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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"

28234 results found.

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

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