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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"

42583 results found.

  1. EP260316a: refined analysis of the EP-WXT and EP-FXT observations
  2. IceCube-260315A: Upper limits from a search for additional neutrino events in IceCube
  3. EP260316a: Xinglong optical upper limit
  4. GRB 260316B: Fermi GBM Final Real-time Localization
  5. EP260316a: optical upper limit with Kinder observations
  6. EP260316a / GRB 260316A : Fermi-GBM Sub-Threshold Detection
  7. GRB 260314A: Glowbug gamma-ray detection
  8. The EP-WXT trigger 00199258890 (EP260316a): a correction to the trigger time and FXT automatic follow-up
  9. IceCube-260315A: COLIBRÍ optical observations
  10. EP260314a: Xinglong optical upper limit
  11. EP260314a: optical upper limit with Kinder observations
  12. IceCube Alert-260315A/AT2026fpm Automatic MASTER optical blue counterpart candidate
  13. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
  14. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS optical observations
  15. GRB 260310A / AT 2026fgk: iTelescope optical observations
  16. EP260314a: COLIBRÍ optical upper limit
  17. GRID detection of GRB 260312B
  18. IceCube-260315A - IceCube observation of a high-energy neutrino candidate track-like event
  19. EP260314a: refined analysis of the EP-WXT and EP-FXT observations
  20. EP260314a: BOOTES-6/DPR optical upper limits at early times
  21. EP260314a: Global MASTER-Net observations report
  22. EP260314a: SVOM/VT optical candidate
  23. Fermi trigger No 795185313: Global MASTER-Net observations report
  24. IceCube Alert 260315A: Global MASTER-Net observations report
  25. EP260314a: Einstein Probe detection of an X-ray transient
  26. The EP-WXT trigger 01709258851: Las Cumbres upper limit
  27. GRB 260314A: GECAM-B observation of a burst
  28. Fermi Gamma-ray Burst Monitor trigger 795185313/260314534 is not a GRB
  29. GRB 260310A / AT2026fgk: SAO RAS optical observations
  30. GRB 260310A/AT2026fgk: radio detection at 15GHz
  31. GRB 260310A / AT2026fgk: TNG NIR detection
  32. GRB 260310A / AT2026fgk: OASDG optical observations
  33. GRB 260310A / AT2026fgk: Multiband optical follow-up with Kinder observations
  34. GRB 260310A / AT 2026fgk: COLIBRÍ continuing optical observations
  35. GRB 260310A / AT2026fgk: further CAHA 1.23m telescope optical observations suggest shallow decay
  36. Fermi GRB 260314A: Global MASTER-Net observations report
  37. Fermi GRB 260313A: Global MASTER-Net observations report
  38. GRB 260314A: Fermi GBM Final Real-time Localization
  39. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  40. GRB 260313A: A Correction to the Fermi GBM Final Localization
  41. GRB 260310A: Einstein Probe Follow-up X-ray Telescope (FXT) Detection
  42. GRB 260310A/AT 2026fgk: J-band observations by the SYSU 80 cm infrared telescope
  43. GRB 260310B: Insight-HXMT/HE detection
  44. GRB 260310A/AT 2026fgk: DDOTI Optical Detection
  45. GRB 260310A: NOT optical polarimetry
  46. GRB 260312B: AstroSat CZTI detection
  47. Swift BAT trigger 1500295: A solar flare
  48. GRB 260313A: Fermi GBM Final Real-time Localization
  49. GRB 260310A/AT 2026fgk: Bok spectroscopic observation
  50. Swift BAT trigger 1500287: A solar flare
  51. GRB 260310A / AT2026fgk: OSIRIS+/GTC spectroscopy confirms redshift z = 0.153
  52. GRB 260308A: Insight-HXMT/HE detection
  53. GRB 260307A: CALET Gamma-Ray Burst Monitor detection
  54. GRB 260310A / AT 2026fgk: Location in the Epeak - Eiso diagram
  55. GRB 260310A / AT 2026fgk: COLIBRÍ optical observations
  56. GRB 260310A / AT2026fgk: CAHA 1.23m telescope optical observations
  57. GRB 260310A / AT2026fgk : MASTER OT rebrightening during 7h observations
  58. GRB260310A / AT2026fgk: P200 Spectroscopy
  59. GRB 260312B: Glowbug gamma-ray detection
  60. GRB 260310A: Fermi GBM Observation
  61. GRB 260310A: potential optical counterpart
  62. Fermi GRB 260312B: Global MASTER-Net observations report
  63. Fermi GRB 260311B: Global MASTER-Net observations report
  64. Swift BAT trigger 1500148: A solar flare
  65. GRB 260312B: BALROG localization (Fermi Trigger 795001611 / GRB 260312407)
  66. GRB 260312B: Fermi GBM Final Real-time Localization
  67. The EP-WXT trigger 01709258843 is not a real source
  68. GRB 260310B: GECAM-B observation of a burst
  69. Retraction of GCN 43965: GRB is actually solar flare
  70. GRB 260312A: Swift detection of a burst
  71. GRB 260311B: Fermi GBM Final Real-time Localization
  72. GRB 260131A/B: radio detection with the VLA
  73. EP260302a: MeerKAT radio counterpart
  74. GRB260307A: GECAM-B observation of a burst
  75. GRB 260308A: SVOM/GRM observation of a short GRB
  76. EP260306a: Mondy optical upper limit
  77. GRB 260310A: AstroSat CZTI detection of a long burst
  78. GRB 260311A: Fermi GBM Final Real-time Localization
  79. Fermi GRB 260310B: Global MASTER-Net observations report
  80. GRB 260310B: Fermi GBM Final Real-time Localization
  81. Fermi GRB 260310A: Global MASTER-Net observations report
  82. GRB 260307B: SVOM/ECLAIRs refined analysis
  83. GRB 260208A: radio detection with the VLA
  84. GRB 260310A: Fermi GBM Final Real-time Localization
  85. GRB 260307A: Glowbug gamma-ray detection
  86. GRB 260308A: Fermi GBM Final Real-time Localization
  87. Fermi GBM Sub-Threshold Detection of GRB 260307B
  88. GRB 260307B: Mephisto optical upper limits
  89. GRB 260307B: possible NOT optical counterpart
  90. GRB 260307B: SVOM/VT upper limit with X band data analysis
  91. Fermi GRB 260307A: Global MASTER-Net observations report
  92. GRB260307B: GROWTH-India Telescope optical upper limit
  93. GRB 260307B: SVOM/VT optical candidate
  94. GRB 260307B: SVOM/C-GFT upper limit
  95. GRB 260307B: SVOM detection of a burst
  96. GRB 260307A: Fermi GBM Final Localization
  97. GRB 260211A: late-time NOT i-band observations consistent with archival flux
  98. EP260306a: refined analysis of the EP-WXT and EP-FXT observations
  99. GRB 260207A: TESS Detection and Possible VLA Counterpart
  100. EP260302a: SVOM/VT optical observation

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