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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. Swift BAT trigger 1500295: A solar flare
  2. GRB 260313A: Fermi GBM Final Real-time Localization
  3. GRB 260310A/AT 2026fgk: Bok spectroscopic observation
  4. Swift BAT trigger 1500287: A solar flare
  5. GRB 260310A / AT2026fgk: OSIRIS+/GTC spectroscopy confirms redshift z = 0.153
  6. GRB 260308A: Insight-HXMT/HE detection
  7. GRB 260307A: CALET Gamma-Ray Burst Monitor detection
  8. GRB 260310A / AT 2026fgk: Location in the Epeak - Eiso diagram
  9. GRB 260310A / AT 2026fgk: COLIBRÍ optical observations
  10. GRB 260310A / AT2026fgk: CAHA 1.23m telescope optical observations
  11. GRB 260310A / AT2026fgk : MASTER OT rebrightening during 7h observations
  12. GRB260310A / AT2026fgk: P200 Spectroscopy
  13. GRB 260312B: Glowbug gamma-ray detection
  14. GRB 260310A: Fermi GBM Observation
  15. GRB 260310A: potential optical counterpart
  16. Fermi GRB 260312B: Global MASTER-Net observations report
  17. Fermi GRB 260311B: Global MASTER-Net observations report
  18. Swift BAT trigger 1500148: A solar flare
  19. GRB 260312B: BALROG localization (Fermi Trigger 795001611 / GRB 260312407)
  20. GRB 260312B: Fermi GBM Final Real-time Localization
  21. The EP-WXT trigger 01709258843 is not a real source
  22. GRB 260310B: GECAM-B observation of a burst
  23. Retraction of GCN 43965: GRB is actually solar flare
  24. GRB 260312A: Swift detection of a burst
  25. GRB 260311B: Fermi GBM Final Real-time Localization
  26. GRB 260131A/B: radio detection with the VLA
  27. EP260302a: MeerKAT radio counterpart
  28. GRB260307A: GECAM-B observation of a burst
  29. GRB 260308A: SVOM/GRM observation of a short GRB
  30. EP260306a: Mondy optical upper limit
  31. GRB 260310A: AstroSat CZTI detection of a long burst
  32. GRB 260311A: Fermi GBM Final Real-time Localization
  33. Fermi GRB 260310B: Global MASTER-Net observations report
  34. GRB 260310B: Fermi GBM Final Real-time Localization
  35. Fermi GRB 260310A: Global MASTER-Net observations report
  36. GRB 260307B: SVOM/ECLAIRs refined analysis
  37. GRB 260208A: radio detection with the VLA
  38. GRB 260310A: Fermi GBM Final Real-time Localization
  39. GRB 260307A: Glowbug gamma-ray detection
  40. GRB 260308A: Fermi GBM Final Real-time Localization
  41. Fermi GBM Sub-Threshold Detection of GRB 260307B
  42. GRB 260307B: Mephisto optical upper limits
  43. GRB 260307B: possible NOT optical counterpart
  44. GRB 260307B: SVOM/VT upper limit with X band data analysis
  45. Fermi GRB 260307A: Global MASTER-Net observations report
  46. GRB260307B: GROWTH-India Telescope optical upper limit
  47. GRB 260307B: SVOM/VT optical candidate
  48. GRB 260307B: SVOM/C-GFT upper limit
  49. GRB 260307B: SVOM detection of a burst
  50. GRB 260307A: Fermi GBM Final Localization
  51. GRB 260211A: late-time NOT i-band observations consistent with archival flux
  52. EP260306a: refined analysis of the EP-WXT and EP-FXT observations
  53. GRB 260207A: TESS Detection and Possible VLA Counterpart
  54. EP260302a: SVOM/VT optical observation
  55. EP260306a: Gemini-North redshift z = 4.773
  56. EP260306a: SVOM/VT optical observation
  57. EP260302a: Gemini-South redshift z = 1.535
  58. EP260306a: COLIBRÍ optical observations of the fading and red counterpart
  59. EP260306a: Einstein Probe detection of an X-ray transient
  60. The EP-WXT trigger 01709258759: Las Cumbres discovery of the optical counterpart
  61. EP260302a: Optical afterglow rebrightening
  62. GRB 260228A: further EP-FXT observations and X-ray afterglow confirmation
  63. GRB 260303A: 1.3m DFOT optical upper limit (duplicate submission)
  64. GRB 260303A: 1.3m DFOT optical upper limit
  65. EP260214b: ATCA 6 GHz observations
  66. GRB 260211A: SVOM/VT optical rebrightening at 20 days after the burst, SN candidate
  67. GRB 260303A: SVOM/ECLAIRs refined analysis
  68. Fermi GRB 260305A: Global MASTER-Net observations report
  69. GRB 260305A: Fermi GBM Final Real-time Localization
  70. GRB 260303B: AstroSat CZTI detection
  71. GRB 260304A: AstroSat CZTI detection of a long burst
  72. SVOM/sb26030408: SVOM detection of an X-ray transient likely associated with Beta Persei
  73. GRB 260303A: SVOM/VT optical observations
  74. GRB 260303A: J-band observations with WINTER
  75. GRB 260303B: NuSTAR detection of prompt emission
  76. EP260302a: Global MASTER-Net observations report
  77. Fermi GRB 260303B: Global MASTER-Net observations report
  78. IceCube-260217A: No Candidate Transients from the Zwicky Transient Facility
  79. GRB 260228A: SVOM/ECLAIRs refined analysis
  80. GRB 260225A: SVOM/ECLAIRs refined analysis
  81. GRB 260303B: BALROG localization (Fermi Trigger 794237065 / GRB 260303559)
  82. GRB 260303B: Fermi GBM Final Real-time Localization
  83. EP260302a: analysis of the follow-up EP-FXT observation
  84. EP260227a: Gemini-South optical observations
  85. EP260302a: LCO observations
  86. EP260302a: BOOTES-7 optical counterpart detection at early times
  87. GRB 260303A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  88. GRB 260303A: SVOM detection of a burst
  89. GRB 260228A: EP-FXT follow-up observation
  90. EP260302a: Einstein Probe detection of an X-ray transient
  91. The EP-WXT trigger 01709258736: Las Cumbres discovery of the optical counterpart
  92. GRB 251130B: TERI Gamma-ray detection
  93. GRB 260208A: TERI Gamma-ray detection
  94. GRB 260302A: Fermi GBM Final Real-time Localization
  95. EP260227a: Mondy optical observations
  96. GRB 260228A: CAHA 2.2m telescope optical upper limit
  97. GRB 260228A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  98. EP260227a: Mephisto optical detection
  99. GRID detection of GRB 260225D
  100. EP-WXT trigger 01709258652: 50cm Telescope multi-band observations

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