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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 260311B: Fermi GBM Final Real-time Localization
  2. GRB 260131A/B: radio detection with the VLA
  3. EP260302a: MeerKAT radio counterpart
  4. GRB260307A: GECAM-B observation of a burst
  5. GRB 260308A: SVOM/GRM observation of a short GRB
  6. EP260306a: Mondy optical upper limit
  7. GRB 260310A: AstroSat CZTI detection of a long burst
  8. GRB 260311A: Fermi GBM Final Real-time Localization
  9. Fermi GRB 260310B: Global MASTER-Net observations report
  10. GRB 260310B: Fermi GBM Final Real-time Localization
  11. Fermi GRB 260310A: Global MASTER-Net observations report
  12. GRB 260307B: SVOM/ECLAIRs refined analysis
  13. GRB 260208A: radio detection with the VLA
  14. GRB 260310A: Fermi GBM Final Real-time Localization
  15. GRB 260307A: Glowbug gamma-ray detection
  16. GRB 260308A: Fermi GBM Final Real-time Localization
  17. Fermi GBM Sub-Threshold Detection of GRB 260307B
  18. GRB 260307B: Mephisto optical upper limits
  19. GRB 260307B: possible NOT optical counterpart
  20. GRB 260307B: SVOM/VT upper limit with X band data analysis
  21. Fermi GRB 260307A: Global MASTER-Net observations report
  22. GRB260307B: GROWTH-India Telescope optical upper limit
  23. GRB 260307B: SVOM/VT optical candidate
  24. GRB 260307B: SVOM/C-GFT upper limit
  25. GRB 260307B: SVOM detection of a burst
  26. GRB 260307A: Fermi GBM Final Localization
  27. GRB 260211A: late-time NOT i-band observations consistent with archival flux
  28. EP260306a: refined analysis of the EP-WXT and EP-FXT observations
  29. GRB 260207A: TESS Detection and Possible VLA Counterpart
  30. EP260302a: SVOM/VT optical observation
  31. EP260306a: Gemini-North redshift z = 4.773
  32. EP260306a: SVOM/VT optical observation
  33. EP260302a: Gemini-South redshift z = 1.535
  34. EP260306a: COLIBRÍ optical observations of the fading and red counterpart
  35. EP260306a: Einstein Probe detection of an X-ray transient
  36. The EP-WXT trigger 01709258759: Las Cumbres discovery of the optical counterpart
  37. EP260302a: Optical afterglow rebrightening
  38. GRB 260228A: further EP-FXT observations and X-ray afterglow confirmation
  39. GRB 260303A: 1.3m DFOT optical upper limit (duplicate submission)
  40. GRB 260303A: 1.3m DFOT optical upper limit
  41. EP260214b: ATCA 6 GHz observations
  42. GRB 260211A: SVOM/VT optical rebrightening at 20 days after the burst, SN candidate
  43. GRB 260303A: SVOM/ECLAIRs refined analysis
  44. Fermi GRB 260305A: Global MASTER-Net observations report
  45. GRB 260305A: Fermi GBM Final Real-time Localization
  46. GRB 260303B: AstroSat CZTI detection
  47. GRB 260304A: AstroSat CZTI detection of a long burst
  48. SVOM/sb26030408: SVOM detection of an X-ray transient likely associated with Beta Persei
  49. GRB 260303A: SVOM/VT optical observations
  50. GRB 260303A: J-band observations with WINTER
  51. GRB 260303B: NuSTAR detection of prompt emission
  52. EP260302a: Global MASTER-Net observations report
  53. Fermi GRB 260303B: Global MASTER-Net observations report
  54. IceCube-260217A: No Candidate Transients from the Zwicky Transient Facility
  55. GRB 260228A: SVOM/ECLAIRs refined analysis
  56. GRB 260225A: SVOM/ECLAIRs refined analysis
  57. GRB 260303B: BALROG localization (Fermi Trigger 794237065 / GRB 260303559)
  58. GRB 260303B: Fermi GBM Final Real-time Localization
  59. EP260302a: analysis of the follow-up EP-FXT observation
  60. EP260227a: Gemini-South optical observations
  61. EP260302a: LCO observations
  62. EP260302a: BOOTES-7 optical counterpart detection at early times
  63. GRB 260303A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  64. GRB 260303A: SVOM detection of a burst
  65. GRB 260228A: EP-FXT follow-up observation
  66. EP260302a: Einstein Probe detection of an X-ray transient
  67. The EP-WXT trigger 01709258736: Las Cumbres discovery of the optical counterpart
  68. GRB 251130B: TERI Gamma-ray detection
  69. GRB 260208A: TERI Gamma-ray detection
  70. GRB 260302A: Fermi GBM Final Real-time Localization
  71. EP260227a: Mondy optical observations
  72. GRB 260228A: CAHA 2.2m telescope optical upper limit
  73. GRB 260228A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  74. EP260227a: Mephisto optical detection
  75. GRID detection of GRB 260225D
  76. EP-WXT trigger 01709258652: 50cm Telescope multi-band observations
  77. EP260227a: further LCO observations
  78. EP260227a: SVOM/VT optical observation
  79. GRB 260228A: SVOM/VT optical upper limits
  80. GRB 260225D: SVOM/GRM observation
  81. EP260227A: 3.6m DOT optical afterglow detection
  82. GRB 260225B: SVOM/GRM observation
  83. GRB 260228A: SVOM detection of a burst
  84. EP260227a: FTW optical and NIR observations
  85. EP260227a: Liverpool Telescope optical observations
  86. EP260227a: LCOGT Optical Observations
  87. GRB 260226A: Asiago r-band upper limit
  88. EP260227a: Thai National Telescope observations
  89. EP260227a: likely GTC/OSIRIS+ redshift z = 2.714
  90. EP260227a: Liverpool Telescope observations
  91. EP260227a: COLIBRÍ optical observations
  92. EP260227a: NOT optical observations
  93. GRB 260225A: SVOM/VT optical continued observations and upper limit
  94. GRID detection of GRB 260223A
  95. EP260227a: Global MASTER-Net observations report
  96. EP260227a: Einstein Probe detection of an X-ray transient and refined analysis
  97. The EP-WXT trigger 01709258681 (EP260227a?): Las Cumbres follow-up observation of the optical counterpart
  98. EP/WXT trigger 01709258681 (EP260227a?): LCO candidate afterglow
  99. IceCube cascade alert 142200_1517143 retraction
  100. GRB 260226A: Insight-HXMT/HE detection of the very bright burst

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