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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"

20833 results found.

  1. EP260901a: Global MASTER-Net observations report
  2. IceCube-260827A: No transient candidates from the Zwicky Transient Facility
  3. GRB 260831B / sb26083106: SVOM/VT optical variability of V* GK Per
  4. NuSTAR Transient 260828: LCO Optical Upper Limits
  5. EP260901a: EP-WXT detection of a fast X-ray transient
  6. EP260830a: Global MASTER-Net observations report
  7. EP260830a: EP-WXT detection of a fast X-ray transient
  8. NuSTAR 260828: a 1100s hard X-ray transient
  9. EP260727a: ATCA 10 GHz detection
  10. Fermi-LAT Gamma-ray Observations of IceCube-260827A
  11. Fermi-LAT Gamma-ray Observations of IceCube-260825A
  12. GRB 260818B: VLT optical and nIR observations
  13. GRB 260818B: TNG NIR observations
  14. MAXI GRB260827.40: Global MASTER-Net observations report
  15. The EP-WXT trigger 01709291839 is likely the known LMXB 4U 1745-203
  16. GRB 260818B: 6 GHz VLA observations
  17. GRB 260818B: SVOM/VT optical upper limit and continuous observations
  18. GRB 260818B: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  19. GRB 260808B: SAO RAS observations of the optical rebrightening
  20. EP260822a: Global MASTER-Net observations report
  21. EP Alert 260820.31: Global MASTER-Net observations report
  22. IceCube-260825A: No transient candidates from the Zwicky Transient Facility
  23. GRB 260807A: EP-FXT follow-up observations
  24. GRB 260822A: SVOM/ECLAIRs refined analysis
  25. GRB 260809A: SVOM/ECLAIRs refined analysis
  26. GRB 260822A: SVOM/VT optical upper limits
  27. IceCube Alert 260825A: Global MASTER-Net observations report
  28. GRB 260822A: PRIME near-infrared upper limits from multiple epochs
  29. GRB 260822A: EP/FXT follow-up observations
  30. GRB 260822A: the candidate optical afterglow is an unrelated type-Ia SN
  31. GRB 260818A: further EP-FXT observations and X-ray afterglow confirmation
  32. GRB 260822A: GOTO optical counterpart detection
  33. GRB 260822A: SVOM/VT optical detection of COLIBRÍ candidate
  34. GRB 260822A: SVOM/COLIBRÍ (FM-GFT) possible optical counterpart candidate
  35. EP260822a: Einstein Probe detection of a fast X-ray transient
  36. GRB 260822A: LCO optical upper limits
  37. GRB 260822A: GOTO optical upper limit
  38. GRB 260822A: SVOM detection of a short burst
  39. Fermi-LAT Gamma-ray Observations of IceCube-260821A
  40. Fermi-LAT Gamma-ray Observations of IceCube-260807A
  41. GRB 260818B: VLA radio observations
  42. GRB 260818B: SVOM/C-GFT optical upper limit
  43. IceCube Alert 260821A: Global MASTER-Net observations report
  44. GRB 260818A: J-band observations with WINTER
  45. GRB 260818B: SVOM/ECLAIRs refined analysis
  46. GRB 260818A: SVOM/ECLAIRs refined analysis
  47. GRB 260818B: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  48. EP260806a: SAO RAS multicolor optical observations
  49. EP260812a: AbAO optical upper limit
  50. GRB 260818A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  51. EP260806a: NUTTELA-TAO optical observations
  52. EP260812a: AZT-22 optical upper limit
  53. EP260812b: GTC/OSIRIS+ tentative spectroscopic redshift z = 2.034
  54. EP260806a: WFST optical observations
  55. EP260812b: Optical upper limit with Kinder
  56. GRB 260808B: Liverpool Telescope further optical observations
  57. EP260812a: NOT and Liverpool Telescope upper limits:
  58. EP260812b: Liverpool Telescope observations
  59. EP260812b: GOTO detection of the optical counterpart
  60. EP260812a: SVOM/C-GFT optical upper limit
  61. EP260812b: COLIBRÍ optical observations
  62. EP trigger #01709278129 (EP260812b?): NOT optical counterpart
  63. GRB 260808B: SVOM/COLIBRÍ (FM-GFT) confirmation of the optical rebrightening
  64. GRB 260809A: SAO RAS optical observations
  65. GRB 260808B: SAO RAS optical observations
  66. GRB 260808B: SVOM/VT optical re-brightening at day 3
  67. GRB 260807A: SVOM/ECLAIRs refined analysis
  68. EP260806a: MAO/AZT-22 optical observations
  69. GRB260808B: MAO/AZT-22 optical observations
  70. GRB 260809A: J-band upper limit with WINTER
  71. GRB 260809A: SVOM/COLIBRÍ (FM-GFT) optical observation
  72. GRB 260808B: SVOM/COLIBRÍ (FM-GFT) optical observation
  73. GRB 260809A: NOT optical observations
  74. GRB260809A: MAO/AZT-22 optical observations
  75. GRB260809A: OHP/T193 optical observations
  76. GRB 260809A: SVOM/VT optical counterpart
  77. EP260809a: J-band upper limit with WINTER
  78. GRB 260808B: J-band upper limit with WINTER
  79. GRB 260808B: SVOM/ECLAIRs refined analysis
  80. GRB 260808B: Liverpool Telescope optical observations
  81. GRB 260808B: NOT optical observations
  82. GRB 260808B: LCO optical observations
  83. EP260809a: COLIBRÍ optical observations
  84. EP260809a: OHP/T193 optical observations
  85. GRB260808B: OHP/T193 optical observations
  86. GRB 260808B: SVOM/VT optical afterglow confirmation
  87. Fermi GRB 260808A: Global MASTER-Net observations report
  88. EP260806a: ZTF serendipitous detection of ZTF26abmjjnm / AT 2026yeh
  89. IceCube Alert 260807A: Global MASTER-Net observations report
  90. IceCube-260805A: One candidate from the Zwicky Transient Facility
  91. EP260806a: COLIBRÍ optical observations
  92. EP260806a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  93. EP260806a: Liverpool Telescope observations of the counterpart show a blue colour
  94. EP260731a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  95. Fermi GRB 260805A: Global MASTER-Net observations report
  96. AT 2026wki: EP/FXT follow-up observations
  97. GRB 260708A / SN 2026stf: Spectroscopic host redshift z = 0.055 and confirmation of an associated type Ic-BL supernova
  98. GRB 260708A: LCO further optical observations show supernova features
  99. Fermi GRB 260802B: Global MASTER-Net observations report
  100. GRB 260802A / EP J223759.5+531421: SVOM/VT optical upper limit

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