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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"

37516 results found.

  1. GRB 260610B / AT2026owq: further SAO RAS optical observations
  2. GRB 260610b: Liverpool Telescope optical observations
  3. GRB 260611B: CALET Gamma-Ray Burst Monitor detection
  4. GRB 260610B / AT2026owq: SVOM/VT optical observations
  5. GRB 260610B / AT2026owq: OASDG optical observations
  6. GRB 260610B: IAC-80 Optical observations
  7. GRB 260610B / AT2026owq: SAO RAS optical observations
  8. GRB 260611B: Fermi GBM Final Real-time Localization
  9. EP260601a: VLT/X-shooter spectroscopic host galaxy redshift z = 1.068
  10. GRB 260610B: optical counterpart shows spectroscopic redshift of z=0.473
  11. GRB 260610B / AT 2026owq: COLIBRÍ optical observations
  12. GRB 260610B / AT2026owq: Early ATLAS observations
  13. GRB 260610B: TRT optical observation
  14. GRB 260611A: Fermi GBM Final Real-time Localization
  15. GRB 260610B: DDOTI optical observations
  16. GRB 260610B: GOTO optical counterpart candidate
  17. GRB 260610B: Fermi GBM Final Localization
  18. IceCube-260610A - IceCube observation of a high-energy neutrino candidate track-like event
  19. GRB 260515A: SOAR optical observations
  20. Konus-Wind detection of GRB 260601A
  21. IPN triangulation of GRB 260601A (short/hard)
  22. GRB 260610A: Fermi GBM Final Real-time Localization (duplicate submission)
  23. GRB 260610A: Fermi GBM Final Real-time Localization
  24. GRB 260609A: Fermi GBM Final Localization
  25. Konus-Wind detection of GRB 260604C
  26. GRB 260608A: Fermi GRB Observation
  27. GRB 260604C: AstroSat CZTI detection
  28. IPN triangulation of GRB 260601B / EP260601a
  29. GRB 260604C: SVOM/ECLAIRs refined analysis
  30. GRB 260608A: SVOM/ECLAIRs refined analysis
  31. Konus-Wind detection of GRB 260607B
  32. GRB 260607B: GECAM-B observation
  33. GRB 260608C: Fermi GBM Final Real-time Localization (duplicate submission)
  34. GRB 260608C: Fermi GBM Final Real-time Localization
  35. GRB 260604C: further SAO RAS optical observations
  36. GRB 260607A: AT2026ong (GOTO26fqf) is a type-Ia SN
  37. GRB 260607A / GOTO26fqf / AT2026ong: COLIBRÍ optical observations
  38. GRB 260608B: Fermi GBM Final Localization
  39. GRB 260604C: SVOM/COLIBRÍ (FM-GFT) colour evolution and confirmation of the late rebrightening
  40. GRB 260604C: SVOM/C-GFT upper limit
  41. GRB 260607B: AstroSat CZTI detection
  42. GRB 260608A: SVOM detection of a burst
  43. GRB 260608A: Fermi GBM Final Real-time Localization (duplicate submission)
  44. GRB 260608A: Fermi GBM Final Real-time Localization
  45. GRB 260607A: TRT optical observations
  46. GRB 260604C: GRANDMA further observations
  47. GRB 260607A: GOTO tentative optical counterpart candidate GOTO26fqf / AT2026ong
  48. GRB 260604A: SVOM/GRM detection
  49. GRB 260604C: Mondy optical observations: evidence of a possible brightening
  50. GRB 260607B: Fermi GBM Observation
  51. GRB 260607B: Fermi-LAT detection
  52. GRB 260607B: Fermi GBM Final Localization Correction
  53. GRB 260604C: Simeiz Zeiss-1000 optical observations of the afterglow
  54. GRB 260604C: OPD1.6m - GRANDMA observations - detection
  55. GRB 260607A: Fermi GBM Final Real-time Localization (duplicate submission)
  56. GRB 260607A: Fermi GBM Final Real-time Localization
  57. GRB 260604C: GECAM-B observation
  58. GRB 260604C: 6 GHz VLA observations
  59. GRB 260604C: SAO RAS optical observations
  60. GRB 260604C: GRANDMA observations
  61. GRB 260604B: SVOM/GRM detection
  62. GRB 260605A: Insight-HXMT/HE detection
  63. GRB260603A: SVOM/ECLAIRs refined analysis
  64. GRB 260604A: Glowbug gamma-ray detection
  65. GRB 260604C: LCO optical upper limit
  66. GRB 260604C: Liverpool Telescope optical detection
  67. GRB 260601B / EP260601a: AstroSat CZTI detection
  68. GRB 260527A/EP260527a: 6 GHz VLA observations
  69. GRB 260604C: GOTO detections of the optical afterglow
  70. GRB 260604C: Correction to GCN 44828
  71. GRB 260604C: Kilonova-Catcher optical afterglow detection
  72. GRB 260604C: SVOM/COLIBRÍ (FM-GFT) optical observations
  73. GRB 260604C: Jinshan optical observations
  74. GRB 260604C: Fermi GBM Observation
  75. GRB 260604C: LAST detection of optical counterpart candidate
  76. GRB 260604C: MASTER OT J145749.59+284903.0 optical counterpart discovery
  77. Fermi GRB 260604C: Global MASTER-Net observations report
  78. Fermi GRB 260604C: Global MASTER-Net observations report
  79. GRB 260604C: SVOM detection of a long burst
  80. GRB 260604C: Fermi GBM Final Real-time Localization
  81. GRB 260515A: SVOM/VT optical detection at about 18 days post trigger
  82. GRB 260603A: NOT optical observations
  83. GRB 260603A: Simeiz Zeiss-1000 optical upper limit
  84. GRB 260604B: Fermi GBM Final Real-time Localization
  85. GRB 260601A: CALET Gamma-Ray Burst Monitor detection
  86. GRB 260604A: Fermi GBM Final Real-time Localization
  87. GRB 260603B: Fermi GBM Final Localization
  88. Konus-Wind detection of GRB 260601B/EP260601a
  89. GRB 260603A: EP-FXT follow-up observation
  90. EP260601a/GRB 260601B: EP-FXT follow-up observation
  91. GRB 260601B / EP260601a: Mondy optical upper limit
  92. GRB 260601B/EP260601a: Glowbug gamma-ray detection
  93. GRB 260603A: Kilonova-Catcher optical upper limit
  94. GRB 260603A: SVOM/VT optical observations
  95. GRB 260603A: SVOM/COLIBRÍ (FM-GFT) photometric redshift z = 3.57
  96. Fermi trigger No 802141998: Global MASTER-Net observations report
  97. GRB 260601A: SVOM/GRM observation of a short burst
  98. GRB 260603A: SVOM/COLIBRÍ (GFT-FM) optical counterpart candidate
  99. GRB 260603A: SVOM detection of a burst
  100. GRB 260601B/EP260601a: Insight-HXMT detection

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