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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 260223A: 7DT detection and Medium-band SED of Afterglow
  2. EP260214a: VLT/FORS2 optical observations
  3. GRB 260225A: WINTER J-band upper limit
  4. GRB 260226A: CALET Gamma-Ray Burst Monitor detection
  5. GRB 260226A: COLIBRÍ optical upper limits
  6. GRB 260226A: LCOGT Optical Upper Limit
  7. EP-WXT trigger 01709258652: SVOM/C-GFT confirmation of a stellar flare
  8. GRB 260225D: Glowbug gamma-ray detection of a likely short burst
  9. GRB 260226A: Glowbug gamma-ray detection
  10. GRB 260226A: NuSTAR detection of bright prompt emission
  11. GRB 260226A : GROWTH-India Telescope optical observations
  12. GRB 260226A: LAST optical upper limit
  13. GRB 260226A: Fermi GBM observation
  14. GRB 260226A: Fermi-LAT refined analysis
  15. The EP-WXT trigger 01709258652 is likely a flaring star
  16. LAT GRB260226.44: Global MASTER-Net observations report
  17. Fermi GRB 260226A: Global MASTER-Net observations report
  18. GRB 260226A: AstroSat CZTI detection of bright long burst
  19. EP260214a: VLA 6 GHz detection
  20. GRB 260226A: Fermi-LAT detection of a bright burst
  21. GRB 260226A???: BALROG localization (Fermi Trigger 793795080 / GRB 260226443)
  22. EP260224a: LCO optical upper limits
  23. GRB260225A: SVOM/ECLAIRs refined position
  24. GRB 260226A: Fermi GBM Final Real-time Localization
  25. GRB 260225A: EP-FXT follow-up observation
  26. GRB 260225A: SVOM/VT optical observation
  27. GRB 260225A: SVOM/COLIBRÍ (FM-GFT) Detection of an Optical Counterpart Candidate
  28. GRB 260225C: Fermi GBM Final Real-time Localization
  29. GRB 260223A: Fermi GBM Observation
  30. GRB 260225A: SVOM/VT optical upper limits
  31. GRB 260225B: Fermi GBM Final Real-time Localization
  32. EP260126a: VLA 6 GHz detection
  33. EP260223a: Liverpool Telescope upper limits
  34. GRB 260225A: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  35. GRB 260225A: SVOM detection of a burst
  36. EP260224a: Einstein Probe detection of an X-ray transient
  37. EP 260225.148: COLIBRÍ Confirmation of flaring star
  38. EP260223a: Xinglong optical upper limit
  39. The EP-WXT trigger 01709258631 is likely a flaring star
  40. GRB 260223A: Glowbug gamma-ray detection
  41. EP260213a: Mephisto optical upper limits
  42. EP260223a: EP-FXT follow-up observation
  43. sb26021801: SVOM/VT optical upper limits
  44. GRB 260223A: COLIBRÍ optical afterglow decay confirmation
  45. sb26021801: SVOM/C-GFT upper limit
  46. EP260223a: COLIBRÍ optical upper limits
  47. EP260223a: Einstein Probe detection of an X-ray transient
  48. GRB 260223A: SVOM/VT optical observation
  49. GRB 260223A: SVOM/GRM observation
  50. GRB 260223A: COLIBRÍ further optical observations and a brightening
  51. EP260221a: Optical upper limit with Kinder observations
  52. GRB 260223A: COLIBRÍ optical observations
  53. GRB 260223A: DDOTI Optical Candidate
  54. GRB 260223A: BALROG localization (Fermi Trigger 793512674 / GRB 260223174)
  55. Fermi GRB 260223A: Global MASTER-Net observations report
  56. GRB 260223A: Fermi GBM Final Real-time Localization
  57. EP260221a: Liverpool Telescope detection of COLIBRÍ counterpart candidate
  58. EP260221a: COLIBRÍ optical counterpart candidate
  59. EP260221a: Gemini South z-band upper limit
  60. GRB 260222A: Fermi GBM Final Real-time Localization
  61. EP260221a: Global MASTER-Net observations report
  62. EP260221a: EP-FXT follow-up observation
  63. Fermi GRB 260221B: Global MASTER-Net observations report
  64. GRB 260221B: Fermi GBM Final Real-time Localization
  65. EP-WXT01709258519: Xinglong optical upper limit
  66. EP260221a: Xinglong optical upper limit
  67. Fermi GRB 260221A: Global MASTER-Net observations report
  68. ZTF26aaglqak/AT2026dbl: COLIBRÍ Optical Observations
  69. GRB 260221A: Fermi GBM Final Real-time Localization
  70. EP260221a: GOTO optical upper limit
  71. EP260221a: COLIBRÍ optical upper limit
  72. SVOM alert sb26021801: LCO optical upper limit
  73. EP260221a: Einstein Probe detection of an X-ray transient
  74. The EP-WXT trigger 01709258519 is likely caused by Mrk 421
  75. GRB 260219A: AstroSat CZTI detection
  76. IceCube-260217A: Upper limits from a search for additional neutrino events in IceCube
  77. GRB 260219A: GECAM-B observation of a long burst
  78. Fermi GRB 260219A: Global MASTER-Net observations report
  79. GRB 260219A: Fermi GBM Final Real-time Localization
  80. SVOM alert sb26021801: LAST optical upper limit
  81. sb26021801: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  82. IceCube Alert 260217A: Global MASTER-Net observations report
  83. Fermi-LAT Gamma-ray Observations of IceCube-260217A
  84. GRB 260217A: Fermi GBM Final Localization
  85. GRB 260214B/EP260214b: SVOM/ECLAIRs detection through targeted search
  86. sb26021801: SVOM detection of a long faint X-ray transient
  87. The EP-WXT trigger 01709258455 is likely a flaring star
  88. EP-WXT 01709258455: NOT optical upper limits
  89. EP260214b: Mondy optical observations
  90. EP260214b: 1.3m DFOT optical upper limit
  91. EP260210a: Mondy optical upper limits
  92. Konus-Wind detection of GRB 260212A
  93. GRB 260208A: AbAO and Terskol optical upper limits
  94. GRB 260208A: continued Mondy optical observations
  95. IPN triangulation of GRB 260212A
  96. IceCube-260217A - IceCube observation of a high-energy neutrino candidate track-like event
  97. GRB 260213A: GECAM-B observation of a short burst
  98. GRB 260216A: Fermi Gamma-ray Burst Monitor trigger 792969362/260216886 is not a GRB
  99. GRB 260216A: Fermi GBM Final Real-time Localization
  100. EP260214b: Liverpool Telescope optical observations

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