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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"

22056 results found.

  1. EP260812b: GOTO detection of the optical counterpart
  2. EP260812a: SVOM/C-GFT optical upper limit
  3. EP260812b: COLIBRÍ optical observations
  4. EP trigger #01709278129 (EP260812b?): NOT optical counterpart
  5. GRB 260808B: SVOM/COLIBRÍ (FM-GFT) confirmation of the optical rebrightening
  6. GRB 260809A: SAO RAS optical observations
  7. GRB 260808B: SAO RAS optical observations
  8. GRB 260808B: SVOM/VT optical re-brightening at day 3
  9. GRB 260806A: CALET Gamma-Ray Burst Monitor detection
  10. GRB 260807A: SVOM/ECLAIRs refined analysis
  11. EP260806a: MAO/AZT-22 optical observations
  12. GRB260808B: MAO/AZT-22 optical observations
  13. GRB 250607A: SVOM/ECLAIRs detection through offline targeted search
  14. GRB 260809A: J-band upper limit with WINTER
  15. GRB 260809A: SVOM/COLIBRÍ (FM-GFT) optical observation
  16. GRB 260808B: SVOM/COLIBRÍ (FM-GFT) optical observation
  17. GRB 260809A: NOT optical observations
  18. GRB260809A: MAO/AZT-22 optical observations
  19. GRB260809A: OHP/T193 optical observations
  20. GRB 260809A: SVOM/VT optical counterpart
  21. EP260809a: J-band upper limit with WINTER
  22. GRB 260808B: J-band upper limit with WINTER
  23. GRB 260808B: SVOM/ECLAIRs refined analysis
  24. GRB 260808B: Liverpool Telescope optical observations
  25. GRB 260808B: NOT optical observations
  26. GRB 260808B: LCO optical observations
  27. EP260809a: COLIBRÍ optical observations
  28. EP260809a: OHP/T193 optical observations
  29. GRB260808B: OHP/T193 optical observations
  30. GRB 260808B: SVOM/VT optical afterglow confirmation
  31. Fermi GRB 260808A: Global MASTER-Net observations report
  32. EP260806a: ZTF serendipitous detection of ZTF26abmjjnm / AT 2026yeh
  33. IceCube Alert 260807A: Global MASTER-Net observations report
  34. IceCube-260805A: One candidate from the Zwicky Transient Facility
  35. EP260806a: COLIBRÍ optical observations
  36. EP260806a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  37. EP260806a: Liverpool Telescope observations of the counterpart show a blue colour
  38. EP260731a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  39. Fermi GRB 260805A: Global MASTER-Net observations report
  40. AT 2026wki: EP/FXT follow-up observations
  41. GRB 260708A / SN 2026stf: Spectroscopic host redshift z = 0.055 and confirmation of an associated type Ic-BL supernova
  42. GRB 260708A: LCO further optical observations show supernova features
  43. Fermi GRB 260802B: Global MASTER-Net observations report
  44. GRB 260802A / EP J223759.5+531421: SVOM/VT optical upper limit
  45. GRB 260802A: SVOM/VT optical upper limits from VHF data
  46. GRB 260802A / EP J223759.5+531421: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  47. GRB 260727A: EP-FXT further follow-up observations and candidate afterglow
  48. GRB 260618B: SVOM/VT continued optical observations indicated a steeper and redder decay
  49. Fermi-LAT Gamma-ray Observations of IceCube-260722A
  50. EP260731a: COLIBRÍ optical upper limit
  51. GRB 260727A: SVOM/ECLAIRs refined analysis
  52. GRB 260726A: SVOM/ECLAIRs refined analysis
  53. EP 260729a: Ondrejov D50 optical detection supports stellar flare origin
  54. EP260727a: SAO RAS optical observations
  55. GRB 260727A: AbAO and SAO RAS optical observations
  56. GRB 260726A: EP-FXT follow-up observations
  57. EP260727a: OHP/T193 optical observations
  58. Konus-Wind detection of GRB 260727A
  59. GRB 260726A: Liverpool Telescope optical observations
  60. EP260727a: NUTTELA-TAO Early Optical Limits
  61. GRB 260727A: EP/FXT follow-up observations
  62. GRB 260726A: J-band upper limit with WINTER
  63. GRB 260727A: J-band upper limit with WINTER
  64. GRB 260726A: SVOM/VT optical candidate
  65. GRB 260727A / SVOM sb26072702: RAPAS optical non-detection
  66. GRB 260727A: GOTO early optical upper limit
  67. GRB 260727A: Kilonova-Catcher optical upper limit
  68. Fermi GRB 260726A: Global MASTER-Net observations report
  69. GRB 260727A: SVOM detection of a bright long burst
  70. IceCube-260722A: Classification of ZTF26abjbxfs/SN 2026vts as a Type Ia Supernova
  71. EP260723a: further EP-FXT follow-up observation
  72. EP260725a: EP-WXT detection of an X-ray transient
  73. EP260723a: Continued Liverpool Telescope observations suggest hours long optical plateau or rebrightening
  74. EP260723a: EP-FXT follow-up observation
  75. GRB 260718A: SVOM/ECLAIRs refined analysis
  76. EP260723a: COLIBRÍ optical observations
  77. EP260723a: EP-WXT detection of a fast X-ray transient
  78. IceCube-260722A: One candidate from the Zwicky Transient Facility (ZTF)
  79. IceCube Alert 260722A: Global MASTER-Net observations report
  80. Konus-Wind detection of GRB 260721A
  81. Konus-Wind detection of GRB 260714B
  82. SVOM trigger sb26071506: SVOM/VT confirmation of a stellar flare
  83. GRB 260705A: Retraction of optical counterpart
  84. Fermi trigger No 806104130: Global MASTER-Net observations report
  85. Fermi GRB 260718A: Global MASTER-Net observations report
  86. GRB 260718A : GRANDMA and KNC upper limits
  87. GRB 260718A: SVOM/VT optical upper limits
  88. GRB 260718A: SVOM detection of a burst
  89. GRB 260310A / AT2026fgk: Late-time Chandra Detection
  90. GRB 260714B: COLIBRÍ optical counterpart candidate
  91. SVOM sb26071506: Global MASTER-Net observations report
  92. IceCube-260712A: No candidates with the Zwicky Transient Facility (ZTF)
  93. IceCube-260712A: LAST optical follow-up observations of the IceCube neutrino candidate
  94. GRB 260706A: ATCA detection of possible radio counterpart
  95. GRB 260705A: ATCA radio observations
  96. GRB 260619A: SVOM/VT continuous optical observations
  97. GRB 260618B: SVOM/VT optical observations indicate shallow decay and reddening
  98. GRB 260708A: slowly decaying X-ray emission observed by EP/FXT
  99. EP260623a: KAIT optical observations
  100. GRB 260708A: GRANDMA Optical Observations

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