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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"

28231 results found.

  1. EP260507a: Einstein Probe detection of an X-ray transient
  2. GRB 260506B: BALROG localization (Fermi Trigger 799765648 / GRB 260506547)
  3. Fermi GRB 260506A: Global MASTER-Net observations report
  4. IceCube Alert 260505A: Global MASTER-Net observations report
  5. GRB 260430B: Glowbug gamma-ray detection
  6. GRB 260421B: radio observation with the VLA
  7. Fermi-LAT Gamma-ray Observations of IceCube-260504A
  8. GRB 260430B: AstroSat CZTI detection of a long burst
  9. GRB 260502A: SVOM/GRM observation of a short GRB
  10. GRB 260503A: SVOM/GRM observation of a GRB
  11. Konus-Wind detection of GRB 260411C
  12. GRB 260504B: REM optical/NIR observations
  13. GRB 260504B: LCO z-band upper limit
  14. SVOM GRB 260504B: MASTER-OAFA optical observations
  15. GRB 260504B: SVOM detection of a short burst
  16. Fermi GRB 260504A: Global MASTER-Net observations report
  17. SVOM/GRM observation of a bright burst from SGR 1E1841-045
  18. GRB 260429B / EP260429a: EP-FXT follow-up observation
  19. EP260502a: Einstein Probe detection of an X-ray transient
  20. GRB 260429A: SVOM/GRM observation of a short burst
  21. SN 2026kid: Optical follow-up with small-aperture telescopes in Spain and China
  22. EP260429a: Global MASTER-Net observations report
  23. EP260430a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  24. GRB 260424B: AstroSat CZTI detection
  25. GRB 260429B / EP260429a: COLIBRÍ optical upper limit
  26. EP260429a: LCO optical upper limits
  27. EP260430a: LCO optical upper limits
  28. GRB 260430A / EP260430a: COLIBRÍ optical upper limit
  29. GRB 260429A: Fermi GBM Detection
  30. Fermi GRB 260429A: Global MASTER-Net observations report
  31. EP260430a: Global MASTER-Net observations report
  32. EP260430a: Einstein Probe detection of an X-ray transient
  33. EP260429a: EP-WXT detection of a fast X-ray transient
  34. GRB 260428A: SVOM/GRM observation of a possible short burst with extended emission
  35. IceCube-260425A: Upper limits from a search for additional neutrino events in IceCube
  36. Fermi GRB 260428A: Global MASTER-Net observations report
  37. EP260416a: Mondy and Terskol optical upper limits
  38. GRB 260424B: Glowbug gamma-ray detection of a short burst
  39. GRB 260424B: COLIBRÍ optical upper limit
  40. Fermi-LAT Gamma-ray Observations of IceCube-260425A
  41. GRB 260305A: likely detection by Fermi-LAT and the LAT gamma-ray position
  42. IceCube Alert 260425A: Global MASTER-Net observations report
  43. Fermi trigger No 798737427: Global MASTER-Net observations report
  44. GRB 260401A: cubesat Avion detection
  45. EP260321a: Upper limits from ATCA radio observations
  46. GRB 260421B: Kilonova-Catcher optical afterglow detection
  47. The EP-WXT trigger 01709258652: Mondy optical observations
  48. EP260416a: Mondy optical observations
  49. GRB 260421B: 3.6m DOT optical observation
  50. EP260416a: ZTSh R band observations
  51. IceCube-Cascade 260418A: Upper limits from a search for additional neutrino events in IceCube
  52. GRB 260421B: SVOM/GRM observation
  53. GRB260421B: J band upper limit by SYSU 80cm infrared telescope
  54. GRB 260421B: EP-FXT follow-up observation
  55. GOTO26djh/AT2026jpw: ATCA radio detection
  56. GRB 260421B: J-band upper limit with WINTER
  57. GRB 260421B: LCO optical counterpart detection
  58. GRB 260421B: Fermi GBM Observation
  59. GOTO26djh/AT2026jpw: radio detection at 15GHz
  60. GRB 260421B: SVOM/VT optical observations
  61. EP260416a: J band upper limit by SYSU 80cm infrared telescope
  62. GRB 260310A: Late-time Chandra X-ray Detection
  63. EP260416a: 1.3m DFOT optical observation
  64. Fermi GRB 260421C: Global MASTER-Net observations report
  65. GRB 260421B: VLT/X-shooter spectroscopic redshift z = 2.115
  66. Fermi GRB 260421B: Global MASTER-Net observations report
  67. GRB 260421B: LCO optical afterglow confirmation
  68. GRB 260421B: SVOM/COLIBRÍ (FM-GFT) optical detection of a candidate counterpart
  69. GRB 260421B: TRT optical counterpart detection
  70. GRB 260421B: SVOM detection of a long burst
  71. GRB 260421B: BALROG localization (Fermi Trigger 798437606 / GRB 260421176)
  72. Fermi GRB 260421A: Global MASTER-Net observations report
  73. EP260321a: VLA radio follow-up
  74. GRB 260412A: LCOGT Optical Upper Limits
  75. EP260416a: Optical follow-up observations with Kinder
  76. GOTO26djh/AT2026jpw: CrAO and Mondy optical observations of the transient
  77. GRB 260417A: SVOM/GRM observation
  78. EP260321A/AT2026gzf: Optical observation from 1.3m DFOT
  79. Fermi trigger No 798275385: Global MASTER-Net observations report
  80. EP260417a: GROWTH-India Telescope optical upper limit
  81. Fermi GRB 260417B: Global MASTER-Net observations report
  82. EP260417b: GROWTH-India Telescope optical upper limit
  83. EP260416a: Ondrejov D50 optical detection
  84. EP260417a: Global MASTER-Net observations report
  85. EP260417a/GRB 260417A: refined analysis of the EP-WXT and follow-up EP-FXT observations
  86. EP260416a: GMG Optical Observation
  87. Fermi GRB 260417A: Global MASTER-Net observations report
  88. EP260416a: LCO observations confirm end of flaring phase
  89. EP260324a / AT2026hir: Further multiband optical follow-up with the PKU 60cm Telescope
  90. EP260417a: TRT optical counterpart detection
  91. EP260417a: Einstein Probe detection of an X-ray transient
  92. EP260416a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  93. EP260417b: Einstein Probe detection of a fast X-ray transient
  94. EP260416a: KAIT optical upper limit
  95. EP260416a: COLIBRÍ confirmation of the optical rebrightening
  96. EP260416a: WFST optical observations and rebrightening
  97. GOTO26djh/AT2026jpw: ZTSh R,I bands observations of the transient
  98. GOTO26djh/AT2026jpw: SVOM/VT optical observation
  99. GRB 260415B: Glowbug gamma-ray detection
  100. GRB 260411B: Glowbug gamma-ray detection

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