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

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