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

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