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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. EP260227A: 3.6m DOT optical afterglow detection
  2. GRB 260225B: SVOM/GRM observation
  3. GRB 260228A: SVOM detection of a burst
  4. EP260227a: FTW optical and NIR observations
  5. EP260227a: Liverpool Telescope optical observations
  6. EP260227a: LCOGT Optical Observations
  7. GRB 260226A: Asiago r-band upper limit
  8. EP260227a: Thai National Telescope observations
  9. EP260227a: likely GTC/OSIRIS+ redshift z = 2.714
  10. EP260227a: Liverpool Telescope observations
  11. EP260227a: COLIBRÍ optical observations
  12. EP260227a: NOT optical observations
  13. GRB 260225A: SVOM/VT optical continued observations and upper limit
  14. GRID detection of GRB 260223A
  15. EP260227a: Global MASTER-Net observations report
  16. EP260227a: Einstein Probe detection of an X-ray transient and refined analysis
  17. The EP-WXT trigger 01709258681 (EP260227a?): Las Cumbres follow-up observation of the optical counterpart
  18. EP/WXT trigger 01709258681 (EP260227a?): LCO candidate afterglow
  19. IceCube cascade alert 142200_1517143 retraction
  20. GRB 260226A: Insight-HXMT/HE detection of the very bright burst
  21. Konus-Wind detection of GRB 260226A
  22. GRB 260223A: 7DT detection and Medium-band SED of Afterglow
  23. EP260214a: VLT/FORS2 optical observations
  24. GRB 260225A: WINTER J-band upper limit
  25. GRB 260226A: CALET Gamma-Ray Burst Monitor detection
  26. GRB 260226A: COLIBRÍ optical upper limits
  27. GRB 260226A: LCOGT Optical Upper Limit
  28. EP-WXT trigger 01709258652: SVOM/C-GFT confirmation of a stellar flare
  29. GRB 260225D: Glowbug gamma-ray detection of a likely short burst
  30. GRB 260226A: Glowbug gamma-ray detection
  31. GRB 260226A: NuSTAR detection of bright prompt emission
  32. GRB 260226A : GROWTH-India Telescope optical observations
  33. GRB 260226A: LAST optical upper limit
  34. GRB 260226A: Fermi GBM observation
  35. GRB 260226A: Fermi-LAT refined analysis
  36. The EP-WXT trigger 01709258652 is likely a flaring star
  37. LAT GRB260226.44: Global MASTER-Net observations report
  38. Fermi GRB 260226A: Global MASTER-Net observations report
  39. GRB 260226A: AstroSat CZTI detection of bright long burst
  40. EP260214a: VLA 6 GHz detection
  41. GRB 260226A: Fermi-LAT detection of a bright burst
  42. GRB 260226A???: BALROG localization (Fermi Trigger 793795080 / GRB 260226443)
  43. EP260224a: LCO optical upper limits
  44. GRB260225A: SVOM/ECLAIRs refined position
  45. GRB 260226A: Fermi GBM Final Real-time Localization
  46. GRB 260225A: EP-FXT follow-up observation
  47. GRB 260225A: SVOM/VT optical observation
  48. GRB 260225A: SVOM/COLIBRÍ (FM-GFT) Detection of an Optical Counterpart Candidate
  49. GRB 260225C: Fermi GBM Final Real-time Localization
  50. GRB 260223A: Fermi GBM Observation
  51. GRB 260225A: SVOM/VT optical upper limits
  52. GRB 260225B: Fermi GBM Final Real-time Localization
  53. EP260126a: VLA 6 GHz detection
  54. EP260223a: Liverpool Telescope upper limits
  55. GRB 260225A: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  56. GRB 260225A: SVOM detection of a burst
  57. EP260224a: Einstein Probe detection of an X-ray transient
  58. EP 260225.148: COLIBRÍ Confirmation of flaring star
  59. EP260223a: Xinglong optical upper limit
  60. The EP-WXT trigger 01709258631 is likely a flaring star
  61. GRB 260223A: Glowbug gamma-ray detection
  62. EP260213a: Mephisto optical upper limits
  63. EP260223a: EP-FXT follow-up observation
  64. sb26021801: SVOM/VT optical upper limits
  65. GRB 260223A: COLIBRÍ optical afterglow decay confirmation
  66. sb26021801: SVOM/C-GFT upper limit
  67. EP260223a: COLIBRÍ optical upper limits
  68. EP260223a: Einstein Probe detection of an X-ray transient
  69. GRB 260223A: SVOM/VT optical observation
  70. GRB 260223A: SVOM/GRM observation
  71. GRB 260223A: COLIBRÍ further optical observations and a brightening
  72. EP260221a: Optical upper limit with Kinder observations
  73. GRB 260223A: COLIBRÍ optical observations
  74. GRB 260223A: DDOTI Optical Candidate
  75. GRB 260223A: BALROG localization (Fermi Trigger 793512674 / GRB 260223174)
  76. Fermi GRB 260223A: Global MASTER-Net observations report
  77. GRB 260223A: Fermi GBM Final Real-time Localization
  78. EP260221a: Liverpool Telescope detection of COLIBRÍ counterpart candidate
  79. EP260221a: COLIBRÍ optical counterpart candidate
  80. EP260221a: Gemini South z-band upper limit
  81. GRB 260222A: Fermi GBM Final Real-time Localization
  82. EP260221a: Global MASTER-Net observations report
  83. EP260221a: EP-FXT follow-up observation
  84. Fermi GRB 260221B: Global MASTER-Net observations report
  85. GRB 260221B: Fermi GBM Final Real-time Localization
  86. EP-WXT01709258519: Xinglong optical upper limit
  87. EP260221a: Xinglong optical upper limit
  88. Fermi GRB 260221A: Global MASTER-Net observations report
  89. ZTF26aaglqak/AT2026dbl: COLIBRÍ Optical Observations
  90. GRB 260221A: Fermi GBM Final Real-time Localization
  91. EP260221a: GOTO optical upper limit
  92. EP260221a: COLIBRÍ optical upper limit
  93. SVOM alert sb26021801: LCO optical upper limit
  94. EP260221a: Einstein Probe detection of an X-ray transient
  95. The EP-WXT trigger 01709258519 is likely caused by Mrk 421
  96. GRB 260219A: AstroSat CZTI detection
  97. IceCube-260217A: Upper limits from a search for additional neutrino events in IceCube
  98. GRB 260219A: GECAM-B observation of a long burst
  99. Fermi GRB 260219A: Global MASTER-Net observations report
  100. GRB 260219A: Fermi GBM Final Real-time Localization

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