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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"
  1. GRB 260608C: Fermi GBM Final Real-time Localization (duplicate submission)
  2. GRB 260608C: Fermi GBM Final Real-time Localization
  3. GRB 260604C: further SAO RAS optical observations
  4. GRB 260607A: AT2026ong (GOTO26fqf) is a type-Ia SN
  5. GRB 260607A / GOTO26fqf / AT2026ong: COLIBRÍ optical observations
  6. GRB 260608B: Fermi GBM Final Localization
  7. GRB 260604C: SVOM/COLIBRÍ (FM-GFT) colour evolution and confirmation of the late rebrightening
  8. GRB 260604C: SVOM/C-GFT upper limit
  9. GRB 260607B: AstroSat CZTI detection
  10. GRB 260608A: SVOM detection of a burst
  11. GRB 260608A: Fermi GBM Final Real-time Localization (duplicate submission)
  12. GRB 260608A: Fermi GBM Final Real-time Localization
  13. EP260605a: EP-FXT follow-up observation
  14. GRB 260607A: TRT optical observations
  15. GRB 260604C: GRANDMA further observations
  16. GRB 260607A: GOTO tentative optical counterpart candidate GOTO26fqf / AT2026ong
  17. GRB 260604A: SVOM/GRM detection
  18. GRB 260604C: Mondy optical observations: evidence of a possible brightening
  19. GRB 260607B: Fermi GBM Observation
  20. GRB 260607B: Fermi-LAT detection
  21. GRB 260607B: Fermi GBM Final Localization Correction
  22. GRB 260604C: Simeiz Zeiss-1000 optical observations of the afterglow
  23. GRB 260604C: OPD1.6m - GRANDMA observations - detection
  24. GRB 260607A: Fermi GBM Final Real-time Localization (duplicate submission)
  25. GRB 260607A: Fermi GBM Final Real-time Localization
  26. GRB 260604C: GECAM-B observation
  27. GRB 260604C: 6 GHz VLA observations
  28. GRB 260604C: SAO RAS optical observations
  29. GRB 260604C: GRANDMA observations
  30. GRB 260604B: SVOM/GRM detection
  31. GRB 260605A: Insight-HXMT/HE detection
  32. GRB260603A: SVOM/ECLAIRs refined analysis
  33. EP260605a: Einstein Probe detection of a fast X-ray transient
  34. EP260603a: COLIBRÍ optical upper limit
  35. GRB 260604A: Glowbug gamma-ray detection
  36. GRB 260604C: LCO optical upper limit
  37. GRB 260604C: Liverpool Telescope optical detection
  38. The EP-WXT trigger 01709267001 is likely a flaring star
  39. EP260602d: EP-FXT follow-up observation
  40. EP260602c: EP-FXT follow-up observation
  41. GRB 260601B / EP260601a: AstroSat CZTI detection
  42. GRB 260527A/EP260527a: 6 GHz VLA observations
  43. GRB 260604C: GOTO detections of the optical afterglow
  44. GRB 260604C: Correction to GCN 44828
  45. GRB 260604C: Kilonova-Catcher optical afterglow detection
  46. GRB 260604C: SVOM/COLIBRÍ (FM-GFT) optical observations
  47. The EP-WXT trigger 01709266798 is likely a flaring star
  48. GRB 260604C: Jinshan optical observations
  49. GRB 260604C: Fermi GBM Observation
  50. EP260602d: J-band upper limit with WINTER
  51. EP260602b: J-band upper limit with WINTER
  52. GRB 260604C: LAST detection of optical counterpart candidate
  53. GRB 260604C: MASTER OT J145749.59+284903.0 optical counterpart discovery
  54. Fermi GRB 260604C: Global MASTER-Net observations report
  55. Fermi GRB 260604C: Global MASTER-Net observations report
  56. SVOM GRB260604.85: Global MASTER-Net observations report
  57. GRB 260604C: SVOM detection of a long burst
  58. GRB 260604C: Fermi GBM Final Real-time Localization
  59. GRB 260515A: SVOM/VT optical detection at about 18 days post trigger
  60. GRB 260603A: NOT optical observations
  61. GRB 260603A: Simeiz Zeiss-1000 optical upper limit
  62. GRB 260604B: Fermi GBM Final Real-time Localization
  63. GRB 260601A: CALET Gamma-Ray Burst Monitor detection
  64. EP260602a: EP-FXT follow-up observation
  65. EP260603a: Global MASTER-Net observations report
  66. EP260603a: Einstein Probe detection of a fast X-ray transient
  67. EP260602d: Optical Upper limits with kinder observations
  68. GRB 260604A: Fermi GBM Final Real-time Localization
  69. EP260602b: Liverpool Telescope observations
  70. EP260602a: Liverpool Telescope optical upper limits
  71. EP260602b: Liverpool Telescope and LCO observations
  72. GRB 260603B: Fermi GBM Final Localization
  73. EP260602a: GTC and Liverpool Telescope optical observations
  74. Konus-Wind detection of GRB 260601B/EP260601a
  75. GRB 260603A: EP-FXT follow-up observation
  76. EP260601a/GRB 260601B: EP-FXT follow-up observation
  77. GRB 260601B / EP260601a: Mondy optical upper limit
  78. EP260602b: EP-FXT follow-up observation
  79. GRB 260601B/EP260601a: Glowbug gamma-ray detection
  80. GRB 260603A: Kilonova-Catcher optical upper limit
  81. GRB 260603A: SVOM/VT optical observations
  82. EP260602a: NOT NIR J-band observations
  83. GRB 260603A: SVOM/COLIBRÍ (FM-GFT) photometric redshift z = 3.57
  84. EP260602d: Einstein Probe detection of a fast X-ray transient
  85. Fermi trigger No 802141998: Global MASTER-Net observations report
  86. EP260602a: SVOM/VT optical magnitudes correction
  87. GRB 260601A: SVOM/GRM observation of a short burst
  88. EP260602c: Einstein Probe detection of a fast X-ray transient
  89. GRB 260603A: SVOM/COLIBRÍ (GFT-FM) optical counterpart candidate
  90. EP260602a: COLIBRÍ optical observations
  91. GRB260601B/EP260601a: NOT near-infrared observations
  92. SVOM GRB260603.23: Global MASTER-Net observations report
  93. GRB 260603A: SVOM detection of a burst
  94. EP260602b: Einstein Probe detection of a fast X-ray transient
  95. GRB 260601B/EP260601a: Insight-HXMT detection
  96. Fermi GRB 260602B: Global MASTER-Net observations report
  97. Fermi GRB 260602B: Global MASTER-Net observations report
  98. EP260530a: Xinglong optical spectroscopy of EP260530a / AT 2026nwl
  99. EP260602a: SVOM/VT optical candidate
  100. EP-WXT trigger 01709266414 (EP260602b): JinShan optical counterpart detection

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