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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"

21784 results found.

  1. GRB 260809A: J-band upper limit with WINTER
  2. GRB 260809A: SVOM/COLIBRÍ (FM-GFT) optical observation
  3. GRB 260808B: SVOM/COLIBRÍ (FM-GFT) optical observation
  4. GRB 260809A: NOT optical observations
  5. GRB260809A: MAO/AZT-22 optical observations
  6. GRB260809A: OHP/T193 optical observations
  7. GRB 260809A: SVOM/VT optical counterpart
  8. EP260809a: J-band upper limit with WINTER
  9. GRB 260808B: J-band upper limit with WINTER
  10. GRB 260808B: SVOM/ECLAIRs refined analysis
  11. GRB 260808B: Liverpool Telescope optical observations
  12. GRB 260808B: NOT optical observations
  13. GRB 260808B: LCO optical observations
  14. EP260809a: COLIBRÍ optical observations
  15. EP260809a: OHP/T193 optical observations
  16. GRB260808B: OHP/T193 optical observations
  17. GRB 260808B: SVOM/VT optical afterglow confirmation
  18. Fermi GRB 260808A: Global MASTER-Net observations report
  19. EP260806a: ZTF serendipitous detection of ZTF26abmjjnm / AT 2026yeh
  20. IceCube Alert 260807A: Global MASTER-Net observations report
  21. IceCube-260805A: One candidate from the Zwicky Transient Facility
  22. EP260806a: COLIBRÍ optical observations
  23. EP260806a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  24. EP260806a: SVOM/VT optical observation
  25. EP260806a: Liverpool Telescope observations of the counterpart show a blue colour
  26. EP260806a: OSIRIS+/GTC redshift z=0.089
  27. EP260731a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  28. EP260806a: LCO likely optical counterpart
  29. Fermi GRB 260805A: Global MASTER-Net observations report
  30. AT 2026wki: EP/FXT follow-up observations
  31. GRB 260708A / SN 2026stf: Spectroscopic host redshift z = 0.055 and confirmation of an associated type Ic-BL supernova
  32. GRB 260708A: LCO further optical observations show supernova features
  33. Fermi GRB 260802B: Global MASTER-Net observations report
  34. GRB 260802A / EP J223759.5+531421: SVOM/VT optical upper limit
  35. GRB 260802A: SVOM/VT optical upper limits from VHF data
  36. GRB 260802A / EP J223759.5+531421: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  37. GRB 260727A: EP-FXT further follow-up observations and candidate afterglow
  38. GRB 260618B: SVOM/VT continued optical observations indicated a steeper and redder decay
  39. Fermi-LAT Gamma-ray Observations of IceCube-260722A
  40. EP260731a: COLIBRÍ optical upper limit
  41. GRB 260727A: SVOM/ECLAIRs refined analysis
  42. GRB 260726A: SVOM/ECLAIRs refined analysis
  43. EP260727a: VLT/X-shooter spectroscopic redshift z = 2.817
  44. EP260727a: SAO RAS optical observations
  45. GRB 260727A: AbAO and SAO RAS optical observations
  46. GRB 260726A: EP-FXT follow-up observations
  47. EP260727a: OHP/T193 optical observations
  48. GRB 260726A: Liverpool Telescope optical observations
  49. EP260727a: NUTTELA-TAO Early Optical Limits
  50. GRB 260727A: EP/FXT follow-up observations
  51. GRB 260726A: J-band upper limit with WINTER
  52. GRB 260727A: J-band upper limit with WINTER
  53. GRB 260726A: SVOM/VT optical candidate
  54. GRB 260727A / SVOM sb26072702: RAPAS optical non-detection
  55. EP260723a: SVOM/ECLAIRs Upper Limit
  56. GRB 260727A: GOTO early optical upper limit
  57. GRB 260727A: Kilonova-Catcher optical upper limit
  58. Fermi GRB 260726A: Global MASTER-Net observations report
  59. GRB 260727A: SVOM detection of a bright long burst
  60. IceCube-260722A: Classification of ZTF26abjbxfs/SN 2026vts as a Type Ia Supernova
  61. EP260723a: further EP-FXT follow-up observation
  62. EP260725a: EP-WXT detection of an X-ray transient
  63. EP260723a: Continued Liverpool Telescope observations suggest hours long optical plateau or rebrightening
  64. EP260723a: EP-FXT follow-up observation
  65. GRB 260718A: SVOM/ECLAIRs refined analysis
  66. EP260723a: COLIBRÍ optical observations
  67. EP260723a: Liverpool Telescope likely optical counterpart
  68. EP260723a: EP-WXT detection of a fast X-ray transient
  69. IceCube-260722A: One candidate from the Zwicky Transient Facility (ZTF)
  70. IceCube Alert 260722A: Global MASTER-Net observations report
  71. SVOM trigger sb26071506: SVOM/VT confirmation of a stellar flare
  72. GRB 260705A: Retraction of optical counterpart
  73. Fermi trigger No 806104130: Global MASTER-Net observations report
  74. Fermi GRB 260718A: Global MASTER-Net observations report
  75. GRB 260718A : GRANDMA and KNC upper limits
  76. GRB 260718A: SVOM/VT optical upper limits
  77. GRB 260718A: SVOM detection of a burst
  78. GRB 260310A / AT2026fgk: Late-time Chandra Detection
  79. GRB 260714B: COLIBRÍ optical counterpart candidate
  80. SVOM sb26071506: Global MASTER-Net observations report
  81. IceCube-260712A: No candidates with the Zwicky Transient Facility (ZTF)
  82. EP260703a: SVOM/ECLAIRs Upper Limit
  83. IceCube-260712A: LAST optical follow-up observations of the IceCube neutrino candidate
  84. GRB 260706A: ATCA detection of possible radio counterpart
  85. GRB 260705A: ATCA radio observations
  86. GRB 260619A: SVOM/VT continuous optical observations
  87. GRB 260618B: SVOM/VT optical observations indicate shallow decay and reddening
  88. GRB 260708A: slowly decaying X-ray emission observed by EP/FXT
  89. EP260623a: KAIT optical observations
  90. GRB 260708A: GRANDMA Optical Observations
  91. Fermi-LAT Gamma-ray Observations of IceCube-260712A
  92. Fermi-LAT Gamma-ray Observations of IceCube-260708A
  93. Fermi-LAT Gamma-ray Observations of IceCube-260704A
  94. GRB 260708A: LCO optical observations
  95. EP260711a: Einstein Probe detection of an X-ray transient
  96. IceCube-260708A: Observations with the Vera C. Rubin Observatory
  97. EP-WXT trigger 0170924151 : RAPAS optical counterpart candidate detection
  98. GRB 260704A: SVOM/ECLAIRs refined analysis
  99. GRB 260706A : GRANDMA Upper limits
  100. GRB 260708A: Kilonova-Catcher optical afterglow detection

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