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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"

27255 results found.

  1. GRB 260510C: SVOM detection of a burst
  2. GRB 260510B: LCO optical upper limits
  3. EP260509a: Einstein Probe detection of an X-ray transient
  4. GRB 260509A: Liverpool Telescope optical observations
  5. GRB 260510B: SVOM detection of a burst
  6. GRB 260509A: LCO optical observations
  7. SVOM GRB 260509A: MASTER-OAFA optical observation
  8. Fermi GRB 260510A: Global MASTER-Net observations report
  9. GRB 260509A: KAIT optical observations
  10. GRB 260509A: SVOM/COLIBRÍ (FM-GFT) observations
  11. GRB 260509A: SVOM/VT optical candidate with VHF data
  12. GRB 260509A: LCO optical counterpart detection
  13. GRB 260509A: SVOM detection of a burst
  14. IceCube-260504A: Upper limits from a search for additional neutrino events in IceCube
  15. EP260507a: REM optical/NIR observations
  16. EP260507a: refined analysis of the EP-WXT and EP-FXT observations
  17. GRB 260507B / EP260507a: Fermi-GBM Sub-Threshold Detection
  18. EP260507a: COLIBRÍ optical observations
  19. EP260507a: NOT optical observations
  20. EP260507a: further Liverpool Telescope observations
  21. EP260507a: Liverpool Telescope optical upper limits
  22. EP260507a: TRT optical counterpart detection
  23. EP260507a: Kinder optical counterpart candidate
  24. EP260507a: LCO optical counterpart
  25. EP260507a: Einstein Probe detection of an X-ray transient
  26. GRB 260506B: BALROG localization (Fermi Trigger 799765648 / GRB 260506547)
  27. Fermi GRB 260506A: Global MASTER-Net observations report
  28. IceCube Alert 260505A: Global MASTER-Net observations report
  29. GRB 260430B: Glowbug gamma-ray detection
  30. GRB 260421B: radio observation with the VLA
  31. Fermi-LAT Gamma-ray Observations of IceCube-260504A
  32. GRB 260430B: AstroSat CZTI detection of a long burst
  33. GRB 260502A: SVOM/GRM observation of a short GRB
  34. GRB 260503A: SVOM/GRM observation of a GRB
  35. Konus-Wind detection of GRB 260411C
  36. GRB 260504B: REM optical/NIR observations
  37. GRB 260504B: LCO z-band upper limit
  38. SVOM GRB 260504B: MASTER-OAFA optical observations
  39. GRB 260504B: SVOM detection of a short burst
  40. Fermi GRB 260504A: Global MASTER-Net observations report
  41. SVOM/GRM observation of a bright burst from SGR 1E1841-045
  42. GRB 260429B / EP260429a: EP-FXT follow-up observation
  43. EP260502a: Einstein Probe detection of an X-ray transient
  44. GRB 260429A: SVOM/GRM observation of a short burst
  45. SN 2026kid: Optical follow-up with small-aperture telescopes in Spain and China
  46. EP260429a: Global MASTER-Net observations report
  47. EP260430a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  48. GRB 260424B: AstroSat CZTI detection
  49. GRB 260429B / EP260429a: COLIBRÍ optical upper limit
  50. EP260429a: LCO optical upper limits
  51. EP260430a: LCO optical upper limits
  52. GRB 260430A / EP260430a: COLIBRÍ optical upper limit
  53. GRB 260429A: Fermi GBM Detection
  54. Fermi GRB 260429A: Global MASTER-Net observations report
  55. EP260430a: Global MASTER-Net observations report
  56. EP260430a: Einstein Probe detection of an X-ray transient
  57. EP260429a: EP-WXT detection of a fast X-ray transient
  58. GRB 260428A: SVOM/GRM observation of a possible short burst with extended emission
  59. IceCube-260425A: Upper limits from a search for additional neutrino events in IceCube
  60. Fermi GRB 260428A: Global MASTER-Net observations report
  61. EP260416a: Mondy and Terskol optical upper limits
  62. GRB 260424B: Glowbug gamma-ray detection of a short burst
  63. GRB 260424B: COLIBRÍ optical upper limit
  64. Fermi-LAT Gamma-ray Observations of IceCube-260425A
  65. GRB 260305A: likely detection by Fermi-LAT and the LAT gamma-ray position
  66. IceCube Alert 260425A: Global MASTER-Net observations report
  67. Fermi trigger No 798737427: Global MASTER-Net observations report
  68. GRB 260401A: cubesat Avion detection
  69. EP260321a: Upper limits from ATCA radio observations
  70. GRB 260421B: Kilonova-Catcher optical afterglow detection
  71. The EP-WXT trigger 01709258652: Mondy optical observations
  72. EP260416a: Mondy optical observations
  73. GRB 260421B: 3.6m DOT optical observation
  74. EP260416a: ZTSh R band observations
  75. IceCube-Cascade 260418A: Upper limits from a search for additional neutrino events in IceCube
  76. GRB 260421B: SVOM/GRM observation
  77. GRB260421B: J band upper limit by SYSU 80cm infrared telescope
  78. GRB 260421B: EP-FXT follow-up observation
  79. GOTO26djh/AT2026jpw: ATCA radio detection
  80. GRB 260421B: J-band upper limit with WINTER
  81. GRB 260421B: LCO optical counterpart detection
  82. GRB 260421B: Fermi GBM Observation
  83. GOTO26djh/AT2026jpw: radio detection at 15GHz
  84. GRB 260421B: SVOM/VT optical observations
  85. EP260416a: J band upper limit by SYSU 80cm infrared telescope
  86. GRB 260310A: Late-time Chandra X-ray Detection
  87. EP260416a: 1.3m DFOT optical observation
  88. Fermi GRB 260421C: Global MASTER-Net observations report
  89. GRB 260421B: VLT/X-shooter spectroscopic redshift z = 2.115
  90. Fermi GRB 260421B: Global MASTER-Net observations report
  91. GRB 260421B: LCO optical afterglow confirmation
  92. GRB 260421B: SVOM/COLIBRÍ (FM-GFT) optical detection of a candidate counterpart
  93. GRB 260421B: TRT optical counterpart detection
  94. GRB 260421B: SVOM detection of a long burst
  95. GRB 260421B: BALROG localization (Fermi Trigger 798437606 / GRB 260421176)
  96. Fermi GRB 260421A: Global MASTER-Net observations report
  97. EP260321a: VLA radio follow-up
  98. GRB 260412A: LCOGT Optical Upper Limits
  99. EP260416a: Optical follow-up observations with Kinder
  100. GOTO26djh/AT2026jpw: CrAO and Mondy optical observations of the transient

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