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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"

27015 results found.

  1. GRID detection of GRB 260312B
  2. EP260314a: refined analysis of the EP-WXT and EP-FXT observations
  3. EP260314a: BOOTES-6/DPR optical upper limits at early times
  4. EP260314a: Global MASTER-Net observations report
  5. EP260314a: SVOM/VT optical candidate
  6. Fermi trigger No 795185313: Global MASTER-Net observations report
  7. IceCube Alert 260315A: Global MASTER-Net observations report
  8. EP260314a: Einstein Probe detection of an X-ray transient
  9. The EP-WXT trigger 01709258851: Las Cumbres upper limit
  10. GRB 260314A: GECAM-B observation of a burst
  11. Fermi Gamma-ray Burst Monitor trigger 795185313/260314534 is not a GRB
  12. GRB 260310A / AT2026fgk: SAO RAS optical observations
  13. GRB 260310A / AT2026fgk: TNG NIR detection
  14. GRB 260310A / AT2026fgk: OASDG optical observations
  15. GRB 260310A / AT 2026fgk: COLIBRÍ continuing optical observations
  16. GRB 260310A / AT2026fgk: further CAHA 1.23m telescope optical observations suggest shallow decay
  17. Fermi GRB 260314A: Global MASTER-Net observations report
  18. Fermi GRB 260313A: Global MASTER-Net observations report
  19. GRB 260314A: Fermi GBM Final Real-time Localization
  20. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  21. GRB 260313A: A Correction to the Fermi GBM Final Localization
  22. GRB 260310A/AT 2026fgk: J-band observations by the SYSU 80 cm infrared telescope
  23. GRB 260310A/AT 2026fgk: DDOTI Optical Detection
  24. GRB 260310A: NOT optical polarimetry
  25. Swift BAT trigger 1500295: A solar flare
  26. GRB 260313A: Fermi GBM Final Real-time Localization
  27. Swift BAT trigger 1500287: A solar flare
  28. GRB 260310A / AT2026fgk: OSIRIS+/GTC spectroscopy confirms redshift z = 0.153
  29. GRB 260307A: CALET Gamma-Ray Burst Monitor detection
  30. GRB 260310A / AT 2026fgk: COLIBRÍ optical observations
  31. GRB 260310A / AT2026fgk: CAHA 1.23m telescope optical observations
  32. GRB260310A / AT2026fgk: P200 Spectroscopy
  33. GRB 260310A: Fermi GBM Observation
  34. Fermi GRB 260312B: Global MASTER-Net observations report
  35. Fermi GRB 260311B: Global MASTER-Net observations report
  36. Swift BAT trigger 1500148: A solar flare
  37. GRB 260312B: BALROG localization (Fermi Trigger 795001611 / GRB 260312407)
  38. GRB 260312B: Fermi GBM Final Real-time Localization
  39. The EP-WXT trigger 01709258843 is not a real source
  40. GRB 260310B: GECAM-B observation of a burst
  41. GRB 260312A: Swift detection of a burst
  42. GRB 260311B: Fermi GBM Final Real-time Localization
  43. GRB260307A: GECAM-B observation of a burst
  44. GRB 260308A: SVOM/GRM observation of a short GRB
  45. GRB 260311A: Fermi GBM Final Real-time Localization
  46. Fermi GRB 260310B: Global MASTER-Net observations report
  47. GRB 260310B: Fermi GBM Final Real-time Localization
  48. Fermi GRB 260310A: Global MASTER-Net observations report
  49. GRB 260307B: SVOM/ECLAIRs refined analysis
  50. GRB 260310A: Fermi GBM Final Real-time Localization
  51. GRB 260307A: Glowbug gamma-ray detection
  52. GRB 260308A: Fermi GBM Final Real-time Localization
  53. Fermi GBM Sub-Threshold Detection of GRB 260307B
  54. GRB 260307B: Mephisto optical upper limits
  55. GRB 260307B: possible NOT optical counterpart
  56. GRB 260307B: SVOM/VT upper limit with X band data analysis
  57. Fermi GRB 260307A: Global MASTER-Net observations report
  58. GRB260307B: GROWTH-India Telescope optical upper limit
  59. GRB 260307B: SVOM/VT optical candidate
  60. GRB 260307B: SVOM/C-GFT upper limit
  61. GRB 260307B: SVOM detection of a burst
  62. GRB 260307A: Fermi GBM Final Localization
  63. GRB 260211A: late-time NOT i-band observations consistent with archival flux
  64. EP260306a: refined analysis of the EP-WXT and EP-FXT observations
  65. EP260302a: SVOM/VT optical observation
  66. EP260306a: Gemini-North redshift z = 4.773
  67. EP260306a: SVOM/VT optical observation
  68. EP260302a: Gemini-South redshift z = 1.535
  69. EP260306a: COLIBRÍ optical observations of the fading and red counterpart
  70. EP260306a: Einstein Probe detection of an X-ray transient
  71. The EP-WXT trigger 01709258759: Las Cumbres discovery of the optical counterpart
  72. EP260302a: Optical afterglow rebrightening
  73. GRB 260228A: further EP-FXT observations and X-ray afterglow confirmation
  74. GRB 260303A: 1.3m DFOT optical upper limit
  75. EP260214b: ATCA 6 GHz observations
  76. GRB 260211A: SVOM/VT optical rebrightening at 20 days after the burst, SN candidate
  77. GRB 260303A: SVOM/ECLAIRs refined analysis
  78. Fermi GRB 260305A: Global MASTER-Net observations report
  79. GRB 260305A: Fermi GBM Final Real-time Localization
  80. SVOM/sb26030408: SVOM detection of an X-ray transient likely associated with Beta Persei
  81. GRB 260303A: SVOM/VT optical observations
  82. GRB 260303A: J-band observations with WINTER
  83. EP260302a: Global MASTER-Net observations report
  84. Fermi GRB 260303B: Global MASTER-Net observations report
  85. GRB 260228A: SVOM/ECLAIRs refined analysis
  86. GRB 260225A: SVOM/ECLAIRs refined analysis
  87. GRB 260303B: BALROG localization (Fermi Trigger 794237065 / GRB 260303559)
  88. GRB 260303B: Fermi GBM Final Real-time Localization
  89. EP260302a: analysis of the follow-up EP-FXT observation
  90. EP260302a: LCO observations
  91. EP260302a: BOOTES-7 optical counterpart detection at early times
  92. GRB 260303A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  93. GRB 260303A: SVOM detection of a burst
  94. GRB 260228A: EP-FXT follow-up observation
  95. EP260302a: Einstein Probe detection of an X-ray transient
  96. The EP-WXT trigger 01709258736: Las Cumbres discovery of the optical counterpart
  97. GRB 260302A: Fermi GBM Final Real-time Localization
  98. GRB 260228A: CAHA 2.2m telescope optical upper limit
  99. GRB 260228A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  100. EP260227a: Mephisto optical detection

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