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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"

5401 results found.

  1. GRB 260131B: MAXI/GSC detection
  2. Fermi GRB 260129A: Global MASTER-Net observations report
  3. GRB 260128B: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  4. GRB 260129B: Fermi GBM Final Localization
  5. Fermi GRB 260127A: Global MASTER-Net observations report
  6. GRB 260127B: GOTO candidate optical counterpart
  7. EP260119a: Mondy and SAO RAS optical upper limits
  8. Fermi GRB 260120C: Global MASTER-Net observations report
  9. EP260116a: COLIBRÍ further observations
  10. SVOM GRB260121.06: Global MASTER-Net observations report
  11. EP260116a: COLIBRÍ observations of a tentative optical rebrightening
  12. EP260119a: Global MASTER-Net observations report
  13. Fermi GRB 260115A: Global MASTER-Net observations report
  14. GRB260114A: STEP/T80S optical limits
  15. GRB 251222A: radio detection with the VLA
  16. GRB 260114A: COLIBRÍ optical upper limits
  17. EP260110a: NOT and GTC Optical and Near-Infrared Observations
  18. GRB 260111A: GOTO optical upper limits
  19. Swift trigger 1436759 is not an astrophysical event
  20. GRB 260109A: Fermi GBM Final Real-time Localization
  21. Fermi GRB 260107A: Global MASTER-Net observations report
  22. GRB 260102A: AbAO optical observations
  23. Fermi GRB 260105A: Global MASTER-Net observations report
  24. Fermi GRB 260105B: Global MASTER-Net observations report
  25. FRB 20251229A: A potentially hyperactive repeating fast radio burst source
  26. GRB 260101A: COLIBRÍ optical upper limits
  27. EP260105a: Global MASTER-Net observations report
  28. Fermi GRB 260104B: Global MASTER-Net observations report
  29. GRB 260101A: COLIBRÍ optical observations
  30. SVOM GRB260103.08: Global MASTER-Net observations report
  31. GRB 260102B: Fermi GBM Final Real-time Localization
  32. Fermi GBM Sub-Threshold Detection of GRB 260102A
  33. EP260101a: Global MASTER-Net observations report
  34. GRB 260102A: SVOM detection of a burst
  35. Fermi GRB 251228A: Global MASTER-Net observations report
  36. SVOM GRB251227.07: Global MASTER-Net observations report
  37. IceCube Alert 251225.84: Global MASTER-Net observations report
  38. EP251222a: NTT/ULTRACAM optical observations
  39. GRB 251222A / EP251222b: VLT/X-shooter spectroscopic redshift z = 3.171
  40. EP251221a: NOT optical upper limit
  41. IceCube-251218A: COLIBRÍ optical upper limits
  42. Fermi GRB 251215A: Global MASTER-Net observations report
  43. GRB 251203B: AbAO optical observations
  44. GRB 251214B: COLIBRÍ observations of the afterglow
  45. GRB 251214B: SVOM/C-GFT optical observations
  46. GRB 251214B: Swift detection of a burst with an optical counterpart
  47. EP251212a: Global MASTER-Net observations report
  48. GRB 251209A: NuSTAR detection of prompt emission
  49. EP251130a: Mondy and AbAO optical observations
  50. GRB 251209A: Fermi GBM Final Real-time Localization
  51. GRB 251208D: Swift-XRT observations
  52. GRB 251129A: e-MERLIN C-band observations
  53. LAT GRB251208.43: Global MASTER-Net observations report
  54. GRB 251205A: Liverpool Telescope further optical follow-up observations
  55. SVOM GRB251208D: Global MASTER-Net observations report
  56. GRB 251203A: AstroSat CZTI detection
  57. Fermi Gamma-ray Burst Monitor trigger 786496343/251203967 is not a GRB
  58. GRB 251203C: SVOM/VT optical counterpart
  59. GRB 251203C: EP-FXT follow-up observation
  60. GRB 251203B: Swift-XRT observations
  61. GRB 251203C: LCO optical upper limits
  62. GRB 251203B: LCO optical upper limits
  63. GRB 251202A / EP251202a: Liverpool Telescope optical follow-up observations
  64. SVOM GRB251203.77: Global MASTER-Net observations report
  65. SVOM GRB251203B: Global MASTER-Net observations report
  66. GRB 251203A: Fermi GBM Final Real-time Localization
  67. GRB 251202B: Fermi GBM Final Real-time Localization
  68. GRB 251202A: GOTO optical afterglow detection
  69. EP251130a: SAO RAS optical observations
  70. GRB 251201A: MAXI/GSC detection
  71. GRB 251129A / EP251129a: SVOM/VT optical fading
  72. EP251129a: Global MASTER-Net observations report
  73. GRB 251129A: SVOM/VT optical counterpart confirmation with VHF data
  74. SVOM GRB251129A: Global MASTER-Net observations report
  75. GRB 251127A: Glowbug gamma-ray detection
  76. Fermi GRB 251127A: Global MASTER-Net observations report
  77. GRB 251127A: Fermi GBM Final Real-time Localization
  78. Fermi GRB 251125A: Global MASTER-Net observations report
  79. GRB 251124A: Fermi GBM Localization by automated pipeline
  80. GRB 251122A/EP251122A: 1.3m DFOT optical detection
  81. GRB 251115A: Fermi GBM Observation
  82. Fermi Gamma-ray Burst Monitor trigger 785388351 / 251121143 is not a GRB
  83. GRB 251018A: FRAM-Auger optical detection
  84. EP251118a: GOTO optical afterglow detection
  85. EP251118a: Global MASTER-Net observations report
  86. LAT GRB251118.86: Global MASTER-Net observations report
  87. EP251118a: NOT candidate optical counterpart
  88. SVOM GRB251116C: Global MASTER-Net observations report
  89. GRB 251115A: Fermi-LAT detection
  90. Fermi GRB 251115A: Global MASTER-Net observations report
  91. GRB 251115A: Fermi GBM Final Real-time Localization
  92. LIGO/Virgo/KAGRA S251112cm: DECam GW-MMADS candidates
  93. LIGO/Virgo/KAGRA S251112cm: Swift XRT observations, 20 X-ray sources
  94. LIGO/Virgo/KAGRA S251112cm: Detection of two young transients by BlackGEM/MeerLICHT: AT2025adgp and AT2025adgq
  95. LIGO/Virgo/KAGRA S251112cm: Initial GOTO-South observations
  96. GRB 251108B: Glowbug gamma-ray detection
  97. GRB 251111A: Swift-XRT afterglow detection
  98. GRB 251013C: Chandra X-ray observations and jet break detection
  99. GRB 251111A: SVOM/COLIBRÍ (FM-GFT) optical counterpart detection
  100. Fermi trigger No 784279167: Global MASTER-Net observations report

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