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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"

27242 results found.

  1. GRB 260509A: SVOM detection of a burst
  2. IceCube-260504A: Upper limits from a search for additional neutrino events in IceCube
  3. EP260507a: REM optical/NIR observations
  4. EP260507a: refined analysis of the EP-WXT and EP-FXT observations
  5. GRB 260507B / EP260507a: Fermi-GBM Sub-Threshold Detection
  6. EP260507a: COLIBRÍ optical observations
  7. EP260507a: NOT optical observations
  8. EP260507a: further Liverpool Telescope observations
  9. EP260507a: Liverpool Telescope optical upper limits
  10. EP260507a: TRT optical counterpart detection
  11. EP260507a: Kinder optical counterpart candidate
  12. EP260507a: LCO optical counterpart
  13. EP260507a: Einstein Probe detection of an X-ray transient
  14. GRB 260506B: BALROG localization (Fermi Trigger 799765648 / GRB 260506547)
  15. Fermi GRB 260506A: Global MASTER-Net observations report
  16. IceCube Alert 260505A: Global MASTER-Net observations report
  17. GRB 260430B: Glowbug gamma-ray detection
  18. GRB 260421B: radio observation with the VLA
  19. Fermi-LAT Gamma-ray Observations of IceCube-260504A
  20. GRB 260430B: AstroSat CZTI detection of a long burst
  21. GRB 260502A: SVOM/GRM observation of a short GRB
  22. GRB 260503A: SVOM/GRM observation of a GRB
  23. Konus-Wind detection of GRB 260411C
  24. GRB 260504B: REM optical/NIR observations
  25. GRB 260504B: LCO z-band upper limit
  26. SVOM GRB 260504B: MASTER-OAFA optical observations
  27. GRB 260504B: SVOM detection of a short burst
  28. Fermi GRB 260504A: Global MASTER-Net observations report
  29. SVOM/GRM observation of a bright burst from SGR 1E1841-045
  30. GRB 260429B / EP260429a: EP-FXT follow-up observation
  31. EP260502a: Einstein Probe detection of an X-ray transient
  32. GRB 260429A: SVOM/GRM observation of a short burst
  33. SN 2026kid: Optical follow-up with small-aperture telescopes in Spain and China
  34. EP260429a: Global MASTER-Net observations report
  35. EP260430a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  36. GRB 260424B: AstroSat CZTI detection
  37. GRB 260429B / EP260429a: COLIBRÍ optical upper limit
  38. EP260429a: LCO optical upper limits
  39. EP260430a: LCO optical upper limits
  40. GRB 260430A / EP260430a: COLIBRÍ optical upper limit
  41. GRB 260429A: Fermi GBM Detection
  42. Fermi GRB 260429A: Global MASTER-Net observations report
  43. EP260430a: Global MASTER-Net observations report
  44. EP260430a: Einstein Probe detection of an X-ray transient
  45. EP260429a: EP-WXT detection of a fast X-ray transient
  46. GRB 260428A: SVOM/GRM observation of a possible short burst with extended emission
  47. IceCube-260425A: Upper limits from a search for additional neutrino events in IceCube
  48. Fermi GRB 260428A: Global MASTER-Net observations report
  49. EP260416a: Mondy and Terskol optical upper limits
  50. GRB 260424B: Glowbug gamma-ray detection of a short burst
  51. GRB 260424B: COLIBRÍ optical upper limit
  52. Fermi-LAT Gamma-ray Observations of IceCube-260425A
  53. GRB 260305A: likely detection by Fermi-LAT and the LAT gamma-ray position
  54. IceCube Alert 260425A: Global MASTER-Net observations report
  55. Fermi trigger No 798737427: Global MASTER-Net observations report
  56. GRB 260401A: cubesat Avion detection
  57. EP260321a: Upper limits from ATCA radio observations
  58. GRB 260421B: Kilonova-Catcher optical afterglow detection
  59. The EP-WXT trigger 01709258652: Mondy optical observations
  60. EP260416a: Mondy optical observations
  61. GRB 260421B: 3.6m DOT optical observation
  62. EP260416a: ZTSh R band observations
  63. IceCube-Cascade 260418A: Upper limits from a search for additional neutrino events in IceCube
  64. GRB 260421B: SVOM/GRM observation
  65. GRB260421B: J band upper limit by SYSU 80cm infrared telescope
  66. GRB 260421B: EP-FXT follow-up observation
  67. GOTO26djh/AT2026jpw: ATCA radio detection
  68. GRB 260421B: J-band upper limit with WINTER
  69. GRB 260421B: LCO optical counterpart detection
  70. GRB 260421B: Fermi GBM Observation
  71. GOTO26djh/AT2026jpw: radio detection at 15GHz
  72. GRB 260421B: SVOM/VT optical observations
  73. EP260416a: J band upper limit by SYSU 80cm infrared telescope
  74. GRB 260310A: Late-time Chandra X-ray Detection
  75. EP260416a: 1.3m DFOT optical observation
  76. Fermi GRB 260421C: Global MASTER-Net observations report
  77. GRB 260421B: VLT/X-shooter spectroscopic redshift z = 2.115
  78. Fermi GRB 260421B: Global MASTER-Net observations report
  79. GRB 260421B: LCO optical afterglow confirmation
  80. GRB 260421B: SVOM/COLIBRÍ (FM-GFT) optical detection of a candidate counterpart
  81. GRB 260421B: TRT optical counterpart detection
  82. GRB 260421B: SVOM detection of a long burst
  83. GRB 260421B: BALROG localization (Fermi Trigger 798437606 / GRB 260421176)
  84. Fermi GRB 260421A: Global MASTER-Net observations report
  85. EP260321a: VLA radio follow-up
  86. GRB 260412A: LCOGT Optical Upper Limits
  87. EP260416a: Optical follow-up observations with Kinder
  88. GOTO26djh/AT2026jpw: CrAO and Mondy optical observations of the transient
  89. GRB 260417A: SVOM/GRM observation
  90. EP260321A/AT2026gzf: Optical observation from 1.3m DFOT
  91. Fermi trigger No 798275385: Global MASTER-Net observations report
  92. EP260417a: GROWTH-India Telescope optical upper limit
  93. Fermi GRB 260417B: Global MASTER-Net observations report
  94. EP260417b: GROWTH-India Telescope optical upper limit
  95. EP260416a: Ondrejov D50 optical detection
  96. EP260417a: Global MASTER-Net observations report
  97. EP260417a/GRB 260417A: refined analysis of the EP-WXT and follow-up EP-FXT observations
  98. EP260416a: GMG Optical Observation
  99. Fermi GRB 260417A: Global MASTER-Net observations report
  100. EP260416a: LCO observations confirm end of flaring phase

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