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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. EP260306a: refined analysis of the EP-WXT and EP-FXT observations
  2. GRB 260207A: TESS Detection and Possible VLA Counterpart
  3. EP260302a: SVOM/VT optical observation
  4. EP260306a: Gemini-North redshift z = 4.773
  5. EP260306a: SVOM/VT optical observation
  6. EP260302a: Gemini-South redshift z = 1.535
  7. EP260306a: COLIBRÍ optical observations of the fading and red counterpart
  8. EP260306a: Einstein Probe detection of an X-ray transient
  9. The EP-WXT trigger 01709258759: Las Cumbres discovery of the optical counterpart
  10. EP260302a: Optical afterglow rebrightening
  11. GRB 260228A: further EP-FXT observations and X-ray afterglow confirmation
  12. GRB 260303A: 1.3m DFOT optical upper limit (duplicate submission)
  13. GRB 260303A: 1.3m DFOT optical upper limit
  14. EP260214b: ATCA 6 GHz observations
  15. GRB 260211A: SVOM/VT optical rebrightening at 20 days after the burst, SN candidate
  16. GRB 260303A: SVOM/ECLAIRs refined analysis
  17. Fermi GRB 260305A: Global MASTER-Net observations report
  18. GRB 260305A: Fermi GBM Final Real-time Localization
  19. GRB 260303B: AstroSat CZTI detection
  20. GRB 260304A: AstroSat CZTI detection of a long burst
  21. SVOM/sb26030408: SVOM detection of an X-ray transient likely associated with Beta Persei
  22. GRB 260303A: SVOM/VT optical observations
  23. GRB 260303A: J-band observations with WINTER
  24. GRB 260303B: NuSTAR detection of prompt emission
  25. EP260302a: Global MASTER-Net observations report
  26. Fermi GRB 260303B: Global MASTER-Net observations report
  27. IceCube-260217A: No Candidate Transients from the Zwicky Transient Facility
  28. GRB 260228A: SVOM/ECLAIRs refined analysis
  29. GRB 260225A: SVOM/ECLAIRs refined analysis
  30. GRB 260303B: BALROG localization (Fermi Trigger 794237065 / GRB 260303559)
  31. GRB 260303B: Fermi GBM Final Real-time Localization
  32. EP260302a: analysis of the follow-up EP-FXT observation
  33. EP260227a: Gemini-South optical observations
  34. EP260302a: LCO observations
  35. EP260302a: BOOTES-7 optical counterpart detection at early times
  36. GRB 260303A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  37. GRB 260303A: SVOM detection of a burst
  38. GRB 260228A: EP-FXT follow-up observation
  39. EP260302a: Einstein Probe detection of an X-ray transient
  40. The EP-WXT trigger 01709258736: Las Cumbres discovery of the optical counterpart
  41. GRB 251130B: TERI Gamma-ray detection
  42. GRB 260208A: TERI Gamma-ray detection
  43. GRB 260302A: Fermi GBM Final Real-time Localization
  44. EP260227a: Mondy optical observations
  45. GRB 260228A: CAHA 2.2m telescope optical upper limit
  46. GRB 260228A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  47. EP260227a: Mephisto optical detection
  48. GRID detection of GRB 260225D
  49. EP-WXT trigger 01709258652: 50cm Telescope multi-band observations
  50. EP260227a: further LCO observations
  51. EP260227a: SVOM/VT optical observation
  52. GRB 260228A: SVOM/VT optical upper limits
  53. GRB 260225D: SVOM/GRM observation
  54. EP260227A: 3.6m DOT optical afterglow detection
  55. GRB 260225B: SVOM/GRM observation
  56. GRB 260228A: SVOM detection of a burst
  57. EP260227a: FTW optical and NIR observations
  58. EP260227a: Liverpool Telescope optical observations
  59. EP260227a: LCOGT Optical Observations
  60. GRB 260226A: Asiago r-band upper limit
  61. EP260227a: Thai National Telescope observations
  62. EP260227a: likely GTC/OSIRIS+ redshift z = 2.714
  63. EP260227a: Liverpool Telescope observations
  64. EP260227a: COLIBRÍ optical observations
  65. EP260227a: NOT optical observations
  66. GRB 260225A: SVOM/VT optical continued observations and upper limit
  67. GRID detection of GRB 260223A
  68. EP260227a: Global MASTER-Net observations report
  69. EP260227a: Einstein Probe detection of an X-ray transient and refined analysis
  70. The EP-WXT trigger 01709258681 (EP260227a?): Las Cumbres follow-up observation of the optical counterpart
  71. EP/WXT trigger 01709258681 (EP260227a?): LCO candidate afterglow
  72. IceCube cascade alert 142200_1517143 retraction
  73. GRB 260226A: Insight-HXMT/HE detection of the very bright burst
  74. Konus-Wind detection of GRB 260226A
  75. GRB 260223A: 7DT detection and Medium-band SED of Afterglow
  76. EP260214a: VLT/FORS2 optical observations
  77. GRB 260225A: WINTER J-band upper limit
  78. GRB 260226A: CALET Gamma-Ray Burst Monitor detection
  79. GRB 260226A: COLIBRÍ optical upper limits
  80. GRB 260226A: LCOGT Optical Upper Limit
  81. EP-WXT trigger 01709258652: SVOM/C-GFT confirmation of a stellar flare
  82. GRB 260225D: Glowbug gamma-ray detection of a likely short burst
  83. GRB 260226A: Glowbug gamma-ray detection
  84. GRB 260226A: NuSTAR detection of bright prompt emission
  85. GRB 260226A : GROWTH-India Telescope optical observations
  86. GRB 260226A: LAST optical upper limit
  87. GRB 260226A: Fermi GBM observation
  88. GRB 260226A: Fermi-LAT refined analysis
  89. The EP-WXT trigger 01709258652 is likely a flaring star
  90. LAT GRB260226.44: Global MASTER-Net observations report
  91. Fermi GRB 260226A: Global MASTER-Net observations report
  92. GRB 260226A: AstroSat CZTI detection of bright long burst
  93. EP260214a: VLA 6 GHz detection
  94. GRB 260226A: Fermi-LAT detection of a bright burst
  95. GRB 260226A???: BALROG localization (Fermi Trigger 793795080 / GRB 260226443)
  96. EP260224a: LCO optical upper limits
  97. GRB260225A: SVOM/ECLAIRs refined position
  98. GRB 260226A: Fermi GBM Final Real-time Localization
  99. GRB 260225A: EP-FXT follow-up observation
  100. GRB 260225A: SVOM/VT optical observation

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