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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 260510B: LCO optical upper limits
  2. EP260509a: Einstein Probe detection of an X-ray transient
  3. GRB 260509A: Liverpool Telescope optical observations
  4. GRB 260510B: SVOM detection of a burst
  5. GRB 260509A: LCO optical observations
  6. SVOM GRB 260509A: MASTER-OAFA optical observation
  7. Fermi GRB 260510A: Global MASTER-Net observations report
  8. GRB 260509A: KAIT optical observations
  9. GRB 260509A: SVOM/COLIBRÍ (FM-GFT) observations
  10. GRB 260509A: SVOM/VT optical candidate with VHF data
  11. GRB 260509A: LCO optical counterpart detection
  12. GRB 260509A: SVOM detection of a burst
  13. IceCube-260504A: Upper limits from a search for additional neutrino events in IceCube
  14. EP260507a: REM optical/NIR observations
  15. EP260507a: refined analysis of the EP-WXT and EP-FXT observations
  16. GRB 260507B / EP260507a: Fermi-GBM Sub-Threshold Detection
  17. EP260507a: COLIBRÍ optical observations
  18. EP260507a: NOT optical observations
  19. EP260507a: further Liverpool Telescope observations
  20. EP260507a: Liverpool Telescope optical upper limits
  21. EP260507a: TRT optical counterpart detection
  22. EP260507a: Kinder optical counterpart candidate
  23. EP260507a: LCO optical counterpart
  24. EP260507a: Einstein Probe detection of an X-ray transient
  25. GRB 260506B: BALROG localization (Fermi Trigger 799765648 / GRB 260506547)
  26. Fermi GRB 260506A: Global MASTER-Net observations report
  27. IceCube Alert 260505A: Global MASTER-Net observations report
  28. GRB 260430B: Glowbug gamma-ray detection
  29. GRB 260421B: radio observation with the VLA
  30. Fermi-LAT Gamma-ray Observations of IceCube-260504A
  31. GRB 260430B: AstroSat CZTI detection of a long burst
  32. GRB 260502A: SVOM/GRM observation of a short GRB
  33. GRB 260503A: SVOM/GRM observation of a GRB
  34. Konus-Wind detection of GRB 260411C
  35. GRB 260504B: REM optical/NIR observations
  36. GRB 260504B: LCO z-band upper limit
  37. SVOM GRB 260504B: MASTER-OAFA optical observations
  38. GRB 260504B: SVOM detection of a short burst
  39. Fermi GRB 260504A: Global MASTER-Net observations report
  40. SVOM/GRM observation of a bright burst from SGR 1E1841-045
  41. GRB 260429B / EP260429a: EP-FXT follow-up observation
  42. EP260502a: Einstein Probe detection of an X-ray transient
  43. GRB 260429A: SVOM/GRM observation of a short burst
  44. SN 2026kid: Optical follow-up with small-aperture telescopes in Spain and China
  45. EP260429a: Global MASTER-Net observations report
  46. EP260430a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  47. GRB 260424B: AstroSat CZTI detection
  48. GRB 260429B / EP260429a: COLIBRÍ optical upper limit
  49. EP260429a: LCO optical upper limits
  50. EP260430a: LCO optical upper limits
  51. GRB 260430A / EP260430a: COLIBRÍ optical upper limit
  52. GRB 260429A: Fermi GBM Detection
  53. Fermi GRB 260429A: Global MASTER-Net observations report
  54. EP260430a: Global MASTER-Net observations report
  55. EP260430a: Einstein Probe detection of an X-ray transient
  56. EP260429a: EP-WXT detection of a fast X-ray transient
  57. GRB 260428A: SVOM/GRM observation of a possible short burst with extended emission
  58. IceCube-260425A: Upper limits from a search for additional neutrino events in IceCube
  59. Fermi GRB 260428A: Global MASTER-Net observations report
  60. EP260416a: Mondy and Terskol optical upper limits
  61. GRB 260424B: Glowbug gamma-ray detection of a short burst
  62. GRB 260424B: COLIBRÍ optical upper limit
  63. Fermi-LAT Gamma-ray Observations of IceCube-260425A
  64. GRB 260305A: likely detection by Fermi-LAT and the LAT gamma-ray position
  65. IceCube Alert 260425A: Global MASTER-Net observations report
  66. Fermi trigger No 798737427: Global MASTER-Net observations report
  67. GRB 260401A: cubesat Avion detection
  68. EP260321a: Upper limits from ATCA radio observations
  69. GRB 260421B: Kilonova-Catcher optical afterglow detection
  70. The EP-WXT trigger 01709258652: Mondy optical observations
  71. EP260416a: Mondy optical observations
  72. GRB 260421B: 3.6m DOT optical observation
  73. EP260416a: ZTSh R band observations
  74. IceCube-Cascade 260418A: Upper limits from a search for additional neutrino events in IceCube
  75. GRB 260421B: SVOM/GRM observation
  76. GRB260421B: J band upper limit by SYSU 80cm infrared telescope
  77. GRB 260421B: EP-FXT follow-up observation
  78. GOTO26djh/AT2026jpw: ATCA radio detection
  79. GRB 260421B: J-band upper limit with WINTER
  80. GRB 260421B: LCO optical counterpart detection
  81. GRB 260421B: Fermi GBM Observation
  82. GOTO26djh/AT2026jpw: radio detection at 15GHz
  83. GRB 260421B: SVOM/VT optical observations
  84. EP260416a: J band upper limit by SYSU 80cm infrared telescope
  85. GRB 260310A: Late-time Chandra X-ray Detection
  86. EP260416a: 1.3m DFOT optical observation
  87. Fermi GRB 260421C: Global MASTER-Net observations report
  88. GRB 260421B: VLT/X-shooter spectroscopic redshift z = 2.115
  89. Fermi GRB 260421B: Global MASTER-Net observations report
  90. GRB 260421B: LCO optical afterglow confirmation
  91. GRB 260421B: SVOM/COLIBRÍ (FM-GFT) optical detection of a candidate counterpart
  92. GRB 260421B: TRT optical counterpart detection
  93. GRB 260421B: SVOM detection of a long burst
  94. GRB 260421B: BALROG localization (Fermi Trigger 798437606 / GRB 260421176)
  95. Fermi GRB 260421A: Global MASTER-Net observations report
  96. EP260321a: VLA radio follow-up
  97. GRB 260412A: LCOGT Optical Upper Limits
  98. EP260416a: Optical follow-up observations with Kinder
  99. GOTO26djh/AT2026jpw: CrAO and Mondy optical observations of the transient
  100. GRB 260417A: SVOM/GRM observation

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