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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"

31729 results found.

  1. EP260507a: Liverpool Telescope optical upper limits
  2. EP260507a: GOTO optical counterpart detection
  3. EP260507a: TRT optical counterpart detection
  4. EP260507a: Kinder optical counterpart candidate
  5. EP260507a: LCO optical counterpart
  6. GRB 260504B: AstroSat CZTI detection
  7. GRB 260504B: SVOM/ECLAIRs refined analysis
  8. EP260502a is likely a flaring star
  9. Fermi GRB 260506A: Global MASTER-Net observations report
  10. GRB 260503A: GECAM-B observation of a burst
  11. GRB 260430B: Glowbug gamma-ray detection
  12. GRB 260504B: SVOM/VT optical upper limits
  13. GRB 260421B: radio observation with the VLA
  14. Konus-Wind detection of a burst from SGR 1E1841-045 on 2026 May 2
  15. Konus-Wind detection of GRB 260504B (short/hard)
  16. GRB 260504B: GECAM-B detection
  17. Fermi-LAT Gamma-ray Observations of IceCube-260504A
  18. GRB 260504B: SVOM/GRM spectral analysis
  19. GRB 260504B: SVOM/MXT refined analysis and potential detection
  20. GRB 260504B: EP-FXT upper limit
  21. GRB 260502A: SVOM/GRM observation of a short GRB
  22. GRB 260503A: SVOM/GRM observation of a GRB
  23. IceCube-260504A - IceCube observation of a high-energy neutrino candidate track-like event
  24. GRB 260310A / AT2026fgk: photometric monitoring and tentative maximum of a possible SN
  25. GRB 260504B: REM optical/NIR observations
  26. IPN triangulation of GRB 260429A
  27. IPN triangulation of GRB 260428A
  28. GRB 260504B: AST3-2 i-band upper limit
  29. GRB 260504B: LCO z-band upper limit
  30. SVOM GRB 260504B: MASTER-OAFA optical observations
  31. Fermi GRB 260504A: Global MASTER-Net observations report
  32. SVOM/GRM observation of a bright burst from SGR 1E1841-045
  33. GRB 260502A: GECAM-B observation of a short burst
  34. IPN triangulation of a bright burst from SGR 1E1841-045
  35. GRB 260429B / EP260429a: EP-FXT follow-up observation
  36. EP260502a: BOOTES-7 observations of a fading catalogued source close to the X-ray position
  37. GRB 260429B / EP260429a: AstroSat CZTI detection
  38. EP260502a: BOOTES-7: early optical upper limit
  39. EP260502a: Las Cumbres upper limit
  40. GRB 260429A: SVOM/GRM observation of a short burst
  41. EP260429a: Global MASTER-Net observations report
  42. EP260430a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  43. GRB 260424B: AstroSat CZTI detection
  44. GRB 260429B / EP260429a: COLIBRÍ optical upper limit
  45. EP260429a: LCO optical upper limits
  46. EP260430a: LCO optical upper limits
  47. GRB 260430A / EP260430a: COLIBRÍ optical upper limit
  48. Fermi GRB 260429A: Global MASTER-Net observations report
  49. EP260430a: Global MASTER-Net observations report
  50. GRB 260428A: SVOM/GRM observation of a possible short burst with extended emission
  51. GRB 260428A: GECAM-B detection of a possible long duration Type I burst
  52. IceCube-260425A: Upper limits from a search for additional neutrino events in IceCube
  53. GRB 260428A: AstroSat CZTI detection
  54. Fermi GRB 260428A: Global MASTER-Net observations report
  55. EP260416a: Mondy and Terskol optical upper limits
  56. GRB 260424B: Glowbug gamma-ray detection of a short burst
  57. GRB 260424B: COLIBRÍ optical upper limit
  58. Konus-Wind detection of GRB 260424B
  59. Fermi-LAT Gamma-ray Observations of IceCube-260425A
  60. EP260321a/SN 2026gzf: spectroscopy at Mondy observatory
  61. IPN triangulation of GRB 260424B (short)
  62. IceCube-260425A - IceCube observation of a high-energy neutrino candidate track-like event
  63. GRB 260305A: likely detection by Fermi-LAT and the LAT gamma-ray position
  64. GRB 260401A: cubesat Avion detection
  65. EP260321a: Upper limits from ATCA radio observations
  66. GRB 260421B: Kilonova-Catcher optical afterglow detection
  67. GRB 260421B: Insight-HXMT/HE detection
  68. The EP-WXT trigger 01709258652: Mondy optical observations
  69. GRB 250328A: VLT host galaxy discovery and redshift z = 1.250
  70. EP260416a: Mondy optical observations
  71. GRB 260421B: SVOM/ECLAIRs refined analysis
  72. GRB 260421B: 3.6m DOT optical observation
  73. EP260416a: ZTSh R band observations
  74. EP-WXT trigger 01709260362: FRAM-ORM optical observations confirm flaring star G 151-9
  75. EP250512a / GRB 250512B: VLT/X-shooter host galaxy identification and redshift z = 1.773
  76. GRB 250530A: VLT/X-shooter host galaxy redshift z = 1.486
  77. GRB 260419A: AstroSat CZTI detection
  78. GRB 260421B: SVOM/GRM observation
  79. GRB260421B: J band upper limit by SYSU 80cm infrared telescope
  80. GRB 260421B: EP-FXT follow-up observation
  81. GOTO26djh/AT2026jpw: ATCA radio detection
  82. GRB 260421B: J-band upper limit with WINTER
  83. GRB 260421B: LCO optical counterpart detection
  84. GRB 260421B: Fermi GBM Observation
  85. GRB 260421A: AstroSat CZTI detection
  86. GOTO26djh/AT2026jpw: radio detection at 15GHz
  87. GRB 260412A: SVOM/ECLAIRs refined analysis
  88. GRB 260421B: SVOM/VT optical observations
  89. EP260416a: J band upper limit by SYSU 80cm infrared telescope
  90. GRB 260310A: Late-time Chandra X-ray Detection
  91. GRB 260418A: Insight-HXMT/HE detection
  92. EP260416a: 1.3m DFOT optical observation
  93. GRB 260415A: CALET Gamma-Ray Burst Monitor detection
  94. GRB 260415B: CALET Gamma-Ray Burst Monitor detection
  95. Fermi GRB 260421C: Global MASTER-Net observations report
  96. GRB 260421B: VLT/X-shooter spectroscopic redshift z = 2.115
  97. Fermi GRB 260421B: Global MASTER-Net observations report
  98. GRB 260421B: BOOTES-7 early optical afterglow detection
  99. GRB 260421B: LCO optical afterglow confirmation
  100. GRB 260421B: SVOM/COLIBRÍ (FM-GFT) optical detection of a candidate counterpart

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