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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"

21760 results found.

  1. GRB 260610b: Liverpool Telescope optical observations
  2. EP260610b: Liverpool Telescope optical upper limits
  3. The EP-WXT trigger 01709269176: SVOM/C-GFT confirmation of a stellar flare
  4. GRB 260610B / AT2026owq: SAO RAS optical observations
  5. EP260610b: refined analysis of the EP-WXT and follow-up EP-FXT observations
  6. GRB 260610B / AT 2026owq: COLIBRÍ optical observations
  7. GRB 260610B / AT2026owq: Early ATLAS observations
  8. GRB 260610B: TRT optical observation
  9. EP260610a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  10. EP260610b: COLIBRÍ optical observations
  11. GRB 260610B: DDOTI optical observations
  12. EP260610b: MAO/AZT-22 optical observations
  13. GRB 260610B: GOTO optical counterpart candidate
  14. EP260610b: NOT optical observation
  15. EP260610b: SVOM/VT optical confirmation with blue color
  16. GRB 260515A: SOAR optical observations
  17. EP260610a: SVOM/VT optical upper limits
  18. EP260610b: Einstein Probe detection of an X-ray transient
  19. Konus-Wind detection of GRB 260601A
  20. EP260610a: COLIBRÍ optical upper limits
  21. EP260610a: Einstein Probe detection of a fast X-ray transient
  22. Konus-Wind detection of GRB 260604C
  23. GRB 260604C: SVOM/ECLAIRs refined analysis
  24. GRB 260608A: SVOM/ECLAIRs refined analysis
  25. Konus-Wind detection of GRB 260607B
  26. GRB 260604C: further SAO RAS optical observations
  27. GRB 260607A / GOTO26fqf / AT2026ong: COLIBRÍ optical observations
  28. GRB 260604C: SVOM/COLIBRÍ (FM-GFT) colour evolution and confirmation of the late rebrightening
  29. GRB 260604C: SVOM/C-GFT upper limit
  30. GRB 260607B: AstroSat CZTI detection
  31. EP260605a: EP-FXT follow-up observation
  32. GRB 260607A: TRT optical observations
  33. GRB 260607A: GOTO tentative optical counterpart candidate GOTO26fqf / AT2026ong
  34. GRB 260604A: SVOM/GRM detection
  35. GRB 260604C: Mondy optical observations: evidence of a possible brightening
  36. GRB 260607B: Fermi-LAT detection
  37. GRB 260604C: Simeiz Zeiss-1000 optical observations of the afterglow
  38. GRB 260604C: OPD1.6m - GRANDMA observations - detection
  39. GRB 260604C: 6 GHz VLA observations
  40. GRB 260604C: SAO RAS optical observations
  41. GRB 260604B: SVOM/GRM detection
  42. GRB260603A: SVOM/ECLAIRs refined analysis
  43. EP260605a: Einstein Probe detection of a fast X-ray transient
  44. EP260603a: COLIBRÍ optical upper limit
  45. GRB 260604C: LCO optical upper limit
  46. GRB 260604C: Liverpool Telescope optical detection
  47. EP260602d: EP-FXT follow-up observation
  48. EP260602c: EP-FXT follow-up observation
  49. GRB 260527A/EP260527a: 6 GHz VLA observations
  50. GRB 260604C: Kilonova-Catcher optical afterglow detection
  51. GRB 260604C: SVOM/COLIBRÍ (FM-GFT) optical observations
  52. GRB 260604C: Jinshan optical observations
  53. EP260602d: J-band upper limit with WINTER
  54. EP260602b: J-band upper limit with WINTER
  55. GRB 260604C: LAST detection of optical counterpart candidate
  56. GRB 260604C: SVOM detection of a long burst
  57. GRB 260603A: Simeiz Zeiss-1000 optical upper limit
  58. EP260602a: EP-FXT follow-up observation
  59. EP260603a: Einstein Probe detection of a fast X-ray transient
  60. EP260602d: Optical Upper limits with kinder observations
  61. EP260602b: Liverpool Telescope observations
  62. EP260602a: Liverpool Telescope optical upper limits
  63. EP260602b: Liverpool Telescope and LCO observations
  64. EP260602a: GTC and Liverpool Telescope optical observations
  65. Konus-Wind detection of GRB 260601B/EP260601a
  66. GRB 260601B / EP260601a: Mondy optical upper limit
  67. EP260602b: EP-FXT follow-up observation
  68. GRB 260603A: Kilonova-Catcher optical upper limit
  69. GRB 260603A: SVOM/VT optical observations
  70. EP260602a: NOT NIR J-band observations
  71. GRB 260603A: SVOM/COLIBRÍ (FM-GFT) photometric redshift z = 3.57
  72. EP260602d: Einstein Probe detection of a fast X-ray transient
  73. GRB 260601A: SVOM/GRM observation of a short burst
  74. EP260602c: Einstein Probe detection of a fast X-ray transient
  75. GRB 260603A: SVOM/COLIBRÍ (GFT-FM) optical counterpart candidate
  76. EP260602a: COLIBRÍ optical observations
  77. GRB260601B/EP260601a: NOT near-infrared observations
  78. GRB 260603A: SVOM detection of a burst
  79. EP260602b: Einstein Probe detection of a fast X-ray transient
  80. EP260602a: SVOM/VT optical candidate
  81. EP-WXT trigger 01709266414 (EP260602b): JinShan optical counterpart detection
  82. GRB 260601B/EP260601a: J-band upper limit with WINTER
  83. EP260530a/AT 2026nwl: COLIBRÍ optical follow up
  84. EP260530a/AT 2026nwl: KAIT optical observations
  85. EP260602a: Optical upper limits with Kinder observations
  86. EP260602a: Einstein Probe detection of a fast X-ray transient
  87. GRB 260601B/EP260601a: SVOM/VT optical observations
  88. GRB 260601B/EP260601a: GECAM-B analysis suggests a possible long duration Type I burst
  89. EP260601a: Einstein Probe detection of an X-ray transient
  90. EP-WXT trigger 01709266307 (EP260601a): COLIBRÍ optical observations
  91. EP-WXT trigger 01709266307 (EP260601a): JinShan optical counterpart detection
  92. EP260530a/AT 2026nwl: COLIBRÍ optical observations
  93. GRB 260530C: SVOM/ECLAIRs detection of a burst through on-ground search
  94. GRB 260531B: GECAM-B observation
  95. GRB 260518B: SVOM/ECLAIRs detection of a soft burst possibly associated with EP 260518a and AT 2026ndp
  96. AT2026nik: EP-FXT X-ray counterpart
  97. AT 2026nuz: COLIBRÍ optical observations
  98. EP260527a/GRB 260527A: optical upper limit with Kinder observations
  99. GRB 260429B / EP260429a: COLIBRÍ optical counterpart candidate
  100. GRB 260527A/EP260527a: VLT/X-shooter tentative redshift

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