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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"

27339 results found.

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

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