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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"

32489 results found.

  1. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  2. Fermi GRB 260318A: Global MASTER-Net observations report
  3. IceCube-260315A: No Candidate Transients from the Zwicky Transient Facility
  4. Fermi Gamma-ray Burst Monitor trigger 795096033/260312500 (GRB 260313A) is unlikely to be a GRB
  5. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  6. GRB 260310A / AT 2026fgk: radio detection with the VLA
  7. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  8. GRB 260310A / AT2026fgk: LCO optical observations
  9. IceCube-260315A/AT2026fpm: EP-FXT follow-up observation
  10. GRB 260316B: GECAM-B observation
  11. GRB 260316B: SVOM/GRM observation
  12. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  13. EP260316a: COLIBRÍ faint optical counterpart candidate
  14. Fermi-LAT Gamma-ray Observations of IceCube-260315A
  15. GRB 260316B: AstroSat CZTI detection
  16. EP260316a: refined analysis of the EP-WXT and EP-FXT observations
  17. IceCube-260315A: Upper limits from a search for additional neutrino events in IceCube
  18. EP260316a: Xinglong optical upper limit
  19. EP260316a: optical upper limit with Kinder observations
  20. EP260316a / GRB 260316A : Fermi-GBM Sub-Threshold Detection
  21. GRB 260314A: Glowbug gamma-ray detection
  22. IceCube-260315A: COLIBRÍ optical observations
  23. EP260314a: Xinglong optical upper limit
  24. EP260314a: optical upper limit with Kinder observations
  25. IceCube Alert-260315A/AT2026fpm Automatic MASTER optical blue counterpart candidate
  26. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
  27. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS optical observations
  28. GRB 260310A / AT 2026fgk: iTelescope optical observations
  29. EP260314a: COLIBRÍ optical upper limit
  30. GRID detection of GRB 260312B
  31. IceCube-260315A - IceCube observation of a high-energy neutrino candidate track-like event
  32. EP260314a: refined analysis of the EP-WXT and EP-FXT observations
  33. EP260314a: Global MASTER-Net observations report
  34. EP260314a: SVOM/VT optical candidate
  35. GRB 260314A: GECAM-B observation of a burst
  36. GRB 260310A / AT2026fgk: SAO RAS optical observations
  37. GRB 260310A/AT2026fgk: radio detection at 15GHz
  38. GRB 260310A / AT2026fgk: TNG NIR detection
  39. GRB 260310A / AT2026fgk: OASDG optical observations
  40. GRB 260310A / AT2026fgk: Multiband optical follow-up with Kinder observations
  41. GRB 260310A / AT 2026fgk: COLIBRÍ continuing optical observations
  42. GRB 260310A / AT2026fgk: further CAHA 1.23m telescope optical observations suggest shallow decay
  43. Fermi GRB 260314A: Global MASTER-Net observations report
  44. Fermi GRB 260313A: Global MASTER-Net observations report
  45. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  46. GRB 260313A: A Correction to the Fermi GBM Final Localization
  47. GRB 260310A: Einstein Probe Follow-up X-ray Telescope (FXT) Detection
  48. GRB 260310A/AT 2026fgk: J-band observations by the SYSU 80 cm infrared telescope
  49. GRB 260310B: Insight-HXMT/HE detection
  50. GRB 260310A/AT 2026fgk: DDOTI Optical Detection
  51. GRB 260310A: NOT optical polarimetry
  52. GRB 260312B: AstroSat CZTI detection
  53. GRB 260310A/AT 2026fgk: Bok spectroscopic observation
  54. GRB 260310A / AT2026fgk: OSIRIS+/GTC spectroscopy confirms redshift z = 0.153
  55. GRB 260308A: Insight-HXMT/HE detection
  56. GRB 260307A: CALET Gamma-Ray Burst Monitor detection
  57. GRB 260310A / AT 2026fgk: Location in the Epeak - Eiso diagram
  58. GRB 260310A / AT 2026fgk: COLIBRÍ optical observations
  59. GRB 260310A / AT2026fgk: CAHA 1.23m telescope optical observations
  60. GRB 260310A / AT2026fgk : MASTER OT rebrightening during 7h observations
  61. GRB260310A / AT2026fgk: P200 Spectroscopy
  62. GRB 260312B: Glowbug gamma-ray detection
  63. GRB 260310A: Fermi GBM Observation
  64. GRB 260310A: potential optical counterpart
  65. Fermi GRB 260312B: Global MASTER-Net observations report
  66. Fermi GRB 260311B: Global MASTER-Net observations report
  67. GRB 260310B: GECAM-B observation of a burst
  68. Retraction of GCN 43965: GRB is actually solar flare
  69. GRB 260131A/B: radio detection with the VLA
  70. EP260302a: MeerKAT radio counterpart
  71. GRB260307A: GECAM-B observation of a burst
  72. GRB 260308A: SVOM/GRM observation of a short GRB
  73. EP260306a: Mondy optical upper limit
  74. GRB 260310A: AstroSat CZTI detection of a long burst
  75. Fermi GRB 260310B: Global MASTER-Net observations report
  76. Fermi GRB 260310A: Global MASTER-Net observations report
  77. GRB 260307B: SVOM/ECLAIRs refined analysis
  78. GRB 260208A: radio detection with the VLA
  79. GRB 260307A: Glowbug gamma-ray detection
  80. Fermi GBM Sub-Threshold Detection of GRB 260307B
  81. GRB 260307B: Mephisto optical upper limits
  82. GRB 260307B: possible NOT optical counterpart
  83. GRB 260307B: SVOM/VT upper limit with X band data analysis
  84. Fermi GRB 260307A: Global MASTER-Net observations report
  85. GRB260307B: GROWTH-India Telescope optical upper limit
  86. GRB 260307B: SVOM/VT optical candidate
  87. GRB 260307B: SVOM/C-GFT upper limit
  88. GRB 260211A: late-time NOT i-band observations consistent with archival flux
  89. EP260306a: refined analysis of the EP-WXT and EP-FXT observations
  90. GRB 260207A: TESS Detection and Possible VLA Counterpart
  91. EP260302a: SVOM/VT optical observation
  92. EP260306a: Gemini-North redshift z = 4.773
  93. EP260306a: SVOM/VT optical observation
  94. EP260302a: Gemini-South redshift z = 1.535
  95. EP260306a: COLIBRÍ optical observations of the fading and red counterpart
  96. EP260306a: Einstein Probe detection of an X-ray transient
  97. EP260302a: Optical afterglow rebrightening
  98. GRB 260228A: further EP-FXT observations and X-ray afterglow confirmation
  99. GRB 260303A: 1.3m DFOT optical upper limit (duplicate submission)
  100. GRB 260303A: 1.3m DFOT optical upper limit

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