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

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