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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').
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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"

43672 results found.

  1. GRB 260610B / AT2026owq: GRANDMA optical observations
  2. GRB 260610B / AT2026owq: further SAO RAS optical observations
  3. EP260605a: COLIBRÍ optical upper limits
  4. GRB 260610b: Liverpool Telescope optical observations
  5. EP260610b: Liverpool Telescope optical upper limits
  6. IceCube-260610A: No candidates from the Zwicky Transient Facility
  7. IceCube-260610A: EP-FXT follow-up observation
  8. GRB 260611B: CALET Gamma-Ray Burst Monitor detection
  9. The EP-WXT trigger 01709269176: SVOM/C-GFT confirmation of a stellar flare
  10. GRB 260610B / AT2026owq: SVOM/VT optical observations
  11. GRB 260610B / AT2026owq: OASDG optical observations
  12. GRB 260610B: IAC-80 Optical observations
  13. GRB 260610B / AT2026owq: SAO RAS optical observations
  14. GRB 260611B: Fermi GBM Final Real-time Localization
  15. EP260601a: VLT/X-shooter spectroscopic host galaxy redshift z = 1.068
  16. EP260610b: GTC likely spectroscopic redshift z = 1.10
  17. GRB 260610B: optical counterpart shows spectroscopic redshift of z=0.473
  18. The EP-WXT trigger 01709269176 is likely a flaring star
  19. EP260610b: refined analysis of the EP-WXT and follow-up EP-FXT observations
  20. GRB 260610B / AT 2026owq: COLIBRÍ optical observations
  21. GRB 260610B / AT2026owq: Early ATLAS observations
  22. GRB 260610B: TRT optical observation
  23. EP260610a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  24. GRB 260611A: Fermi GBM Final Real-time Localization
  25. EP260610b: COLIBRÍ optical observations
  26. GRB 260610B: DDOTI optical observations
  27. EP260610b: MAO/AZT-22 optical observations
  28. GRB 260610B: GOTO optical counterpart candidate
  29. EP260610b: NOT optical observation
  30. GRB 260610B: Fermi GBM Final Localization
  31. EP260610b: SVOM/VT optical confirmation with blue color
  32. IceCube-260610A - IceCube observation of a high-energy neutrino candidate track-like event
  33. GRB 260515A: SOAR optical observations
  34. EP260610b: Gemini North optical counterpart candidate
  35. EP260610a: SVOM/VT optical upper limits
  36. EP260610b: Einstein Probe detection of an X-ray transient
  37. Konus-Wind detection of GRB 260601A
  38. IPN triangulation of GRB 260601A (short/hard)
  39. GRB 260610A: Fermi GBM Final Real-time Localization (duplicate submission)
  40. GRB 260610A: Fermi GBM Final Real-time Localization
  41. EP260610a: COLIBRÍ optical upper limits
  42. EP260610a: Einstein Probe detection of a fast X-ray transient
  43. GRB 260609A: Fermi GBM Final Localization
  44. Konus-Wind detection of GRB 260604C
  45. GRB 260608A: Fermi GRB Observation
  46. GRB 260604C: AstroSat CZTI detection
  47. IPN triangulation of GRB 260601B / EP260601a
  48. GRB 260604C: SVOM/ECLAIRs refined analysis
  49. GRB 260608A: SVOM/ECLAIRs refined analysis
  50. Konus-Wind detection of GRB 260607B
  51. GRB 260607B: GECAM-B observation
  52. GRB 260608C: Fermi GBM Final Real-time Localization (duplicate submission)
  53. GRB 260608C: Fermi GBM Final Real-time Localization
  54. GRB 260604C: further SAO RAS optical observations
  55. GRB 260607A: AT2026ong (GOTO26fqf) is a type-Ia SN
  56. GRB 260607A / GOTO26fqf / AT2026ong: COLIBRÍ optical observations
  57. GRB 260608B: Fermi GBM Final Localization
  58. GRB 260604C: SVOM/COLIBRÍ (FM-GFT) colour evolution and confirmation of the late rebrightening
  59. GRB 260604C: SVOM/C-GFT upper limit
  60. GRB 260607B: AstroSat CZTI detection
  61. GRB 260608A: SVOM detection of a burst
  62. GRB 260608A: Fermi GBM Final Real-time Localization (duplicate submission)
  63. GRB 260608A: Fermi GBM Final Real-time Localization
  64. EP260605a: EP-FXT follow-up observation
  65. GRB 260607A: TRT optical observations
  66. GRB 260604C: GRANDMA further observations
  67. GRB 260607A: GOTO tentative optical counterpart candidate GOTO26fqf / AT2026ong
  68. GRB 260604A: SVOM/GRM detection
  69. GRB 260604C: Mondy optical observations: evidence of a possible brightening
  70. GRB 260607B: Fermi GBM Observation
  71. GRB 260607B: Fermi-LAT detection
  72. GRB 260607B: Fermi GBM Final Localization Correction
  73. GRB 260604C: Simeiz Zeiss-1000 optical observations of the afterglow
  74. GRB 260604C: OPD1.6m - GRANDMA observations - detection
  75. GRB 260607A: Fermi GBM Final Real-time Localization (duplicate submission)
  76. GRB 260607A: Fermi GBM Final Real-time Localization
  77. GRB 260604C: GECAM-B observation
  78. GRB 260604C: 6 GHz VLA observations
  79. GRB 260604C: SAO RAS optical observations
  80. GRB 260604C: GRANDMA observations
  81. GRB 260604B: SVOM/GRM detection
  82. GRB 260605A: Insight-HXMT/HE detection
  83. GRB260603A: SVOM/ECLAIRs refined analysis
  84. EP260605a: Einstein Probe detection of a fast X-ray transient
  85. EP260603a: COLIBRÍ optical upper limit
  86. GRB 260604A: Glowbug gamma-ray detection
  87. GRB 260604C: LCO optical upper limit
  88. GRB 260604C: Liverpool Telescope optical detection
  89. The EP-WXT trigger 01709267001 is likely a flaring star
  90. EP260602d: EP-FXT follow-up observation
  91. EP260602c: EP-FXT follow-up observation
  92. GRB 260601B / EP260601a: AstroSat CZTI detection
  93. GRB 260527A/EP260527a: 6 GHz VLA observations
  94. GRB 260604C: GOTO detections of the optical afterglow
  95. GRB 260604C: Correction to GCN 44828
  96. GRB 260604C: Kilonova-Catcher optical afterglow detection
  97. GRB 260604C: SVOM/COLIBRÍ (FM-GFT) optical observations
  98. The EP-WXT trigger 01709266798 is likely a flaring star
  99. GRB 260604C: Jinshan optical observations
  100. GRB 260604C: Fermi GBM Observation

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