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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"

20951 results found.

  1. EP260809a: COLIBRÍ optical observations
  2. EP260809a: OHP/T193 optical observations
  3. GRB260808B: OHP/T193 optical observations
  4. GRB 260808B: SVOM/VT optical afterglow confirmation
  5. Fermi GRB 260808A: Global MASTER-Net observations report
  6. EP260806a: ZTF serendipitous detection of ZTF26abmjjnm / AT 2026yeh
  7. IceCube Alert 260807A: Global MASTER-Net observations report
  8. IceCube-260805A: One candidate from the Zwicky Transient Facility
  9. EP260806a: COLIBRÍ optical observations
  10. EP260806a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  11. EP260806a: Liverpool Telescope observations of the counterpart show a blue colour
  12. EP260731a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  13. Fermi GRB 260805A: Global MASTER-Net observations report
  14. AT 2026wki: EP/FXT follow-up observations
  15. GRB 260708A / SN 2026stf: Spectroscopic host redshift z = 0.055 and confirmation of an associated type Ic-BL supernova
  16. GRB 260708A: LCO further optical observations show supernova features
  17. Fermi GRB 260802B: Global MASTER-Net observations report
  18. GRB 260802A / EP J223759.5+531421: SVOM/VT optical upper limit
  19. GRB 260802A: SVOM/VT optical upper limits from VHF data
  20. GRB 260802A / EP J223759.5+531421: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  21. GRB 260727A: EP-FXT further follow-up observations and candidate afterglow
  22. GRB 260618B: SVOM/VT continued optical observations indicated a steeper and redder decay
  23. Fermi-LAT Gamma-ray Observations of IceCube-260722A
  24. EP260731a: COLIBRÍ optical upper limit
  25. GRB 260727A: SVOM/ECLAIRs refined analysis
  26. GRB 260726A: SVOM/ECLAIRs refined analysis
  27. EP260727a: SAO RAS optical observations
  28. GRB 260727A: AbAO and SAO RAS optical observations
  29. GRB 260726A: EP-FXT follow-up observations
  30. EP260727a: OHP/T193 optical observations
  31. GRB 260726A: Liverpool Telescope optical observations
  32. EP260727a: NUTTELA-TAO Early Optical Limits
  33. GRB 260727A: EP/FXT follow-up observations
  34. GRB 260726A: J-band upper limit with WINTER
  35. GRB 260727A: J-band upper limit with WINTER
  36. GRB 260726A: SVOM/VT optical candidate
  37. GRB 260727A / SVOM sb26072702: RAPAS optical non-detection
  38. GRB 260727A: GOTO early optical upper limit
  39. GRB 260727A: Kilonova-Catcher optical upper limit
  40. Fermi GRB 260726A: Global MASTER-Net observations report
  41. GRB 260727A: SVOM detection of a bright long burst
  42. IceCube-260722A: Classification of ZTF26abjbxfs/SN 2026vts as a Type Ia Supernova
  43. EP260723a: further EP-FXT follow-up observation
  44. EP260725a: EP-WXT detection of an X-ray transient
  45. EP260723a: Continued Liverpool Telescope observations suggest hours long optical plateau or rebrightening
  46. EP260723a: EP-FXT follow-up observation
  47. GRB 260718A: SVOM/ECLAIRs refined analysis
  48. EP260723a: COLIBRÍ optical observations
  49. EP260723a: EP-WXT detection of a fast X-ray transient
  50. IceCube-260722A: One candidate from the Zwicky Transient Facility (ZTF)
  51. IceCube Alert 260722A: Global MASTER-Net observations report
  52. SVOM trigger sb26071506: SVOM/VT confirmation of a stellar flare
  53. GRB 260705A: Retraction of optical counterpart
  54. Fermi trigger No 806104130: Global MASTER-Net observations report
  55. Fermi GRB 260718A: Global MASTER-Net observations report
  56. GRB 260718A : GRANDMA and KNC upper limits
  57. GRB 260718A: SVOM/VT optical upper limits
  58. GRB 260718A: SVOM detection of a burst
  59. GRB 260310A / AT2026fgk: Late-time Chandra Detection
  60. GRB 260714B: COLIBRÍ optical counterpart candidate
  61. SVOM sb26071506: Global MASTER-Net observations report
  62. IceCube-260712A: No candidates with the Zwicky Transient Facility (ZTF)
  63. IceCube-260712A: LAST optical follow-up observations of the IceCube neutrino candidate
  64. GRB 260706A: ATCA detection of possible radio counterpart
  65. GRB 260705A: ATCA radio observations
  66. GRB 260619A: SVOM/VT continuous optical observations
  67. GRB 260618B: SVOM/VT optical observations indicate shallow decay and reddening
  68. GRB 260708A: slowly decaying X-ray emission observed by EP/FXT
  69. EP260623a: KAIT optical observations
  70. GRB 260708A: GRANDMA Optical Observations
  71. Fermi-LAT Gamma-ray Observations of IceCube-260712A
  72. Fermi-LAT Gamma-ray Observations of IceCube-260708A
  73. Fermi-LAT Gamma-ray Observations of IceCube-260704A
  74. GRB 260708A: LCO optical observations
  75. EP260711a: Einstein Probe detection of an X-ray transient
  76. IceCube-260708A: Observations with the Vera C. Rubin Observatory
  77. EP-WXT trigger 0170924151 : RAPAS optical counterpart candidate detection
  78. GRB 260704A: SVOM/ECLAIRs refined analysis
  79. GRB 260706A : GRANDMA Upper limits
  80. GRB 260708A: Kilonova-Catcher optical afterglow detection
  81. IceCube-260708A: One candidate from the Zwicky Transient Facility
  82. Fermi LAT GRB 260708A: MASTER OT J150237.02-435307.7 optical counterpart detection
  83. IceCube Alert 260709A: Global MASTER-Net observations report
  84. LAT GRB260708.42: Global MASTER-Net observations report
  85. GRB 260706A: SVOM/VT optical upper limits
  86. GRB 260705A: Candidate Optical Counterpart from SOAR and Gemini-South and Possible Association with GRB 260705B
  87. GRB 260706A: SVOM/ECLAIRs refined analysis
  88. GRB 260704A: SVOM/COLIBRÍ (FM-GFT) possible optical counterpart candidate
  89. GRB 260706A: REM optical/NIR observations
  90. IceCube-260704A: No candidates from the Zwicky Transient Facility
  91. GRB 260705A: SVOM/ECLAIRs refined analysis
  92. IceCube260704A: OHP/T193 optical observations
  93. GRB 260704A: NOT optical upper limits
  94. EP260703a: EP-WXT detection of a fast X-ray transient
  95. EP260628b: EP-WXT detection of an X-ray transient and EP-FXT follow-up observation
  96. Fermi trigger No 804738310: Global MASTER-Net observations report
  97. Fermi GRB 260703A: Global MASTER-Net observations report
  98. GRB 260610B: VLA detection
  99. GRB 260614B: ATCA Radio Upper Limits
  100. GRB 260610B / AT2026owq: SAO RAS, CrAO and INASAN further optical observations and light curve

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