NuSTAR Target of Opportunity (ToO) or Directors Discretionary Time (DDT) observation request

NuSTAR ToO and DDT observation requests will in general not be considered for events or sources that could have been predicted and proposed for in General Observer (GO) programs. This restriction is being adopted as a result of guidance from NASA's 2019 Senior Review.

In particular, requests for observations of the following types of sources and events require special justification describing why the requested observation type could not have been proposed as a GO target:

  • Known or candidate black hole systems
  • Known or candidate pulsar or magnetar systems
  • Candidate counterparts of gravitational wave or astrophysical neutrino detections
  • Nova or Supernova events
  • Luminosity variations from known or candidate AGN (including blazars and Tidal Disruption Events)
  • Observations of the Sun or other Solar system objects
  • Observations of events with specific time constraints
  • Observations coordinated with other observatories that could have been proposed for to joint GO programs
As a specific example, binary systems where periastron intervals are known can be proposed to the GO program, with observations triggered from monitoring of activity by other observatories. Observations that are simultaneous with ground or space based activities can also be proposed to the GO program, even if the exact dates for the coordinated observations are not known at the time of the proposal.

We encourage the community to propose to the various peer reviewed GO programs for NuSTAR ToO observations. Observations of all selected GO ToO observations automatically have the highest priority for scheduling.

Active ToO/DDT observations
EP250702a2x20 ks for NuSTAR GO cycle-11 proposal 11282PI Pasham
IC 4329A20 ks coordinated with XRISMPI Mizumoto
4U 1630-472up to 500 ks coordinated with NICER for the joint NICER / NuSTAR cycle-10 proposal 10216PI Garcia
4U 1630-4723 x 25 ks coordinated with NICER for NuSTAR GO cycle-10 proposal 10309PI Adegoke
Last updated: 2025-07-03 15:30 UTC

Please review the NuSTAR schedules for details of upcoming observations and the table of approved ToO programs from the NuSTAR GO program and joint GO programs with Chandra, XMM-Newton, INTEGRAL, NICER, IXPE, and the Neil Gehrels Swift Observatory.

Principal requester
Name
Institute
Primary Email address
(additional email address can be supplied in the Remarks section below)
Best way to reach me
24 hr Contact info
(Phone numbers etc)
Scientific Justification
Object type
Triggering an approved GO program? If yes, then give mission and GO proposal number:
Scientific Justification

Not required for approved NuSTAR or joint GO ToO proposals

For DDT requests please review the information at the top of this page and emphasize why the observation could not have been proposed to a GO program
(max 2000 characters)
Relevant URLs
(one per line)
Justification for this particular target
(max 1000 characters)
Likelihood of detection, duration,
and recurrence of transient behavior
(max 400 characters)
Response time requested

Note that response times < 48 hours are reserved for GO programs and/or unique astrophysical transients (e.g., local group supernovae, etc.)

Examples: < 24 hours , < 48 hours , within 1 week , at directors discretion (DDT)

Justification for response time

The majority of approved DDT have response times >48 hours to 1 week
(max 1000 characters)
Target details
Target Name
RA (J2000 decimal degrees from 0.0 to 360.0)
Dec (J2000 decimal degrees from -90.0 to 90.0)

from until
Date/time format options are described here. Default is UTC, unless you specify another time zone.

Observing time (kiloseconds)

The minimum exposure time is 20 ks

Note that the majority of approved DDT observations have exposure times of 40 ks or less


Justification for observing time

Give details of any source modeling, particularly for exposure time requests above 40 ks
(max 1000 characters)
Expected NuSTAR count rate

Predicted instrument count rate for both modules using 50% PSF extraction with no dead time


Counts / sec, both telescopes combined, not including background

HEASARC WebPIMMS can be used (set "Into:" field to 'NUSTAR'), is available here

Maximum expected NuSTAR count rate
(in case of flaring, bursts, etc.)
Counts / sec, both telescopes combined, not including background
Approximate expected spectrum
Power law, absorbed, etc.
(max 80 characters)
Source morphology
Coordination with other observatories?
Provide the observatory name(s) and the following details if available:
  • Are you planning on submitting a request?
  • Have observations already been approved?
    • Give proposal number and selection category (A,B,C etc.)
    • or request ID number
  • Have the observations been scheduled?
    • provide any observation timing information
(max 1000 characters)
Other Remarks
(max 1000 characters)

Clicking the Submit! button sends emails and text messages to the NuSTAR operations team. A confirmation email will be sent to the 'Primary Email address' field at the time of submission.

The request will be reviewed by the NuSTAR PI and the operations team and you will be contacted with a decision to approve or decline the request.

NuSTAR data associated with ToO or DDT requests submitted outside of approved GO programs will have no exclusive use period and, when completed, will be available via the public NuSTAR archive. See heasarc.gsfc.nasa.gov/docs/nustar/nustar_archive.html for more information.

A minimal set of data products for ToO/DDT observations performed within the last 14 days is also available as each observation progresses via the NuSTAR quicklook products webpage. Please carefully read the caveats on the use of this data detailed on the quicklook webpage.

Please contact   nustar-help at srl.caltech.edu   if you have any questions.