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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"

26206 results found.

  1. GRB 260314A: GECAM-B observation of a burst
  2. Fermi Gamma-ray Burst Monitor trigger 795185313/260314534 is not a GRB
  3. GRB 260310A / AT2026fgk: SAO RAS optical observations
  4. GRB 260310A / AT2026fgk: TNG NIR detection
  5. GRB 260310A / AT2026fgk: OASDG optical observations
  6. GRB 260310A / AT 2026fgk: COLIBRÍ continuing optical observations
  7. GRB 260310A / AT2026fgk: further CAHA 1.23m telescope optical observations suggest shallow decay
  8. Fermi GRB 260314A: Global MASTER-Net observations report
  9. Fermi GRB 260313A: Global MASTER-Net observations report
  10. GRB 260314A: Fermi GBM Final Real-time Localization
  11. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  12. GRB 260313A: A Correction to the Fermi GBM Final Localization
  13. GRB 260310A/AT 2026fgk: J-band observations by the SYSU 80 cm infrared telescope
  14. GRB 260310A/AT 2026fgk: DDOTI Optical Detection
  15. GRB 260310A: NOT optical polarimetry
  16. Swift BAT trigger 1500295: A solar flare
  17. GRB 260313A: Fermi GBM Final Real-time Localization
  18. Swift BAT trigger 1500287: A solar flare
  19. GRB 260310A / AT2026fgk: OSIRIS+/GTC spectroscopy confirms redshift z = 0.153
  20. GRB 260307A: CALET Gamma-Ray Burst Monitor detection
  21. GRB 260310A / AT 2026fgk: COLIBRÍ optical observations
  22. GRB 260310A / AT2026fgk: CAHA 1.23m telescope optical observations
  23. GRB260310A / AT2026fgk: P200 Spectroscopy
  24. GRB 260310A: Fermi GBM Observation
  25. Fermi GRB 260312B: Global MASTER-Net observations report
  26. Fermi GRB 260311B: Global MASTER-Net observations report
  27. Swift BAT trigger 1500148: A solar flare
  28. GRB 260312B: BALROG localization (Fermi Trigger 795001611 / GRB 260312407)
  29. GRB 260312B: Fermi GBM Final Real-time Localization
  30. The EP-WXT trigger 01709258843 is not a real source
  31. GRB 260310B: GECAM-B observation of a burst
  32. GRB 260312A: Swift detection of a burst
  33. GRB 260311B: Fermi GBM Final Real-time Localization
  34. GRB260307A: GECAM-B observation of a burst
  35. GRB 260308A: SVOM/GRM observation of a short GRB
  36. GRB 260311A: Fermi GBM Final Real-time Localization
  37. Fermi GRB 260310B: Global MASTER-Net observations report
  38. GRB 260310B: Fermi GBM Final Real-time Localization
  39. Fermi GRB 260310A: Global MASTER-Net observations report
  40. GRB 260307B: SVOM/ECLAIRs refined analysis
  41. GRB 260310A: Fermi GBM Final Real-time Localization
  42. GRB 260307A: Glowbug gamma-ray detection
  43. GRB 260308A: Fermi GBM Final Real-time Localization
  44. Fermi GBM Sub-Threshold Detection of GRB 260307B
  45. GRB 260307B: Mephisto optical upper limits
  46. GRB 260307B: possible NOT optical counterpart
  47. GRB 260307B: SVOM/VT upper limit with X band data analysis
  48. Fermi GRB 260307A: Global MASTER-Net observations report
  49. GRB260307B: GROWTH-India Telescope optical upper limit
  50. GRB 260307B: SVOM/VT optical candidate
  51. GRB 260307B: SVOM/C-GFT upper limit
  52. GRB 260307B: SVOM detection of a burst
  53. GRB 260307A: Fermi GBM Final Localization
  54. GRB 260211A: late-time NOT i-band observations consistent with archival flux
  55. EP260306a: refined analysis of the EP-WXT and EP-FXT observations
  56. EP260302a: SVOM/VT optical observation
  57. EP260306a: Gemini-North redshift z = 4.773
  58. EP260306a: SVOM/VT optical observation
  59. EP260302a: Gemini-South redshift z = 1.535
  60. EP260306a: COLIBRÍ optical observations of the fading and red counterpart
  61. EP260306a: Einstein Probe detection of an X-ray transient
  62. The EP-WXT trigger 01709258759: Las Cumbres discovery of the optical counterpart
  63. EP260302a: Optical afterglow rebrightening
  64. GRB 260228A: further EP-FXT observations and X-ray afterglow confirmation
  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. SVOM/sb26030408: SVOM detection of an X-ray transient likely associated with Beta Persei
  72. GRB 260303A: SVOM/VT optical observations
  73. GRB 260303A: J-band observations with WINTER
  74. EP260302a: Global MASTER-Net observations report
  75. Fermi GRB 260303B: Global MASTER-Net observations report
  76. GRB 260228A: SVOM/ECLAIRs refined analysis
  77. GRB 260225A: SVOM/ECLAIRs refined analysis
  78. GRB 260303B: BALROG localization (Fermi Trigger 794237065 / GRB 260303559)
  79. GRB 260303B: Fermi GBM Final Real-time Localization
  80. EP260302a: analysis of the follow-up EP-FXT observation
  81. EP260302a: LCO observations
  82. EP260302a: BOOTES-7 optical counterpart detection at early times
  83. GRB 260303A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  84. GRB 260303A: SVOM detection of a burst
  85. GRB 260228A: EP-FXT follow-up observation
  86. EP260302a: Einstein Probe detection of an X-ray transient
  87. The EP-WXT trigger 01709258736: Las Cumbres discovery of the optical counterpart
  88. GRB 260302A: Fermi GBM Final Real-time Localization
  89. GRB 260228A: CAHA 2.2m telescope optical upper limit
  90. GRB 260228A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  91. EP260227a: Mephisto optical detection
  92. GRID detection of GRB 260225D
  93. EP-WXT trigger 01709258652: 50cm Telescope multi-band observations
  94. EP260227a: SVOM/VT optical observation
  95. GRB 260228A: SVOM/VT optical upper limits
  96. GRB 260225D: SVOM/GRM observation
  97. EP260227A: 3.6m DOT optical afterglow detection
  98. GRB 260225B: SVOM/GRM observation
  99. GRB 260228A: SVOM detection of a burst
  100. EP260227a: FTW optical and NIR observations

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