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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: EP-FXT follow-up observation
  2. EP260302a: Einstein Probe detection of an X-ray transient
  3. The EP-WXT trigger 01709258736: Las Cumbres discovery of the optical counterpart
  4. GRB 251130B: TERI Gamma-ray detection
  5. GRB 260208A: TERI Gamma-ray detection
  6. GRB 260302A: Fermi GBM Final Real-time Localization
  7. EP260227a: Mondy optical observations
  8. GRB 260228A: CAHA 2.2m telescope optical upper limit
  9. GRB 260228A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  10. EP260227a: Mephisto optical detection
  11. GRID detection of GRB 260225D
  12. EP-WXT trigger 01709258652: 50cm Telescope multi-band observations
  13. EP260227a: further LCO observations
  14. EP260227a: SVOM/VT optical observation
  15. GRB 260228A: SVOM/VT optical upper limits
  16. GRB 260225D: SVOM/GRM observation
  17. EP260227A: 3.6m DOT optical afterglow detection
  18. GRB 260225B: SVOM/GRM observation
  19. GRB 260228A: SVOM detection of a burst
  20. EP260227a: FTW optical and NIR observations
  21. EP260227a: Liverpool Telescope optical observations
  22. EP260227a: LCOGT Optical Observations
  23. GRB 260226A: Asiago r-band upper limit
  24. EP260227a: Thai National Telescope observations
  25. EP260227a: likely GTC/OSIRIS+ redshift z = 2.714
  26. EP260227a: Liverpool Telescope observations
  27. EP260227a: COLIBRÍ optical observations
  28. EP260227a: NOT optical observations
  29. GRB 260225A: SVOM/VT optical continued observations and upper limit
  30. GRID detection of GRB 260223A
  31. EP260227a: Global MASTER-Net observations report
  32. EP260227a: Einstein Probe detection of an X-ray transient and refined analysis
  33. The EP-WXT trigger 01709258681 (EP260227a?): Las Cumbres follow-up observation of the optical counterpart
  34. EP/WXT trigger 01709258681 (EP260227a?): LCO candidate afterglow
  35. IceCube cascade alert 142200_1517143 retraction
  36. GRB 260226A: Insight-HXMT/HE detection of the very bright burst
  37. Konus-Wind detection of GRB 260226A
  38. GRB 260223A: 7DT detection and Medium-band SED of Afterglow
  39. EP260214a: VLT/FORS2 optical observations
  40. GRB 260225A: WINTER J-band upper limit
  41. GRB 260226A: CALET Gamma-Ray Burst Monitor detection
  42. GRB 260226A: COLIBRÍ optical upper limits
  43. GRB 260226A: LCOGT Optical Upper Limit
  44. EP-WXT trigger 01709258652: SVOM/C-GFT confirmation of a stellar flare
  45. GRB 260225D: Glowbug gamma-ray detection of a likely short burst
  46. GRB 260226A: Glowbug gamma-ray detection
  47. GRB 260226A: NuSTAR detection of bright prompt emission
  48. GRB 260226A : GROWTH-India Telescope optical observations
  49. GRB 260226A: LAST optical upper limit
  50. GRB 260226A: Fermi GBM observation
  51. GRB 260226A: Fermi-LAT refined analysis
  52. The EP-WXT trigger 01709258652 is likely a flaring star
  53. LAT GRB260226.44: Global MASTER-Net observations report
  54. Fermi GRB 260226A: Global MASTER-Net observations report
  55. GRB 260226A: AstroSat CZTI detection of bright long burst
  56. EP260214a: VLA 6 GHz detection
  57. GRB 260226A: Fermi-LAT detection of a bright burst
  58. GRB 260226A???: BALROG localization (Fermi Trigger 793795080 / GRB 260226443)
  59. EP260224a: LCO optical upper limits
  60. GRB260225A: SVOM/ECLAIRs refined position
  61. GRB 260226A: Fermi GBM Final Real-time Localization
  62. GRB 260225A: EP-FXT follow-up observation
  63. GRB 260225A: SVOM/VT optical observation
  64. GRB 260225A: SVOM/COLIBRÍ (FM-GFT) Detection of an Optical Counterpart Candidate
  65. GRB 260225C: Fermi GBM Final Real-time Localization
  66. GRB 260223A: Fermi GBM Observation
  67. GRB 260225A: SVOM/VT optical upper limits
  68. GRB 260225B: Fermi GBM Final Real-time Localization
  69. EP260126a: VLA 6 GHz detection
  70. EP260223a: Liverpool Telescope upper limits
  71. GRB 260225A: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  72. GRB 260225A: SVOM detection of a burst
  73. EP260224a: Einstein Probe detection of an X-ray transient
  74. EP 260225.148: COLIBRÍ Confirmation of flaring star
  75. EP260223a: Xinglong optical upper limit
  76. The EP-WXT trigger 01709258631 is likely a flaring star
  77. GRB 260223A: Glowbug gamma-ray detection
  78. EP260213a: Mephisto optical upper limits
  79. EP260223a: EP-FXT follow-up observation
  80. sb26021801: SVOM/VT optical upper limits
  81. GRB 260223A: COLIBRÍ optical afterglow decay confirmation
  82. sb26021801: SVOM/C-GFT upper limit
  83. EP260223a: COLIBRÍ optical upper limits
  84. EP260223a: Einstein Probe detection of an X-ray transient
  85. GRB 260223A: SVOM/VT optical observation
  86. GRB 260223A: SVOM/GRM observation
  87. GRB 260223A: COLIBRÍ further optical observations and a brightening
  88. EP260221a: Optical upper limit with Kinder observations
  89. GRB 260223A: COLIBRÍ optical observations
  90. GRB 260223A: DDOTI Optical Candidate
  91. GRB 260223A: BALROG localization (Fermi Trigger 793512674 / GRB 260223174)
  92. Fermi GRB 260223A: Global MASTER-Net observations report
  93. GRB 260223A: Fermi GBM Final Real-time Localization
  94. EP260221a: Liverpool Telescope detection of COLIBRÍ counterpart candidate
  95. EP260221a: COLIBRÍ optical counterpart candidate
  96. EP260221a: Gemini South z-band upper limit
  97. GRB 260222A: Fermi GBM Final Real-time Localization
  98. EP260221a: Global MASTER-Net observations report
  99. EP260221a: EP-FXT follow-up observation
  100. Fermi GRB 260221B: Global MASTER-Net observations report

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