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GCN Circulars

GCN Circulars are rapid bulletins submitted by and distributed to the community. 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"

28235 results found.

  1. EP260507a: TRT optical counterpart detection
  2. EP260507a: Kinder optical counterpart candidate
  3. EP260507a: LCO optical counterpart
  4. EP260507a: Einstein Probe detection of an X-ray transient
  5. GRB 260506B: BALROG localization (Fermi Trigger 799765648 / GRB 260506547)
  6. Fermi GRB 260506A: Global MASTER-Net observations report
  7. IceCube Alert 260505A: Global MASTER-Net observations report
  8. GRB 260430B: Glowbug gamma-ray detection
  9. GRB 260421B: radio observation with the VLA
  10. Fermi-LAT Gamma-ray Observations of IceCube-260504A
  11. GRB 260430B: AstroSat CZTI detection of a long burst
  12. GRB 260502A: SVOM/GRM observation of a short GRB
  13. GRB 260503A: SVOM/GRM observation of a GRB
  14. Konus-Wind detection of GRB 260411C
  15. GRB 260504B: REM optical/NIR observations
  16. GRB 260504B: LCO z-band upper limit
  17. SVOM GRB 260504B: MASTER-OAFA optical observations
  18. GRB 260504B: SVOM detection of a short burst
  19. Fermi GRB 260504A: Global MASTER-Net observations report
  20. SVOM/GRM observation of a bright burst from SGR 1E1841-045
  21. GRB 260429B / EP260429a: EP-FXT follow-up observation
  22. EP260502a: Einstein Probe detection of an X-ray transient
  23. GRB 260429A: SVOM/GRM observation of a short burst
  24. SN 2026kid: Optical follow-up with small-aperture telescopes in Spain and China
  25. EP260429a: Global MASTER-Net observations report
  26. EP260430a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  27. GRB 260424B: AstroSat CZTI detection
  28. GRB 260429B / EP260429a: COLIBRÍ optical upper limit
  29. EP260429a: LCO optical upper limits
  30. EP260430a: LCO optical upper limits
  31. GRB 260430A / EP260430a: COLIBRÍ optical upper limit
  32. GRB 260429A: Fermi GBM Detection
  33. Fermi GRB 260429A: Global MASTER-Net observations report
  34. EP260430a: Global MASTER-Net observations report
  35. EP260430a: Einstein Probe detection of an X-ray transient
  36. EP260429a: EP-WXT detection of a fast X-ray transient
  37. GRB 260428A: SVOM/GRM observation of a possible short burst with extended emission
  38. IceCube-260425A: Upper limits from a search for additional neutrino events in IceCube
  39. Fermi GRB 260428A: Global MASTER-Net observations report
  40. EP260416a: Mondy and Terskol optical upper limits
  41. GRB 260424B: Glowbug gamma-ray detection of a short burst
  42. GRB 260424B: COLIBRÍ optical upper limit
  43. Fermi-LAT Gamma-ray Observations of IceCube-260425A
  44. GRB 260305A: likely detection by Fermi-LAT and the LAT gamma-ray position
  45. IceCube Alert 260425A: Global MASTER-Net observations report
  46. Fermi trigger No 798737427: Global MASTER-Net observations report
  47. GRB 260401A: cubesat Avion detection
  48. EP260321a: Upper limits from ATCA radio observations
  49. GRB 260421B: Kilonova-Catcher optical afterglow detection
  50. The EP-WXT trigger 01709258652: Mondy optical observations
  51. EP260416a: Mondy optical observations
  52. GRB 260421B: 3.6m DOT optical observation
  53. EP260416a: ZTSh R band observations
  54. IceCube-Cascade 260418A: Upper limits from a search for additional neutrino events in IceCube
  55. GRB 260421B: SVOM/GRM observation
  56. GRB260421B: J band upper limit by SYSU 80cm infrared telescope
  57. GRB 260421B: EP-FXT follow-up observation
  58. GOTO26djh/AT2026jpw: ATCA radio detection
  59. GRB 260421B: J-band upper limit with WINTER
  60. GRB 260421B: LCO optical counterpart detection
  61. GRB 260421B: Fermi GBM Observation
  62. GOTO26djh/AT2026jpw: radio detection at 15GHz
  63. GRB 260421B: SVOM/VT optical observations
  64. EP260416a: J band upper limit by SYSU 80cm infrared telescope
  65. GRB 260310A: Late-time Chandra X-ray Detection
  66. EP260416a: 1.3m DFOT optical observation
  67. Fermi GRB 260421C: Global MASTER-Net observations report
  68. GRB 260421B: VLT/X-shooter spectroscopic redshift z = 2.115
  69. Fermi GRB 260421B: Global MASTER-Net observations report
  70. GRB 260421B: LCO optical afterglow confirmation
  71. GRB 260421B: SVOM/COLIBRÍ (FM-GFT) optical detection of a candidate counterpart
  72. GRB 260421B: TRT optical counterpart detection
  73. GRB 260421B: SVOM detection of a long burst
  74. GRB 260421B: BALROG localization (Fermi Trigger 798437606 / GRB 260421176)
  75. Fermi GRB 260421A: Global MASTER-Net observations report
  76. EP260321a: VLA radio follow-up
  77. GRB 260412A: LCOGT Optical Upper Limits
  78. EP260416a: Optical follow-up observations with Kinder
  79. GOTO26djh/AT2026jpw: CrAO and Mondy optical observations of the transient
  80. GRB 260417A: SVOM/GRM observation
  81. EP260321A/AT2026gzf: Optical observation from 1.3m DFOT
  82. Fermi trigger No 798275385: Global MASTER-Net observations report
  83. EP260417a: GROWTH-India Telescope optical upper limit
  84. Fermi GRB 260417B: Global MASTER-Net observations report
  85. EP260417b: GROWTH-India Telescope optical upper limit
  86. EP260416a: Ondrejov D50 optical detection
  87. EP260417a: Global MASTER-Net observations report
  88. EP260417a/GRB 260417A: refined analysis of the EP-WXT and follow-up EP-FXT observations
  89. EP260416a: GMG Optical Observation
  90. Fermi GRB 260417A: Global MASTER-Net observations report
  91. EP260416a: LCO observations confirm end of flaring phase
  92. EP260324a / AT2026hir: Further multiband optical follow-up with the PKU 60cm Telescope
  93. EP260417a: TRT optical counterpart detection
  94. EP260417a: Einstein Probe detection of an X-ray transient
  95. EP260416a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  96. EP260417b: Einstein Probe detection of a fast X-ray transient
  97. EP260416a: KAIT optical upper limit
  98. EP260416a: COLIBRÍ confirmation of the optical rebrightening
  99. EP260416a: WFST optical observations and rebrightening
  100. GOTO26djh/AT2026jpw: ZTSh R,I bands observations of the transient

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