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GCN Circulars

GCN Circulars are rapid astronomical bulletins submitted by and distributed to community members worldwide. They are used to share discoveries, observations, quantitative near-term predictions, requests for follow-up observations, or future observing plans related to high-energy, multi-messenger, and variable or transient astrophysical events. See the documentation for help with subscribing to or submitting Circulars.

Search for Circulars by submitter, subject, or body text (e.g. 'Fermi GRB').
To navigate to a specific circular, enter the associated Circular ID (e.g. 'gcn123', 'Circular 123', or '123').
Advanced Search

To narrow the search results, use advanced search syntax. This allows for specifying which circular field to search (submitter, subject, and/or body). For additional information, refer to the advanced search documentation.

Advanced Search Examples (click to copy):

subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"

45 results found.

  1. LIGO/Virgo/KAGRA S250818k: SAO RAS BTA z-band observations of AT2025ulz
  2. LIGO/Virgo/KAGRA S250818k: GTC/OSIRIS Confirmation of Rebrightening of AT2025ulz
  3. LIGO/Virgo/KAGRA S250818k: VLA upper limits on AT2025ulz
  4. LIGO/Virgo/KAGRA S250818k: nature of the AT2025ulz/ZTF25abjmnnps OT
  5. LIGO/Virgo/KAGRA S250818k: Pan-STARRS imaging confirms re-brightening of SN2025ulz
  6. LIGO/Virgo/KAGRA S250818k: Continued Keck I LRIS spectroscopy of ZTF25abjmnps (AT2025ulz)
  7. LIGO/Virgo/KAGRA S250818k: FTW Observations Show Continued Reddening of AT 2025ulz
  8. LIGO/Virgo/KAGRA S250818k: MASTER predicovery limits of the AT2025ulz/ZTF25abjmnps KN candidate
  9. LIGO/Virgo/KAGRA S250818k: ENGRAVE observations of SN 2025ulz as a type II supernova
  10. LIGO/Virgo/KAGRA S250818k: Swift Observations of AT 2025ulz - Second Epoch
  11. LIGO/Virgo/KAGRA S250818k: CFH/MegaCam follow-up observation for AT2025ulz
  12. LIGO/Virgo/KAGRA S250818k: COLIBRÍ confirmation of rebrightening of AT2025ulz
  13. LIGO/Virgo/KAGRA S250818k: Rebrightening detected with Gemini/GMOS
  14. LIGO/Virgo/KAGRA S250818k: HST nIR detection of AT 2025ulz
  15. LIGO/Virgo/KAGRA S250818k: J-GEM follow-up observation for AT2025ulz
  16. LIGO/Virgo/KAGRA S250818k: PRIME nIR observations of AT2025ulz
  17. LIGO/Virgo/KAGRA S250818k: JinShan optical observations of AT2025ulz
  18. LIGO/Virgo/KAGRA S250818k: GTC/OSIRIS Optical Detection of AT2025ulz
  19. LIGO/Virgo/Kagra S250818k: STEP/T80N upper limits on 2025ulz
  20. LIGO/Virgo/KAGRA S250818k: 3 GHz MeerKAT observations of AT2025ulz
  21. LIGO/Virgo/KAGRA S250818k: Pan-STARRS coverage of the skymap and candidate counterparts
  22. LIGO/Virgo/KAGRA S250818k: NOT optical observations of AT2025ulz
  23. LIGO/Virgo/KAGRA S250818k: GRAWITA TNG NIR observations of AT2025ulz
  24. LIGO/Virgo/KAGRA S250818k: Continued fading and reddening of AT2025ulz from Keck/LRIS imaging observations
  25. LIGO/Virgo/KAGRA S250818k: ENGRAVE observations of AT 2025ulz
  26. LIGO/Virgo/KAGRA S250818k : Tautenburg observations, upper limits
  27. LIGO/Virgo/KAGRA S250818k: GOTO counterpart search and upper limits
  28. LIGO/Virgo/KAGRA S250818k: 10 GHz VLA observations of AT2025ulz
  29. LIGO/Virgo/KAGRA S250818k: WFST pre-discovery limits and follow-up observations of AT 2025ulz
  30. LIGO/Virgo/KAGRA S250818k: EP/FXT observation of AT 2025ulz
  31. LIGO/Virgo/KAGRA S250818k: WINTER J-band observations of AT 2025ulz
  32. LIGO/Virgo/KAGRA S250818k: Pan-STARRS grizy-band imaging and photometry of AT2025ulz
  33. LIGO/Virgo/KAGRA S250818k: Swift observations of AT 2025ulz
  34. LIGO/Virgo/KAGRA S250818k: Multi-band Gemini GMOS Detections
  35. LIGO/Virgo/KAGRA S250818k: ATLAS pre-discovery limits for AT2025ulz
  36. LIGO/Virgo/KAGRA S250818k: AstroSat CZTI non-detection and upper limits
  37. LIGO/Virgo/KAGRA S250818k: Upper limits from Fermi-GBM Observations
  38. LIGO/Virgo/KAGRA S250818k: Updated Sky localization and EM Bright Classification
  39. LIGO/Virgo/KAGRA S250818k: Pan-STARRS pre-detection limits for AT2025ulz
  40. LIGO/Virgo/KAGRA S250818k: Properties of the low-significance GW compact binary merger candidate potentially associated with AT 2025ulz
  41. LIGO/Virgo/KAGRA S250818k: Keck I LRIS spectroscopy of ZTF25abjmnps (AT2025ulz)
  42. LIGO/Virgo/KAGRA S250818k: FTW Fast reddening of AT 2025ulz
  43. LIGO/Virgo/KAGRA S250818k: FTW optical and NIR observations of AT 2025ulz
  44. LIGO/Virgo/KAGRA S250818k: Candidates from the Zwicky Transient Facility
  45. LIGO/Virgo/KAGRA S250818k: Coverage and upper limits from MAXI/GSC observations

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