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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"

41689 results found.

  1. GRB 260610B: GOTO optical counterpart candidate
  2. EP260610b: NOT optical observation
  3. EP260610b: SVOM/VT optical confirmation with blue color
  4. IceCube-260610A - IceCube observation of a high-energy neutrino candidate track-like event
  5. GRB 260515A: SOAR optical observations
  6. EP260610b: Gemini North optical counterpart candidate
  7. EP260610a: SVOM/VT optical upper limits
  8. EP260610b: Einstein Probe detection of an X-ray transient
  9. Konus-Wind detection of GRB 260601A
  10. IPN triangulation of GRB 260601A (short/hard)
  11. GRB 260610A: Fermi GBM Final Real-time Localization (duplicate submission)
  12. EP260610a: COLIBRÍ optical upper limits
  13. EP260610a: Einstein Probe detection of a fast X-ray transient
  14. Konus-Wind detection of GRB 260604C
  15. GRB 260608A: Fermi GRB Observation
  16. GRB 260604C: AstroSat CZTI detection
  17. IPN triangulation of GRB 260601B / EP260601a
  18. GRB 260604C: SVOM/ECLAIRs refined analysis
  19. GRB 260608A: SVOM/ECLAIRs refined analysis
  20. Konus-Wind detection of GRB 260607B
  21. GRB 260607B: GECAM-B observation
  22. GRB 260608C: Fermi GBM Final Real-time Localization (duplicate submission)
  23. GRB 260604C: further SAO RAS optical observations
  24. GRB 260607A: AT2026ong (GOTO26fqf) is a type-Ia SN
  25. GRB 260607A / GOTO26fqf / AT2026ong: COLIBRÍ optical observations
  26. GRB 260604C: SVOM/COLIBRÍ (FM-GFT) colour evolution and confirmation of the late rebrightening
  27. GRB 260604C: SVOM/C-GFT upper limit
  28. GRB 260607B: AstroSat CZTI detection
  29. GRB 260608A: SVOM detection of a burst
  30. GRB 260608A: Fermi GBM Final Real-time Localization (duplicate submission)
  31. EP260605a: EP-FXT follow-up observation
  32. GRB 260607A: TRT optical observations
  33. GRB 260604C: GRANDMA further observations
  34. GRB 260607A: GOTO tentative optical counterpart candidate GOTO26fqf / AT2026ong
  35. GRB 260604A: SVOM/GRM detection
  36. GRB 260604C: Mondy optical observations: evidence of a possible brightening
  37. GRB 260607B: Fermi GBM Observation
  38. GRB 260607B: Fermi-LAT detection
  39. GRB 260607B: Fermi GBM Final Localization Correction
  40. GRB 260604C: Simeiz Zeiss-1000 optical observations of the afterglow
  41. GRB 260604C: OPD1.6m - GRANDMA observations - detection
  42. GRB 260607A: Fermi GBM Final Real-time Localization (duplicate submission)
  43. GRB 260604C: GECAM-B observation
  44. GRB 260604C: 6 GHz VLA observations
  45. GRB 260604C: SAO RAS optical observations
  46. GRB 260604C: GRANDMA observations
  47. GRB 260604B: SVOM/GRM detection
  48. GRB 260605A: Insight-HXMT/HE detection
  49. GRB260603A: SVOM/ECLAIRs refined analysis
  50. EP260605a: Einstein Probe detection of a fast X-ray transient
  51. EP260603a: COLIBRÍ optical upper limit
  52. GRB 260604A: Glowbug gamma-ray detection
  53. GRB 260604C: LCO optical upper limit
  54. GRB 260604C: Liverpool Telescope optical detection
  55. The EP-WXT trigger 01709267001 is likely a flaring star
  56. EP260602d: EP-FXT follow-up observation
  57. EP260602c: EP-FXT follow-up observation
  58. GRB 260601B / EP260601a: AstroSat CZTI detection
  59. GRB 260527A/EP260527a: 6 GHz VLA observations
  60. GRB 260604C: GOTO detections of the optical afterglow
  61. GRB 260604C: Correction to GCN 44828
  62. GRB 260604C: Kilonova-Catcher optical afterglow detection
  63. GRB 260604C: SVOM/COLIBRÍ (FM-GFT) optical observations
  64. The EP-WXT trigger 01709266798 is likely a flaring star
  65. GRB 260604C: Jinshan optical observations
  66. GRB 260604C: Fermi GBM Observation
  67. EP260602d: J-band upper limit with WINTER
  68. EP260602b: J-band upper limit with WINTER
  69. GRB 260604C: LAST detection of optical counterpart candidate
  70. GRB 260604C: MASTER OT J145749.59+284903.0 optical counterpart discovery
  71. Fermi GRB 260604C: Global MASTER-Net observations report
  72. Fermi GRB 260604C: Global MASTER-Net observations report
  73. SVOM GRB260604.85: Global MASTER-Net observations report
  74. GRB 260604C: SVOM detection of a long burst
  75. GRB 260515A: SVOM/VT optical detection at about 18 days post trigger
  76. GRB 260603A: NOT optical observations
  77. GRB 260603A: Simeiz Zeiss-1000 optical upper limit
  78. GRB 260601A: CALET Gamma-Ray Burst Monitor detection
  79. EP260602a: EP-FXT follow-up observation
  80. EP260603a: Global MASTER-Net observations report
  81. EP260603a: Einstein Probe detection of a fast X-ray transient
  82. EP260602d: Optical Upper limits with kinder observations
  83. EP260602b: Liverpool Telescope observations
  84. EP260602a: Liverpool Telescope optical upper limits
  85. EP260602b: Liverpool Telescope and LCO observations
  86. EP260602a: GTC and Liverpool Telescope optical observations
  87. Konus-Wind detection of GRB 260601B/EP260601a
  88. GRB 260603A: EP-FXT follow-up observation
  89. EP260601a/GRB 260601B: EP-FXT follow-up observation
  90. GRB 260601B / EP260601a: Mondy optical upper limit
  91. EP260602b: EP-FXT follow-up observation
  92. GRB 260601B/EP260601a: Glowbug gamma-ray detection
  93. GRB 260603A: Kilonova-Catcher optical upper limit
  94. GRB 260603A: SVOM/VT optical observations
  95. EP260602a: NOT NIR J-band observations
  96. GRB 260603A: SVOM/COLIBRÍ (FM-GFT) photometric redshift z = 3.57
  97. EP260602d: Einstein Probe detection of a fast X-ray transient
  98. Fermi trigger No 802141998: Global MASTER-Net observations report
  99. EP260602a: SVOM/VT optical magnitudes correction
  100. GRB 260601A: SVOM/GRM observation of a short burst

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