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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"

20347 results found.

  1. EP260610b: refined analysis of the EP-WXT and follow-up EP-FXT observations
  2. GRB 260610B / AT 2026owq: COLIBRÍ optical observations
  3. GRB 260610B / AT2026owq: Early ATLAS observations
  4. GRB 260610B: TRT optical observation
  5. EP260610a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  6. EP260610b: COLIBRÍ optical observations
  7. GRB 260610B: DDOTI optical observations
  8. EP260610b: MAO/AZT-22 optical observations
  9. EP260610b: NOT optical observation
  10. EP260610b: SVOM/VT optical confirmation with blue color
  11. GRB 260515A: SOAR optical observations
  12. EP260610a: SVOM/VT optical upper limits
  13. EP260610b: Einstein Probe detection of an X-ray transient
  14. EP260610a: COLIBRÍ optical upper limits
  15. EP260610a: Einstein Probe detection of a fast X-ray transient
  16. Konus-Wind detection of GRB 260604C
  17. GRB 260604C: AstroSat CZTI detection
  18. GRB 260604C: SVOM/ECLAIRs refined analysis
  19. GRB 260608A: SVOM/ECLAIRs refined analysis
  20. Konus-Wind detection of GRB 260607B
  21. GRB 260604C: further SAO RAS optical observations
  22. GRB 260607A / GOTO26fqf / AT2026ong: COLIBRÍ optical observations
  23. GRB 260604C: SVOM/COLIBRÍ (FM-GFT) colour evolution and confirmation of the late rebrightening
  24. GRB 260604C: SVOM/C-GFT upper limit
  25. GRB 260607B: AstroSat CZTI detection
  26. EP260605a: EP-FXT follow-up observation
  27. GRB 260607A: TRT optical observations
  28. GRB 260604A: SVOM/GRM detection
  29. GRB 260604C: Mondy optical observations: evidence of a possible brightening
  30. GRB 260604C: Simeiz Zeiss-1000 optical observations of the afterglow
  31. GRB 260604C: OPD1.6m - GRANDMA observations - detection
  32. GRB 260604C: 6 GHz VLA observations
  33. GRB 260604C: SAO RAS optical observations
  34. GRB 260604B: SVOM/GRM detection
  35. GRB260603A: SVOM/ECLAIRs refined analysis
  36. EP260605a: Einstein Probe detection of a fast X-ray transient
  37. EP260603a: COLIBRÍ optical upper limit
  38. GRB 260604C: LCO optical upper limit
  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: Kilonova-Catcher optical afterglow detection
  44. GRB 260604C: SVOM/COLIBRÍ (FM-GFT) optical observations
  45. GRB 260604C: Jinshan optical observations
  46. EP260602d: J-band upper limit with WINTER
  47. EP260602b: J-band upper limit with WINTER
  48. GRB 260604C: LAST detection of optical counterpart candidate
  49. GRB 260604C: SVOM detection of a long burst
  50. GRB 260604C: Fermi GBM Final Real-time Localization
  51. GRB 260603A: Simeiz Zeiss-1000 optical upper limit
  52. GRB 260604B: Fermi GBM Final Real-time Localization
  53. EP260602a: EP-FXT follow-up observation
  54. EP260603a: Einstein Probe detection of a fast X-ray transient
  55. EP260602d: Optical Upper limits with kinder observations
  56. GRB 260604A: Fermi GBM Final Real-time Localization
  57. EP260602b: Liverpool Telescope observations
  58. EP260602a: Liverpool Telescope optical upper limits
  59. EP260602b: Liverpool Telescope and LCO observations
  60. EP260602a: GTC and Liverpool Telescope optical observations
  61. Konus-Wind detection of GRB 260601B/EP260601a
  62. GRB 260601B / EP260601a: Mondy optical upper limit
  63. EP260602b: EP-FXT follow-up observation
  64. GRB 260603A: Kilonova-Catcher optical upper limit
  65. GRB 260603A: SVOM/VT optical observations
  66. EP260602a: NOT NIR J-band observations
  67. GRB 260603A: SVOM/COLIBRÍ (FM-GFT) photometric redshift z = 3.57
  68. EP260602d: Einstein Probe detection of a fast X-ray transient
  69. GRB 260601A: SVOM/GRM observation of a short burst
  70. EP260602c: Einstein Probe detection of a fast X-ray transient
  71. GRB 260603A: SVOM/COLIBRÍ (GFT-FM) optical counterpart candidate
  72. EP260602a: COLIBRÍ optical observations
  73. GRB260601B/EP260601a: NOT near-infrared observations
  74. EP260602b: Einstein Probe detection of a fast X-ray transient
  75. EP260602a: SVOM/VT optical candidate
  76. EP-WXT trigger 01709266414 (EP260602b): JinShan optical counterpart detection
  77. GRB 260601B/EP260601a: J-band upper limit with WINTER
  78. EP260530a/AT 2026nwl: COLIBRÍ optical follow up
  79. EP260530a/AT 2026nwl: KAIT optical observations
  80. EP260602a: Optical upper limits with Kinder observations
  81. EP260602a: Einstein Probe detection of a fast X-ray transient
  82. GRB 260601B/EP260601a: SVOM/VT optical observations
  83. EP260601a: Einstein Probe detection of an X-ray transient
  84. EP-WXT trigger 01709266307 (EP260601a): COLIBRÍ optical observations
  85. EP-WXT trigger 01709266307 (EP260601a): JinShan optical counterpart detection
  86. EP260530a/AT 2026nwl: COLIBRÍ optical observations
  87. GRB 260530C: SVOM/ECLAIRs detection of a burst through on-ground search
  88. GRB 260518B: SVOM/ECLAIRs detection of a soft burst possibly associated with EP 260518a and AT 2026ndp
  89. AT2026nik: EP-FXT X-ray counterpart
  90. AT 2026nuz: COLIBRÍ optical observations
  91. EP260527a/GRB 260527A: optical upper limit with Kinder observations
  92. GRB 260429B / EP260429a: COLIBRÍ optical counterpart candidate
  93. GRB 260527A/EP260527a: VLT/X-shooter tentative redshift
  94. EP260526a: SVOM/VT optical upper limits
  95. EP260527a / GRB 260527A: VLT detection of the optical and nIR counterpart
  96. EP260527a/GRB 260527A: Infrared J upper limit with MDM/MIRAGE
  97. GRB 260527A: CALET Gamma-Ray Burst Monitor detection
  98. EP260527a/GRB 260527A: EP-FXT follow-up observation
  99. Konus-Wind detection of GRB 260527A (short/hard) ~4 min before EP260527a
  100. EP260527a: SVOM/VT optical observation

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