernova remnants and galaxy clusters.
To support this effort, the SAG will also evaluate the state and impact of various technical capabilities, such as energy range, throughput, and field of view requirements, as well as time-domain monitoring and response strategies. Possibilities to be explored include a flagship-class mission with multiple instruments, or multiple missions operating in tandem. This SAG’s mission is primarily focused on the science case available to different configurations - there should only be high-level discussion about the engineering or budgetary realities associated with any particular design.
The SAG co-chairs were selected by the X-ray SIG (XRSIG) chairs. Membership on the SAG, including volunteers from the PhysPAG and broader astrophysics and technology communities, is open.
The SAG will organize its work into thematic working groups (WGs) corresponding to the science categories to be defined by the SAG co-chairs with inputs from the XRSIG, with an additional WG focused on technical enablers and mission architecture. WG leads will be selected by the XRSIG chairs. Each WG will be responsible for gathering community input through email solicitations, teleconferences, and meetings at venues such as the HEAD and AAS meetings.
The SAG will hold regular virtual meetings and coordinate across WGs. The final deliverable will be a community-vetted report to NASA HQ in 2026 summarizing the science case and technical drivers for future studies of X-ray mission(s).
SAG Chairs
| Name | Institution |
|---|---|
| Chien-Ting Chen | USRA/MSFC |
| Kristin Madsen | GSFC |
| Daniel Stern | JPL |
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