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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"

27241 results found.

  1. GRB 260507B / EP260507a: Fermi-GBM Sub-Threshold Detection
  2. EP260507a: COLIBRÍ optical observations
  3. EP260507a: NOT optical observations
  4. EP260507a: further Liverpool Telescope observations
  5. EP260507a: Liverpool Telescope optical upper limits
  6. EP260507a: TRT optical counterpart detection
  7. EP260507a: Kinder optical counterpart candidate
  8. EP260507a: LCO optical counterpart
  9. EP260507a: Einstein Probe detection of an X-ray transient
  10. GRB 260506B: BALROG localization (Fermi Trigger 799765648 / GRB 260506547)
  11. Fermi GRB 260506A: Global MASTER-Net observations report
  12. IceCube Alert 260505A: Global MASTER-Net observations report
  13. GRB 260430B: Glowbug gamma-ray detection
  14. GRB 260421B: radio observation with the VLA
  15. Fermi-LAT Gamma-ray Observations of IceCube-260504A
  16. GRB 260430B: AstroSat CZTI detection of a long burst
  17. GRB 260502A: SVOM/GRM observation of a short GRB
  18. GRB 260503A: SVOM/GRM observation of a GRB
  19. Konus-Wind detection of GRB 260411C
  20. GRB 260504B: REM optical/NIR observations
  21. GRB 260504B: LCO z-band upper limit
  22. SVOM GRB 260504B: MASTER-OAFA optical observations
  23. GRB 260504B: SVOM detection of a short burst
  24. Fermi GRB 260504A: Global MASTER-Net observations report
  25. SVOM/GRM observation of a bright burst from SGR 1E1841-045
  26. GRB 260429B / EP260429a: EP-FXT follow-up observation
  27. EP260502a: Einstein Probe detection of an X-ray transient
  28. GRB 260429A: SVOM/GRM observation of a short burst
  29. SN 2026kid: Optical follow-up with small-aperture telescopes in Spain and China
  30. EP260429a: Global MASTER-Net observations report
  31. EP260430a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  32. GRB 260424B: AstroSat CZTI detection
  33. GRB 260429B / EP260429a: COLIBRÍ optical upper limit
  34. EP260429a: LCO optical upper limits
  35. EP260430a: LCO optical upper limits
  36. GRB 260430A / EP260430a: COLIBRÍ optical upper limit
  37. GRB 260429A: Fermi GBM Detection
  38. Fermi GRB 260429A: Global MASTER-Net observations report
  39. EP260430a: Global MASTER-Net observations report
  40. EP260430a: Einstein Probe detection of an X-ray transient
  41. EP260429a: EP-WXT detection of a fast X-ray transient
  42. GRB 260428A: SVOM/GRM observation of a possible short burst with extended emission
  43. IceCube-260425A: Upper limits from a search for additional neutrino events in IceCube
  44. Fermi GRB 260428A: Global MASTER-Net observations report
  45. EP260416a: Mondy and Terskol optical upper limits
  46. GRB 260424B: Glowbug gamma-ray detection of a short burst
  47. GRB 260424B: COLIBRÍ optical upper limit
  48. Fermi-LAT Gamma-ray Observations of IceCube-260425A
  49. GRB 260305A: likely detection by Fermi-LAT and the LAT gamma-ray position
  50. IceCube Alert 260425A: Global MASTER-Net observations report
  51. Fermi trigger No 798737427: Global MASTER-Net observations report
  52. GRB 260401A: cubesat Avion detection
  53. EP260321a: Upper limits from ATCA radio observations
  54. GRB 260421B: Kilonova-Catcher optical afterglow detection
  55. The EP-WXT trigger 01709258652: Mondy optical observations
  56. EP260416a: Mondy optical observations
  57. GRB 260421B: 3.6m DOT optical observation
  58. EP260416a: ZTSh R band observations
  59. IceCube-Cascade 260418A: Upper limits from a search for additional neutrino events in IceCube
  60. GRB 260421B: SVOM/GRM observation
  61. GRB260421B: J band upper limit by SYSU 80cm infrared telescope
  62. GRB 260421B: EP-FXT follow-up observation
  63. GOTO26djh/AT2026jpw: ATCA radio detection
  64. GRB 260421B: J-band upper limit with WINTER
  65. GRB 260421B: LCO optical counterpart detection
  66. GRB 260421B: Fermi GBM Observation
  67. GOTO26djh/AT2026jpw: radio detection at 15GHz
  68. GRB 260421B: SVOM/VT optical observations
  69. EP260416a: J band upper limit by SYSU 80cm infrared telescope
  70. GRB 260310A: Late-time Chandra X-ray Detection
  71. EP260416a: 1.3m DFOT optical observation
  72. Fermi GRB 260421C: Global MASTER-Net observations report
  73. GRB 260421B: VLT/X-shooter spectroscopic redshift z = 2.115
  74. Fermi GRB 260421B: Global MASTER-Net observations report
  75. GRB 260421B: LCO optical afterglow confirmation
  76. GRB 260421B: SVOM/COLIBRÍ (FM-GFT) optical detection of a candidate counterpart
  77. GRB 260421B: TRT optical counterpart detection
  78. GRB 260421B: SVOM detection of a long burst
  79. GRB 260421B: BALROG localization (Fermi Trigger 798437606 / GRB 260421176)
  80. Fermi GRB 260421A: Global MASTER-Net observations report
  81. EP260321a: VLA radio follow-up
  82. GRB 260412A: LCOGT Optical Upper Limits
  83. EP260416a: Optical follow-up observations with Kinder
  84. GOTO26djh/AT2026jpw: CrAO and Mondy optical observations of the transient
  85. GRB 260417A: SVOM/GRM observation
  86. EP260321A/AT2026gzf: Optical observation from 1.3m DFOT
  87. Fermi trigger No 798275385: Global MASTER-Net observations report
  88. EP260417a: GROWTH-India Telescope optical upper limit
  89. Fermi GRB 260417B: Global MASTER-Net observations report
  90. EP260417b: GROWTH-India Telescope optical upper limit
  91. EP260416a: Ondrejov D50 optical detection
  92. EP260417a: Global MASTER-Net observations report
  93. EP260417a/GRB 260417A: refined analysis of the EP-WXT and follow-up EP-FXT observations
  94. EP260416a: GMG Optical Observation
  95. Fermi GRB 260417A: Global MASTER-Net observations report
  96. EP260416a: LCO observations confirm end of flaring phase
  97. EP260324a / AT2026hir: Further multiband optical follow-up with the PKU 60cm Telescope
  98. EP260417a: TRT optical counterpart detection
  99. EP260417a: Einstein Probe detection of an X-ray transient
  100. EP260416a: refined analysis of the EP-WXT and autonomous EP-FXT observations

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