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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: Gemini-South optical observations
  2. EP260302a: LCO observations
  3. EP260302a: BOOTES-7 optical counterpart detection at early times
  4. GRB 260303A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  5. GRB 260303A: SVOM detection of a burst
  6. GRB 260228A: EP-FXT follow-up observation
  7. EP260302a: Einstein Probe detection of an X-ray transient
  8. The EP-WXT trigger 01709258736: Las Cumbres discovery of the optical counterpart
  9. GRB 251130B: TERI Gamma-ray detection
  10. GRB 260208A: TERI Gamma-ray detection
  11. GRB 260302A: Fermi GBM Final Real-time Localization
  12. EP260227a: Mondy optical observations
  13. GRB 260228A: CAHA 2.2m telescope optical upper limit
  14. GRB 260228A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  15. EP260227a: Mephisto optical detection
  16. GRID detection of GRB 260225D
  17. EP-WXT trigger 01709258652: 50cm Telescope multi-band observations
  18. EP260227a: further LCO observations
  19. EP260227a: SVOM/VT optical observation
  20. GRB 260228A: SVOM/VT optical upper limits
  21. GRB 260225D: SVOM/GRM observation
  22. EP260227A: 3.6m DOT optical afterglow detection
  23. GRB 260225B: SVOM/GRM observation
  24. GRB 260228A: SVOM detection of a burst
  25. EP260227a: FTW optical and NIR observations
  26. EP260227a: Liverpool Telescope optical observations
  27. EP260227a: LCOGT Optical Observations
  28. GRB 260226A: Asiago r-band upper limit
  29. EP260227a: Thai National Telescope observations
  30. EP260227a: likely GTC/OSIRIS+ redshift z = 2.714
  31. EP260227a: Liverpool Telescope observations
  32. EP260227a: COLIBRÍ optical observations
  33. EP260227a: NOT optical observations
  34. GRB 260225A: SVOM/VT optical continued observations and upper limit
  35. GRID detection of GRB 260223A
  36. EP260227a: Global MASTER-Net observations report
  37. EP260227a: Einstein Probe detection of an X-ray transient and refined analysis
  38. The EP-WXT trigger 01709258681 (EP260227a?): Las Cumbres follow-up observation of the optical counterpart
  39. EP/WXT trigger 01709258681 (EP260227a?): LCO candidate afterglow
  40. IceCube cascade alert 142200_1517143 retraction
  41. GRB 260226A: Insight-HXMT/HE detection of the very bright burst
  42. Konus-Wind detection of GRB 260226A
  43. GRB 260223A: 7DT detection and Medium-band SED of Afterglow
  44. EP260214a: VLT/FORS2 optical observations
  45. GRB 260225A: WINTER J-band upper limit
  46. GRB 260226A: CALET Gamma-Ray Burst Monitor detection
  47. GRB 260226A: COLIBRÍ optical upper limits
  48. GRB 260226A: LCOGT Optical Upper Limit
  49. EP-WXT trigger 01709258652: SVOM/C-GFT confirmation of a stellar flare
  50. GRB 260225D: Glowbug gamma-ray detection of a likely short burst
  51. GRB 260226A: Glowbug gamma-ray detection
  52. GRB 260226A: NuSTAR detection of bright prompt emission
  53. GRB 260226A : GROWTH-India Telescope optical observations
  54. GRB 260226A: LAST optical upper limit
  55. GRB 260226A: Fermi GBM observation
  56. GRB 260226A: Fermi-LAT refined analysis
  57. The EP-WXT trigger 01709258652 is likely a flaring star
  58. LAT GRB260226.44: Global MASTER-Net observations report
  59. Fermi GRB 260226A: Global MASTER-Net observations report
  60. GRB 260226A: AstroSat CZTI detection of bright long burst
  61. EP260214a: VLA 6 GHz detection
  62. GRB 260226A: Fermi-LAT detection of a bright burst
  63. GRB 260226A???: BALROG localization (Fermi Trigger 793795080 / GRB 260226443)
  64. EP260224a: LCO optical upper limits
  65. GRB260225A: SVOM/ECLAIRs refined position
  66. GRB 260226A: Fermi GBM Final Real-time Localization
  67. GRB 260225A: EP-FXT follow-up observation
  68. GRB 260225A: SVOM/VT optical observation
  69. GRB 260225A: SVOM/COLIBRÍ (FM-GFT) Detection of an Optical Counterpart Candidate
  70. GRB 260225C: Fermi GBM Final Real-time Localization
  71. GRB 260223A: Fermi GBM Observation
  72. GRB 260225A: SVOM/VT optical upper limits
  73. GRB 260225B: Fermi GBM Final Real-time Localization
  74. EP260126a: VLA 6 GHz detection
  75. EP260223a: Liverpool Telescope upper limits
  76. GRB 260225A: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  77. GRB 260225A: SVOM detection of a burst
  78. EP260224a: Einstein Probe detection of an X-ray transient
  79. EP 260225.148: COLIBRÍ Confirmation of flaring star
  80. EP260223a: Xinglong optical upper limit
  81. The EP-WXT trigger 01709258631 is likely a flaring star
  82. GRB 260223A: Glowbug gamma-ray detection
  83. EP260213a: Mephisto optical upper limits
  84. EP260223a: EP-FXT follow-up observation
  85. sb26021801: SVOM/VT optical upper limits
  86. GRB 260223A: COLIBRÍ optical afterglow decay confirmation
  87. sb26021801: SVOM/C-GFT upper limit
  88. EP260223a: COLIBRÍ optical upper limits
  89. EP260223a: Einstein Probe detection of an X-ray transient
  90. GRB 260223A: SVOM/VT optical observation
  91. GRB 260223A: SVOM/GRM observation
  92. GRB 260223A: COLIBRÍ further optical observations and a brightening
  93. EP260221a: Optical upper limit with Kinder observations
  94. GRB 260223A: COLIBRÍ optical observations
  95. GRB 260223A: DDOTI Optical Candidate
  96. GRB 260223A: BALROG localization (Fermi Trigger 793512674 / GRB 260223174)
  97. Fermi GRB 260223A: Global MASTER-Net observations report
  98. GRB 260223A: Fermi GBM Final Real-time Localization
  99. EP260221a: Liverpool Telescope detection of COLIBRÍ counterpart candidate
  100. EP260221a: COLIBRÍ optical counterpart candidate

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