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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"

21791 results found.

  1. GRB 260608A: SVOM/ECLAIRs refined analysis
  2. GRB 260604C: further SAO RAS optical observations
  3. GRB 260607A: AT2026ong (GOTO26fqf) is a type-Ia SN
  4. GRB 260607A / GOTO26fqf / AT2026ong: COLIBRÍ optical observations
  5. GRB 260604C: SVOM/COLIBRÍ (FM-GFT) colour evolution and confirmation of the late rebrightening
  6. GRB 260604C: SVOM/C-GFT upper limit
  7. GRB 260607A: TRT optical observations
  8. GRB 260604C: GRANDMA further observations
  9. GRB 260607A: GOTO tentative optical counterpart candidate GOTO26fqf / AT2026ong
  10. GRB 260604C: Mondy optical observations: evidence of a possible brightening
  11. GRB 260604C: Simeiz Zeiss-1000 optical observations of the afterglow
  12. GRB 260604C: OPD1.6m - GRANDMA observations - detection
  13. GRB 260604C: 6 GHz VLA observations
  14. GRB 260604C: SAO RAS optical observations
  15. GRB 260604C: GRANDMA observations
  16. GRB260603A: SVOM/ECLAIRs refined analysis
  17. GRB 260604C: Liverpool Telescope optical detection
  18. EP260602d: EP-FXT follow-up observation
  19. GRB 260527A/EP260527a: 6 GHz VLA observations
  20. GRB 260604C: GOTO detections of the optical afterglow
  21. GRB 260604C: Kilonova-Catcher optical afterglow detection
  22. GRB 260604C: SVOM/COLIBRÍ (FM-GFT) optical observations
  23. GRB 260604C: Jinshan optical observations
  24. EP260602d: J-band upper limit with WINTER
  25. EP260602b: J-band upper limit with WINTER
  26. GRB 260604C: LAST detection of optical counterpart candidate
  27. GRB 260604C: MASTER OT J145749.59+284903.0 optical counterpart discovery
  28. Fermi GRB 260604C: Global MASTER-Net observations report
  29. Fermi GRB 260604C: Global MASTER-Net observations report
  30. SVOM GRB260604.85: Global MASTER-Net observations report
  31. GRB 260604C: SVOM detection of a long burst
  32. GRB 260515A: SVOM/VT optical detection at about 18 days post trigger
  33. GRB 260603A: NOT optical observations
  34. EP260603a: Global MASTER-Net observations report
  35. EP260603a: Einstein Probe detection of a fast X-ray transient
  36. EP260602d: Optical Upper limits with kinder observations
  37. EP260602b: Liverpool Telescope observations
  38. EP260602a: Liverpool Telescope optical upper limits
  39. EP260602b: Liverpool Telescope and LCO observations
  40. EP260602a: GTC and Liverpool Telescope optical observations
  41. GRB 260603A: Kilonova-Catcher optical upper limit
  42. GRB 260603A: SVOM/VT optical observations
  43. EP260602a: NOT NIR J-band observations
  44. GRB 260603A: SVOM/COLIBRÍ (FM-GFT) photometric redshift z = 3.57
  45. Fermi trigger No 802141998: Global MASTER-Net observations report
  46. GRB 260603A: SVOM/COLIBRÍ (GFT-FM) optical counterpart candidate
  47. EP260602a: COLIBRÍ optical observations
  48. GRB260601B/EP260601a: NOT near-infrared observations
  49. SVOM GRB260603.23: Global MASTER-Net observations report
  50. Fermi GRB 260602B: Global MASTER-Net observations report
  51. Fermi GRB 260602B: Global MASTER-Net observations report
  52. EP260530a: Xinglong optical spectroscopy of EP260530a / AT 2026nwl
  53. EP260602a: SVOM/VT optical candidate
  54. EP-WXT trigger 01709266414 (EP260602b): JinShan optical counterpart detection
  55. GRB 260601B/EP260601a: J-band upper limit with WINTER
  56. EP260530a/AT 2026nwl: COLIBRÍ optical follow up
  57. EP260530a/AT 2026nwl: KAIT optical observations
  58. EP260602a: Optical upper limits with Kinder observations
  59. GRB 260601B/EP260601a: SVOM/VT optical observations
  60. GRB 260601B/EP260601a: GECAM-B analysis suggests a possible long duration Type I burst
  61. EP-WXT trigger 01709266307 (EP260601a): COLIBRÍ optical observations
  62. EP-WXT trigger 01709266307 (EP260601a): JinShan optical counterpart detection
  63. GRB 260516D: VLA radio detection
  64. EP260530a/AT 2026nwl: COLIBRÍ optical observations
  65. GRB 260530C: SVOM/ECLAIRs detection of a burst through on-ground search
  66. Fermi GRB 260601A: Global MASTER-Net observations report
  67. GRB 260518B: SVOM/ECLAIRs detection of a soft burst possibly associated with EP 260518a and AT 2026ndp
  68. AT2026nik: EP-FXT X-ray counterpart
  69. Fermi trigger No 801900520: Global MASTER-Net observations report
  70. GRB 260531A: MAXI/GSC detection
  71. AT 2026nuz: COLIBRÍ optical observations
  72. EP260527a/GRB 260527A: further FTW optical and NIR observations
  73. GRB 260527A / EP260527a: VLA radio detection
  74. EP260527a/GRB 260527A: optical upper limit with Kinder observations
  75. GRB 260429B / EP260429a: COLIBRÍ optical counterpart candidate
  76. GRB 260529A: GOTO tentative optical afterglow candidate
  77. GRB 260527A/EP260527a: VLT/X-shooter tentative redshift
  78. Fermi GRB 260529A: Global MASTER-Net observations report
  79. EP260526a: SVOM/VT optical upper limits
  80. GRB 260527A/EP260527a: Gemini GMOS-S Optical Observations
  81. EP260527a / GRB 260527A: VLT detection of the optical and nIR counterpart
  82. EP260527a / GRB 260527A: NOT optical observations
  83. GRB 260527A/EP260527a: FTW optical and NIR observations
  84. EP260527a/GRB 260527A: Infrared J upper limit with MDM/MIRAGE
  85. GRB 260527A: CALET Gamma-Ray Burst Monitor detection
  86. EP260527a: SVOM/VT optical observation
  87. EP260527a: COLIBRÍ optical detection
  88. Fermi trigger No 801580882: Global MASTER-Net observations report
  89. EP260526a: Einstein Probe detection of a fast X-ray transient
  90. Fermi GRB 260526A: Global MASTER-Net observations report
  91. EP-WXT 01709266106: NOT optical upper limits
  92. Fermi GRB 260525A: Global MASTER-Net observations report
  93. Fermi GRB 260523A: Global MASTER-Net observations report
  94. EP260518a (AT2026ndp): LCO observations and Gemini-South Redshift z = 2.28
  95. GRB 260522A: GOTO optical upper limit
  96. Fermi trigger No 801135305: Global MASTER-Net observations report
  97. Fermi GRB 260522A: Global MASTER-Net observations report
  98. EP260518a: Einstein Probe detection of an sub-threshold X-ray transient with counterpart AT 2026ndp
  99. GRB 260509A: SVOM/ECLAIRs refined analysis
  100. GRB 260516D: SVOM/ECLAIRs refined analysis

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