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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. The EP-WXT trigger 01709258652 is likely a flaring star
  2. LAT GRB260226.44: Global MASTER-Net observations report
  3. Fermi GRB 260226A: Global MASTER-Net observations report
  4. GRB 260226A: AstroSat CZTI detection of bright long burst
  5. EP260214a: VLA 6 GHz detection
  6. GRB 260226A: Fermi-LAT detection of a bright burst
  7. GRB 260226A???: BALROG localization (Fermi Trigger 793795080 / GRB 260226443)
  8. EP260224a: LCO optical upper limits
  9. GRB260225A: SVOM/ECLAIRs refined position
  10. GRB 260226A: Fermi GBM Final Real-time Localization
  11. GRB 260225A: EP-FXT follow-up observation
  12. GRB 260225A: SVOM/VT optical observation
  13. GRB 260225A: SVOM/COLIBRÍ (FM-GFT) Detection of an Optical Counterpart Candidate
  14. GRB 260225C: Fermi GBM Final Real-time Localization
  15. GRB 260223A: Fermi GBM Observation
  16. GRB 260225A: SVOM/VT optical upper limits
  17. GRB 260225B: Fermi GBM Final Real-time Localization
  18. EP260126a: VLA 6 GHz detection
  19. EP260223a: Liverpool Telescope upper limits
  20. GRB 260225A: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  21. GRB 260225A: SVOM detection of a burst
  22. EP260224a: Einstein Probe detection of an X-ray transient
  23. EP 260225.148: COLIBRÍ Confirmation of flaring star
  24. EP260223a: Xinglong optical upper limit
  25. The EP-WXT trigger 01709258631 is likely a flaring star
  26. GRB 260223A: Glowbug gamma-ray detection
  27. EP260213a: Mephisto optical upper limits
  28. EP260223a: EP-FXT follow-up observation
  29. sb26021801: SVOM/VT optical upper limits
  30. GRB 260223A: COLIBRÍ optical afterglow decay confirmation
  31. sb26021801: SVOM/C-GFT upper limit
  32. EP260223a: COLIBRÍ optical upper limits
  33. EP260223a: Einstein Probe detection of an X-ray transient
  34. GRB 260223A: SVOM/VT optical observation
  35. GRB 260223A: SVOM/GRM observation
  36. GRB 260223A: COLIBRÍ further optical observations and a brightening
  37. EP260221a: Optical upper limit with Kinder observations
  38. GRB 260223A: COLIBRÍ optical observations
  39. GRB 260223A: DDOTI Optical Candidate
  40. GRB 260223A: BALROG localization (Fermi Trigger 793512674 / GRB 260223174)
  41. Fermi GRB 260223A: Global MASTER-Net observations report
  42. GRB 260223A: Fermi GBM Final Real-time Localization
  43. EP260221a: Liverpool Telescope detection of COLIBRÍ counterpart candidate
  44. EP260221a: COLIBRÍ optical counterpart candidate
  45. EP260221a: Gemini South z-band upper limit
  46. GRB 260222A: Fermi GBM Final Real-time Localization
  47. EP260221a: Global MASTER-Net observations report
  48. EP260221a: EP-FXT follow-up observation
  49. Fermi GRB 260221B: Global MASTER-Net observations report
  50. GRB 260221B: Fermi GBM Final Real-time Localization
  51. EP-WXT01709258519: Xinglong optical upper limit
  52. EP260221a: Xinglong optical upper limit
  53. Fermi GRB 260221A: Global MASTER-Net observations report
  54. ZTF26aaglqak/AT2026dbl: COLIBRÍ Optical Observations
  55. GRB 260221A: Fermi GBM Final Real-time Localization
  56. EP260221a: GOTO optical upper limit
  57. EP260221a: COLIBRÍ optical upper limit
  58. SVOM alert sb26021801: LCO optical upper limit
  59. EP260221a: Einstein Probe detection of an X-ray transient
  60. The EP-WXT trigger 01709258519 is likely caused by Mrk 421
  61. GRB 260219A: AstroSat CZTI detection
  62. IceCube-260217A: Upper limits from a search for additional neutrino events in IceCube
  63. GRB 260219A: GECAM-B observation of a long burst
  64. Fermi GRB 260219A: Global MASTER-Net observations report
  65. GRB 260219A: Fermi GBM Final Real-time Localization
  66. SVOM alert sb26021801: LAST optical upper limit
  67. sb26021801: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  68. IceCube Alert 260217A: Global MASTER-Net observations report
  69. Fermi-LAT Gamma-ray Observations of IceCube-260217A
  70. GRB 260217A: Fermi GBM Final Localization
  71. GRB 260214B/EP260214b: SVOM/ECLAIRs detection through targeted search
  72. sb26021801: SVOM detection of a long faint X-ray transient
  73. The EP-WXT trigger 01709258455 is likely a flaring star
  74. EP-WXT 01709258455: NOT optical upper limits
  75. EP260214b: Mondy optical observations
  76. EP260214b: 1.3m DFOT optical upper limit
  77. EP260210a: Mondy optical upper limits
  78. Konus-Wind detection of GRB 260212A
  79. GRB 260208A: AbAO and Terskol optical upper limits
  80. GRB 260208A: continued Mondy optical observations
  81. IPN triangulation of GRB 260212A
  82. IceCube-260217A - IceCube observation of a high-energy neutrino candidate track-like event
  83. GRB 260213A: GECAM-B observation of a short burst
  84. GRB 260216A: Fermi Gamma-ray Burst Monitor trigger 792969362/260216886 is not a GRB
  85. GRB 260216A: Fermi GBM Final Real-time Localization
  86. EP260214b: Liverpool Telescope optical observations
  87. GRB 260206A: probable hard X-ray burst from 4U 0513-40
  88. EP260214b: Optical upper limit with Kinder observations
  89. EP260214a: Optical upper limits with Kinder observations
  90. EP260214b: EP-FXT follow-up observation
  91. EP260214a / GRB 260214A: Fermi-GBM Sub-Threshold Detection
  92. EP260214b: DDOTI Optical Detection
  93. EP260214b: GROWTH-India Telescope optical upper limit
  94. EP260214a: VLT near-infrared observation
  95. EP260214b: SVOM/VT optical observation
  96. EP260214a: NOT optical upper limits
  97. EP260214a: COLIBRÍ optical upper limits
  98. EP260214b: OHP/T120 optical observations
  99. EP260214a: refined analysis of the EP-FXT observation
  100. EP260214b: LCO optical counterpart detection

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