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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"
  1. GRB 260226A: NuSTAR detection of bright prompt emission
  2. GRB 260226A : GROWTH-India Telescope optical observations
  3. GRB 260226A: LAST optical upper limit
  4. GRB 260226A: Fermi GBM observation
  5. GRB 260226A: Fermi-LAT refined analysis
  6. The EP-WXT trigger 01709258652 is likely a flaring star
  7. LAT GRB260226.44: Global MASTER-Net observations report
  8. Fermi GRB 260226A: Global MASTER-Net observations report
  9. GRB 260226A: AstroSat CZTI detection of bright long burst
  10. EP260214a: VLA 6 GHz detection
  11. GRB 260226A: Fermi-LAT detection of a bright burst
  12. GRB 260226A???: BALROG localization (Fermi Trigger 793795080 / GRB 260226443)
  13. EP260224a: LCO optical upper limits
  14. GRB260225A: SVOM/ECLAIRs refined position
  15. GRB 260226A: Fermi GBM Final Real-time Localization
  16. GRB 260225A: EP-FXT follow-up observation
  17. GRB 260225A: SVOM/VT optical observation
  18. GRB 260225A: SVOM/COLIBRÍ (FM-GFT) Detection of an Optical Counterpart Candidate
  19. GRB 260225C: Fermi GBM Final Real-time Localization
  20. GRB 260223A: Fermi GBM Observation
  21. GRB 260225A: SVOM/VT optical upper limits
  22. GRB 260225B: Fermi GBM Final Real-time Localization
  23. EP260126a: VLA 6 GHz detection
  24. EP260223a: Liverpool Telescope upper limits
  25. GRB 260225A: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  26. GRB 260225A: SVOM detection of a burst
  27. EP260224a: Einstein Probe detection of an X-ray transient
  28. EP 260225.148: COLIBRÍ Confirmation of flaring star
  29. EP260223a: Xinglong optical upper limit
  30. The EP-WXT trigger 01709258631 is likely a flaring star
  31. GRB 260223A: Glowbug gamma-ray detection
  32. EP260213a: Mephisto optical upper limits
  33. EP260223a: EP-FXT follow-up observation
  34. sb26021801: SVOM/VT optical upper limits
  35. GRB 260223A: COLIBRÍ optical afterglow decay confirmation
  36. sb26021801: SVOM/C-GFT upper limit
  37. EP260223a: COLIBRÍ optical upper limits
  38. EP260223a: Einstein Probe detection of an X-ray transient
  39. GRB 260223A: SVOM/VT optical observation
  40. GRB 260223A: SVOM/GRM observation
  41. GRB 260223A: COLIBRÍ further optical observations and a brightening
  42. EP260221a: Optical upper limit with Kinder observations
  43. GRB 260223A: COLIBRÍ optical observations
  44. GRB 260223A: DDOTI Optical Candidate
  45. GRB 260223A: BALROG localization (Fermi Trigger 793512674 / GRB 260223174)
  46. Fermi GRB 260223A: Global MASTER-Net observations report
  47. GRB 260223A: Fermi GBM Final Real-time Localization
  48. EP260221a: Liverpool Telescope detection of COLIBRÍ counterpart candidate
  49. EP260221a: COLIBRÍ optical counterpart candidate
  50. EP260221a: Gemini South z-band upper limit
  51. GRB 260222A: Fermi GBM Final Real-time Localization
  52. EP260221a: Global MASTER-Net observations report
  53. EP260221a: EP-FXT follow-up observation
  54. Fermi GRB 260221B: Global MASTER-Net observations report
  55. GRB 260221B: Fermi GBM Final Real-time Localization
  56. EP-WXT01709258519: Xinglong optical upper limit
  57. EP260221a: Xinglong optical upper limit
  58. Fermi GRB 260221A: Global MASTER-Net observations report
  59. ZTF26aaglqak/AT2026dbl: COLIBRÍ Optical Observations
  60. GRB 260221A: Fermi GBM Final Real-time Localization
  61. EP260221a: GOTO optical upper limit
  62. EP260221a: COLIBRÍ optical upper limit
  63. SVOM alert sb26021801: LCO optical upper limit
  64. EP260221a: Einstein Probe detection of an X-ray transient
  65. The EP-WXT trigger 01709258519 is likely caused by Mrk 421
  66. GRB 260219A: AstroSat CZTI detection
  67. IceCube-260217A: Upper limits from a search for additional neutrino events in IceCube
  68. GRB 260219A: GECAM-B observation of a long burst
  69. Fermi GRB 260219A: Global MASTER-Net observations report
  70. GRB 260219A: Fermi GBM Final Real-time Localization
  71. SVOM alert sb26021801: LAST optical upper limit
  72. sb26021801: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  73. IceCube Alert 260217A: Global MASTER-Net observations report
  74. Fermi-LAT Gamma-ray Observations of IceCube-260217A
  75. GRB 260217A: Fermi GBM Final Localization
  76. GRB 260214B/EP260214b: SVOM/ECLAIRs detection through targeted search
  77. sb26021801: SVOM detection of a long faint X-ray transient
  78. The EP-WXT trigger 01709258455 is likely a flaring star
  79. EP-WXT 01709258455: NOT optical upper limits
  80. EP260214b: Mondy optical observations
  81. EP260214b: 1.3m DFOT optical upper limit
  82. EP260210a: Mondy optical upper limits
  83. Konus-Wind detection of GRB 260212A
  84. GRB 260208A: AbAO and Terskol optical upper limits
  85. GRB 260208A: continued Mondy optical observations
  86. IPN triangulation of GRB 260212A
  87. IceCube-260217A - IceCube observation of a high-energy neutrino candidate track-like event
  88. GRB 260213A: GECAM-B observation of a short burst
  89. GRB 260216A: Fermi Gamma-ray Burst Monitor trigger 792969362/260216886 is not a GRB
  90. GRB 260216A: Fermi GBM Final Real-time Localization
  91. EP260214b: Liverpool Telescope optical observations
  92. GRB 260206A: probable hard X-ray burst from 4U 0513-40
  93. EP260214b: Optical upper limit with Kinder observations
  94. EP260214a: Optical upper limits with Kinder observations
  95. EP260214b: EP-FXT follow-up observation
  96. EP260214a / GRB 260214A: Fermi-GBM Sub-Threshold Detection
  97. EP260214b: DDOTI Optical Detection
  98. EP260214b: GROWTH-India Telescope optical upper limit
  99. EP260214a: VLT near-infrared observation
  100. EP260214b: SVOM/VT optical observation

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