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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"

20358 results found.

  1. GRB 260610B / AT2026owq: further SAO RAS optical observations
  2. EP260605a: COLIBRÍ optical upper limits
  3. GRB 260610b: Liverpool Telescope optical observations
  4. EP260610b: Liverpool Telescope optical upper limits
  5. The EP-WXT trigger 01709269176: SVOM/C-GFT confirmation of a stellar flare
  6. GRB 260610B / AT2026owq: SAO RAS optical observations
  7. GRB 260610B: optical counterpart shows spectroscopic redshift of z=0.473
  8. EP260610b: refined analysis of the EP-WXT and follow-up EP-FXT observations
  9. GRB 260610B / AT 2026owq: COLIBRÍ optical observations
  10. GRB 260610B / AT2026owq: Early ATLAS observations
  11. GRB 260610B: TRT optical observation
  12. EP260610a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  13. EP260610b: COLIBRÍ optical observations
  14. GRB 260610B: DDOTI optical observations
  15. EP260610b: MAO/AZT-22 optical observations
  16. EP260610b: NOT optical observation
  17. EP260610b: SVOM/VT optical confirmation with blue color
  18. GRB 260515A: SOAR optical observations
  19. EP260610a: SVOM/VT optical upper limits
  20. EP260610b: Einstein Probe detection of an X-ray transient
  21. EP260610a: COLIBRÍ optical upper limits
  22. EP260610a: Einstein Probe detection of a fast X-ray transient
  23. Konus-Wind detection of GRB 260604C
  24. GRB 260604C: AstroSat CZTI detection
  25. GRB 260604C: SVOM/ECLAIRs refined analysis
  26. GRB 260608A: SVOM/ECLAIRs refined analysis
  27. Konus-Wind detection of GRB 260607B
  28. GRB 260604C: further SAO RAS optical observations
  29. GRB 260607A / GOTO26fqf / AT2026ong: COLIBRÍ optical observations
  30. GRB 260604C: SVOM/COLIBRÍ (FM-GFT) colour evolution and confirmation of the late rebrightening
  31. GRB 260604C: SVOM/C-GFT upper limit
  32. GRB 260607B: AstroSat CZTI detection
  33. EP260605a: EP-FXT follow-up observation
  34. GRB 260607A: TRT optical observations
  35. GRB 260604A: SVOM/GRM detection
  36. GRB 260604C: Mondy optical observations: evidence of a possible brightening
  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. EP260602d: EP-FXT follow-up observation
  47. EP260602c: EP-FXT follow-up observation
  48. GRB 260601B / EP260601a: AstroSat CZTI detection
  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 260604C: Fermi GBM Final Real-time Localization
  58. GRB 260603A: Simeiz Zeiss-1000 optical upper limit
  59. GRB 260604B: Fermi GBM Final Real-time Localization
  60. EP260602a: EP-FXT follow-up observation
  61. EP260603a: Einstein Probe detection of a fast X-ray transient
  62. EP260602d: Optical Upper limits with kinder observations
  63. GRB 260604A: Fermi GBM Final Real-time Localization
  64. EP260602b: Liverpool Telescope observations
  65. EP260602a: Liverpool Telescope optical upper limits
  66. EP260602b: Liverpool Telescope and LCO observations
  67. EP260602a: GTC and Liverpool Telescope optical observations
  68. Konus-Wind detection of GRB 260601B/EP260601a
  69. GRB 260601B / EP260601a: Mondy optical upper limit
  70. EP260602b: EP-FXT follow-up observation
  71. GRB 260603A: Kilonova-Catcher optical upper limit
  72. GRB 260603A: SVOM/VT optical observations
  73. EP260602a: NOT NIR J-band observations
  74. GRB 260603A: SVOM/COLIBRÍ (FM-GFT) photometric redshift z = 3.57
  75. EP260602d: Einstein Probe detection of a fast X-ray transient
  76. GRB 260601A: SVOM/GRM observation of a short burst
  77. EP260602c: Einstein Probe detection of a fast X-ray transient
  78. GRB 260603A: SVOM/COLIBRÍ (GFT-FM) optical counterpart candidate
  79. EP260602a: COLIBRÍ optical observations
  80. GRB260601B/EP260601a: NOT near-infrared observations
  81. EP260602b: Einstein Probe detection of a fast X-ray transient
  82. EP260602a: SVOM/VT optical candidate
  83. EP-WXT trigger 01709266414 (EP260602b): JinShan optical counterpart detection
  84. GRB 260601B/EP260601a: J-band upper limit with WINTER
  85. EP260530a/AT 2026nwl: COLIBRÍ optical follow up
  86. EP260530a/AT 2026nwl: KAIT optical observations
  87. EP260602a: Optical upper limits with Kinder observations
  88. EP260602a: Einstein Probe detection of a fast X-ray transient
  89. GRB 260601B/EP260601a: SVOM/VT optical observations
  90. EP260601a: Einstein Probe detection of an X-ray transient
  91. EP-WXT trigger 01709266307 (EP260601a): COLIBRÍ optical observations
  92. EP-WXT trigger 01709266307 (EP260601a): JinShan optical counterpart detection
  93. EP260530a/AT 2026nwl: COLIBRÍ optical observations
  94. GRB 260530C: SVOM/ECLAIRs detection of a burst through on-ground search
  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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