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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. Fermi GRB 260311B: Global MASTER-Net observations report
  2. Swift BAT trigger 1500148: A solar flare
  3. GRB 260312B: BALROG localization (Fermi Trigger 795001611 / GRB 260312407)
  4. GRB 260312B: Fermi GBM Final Real-time Localization
  5. The EP-WXT trigger 01709258843 is not a real source
  6. GRB 260310B: GECAM-B observation of a burst
  7. Retraction of GCN 43965: GRB is actually solar flare
  8. GRB 260312A: Swift detection of a burst
  9. GRB 260311B: Fermi GBM Final Real-time Localization
  10. GRB 260131A/B: radio detection with the VLA
  11. EP260302a: MeerKAT radio counterpart
  12. GRB260307A: GECAM-B observation of a burst
  13. GRB 260308A: SVOM/GRM observation of a short GRB
  14. EP260306a: Mondy optical upper limit
  15. GRB 260310A: AstroSat CZTI detection of a long burst
  16. GRB 260311A: Fermi GBM Final Real-time Localization
  17. Fermi GRB 260310B: Global MASTER-Net observations report
  18. GRB 260310B: Fermi GBM Final Real-time Localization
  19. Fermi GRB 260310A: Global MASTER-Net observations report
  20. GRB 260307B: SVOM/ECLAIRs refined analysis
  21. GRB 260208A: radio detection with the VLA
  22. GRB 260310A: Fermi GBM Final Real-time Localization
  23. GRB 260307A: Glowbug gamma-ray detection
  24. GRB 260308A: Fermi GBM Final Real-time Localization
  25. Fermi GBM Sub-Threshold Detection of GRB 260307B
  26. GRB 260307B: Mephisto optical upper limits
  27. GRB 260307B: possible NOT optical counterpart
  28. GRB 260307B: SVOM/VT upper limit with X band data analysis
  29. Fermi GRB 260307A: Global MASTER-Net observations report
  30. GRB260307B: GROWTH-India Telescope optical upper limit
  31. GRB 260307B: SVOM/VT optical candidate
  32. GRB 260307B: SVOM/C-GFT upper limit
  33. GRB 260307B: SVOM detection of a burst
  34. GRB 260307A: Fermi GBM Final Localization
  35. GRB 260211A: late-time NOT i-band observations consistent with archival flux
  36. EP260306a: refined analysis of the EP-WXT and EP-FXT observations
  37. GRB 260207A: TESS Detection and Possible VLA Counterpart
  38. EP260302a: SVOM/VT optical observation
  39. EP260306a: Gemini-North redshift z = 4.773
  40. EP260306a: SVOM/VT optical observation
  41. EP260302a: Gemini-South redshift z = 1.535
  42. EP260306a: COLIBRÍ optical observations of the fading and red counterpart
  43. EP260306a: Einstein Probe detection of an X-ray transient
  44. The EP-WXT trigger 01709258759: Las Cumbres discovery of the optical counterpart
  45. EP260302a: Optical afterglow rebrightening
  46. GRB 260228A: further EP-FXT observations and X-ray afterglow confirmation
  47. GRB 260303A: 1.3m DFOT optical upper limit (duplicate submission)
  48. GRB 260303A: 1.3m DFOT optical upper limit
  49. EP260214b: ATCA 6 GHz observations
  50. GRB 260211A: SVOM/VT optical rebrightening at 20 days after the burst, SN candidate
  51. GRB 260303A: SVOM/ECLAIRs refined analysis
  52. Fermi GRB 260305A: Global MASTER-Net observations report
  53. GRB 260305A: Fermi GBM Final Real-time Localization
  54. GRB 260303B: AstroSat CZTI detection
  55. GRB 260304A: AstroSat CZTI detection of a long burst
  56. SVOM/sb26030408: SVOM detection of an X-ray transient likely associated with Beta Persei
  57. GRB 260303A: SVOM/VT optical observations
  58. GRB 260303A: J-band observations with WINTER
  59. GRB 260303B: NuSTAR detection of prompt emission
  60. EP260302a: Global MASTER-Net observations report
  61. Fermi GRB 260303B: Global MASTER-Net observations report
  62. IceCube-260217A: No Candidate Transients from the Zwicky Transient Facility
  63. GRB 260228A: SVOM/ECLAIRs refined analysis
  64. GRB 260225A: SVOM/ECLAIRs refined analysis
  65. GRB 260303B: BALROG localization (Fermi Trigger 794237065 / GRB 260303559)
  66. GRB 260303B: Fermi GBM Final Real-time Localization
  67. EP260302a: analysis of the follow-up EP-FXT observation
  68. EP260227a: Gemini-South optical observations
  69. EP260302a: LCO observations
  70. EP260302a: BOOTES-7 optical counterpart detection at early times
  71. GRB 260303A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  72. GRB 260303A: SVOM detection of a burst
  73. GRB 260228A: EP-FXT follow-up observation
  74. EP260302a: Einstein Probe detection of an X-ray transient
  75. The EP-WXT trigger 01709258736: Las Cumbres discovery of the optical counterpart
  76. GRB 251130B: TERI Gamma-ray detection
  77. GRB 260208A: TERI Gamma-ray detection
  78. GRB 260302A: Fermi GBM Final Real-time Localization
  79. EP260227a: Mondy optical observations
  80. GRB 260228A: CAHA 2.2m telescope optical upper limit
  81. GRB 260228A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  82. EP260227a: Mephisto optical detection
  83. GRID detection of GRB 260225D
  84. EP-WXT trigger 01709258652: 50cm Telescope multi-band observations
  85. EP260227a: further LCO observations
  86. EP260227a: SVOM/VT optical observation
  87. GRB 260228A: SVOM/VT optical upper limits
  88. GRB 260225D: SVOM/GRM observation
  89. EP260227A: 3.6m DOT optical afterglow detection
  90. GRB 260225B: SVOM/GRM observation
  91. GRB 260228A: SVOM detection of a burst
  92. EP260227a: FTW optical and NIR observations
  93. EP260227a: Liverpool Telescope optical observations
  94. EP260227a: LCOGT Optical Observations
  95. GRB 260226A: Asiago r-band upper limit
  96. EP260227a: Thai National Telescope observations
  97. EP260227a: likely GTC/OSIRIS+ redshift z = 2.714
  98. EP260227a: Liverpool Telescope observations
  99. EP260227a: COLIBRÍ optical observations
  100. EP260227a: NOT optical observations

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