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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"

20901 results found.

  1. GRB 260822A: SVOM/VT optical detection of COLIBRÍ candidate
  2. GRB 260822A: SVOM/COLIBRÍ (FM-GFT) possible optical counterpart candidate
  3. EP260822a: Einstein Probe detection of a fast X-ray transient
  4. GRB 260822A: LCO optical upper limits
  5. GRB 260822A: GOTO optical upper limit
  6. GRB 260822A: SVOM detection of a short burst
  7. Fermi-LAT Gamma-ray Observations of IceCube-260821A
  8. Fermi-LAT Gamma-ray Observations of IceCube-260807A
  9. GRB 260818B: VLA radio observations
  10. GRB 260818B: SVOM/C-GFT optical upper limit
  11. IceCube Alert 260821A: Global MASTER-Net observations report
  12. GRB 260818A: J-band observations with WINTER
  13. GRB 260818B: SVOM/ECLAIRs refined analysis
  14. GRB 260818A: SVOM/ECLAIRs refined analysis
  15. GRB 260818B: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  16. EP260806a: SAO RAS multicolor optical observations
  17. EP260812a: AbAO optical upper limit
  18. GRB 260818A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  19. EP260806a: NUTTELA-TAO optical observations
  20. EP260812a: AZT-22 optical upper limit
  21. EP260812b: GTC/OSIRIS+ tentative spectroscopic redshift z = 2.034
  22. EP260806a: WFST optical observations
  23. EP260812b: Optical upper limit with Kinder
  24. GRB 260808B: Liverpool Telescope further optical observations
  25. EP260812a: NOT and Liverpool Telescope upper limits:
  26. EP260812b: Liverpool Telescope observations
  27. EP260812b: GOTO detection of the optical counterpart
  28. EP260812a: SVOM/C-GFT optical upper limit
  29. EP260812b: COLIBRÍ optical observations
  30. EP trigger #01709278129 (EP260812b?): NOT optical counterpart
  31. GRB 260808B: SVOM/COLIBRÍ (FM-GFT) confirmation of the optical rebrightening
  32. GRB 260809A: SAO RAS optical observations
  33. GRB 260808B: SAO RAS optical observations
  34. GRB 260808B: SVOM/VT optical re-brightening at day 3
  35. GRB 260807A: SVOM/ECLAIRs refined analysis
  36. EP260806a: MAO/AZT-22 optical observations
  37. GRB260808B: MAO/AZT-22 optical observations
  38. GRB 260809A: J-band upper limit with WINTER
  39. GRB 260809A: SVOM/COLIBRÍ (FM-GFT) optical observation
  40. GRB 260808B: SVOM/COLIBRÍ (FM-GFT) optical observation
  41. GRB 260809A: NOT optical observations
  42. GRB260809A: MAO/AZT-22 optical observations
  43. GRB260809A: OHP/T193 optical observations
  44. GRB 260809A: SVOM/VT optical counterpart
  45. EP260809a: J-band upper limit with WINTER
  46. GRB 260808B: J-band upper limit with WINTER
  47. GRB 260808B: SVOM/ECLAIRs refined analysis
  48. GRB 260808B: Liverpool Telescope optical observations
  49. GRB 260808B: NOT optical observations
  50. GRB 260808B: LCO optical observations
  51. EP260809a: COLIBRÍ optical observations
  52. EP260809a: OHP/T193 optical observations
  53. GRB260808B: OHP/T193 optical observations
  54. GRB 260808B: SVOM/VT optical afterglow confirmation
  55. Fermi GRB 260808A: Global MASTER-Net observations report
  56. EP260806a: ZTF serendipitous detection of ZTF26abmjjnm / AT 2026yeh
  57. IceCube Alert 260807A: Global MASTER-Net observations report
  58. IceCube-260805A: One candidate from the Zwicky Transient Facility
  59. EP260806a: COLIBRÍ optical observations
  60. EP260806a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  61. EP260806a: Liverpool Telescope observations of the counterpart show a blue colour
  62. EP260731a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  63. Fermi GRB 260805A: Global MASTER-Net observations report
  64. AT 2026wki: EP/FXT follow-up observations
  65. GRB 260708A / SN 2026stf: Spectroscopic host redshift z = 0.055 and confirmation of an associated type Ic-BL supernova
  66. GRB 260708A: LCO further optical observations show supernova features
  67. Fermi GRB 260802B: Global MASTER-Net observations report
  68. GRB 260802A / EP J223759.5+531421: SVOM/VT optical upper limit
  69. GRB 260802A: SVOM/VT optical upper limits from VHF data
  70. GRB 260802A / EP J223759.5+531421: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  71. GRB 260727A: EP-FXT further follow-up observations and candidate afterglow
  72. GRB 260618B: SVOM/VT continued optical observations indicated a steeper and redder decay
  73. Fermi-LAT Gamma-ray Observations of IceCube-260722A
  74. EP260731a: COLIBRÍ optical upper limit
  75. GRB 260727A: SVOM/ECLAIRs refined analysis
  76. GRB 260726A: SVOM/ECLAIRs refined analysis
  77. EP260727a: SAO RAS optical observations
  78. GRB 260727A: AbAO and SAO RAS optical observations
  79. GRB 260726A: EP-FXT follow-up observations
  80. EP260727a: OHP/T193 optical observations
  81. GRB 260726A: Liverpool Telescope optical observations
  82. EP260727a: NUTTELA-TAO Early Optical Limits
  83. GRB 260727A: EP/FXT follow-up observations
  84. GRB 260726A: J-band upper limit with WINTER
  85. GRB 260727A: J-band upper limit with WINTER
  86. GRB 260726A: SVOM/VT optical candidate
  87. GRB 260727A / SVOM sb26072702: RAPAS optical non-detection
  88. GRB 260727A: GOTO early optical upper limit
  89. GRB 260727A: Kilonova-Catcher optical upper limit
  90. Fermi GRB 260726A: Global MASTER-Net observations report
  91. GRB 260727A: SVOM detection of a bright long burst
  92. IceCube-260722A: Classification of ZTF26abjbxfs/SN 2026vts as a Type Ia Supernova
  93. EP260723a: further EP-FXT follow-up observation
  94. EP260725a: EP-WXT detection of an X-ray transient
  95. EP260723a: Continued Liverpool Telescope observations suggest hours long optical plateau or rebrightening
  96. EP260723a: EP-FXT follow-up observation
  97. GRB 260718A: SVOM/ECLAIRs refined analysis
  98. EP260723a: COLIBRÍ optical observations
  99. EP260723a: EP-WXT detection of a fast X-ray transient
  100. IceCube-260722A: One candidate from the Zwicky Transient Facility (ZTF)

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