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

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