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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"

25710 results found.

  1. GRB 260506B: AstroSat CZTI detection
  2. IceCube-260504A: Upper limits from a search for additional neutrino events in IceCube
  3. EP260507a: REM optical/NIR observations
  4. EP260507a: refined analysis of the EP-WXT and EP-FXT observations
  5. EP260507a: COLIBRÍ optical observations
  6. EP260507a: SVOM/VT optical observations
  7. EP260507a: NOT optical observations
  8. EP260507a: further Liverpool Telescope observations
  9. EP260507a: Liverpool Telescope optical upper limits
  10. EP260507a: TRT optical counterpart detection
  11. EP260507a: Kinder optical counterpart candidate
  12. EP260507a: LCO optical counterpart
  13. EP260507a: Einstein Probe detection of an X-ray transient
  14. GRB 260504B: SVOM/ECLAIRs refined analysis
  15. EP260502a is likely a flaring star
  16. GRB 260430B: Glowbug gamma-ray detection
  17. GRB 260504B: SVOM/VT optical upper limits
  18. GRB 260421B: radio observation with the VLA
  19. Konus-Wind detection of a burst from SGR 1E1841-045 on 2026 May 2
  20. Konus-Wind detection of GRB 260504B (short/hard)
  21. GRB 260504B: GECAM-B detection
  22. Fermi-LAT Gamma-ray Observations of IceCube-260504A
  23. GRB 260504B: SVOM/GRM spectral analysis
  24. GRB 260430B: AstroSat CZTI detection of a long burst
  25. GRB 260504B: EP-FXT upper limit
  26. GRB 260502A: SVOM/GRM observation of a short GRB
  27. GRB 260503A: SVOM/GRM observation of a GRB
  28. Konus-Wind detection of GRB 260415C
  29. GRB 260504B: REM optical/NIR observations
  30. GRB 260504B: AST3-2 i-band upper limit
  31. GRB 260504B: LCO z-band upper limit
  32. SVOM GRB 260504B: MASTER-OAFA optical observations
  33. GRB 260504B: SVOM detection of a short burst
  34. SVOM/GRM observation of a bright burst from SGR 1E1841-045
  35. IPN triangulation of a bright burst from SGR 1E1841-045
  36. The EP-WXT trigger 01709261576 is likely a flaring star
  37. GRB 260429B / EP260429a: EP-FXT follow-up observation
  38. EP260502a: BOOTES-7: early optical upper limit
  39. EP260502a: Einstein Probe detection of an X-ray transient
  40. GRB 260429A: SVOM/GRM observation of a short burst
  41. SN 2026kid: Optical follow-up with small-aperture telescopes in Spain and China
  42. EP260429a: Global MASTER-Net observations report
  43. EP260430a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  44. GRB 260429B / EP260429a: COLIBRÍ optical upper limit
  45. EP260429a: LCO optical upper limits
  46. EP260430a: LCO optical upper limits
  47. GRB 260430A / EP260430a: COLIBRÍ optical upper limit
  48. GRB 260429A: Fermi GBM Detection
  49. EP260430a: Einstein Probe detection of an X-ray transient
  50. EP260429a: EP-WXT detection of a fast X-ray transient
  51. GRB 260428A: SVOM/GRM observation of a possible short burst with extended emission
  52. GRB 260428A: GECAM-B detection of a possible long duration Type I burst
  53. IceCube-260425A: Upper limits from a search for additional neutrino events in IceCube
  54. EP260416a: Mondy and Terskol optical upper limits
  55. GRB 260424B: Glowbug gamma-ray detection of a short burst
  56. GRB 260424B: COLIBRÍ optical upper limit
  57. Konus-Wind detection of GRB 260424B
  58. Fermi-LAT Gamma-ray Observations of IceCube-260425A
  59. GRB 260305A: likely detection by Fermi-LAT and the LAT gamma-ray position
  60. GRB 260401A: cubesat Avion detection
  61. EP260321a: Upper limits from ATCA radio observations
  62. GRB 260421B: Kilonova-Catcher optical afterglow detection
  63. EP260416a: Mondy optical observations
  64. GRB 260421B: SVOM/ECLAIRs refined analysis
  65. GRB 260421B: 3.6m DOT optical observation
  66. EP260416a: ZTSh R band observations
  67. IceCube-Cascade 260418A: Upper limits from a search for additional neutrino events in IceCube
  68. GRB 260419A: AstroSat CZTI detection
  69. GRB 260421B: SVOM/GRM observation
  70. GRB260421B: J band upper limit by SYSU 80cm infrared telescope
  71. The EP-WXT trigger 01709260362 is likely a flaring star
  72. GOTO26djh/AT2026jpw: ATCA radio detection
  73. GRB 260421B: J-band upper limit with WINTER
  74. GRB 260421B: LCO optical counterpart detection
  75. GRB 260421B: Fermi GBM Observation
  76. GOTO26djh/AT2026jpw: radio detection at 15GHz
  77. GRB 260412A: SVOM/ECLAIRs refined analysis
  78. GRB 260421B: SVOM/VT optical observations
  79. EP260416a: J band upper limit by SYSU 80cm infrared telescope
  80. GRB 260310A: Late-time Chandra X-ray Detection
  81. EP260416a: 1.3m DFOT optical observation
  82. GRB 260421B: VLT/X-shooter spectroscopic redshift z = 2.115
  83. GRB 260421B: LCO optical afterglow confirmation
  84. GRB 260421B: SVOM/COLIBRÍ (FM-GFT) optical detection of a candidate counterpart
  85. GRB 260421B: TRT optical counterpart detection
  86. GRB 260421B: SVOM detection of a long burst
  87. EP260321a: VLA radio follow-up
  88. GRB 260412A: LCOGT Optical Upper Limits
  89. The EP-WXT trigger 01709260314 is likely a flaring star
  90. EP260416a: Optical follow-up observations with Kinder
  91. GOTO26djh/AT2026jpw: CrAO and Mondy optical observations of the transient
  92. The EP-WXT trigger 01709260303 is likely a flaring star
  93. GRB 260417A: SVOM/GRM observation
  94. EP260321A/AT2026gzf: Optical observation from 1.3m DFOT
  95. EP260417a: GROWTH-India Telescope optical upper limit
  96. EP260417b: GROWTH-India Telescope optical upper limit
  97. EP260416a: Ondrejov D50 optical detection
  98. EP260417a/GRB 260417A: refined analysis of the EP-WXT and follow-up EP-FXT observations
  99. EP260416a: GMG Optical Observation
  100. EP260416a: LCO observations confirm end of flaring phase

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