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

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