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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"

27640 results found.

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

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