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

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