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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"

28057 results found.

  1. EP260509a: Global MASTER-Net observations report
  2. Fermi GBM Sub-Threshold Detection of GRB 260510B
  3. GRB 260510C: SVOM detection of a burst
  4. GRB 260510B: LCO optical upper limits
  5. EP260509a: Einstein Probe detection of an X-ray transient
  6. GRB 260509A: Liverpool Telescope optical observations
  7. GRB 260510B: SVOM detection of a burst
  8. GRB 260509A: LCO optical observations
  9. SVOM GRB 260509A: MASTER-OAFA optical observation
  10. Fermi GRB 260510A: Global MASTER-Net observations report
  11. GRB 260509A: KAIT optical observations
  12. GRB 260509A: SVOM/COLIBRÍ (FM-GFT) observations
  13. GRB 260509A: SVOM/VT optical candidate with VHF data
  14. GRB 260509A: LCO optical counterpart detection
  15. GRB 260509A: SVOM detection of a burst
  16. IceCube-260504A: Upper limits from a search for additional neutrino events in IceCube
  17. EP260507a: REM optical/NIR observations
  18. EP260507a: refined analysis of the EP-WXT and EP-FXT observations
  19. GRB 260507B / EP260507a: Fermi-GBM Sub-Threshold Detection
  20. EP260507a: COLIBRÍ optical observations
  21. EP260507a: NOT optical observations
  22. EP260507a: further Liverpool Telescope observations
  23. EP260507a: Liverpool Telescope optical upper limits
  24. EP260507a: TRT optical counterpart detection
  25. EP260507a: Kinder optical counterpart candidate
  26. EP260507a: LCO optical counterpart
  27. EP260507a: Einstein Probe detection of an X-ray transient
  28. GRB 260506B: BALROG localization (Fermi Trigger 799765648 / GRB 260506547)
  29. Fermi GRB 260506A: Global MASTER-Net observations report
  30. IceCube Alert 260505A: Global MASTER-Net observations report
  31. GRB 260430B: Glowbug gamma-ray detection
  32. GRB 260421B: radio observation with the VLA
  33. Fermi-LAT Gamma-ray Observations of IceCube-260504A
  34. GRB 260430B: AstroSat CZTI detection of a long burst
  35. GRB 260502A: SVOM/GRM observation of a short GRB
  36. GRB 260503A: SVOM/GRM observation of a GRB
  37. Konus-Wind detection of GRB 260411C
  38. GRB 260504B: REM optical/NIR observations
  39. GRB 260504B: LCO z-band upper limit
  40. SVOM GRB 260504B: MASTER-OAFA optical observations
  41. GRB 260504B: SVOM detection of a short burst
  42. Fermi GRB 260504A: Global MASTER-Net observations report
  43. SVOM/GRM observation of a bright burst from SGR 1E1841-045
  44. GRB 260429B / EP260429a: EP-FXT follow-up observation
  45. EP260502a: Einstein Probe detection of an X-ray transient
  46. GRB 260429A: SVOM/GRM observation of a short burst
  47. SN 2026kid: Optical follow-up with small-aperture telescopes in Spain and China
  48. EP260429a: Global MASTER-Net observations report
  49. EP260430a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  50. GRB 260424B: AstroSat CZTI detection
  51. GRB 260429B / EP260429a: COLIBRÍ optical upper limit
  52. EP260429a: LCO optical upper limits
  53. EP260430a: LCO optical upper limits
  54. GRB 260430A / EP260430a: COLIBRÍ optical upper limit
  55. GRB 260429A: Fermi GBM Detection
  56. Fermi GRB 260429A: Global MASTER-Net observations report
  57. EP260430a: Global MASTER-Net observations report
  58. EP260430a: Einstein Probe detection of an X-ray transient
  59. EP260429a: EP-WXT detection of a fast X-ray transient
  60. GRB 260428A: SVOM/GRM observation of a possible short burst with extended emission
  61. IceCube-260425A: Upper limits from a search for additional neutrino events in IceCube
  62. Fermi GRB 260428A: Global MASTER-Net observations report
  63. EP260416a: Mondy and Terskol optical upper limits
  64. GRB 260424B: Glowbug gamma-ray detection of a short burst
  65. GRB 260424B: COLIBRÍ optical upper limit
  66. Fermi-LAT Gamma-ray Observations of IceCube-260425A
  67. GRB 260305A: likely detection by Fermi-LAT and the LAT gamma-ray position
  68. IceCube Alert 260425A: Global MASTER-Net observations report
  69. Fermi trigger No 798737427: Global MASTER-Net observations report
  70. GRB 260401A: cubesat Avion detection
  71. EP260321a: Upper limits from ATCA radio observations
  72. GRB 260421B: Kilonova-Catcher optical afterglow detection
  73. The EP-WXT trigger 01709258652: Mondy optical observations
  74. EP260416a: Mondy optical observations
  75. GRB 260421B: 3.6m DOT optical observation
  76. EP260416a: ZTSh R band observations
  77. IceCube-Cascade 260418A: Upper limits from a search for additional neutrino events in IceCube
  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. GOTO26djh/AT2026jpw: radio detection at 15GHz
  86. GRB 260421B: SVOM/VT optical observations
  87. EP260416a: J band upper limit by SYSU 80cm infrared telescope
  88. GRB 260310A: Late-time Chandra X-ray Detection
  89. EP260416a: 1.3m DFOT optical observation
  90. Fermi GRB 260421C: Global MASTER-Net observations report
  91. GRB 260421B: VLT/X-shooter spectroscopic redshift z = 2.115
  92. Fermi GRB 260421B: Global MASTER-Net observations report
  93. GRB 260421B: LCO optical afterglow confirmation
  94. GRB 260421B: SVOM/COLIBRÍ (FM-GFT) optical detection of a candidate counterpart
  95. GRB 260421B: TRT optical counterpart detection
  96. GRB 260421B: SVOM detection of a long burst
  97. GRB 260421B: BALROG localization (Fermi Trigger 798437606 / GRB 260421176)
  98. Fermi GRB 260421A: Global MASTER-Net observations report
  99. EP260321a: VLA radio follow-up
  100. GRB 260412A: LCOGT Optical Upper Limits

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