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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"

21792 results found.

  1. GRB 260809A: SAO RAS optical observations
  2. GRB 260808B: SAO RAS optical observations
  3. GRB 260808B: SVOM/VT optical re-brightening at day 3
  4. GRB 260317A: SVOM/ECLAIRs detection through offline targeted search and its possible association to magnetar 1E 1841-04.5
  5. GRB 260807A: SVOM/ECLAIRs refined analysis
  6. EP260806a: MAO/AZT-22 optical observations
  7. GRB260808B: MAO/AZT-22 optical observations
  8. GRB 250607A: SVOM/ECLAIRs detection through offline targeted search
  9. GRB 260809A: J-band upper limit with WINTER
  10. GRB 260809A: SVOM/COLIBRÍ (FM-GFT) optical observation
  11. GRB 260808B: SVOM/COLIBRÍ (FM-GFT) optical observation
  12. GRB 260809A: NOT optical observations
  13. GRB260809A: MAO/AZT-22 optical observations
  14. GRB260809A: OHP/T193 optical observations
  15. GRB 260809A: SVOM/VT optical counterpart
  16. EP260809a: J-band upper limit with WINTER
  17. GRB 260808B: J-band upper limit with WINTER
  18. GRB 260808B: SVOM/ECLAIRs refined analysis
  19. GRB 260808B: Liverpool Telescope optical observations
  20. GRB 260808B: NOT optical observations
  21. GRB 260808B: LCO optical observations
  22. EP260809a: COLIBRÍ optical observations
  23. EP260809a: OHP/T193 optical observations
  24. GRB260808B: OHP/T193 optical observations
  25. GRB 260808B: SVOM/VT optical afterglow confirmation
  26. Fermi GRB 260808A: Global MASTER-Net observations report
  27. EP260806a: ZTF serendipitous detection of ZTF26abmjjnm / AT 2026yeh
  28. IceCube Alert 260807A: Global MASTER-Net observations report
  29. IceCube-260805A: One candidate from the Zwicky Transient Facility
  30. EP260806a: COLIBRÍ optical observations
  31. EP260806a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  32. EP260806a: SVOM/VT optical observation
  33. EP260806a: Liverpool Telescope observations of the counterpart show a blue colour
  34. EP260806a: OSIRIS+/GTC redshift z=0.089
  35. EP260731a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  36. EP260806a: LCO likely optical counterpart
  37. Fermi GRB 260805A: Global MASTER-Net observations report
  38. AT 2026wki: EP/FXT follow-up observations
  39. GRB 260708A / SN 2026stf: Spectroscopic host redshift z = 0.055 and confirmation of an associated type Ic-BL supernova
  40. GRB 260708A: LCO further optical observations show supernova features
  41. Fermi GRB 260802B: Global MASTER-Net observations report
  42. GRB 260802A / EP J223759.5+531421: SVOM/VT optical upper limit
  43. GRB 260802A: SVOM/VT optical upper limits from VHF data
  44. GRB 260802A / EP J223759.5+531421: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  45. GRB 260727A: EP-FXT further follow-up observations and candidate afterglow
  46. GRB 260618B: SVOM/VT continued optical observations indicated a steeper and redder decay
  47. Fermi-LAT Gamma-ray Observations of IceCube-260722A
  48. EP260731a: COLIBRÍ optical upper limit
  49. GRB 260727A: SVOM/ECLAIRs refined analysis
  50. GRB 260726A: SVOM/ECLAIRs refined analysis
  51. EP260727a: VLT/X-shooter spectroscopic redshift z = 2.817
  52. EP260727a: SAO RAS optical observations
  53. GRB 260727A: AbAO and SAO RAS optical observations
  54. GRB 260726A: EP-FXT follow-up observations
  55. EP260727a: OHP/T193 optical observations
  56. GRB 260726A: Liverpool Telescope optical observations
  57. EP260727a: NUTTELA-TAO Early Optical Limits
  58. GRB 260727A: EP/FXT follow-up observations
  59. GRB 260726A: J-band upper limit with WINTER
  60. GRB 260727A: J-band upper limit with WINTER
  61. GRB 260726A: SVOM/VT optical candidate
  62. GRB 260727A / SVOM sb26072702: RAPAS optical non-detection
  63. EP260723a: SVOM/ECLAIRs Upper Limit
  64. GRB 260727A: GOTO early optical upper limit
  65. GRB 260727A: Kilonova-Catcher optical upper limit
  66. Fermi GRB 260726A: Global MASTER-Net observations report
  67. GRB 260727A: SVOM detection of a bright long burst
  68. IceCube-260722A: Classification of ZTF26abjbxfs/SN 2026vts as a Type Ia Supernova
  69. EP260723a: further EP-FXT follow-up observation
  70. EP260725a: EP-WXT detection of an X-ray transient
  71. EP260723a: Continued Liverpool Telescope observations suggest hours long optical plateau or rebrightening
  72. EP260723a: EP-FXT follow-up observation
  73. GRB 260718A: SVOM/ECLAIRs refined analysis
  74. EP260723a: COLIBRÍ optical observations
  75. EP260723a: Liverpool Telescope likely optical counterpart
  76. EP260723a: EP-WXT detection of a fast X-ray transient
  77. IceCube-260722A: One candidate from the Zwicky Transient Facility (ZTF)
  78. IceCube Alert 260722A: Global MASTER-Net observations report
  79. SVOM trigger sb26071506: SVOM/VT confirmation of a stellar flare
  80. GRB 260705A: Retraction of optical counterpart
  81. Fermi trigger No 806104130: Global MASTER-Net observations report
  82. Fermi GRB 260718A: Global MASTER-Net observations report
  83. GRB 260718A : GRANDMA and KNC upper limits
  84. GRB 260718A: SVOM/VT optical upper limits
  85. GRB 260718A: SVOM detection of a burst
  86. GRB 260310A / AT2026fgk: Late-time Chandra Detection
  87. GRB 260714B: COLIBRÍ optical counterpart candidate
  88. SVOM sb26071506: Global MASTER-Net observations report
  89. IceCube-260712A: No candidates with the Zwicky Transient Facility (ZTF)
  90. EP260703a: SVOM/ECLAIRs Upper Limit
  91. IceCube-260712A: LAST optical follow-up observations of the IceCube neutrino candidate
  92. GRB 260706A: ATCA detection of possible radio counterpart
  93. GRB 260705A: ATCA radio observations
  94. GRB 260619A: SVOM/VT continuous optical observations
  95. GRB 260618B: SVOM/VT optical observations indicate shallow decay and reddening
  96. GRB 260708A: slowly decaying X-ray emission observed by EP/FXT
  97. EP260623a: KAIT optical observations
  98. GRB 260708A: GRANDMA Optical Observations
  99. Fermi-LAT Gamma-ray Observations of IceCube-260712A
  100. Fermi-LAT Gamma-ray Observations of IceCube-260708A

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