Skip to main content
Updates to LVK & CHIME Notices, Schema v7.2.3! See news and announcements

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"

16161 results found.

  1. GRB 260211A: SVOM/VT optical observation
  2. GRB 260211A: GOTO optical upper limit
  3. GRB 260211A: LAST optical upper limit
  4. GRB 260210A: SVOM/GRM observation
  5. GRB 260211A: LCO optical upper limits
  6. GRB260131A/B: 3.6m DOT Optical Observations
  7. GRB 260211A: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  8. GRB 260211A: SVOM detection of a burst
  9. EP260209a: COLIBRÍ optical upper limit
  10. EP260209a: LCO optical upper limits
  11. GRB 260208A: LCO detection of the optical counterpart
  12. EP260210a: Optical upper limits with Kinder observations
  13. EP260210a: SVOM/VT optical upper limit
  14. EP260210a: COLIBRÍ optical upper limit
  15. GRB 260208C: SVOM/GRM observation
  16. GRB 260204A: Swift-XRT afterglow detection
  17. GRB260208A: Liverpool Telescope optical follow-up observations
  18. GRB 260208A: NuSTAR detection of prompt emission
  19. GRB 260131A/B: continued Mondy optical observations
  20. GRB 260208B: COLIBRÍ optical observations
  21. GRB 260208A: Mondy optical observations (duplicate submission)
  22. GRB 260208A: Mondy optical observations
  23. GRB 260208A: 1.3m DFOT optical detection
  24. GRB 260208A: COLIBRÍ optical observations
  25. GRB 260208B: EP-FXT observation
  26. GRB 260208A: NOT spectroscopic redshift z = 2.36
  27. GRB 260208A: Liverpool Telescope optical detection
  28. GRB 260208B: SVOM/VT optical candidate
  29. GRB 260208A: Zwicky Transient Facility Follow-Up of a Fermi GRB (Trigger 792220053)
  30. GRB 260208A: SVOM/VT optical observation
  31. GRB 260208A: Swift-XRT observations
  32. GRB 260208B: SVOM/GRM observation of a bright burst
  33. GRB 260208A: Fermi GBM Classification Correction
  34. GRB 260208A: GOTO detection of a potential optical counterpart (GOTO26aob)
  35. GRB 260208A : MASTER bright optical transient inside retracted Fermi error-box
  36. GRB 260207A : MASTER optical counterpart discovery
  37. GRB 260131A/B: Mondy and Terskol optical observations
  38. GRB 260204A: SVOM/VT confirms fading of the optical afterglow
  39. GRB 260204A: Swift-XRT observations
  40. GRB 260204A: LCO optical afterglow detection
  41. GRB 260204A: SVOM/VT optical candidate
  42. GRB 260204A : MASTER Global robotic net optical observations
  43. GRB 260204A: GOTO optical upper limit
  44. GRB 260204A: LCO optical upper limits
  45. GRB 260131A/B: OHP/T193 optical observations
  46. GRB 260131A: KAIT optical observations
  47. GRB 251230A: MeerLICHT afterglow detection
  48. GRB 260131A: FTW optical and NIR observations
  49. GRB 260131A/AT2026bwg: Observations by the Zwicky Transient Facility
  50. GRB 260131A/B: GTC/OSIRIS+ redshift confimation
  51. GRB 260131A/B (AT2026bwg): J-band observations by SYSU 80cm infrared telescope
  52. GRB 260131A/B: EP/FXT X-ray afterglow detection
  53. GRB 260131A/B (AT2026bwg): COLIBRÍ further optical observations
  54. GRB 260131A: NOT spectroscopic redshift z = 1.434
  55. EP260131a: Liverpool Telescope optical upper limits
  56. EP260131a: COLIBRÍ further observations
  57. EP260131a: SVOM/VT optical observation
  58. EP260131a: Xinglong optical upper limit
  59. GRB 260131A/B (AT2026bwg): COLIBRÍ optical observations and confirmation of fading
  60. GRB 260131A/B: GOTO candidate optical counterpart consistent with the MAXI localisation
  61. EP260131a: COLIBRÍ observations of slow optical fading
  62. EP260131a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  63. EP260131a: VLT/X-shooter spectroscopic redshift z = 0.937
  64. EP260131a: NOT early detection of the counterpart in "rapid response mode"
  65. EP260131a: COLIBRÍ optical observations of the counterpart
  66. EP260131a: Las Cumbres detection of an optical counterpart
  67. EP260128a / GRB 260128A: COLIBRÍ optical upper limit
  68. EP260128a / GRB 260128A: NOT and TNG optical and NIR upper limits
  69. GRB 260128B: LCO optical upper limits
  70. GRB 260128B: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  71. EP260128a: J band upper limit by SYSU 80cm infrared telescope
  72. IPN triangulation of GRB 260127B (short)
  73. GRB 260127B: Swift-XRT observations
  74. GRB 260127A: INASAN-Kislovodsk, SAO RAS, and Terskol K-800 optical observations
  75. EP260128a: NOT optical counterpart candidate
  76. EP260128a: Liverpool Telescope optical observations and possible counterpart
  77. EP260128a: LCO optical upper limits
  78. EP260126a: SVOM/VT optical upperlimit
  79. IceCube-260125A: No Candidate Transients from the Zwicky Transient Facility
  80. GRB 260127A: COLIBRÍ optical observations
  81. GRB 260127A: NOT optical observations
  82. EP260126a: Seimei/TriCCS optical upper limit
  83. GRB 260127A : MITSuME Akeno optical afterglow candidate detection
  84. GRB 260127B: GOTO candidate optical counterpart
  85. GRB 260127A: SVOM/C-GFT optical observations
  86. GRB 260127A: LCO optical afterglow discovery
  87. EP260126a: Optical upper limit with Kinder observations
  88. EP260126a: Liverpool Telescope optical upper limits
  89. EP260126a: Further NOT optical upper limits
  90. EP260126a: COLIBRÍ optical upper limits
  91. EP260126a: NOT optical observations
  92. GRB 260125A: NOT optical observations on GOTO26acv / AT 2026bjf
  93. GRB 260125A: GOTO candidate optical counterpart
  94. GRB 260114A: SVOM/VT optical upper limits
  95. GRB 260120B: SVOM/GRM observation
  96. EP260119a: Assy AZT-20 optical observations
  97. EP260119a: Mondy and SAO RAS optical upper limits
  98. IceCube-260115A: No Candidate Transients from the Zwicky Transient Facility
  99. EP260119a: Xinglong optical upper limit
  100. GRB 251122A / EP251122a: VLT/X-shooter host redshift z = 1.765

Advanced

Download all Circulars as a .tar.gz archive (updated once a day):
Questions or comments?
Contact GCN directly.
Have you found a bug in GCN?
Open an issue.
Want to contribute code to GCN?
Get involved on GitHub.

gcn.nasa.gov

A service of the Astrophysics Science Division at NASA Goddard Space Flight Center

Looking for U.S. government information and services? Visit USA.gov