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

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