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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"

12090 results found.

  1. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  2. EP260327a: Xinglong optical upper limit
  3. EP260329b: GOTO detection of optical counterpart
  4. Konus-Wind detection of GRB 260320A
  5. Konus-Wind detection of GRB 260316B
  6. GRB 260330B: SVOM detection of a burst
  7. EP260324a / AT2026hir: g- and r-band optical follow-up with the PKU 60cm Telescope
  8. EP260329b: refined analysis of the EP-WXT and EP-FXT observations
  9. Fermi trigger No 796485221: Global MASTER-Net observations report
  10. EP260329b: Optical follow-up with Kinder observations
  11. EP260329a: Optical upper limit with Kinder observations
  12. EP260329b: Einstein Probe detection of an X-ray transient
  13. EP-WXT trigger 01709259209: TRT optical counterpart detection
  14. EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  15. GRB 260327A: AstroSat CZTI detection of a long burst
  16. EP260327a: Global MASTER-Net observations report
  17. EP260327a: Einstein Probe detection of an X-ray transient
  18. EP260324a: ZTF discovery of the optical counterpart ZTF26aapviim/AT2026hir
  19. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  20. GRID detection of GRB 260320A
  21. GRB260310A: Palomar 60-inch photometry of an extremely bright late-time afterglow with a temporal break at 8 days
  22. GRB 260320A: Glowbug gamma-ray detection
  23. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  24. EP260214b: ATCA 6 GHz detection
  25. EP260321a: further Kinder optical observations
  26. EP260321a: refined analysis of the EP-WXT and EP-FXT observations, implying a possible supernova shock breakout candidate
  27. EP260321a: Kinder observations detect a blue variable star and set limits on a source from the z =0.034 galaxy within the error circle
  28. EP260321a: Einstein Probe detection of an X-ray transient
  29. GRB 260310A / AT 2026fgk: KAIT optical observations
  30. GRB 260320A: NuSTAR detection of prompt emission
  31. GRB 260310A / AT2026fgk: NuSTAR follow-up detection
  32. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  33. NOEMA Detection of GRB 260310A / AT 2026fgk
  34. EP-WXT trigger 01709258989: confirmation of a stellar flare by BOOTES-7
  35. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  36. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  37. GRB 260317A: Fermi GBM Final Localization
  38. Fermi-LAT Gamma-ray Observations of IceCube-260315A
  39. GRB 260316B: AstroSat CZTI detection
  40. EP260316a: optical upper limit with Kinder observations
  41. EP260316a / GRB 260316A : Fermi-GBM Sub-Threshold Detection
  42. The EP-WXT trigger 00199258890 (EP260316a): a correction to the trigger time and FXT automatic follow-up
  43. EP260314a: optical upper limit with Kinder observations
  44. EP260314a: refined analysis of the EP-WXT and EP-FXT observations
  45. EP260314a: Global MASTER-Net observations report
  46. Fermi trigger No 795185313: Global MASTER-Net observations report
  47. EP260314a: Einstein Probe detection of an X-ray transient
  48. GRB 260310A/AT2026fgk: radio detection at 15GHz
  49. GRB 260310A / AT2026fgk: Multiband optical follow-up with Kinder observations
  50. Fermi GRB 260314A: Global MASTER-Net observations report
  51. Fermi GRB 260313A: Global MASTER-Net observations report
  52. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  53. GRB 260310A: Einstein Probe Follow-up X-ray Telescope (FXT) Detection
  54. GRB 260310A/AT 2026fgk: DDOTI Optical Detection
  55. GRB 260312B: AstroSat CZTI detection
  56. Fermi GRB 260311B: Global MASTER-Net observations report
  57. GRB 260310A: AstroSat CZTI detection of a long burst
  58. Fermi GRB 260310B: Global MASTER-Net observations report
  59. Fermi GRB 260310A: Global MASTER-Net observations report
  60. GRB 260308A: Fermi GBM Final Real-time Localization
  61. Fermi GRB 260307A: Global MASTER-Net observations report
  62. EP260306a: refined analysis of the EP-WXT and EP-FXT observations
  63. EP260306a: Einstein Probe detection of an X-ray transient
  64. The EP-WXT trigger 01709258759: Las Cumbres discovery of the optical counterpart
  65. GRB 260211A: SVOM/VT optical rebrightening at 20 days after the burst, SN candidate
  66. Fermi GRB 260305A: Global MASTER-Net observations report
  67. GRB 260303B: AstroSat CZTI detection
  68. GRB 260304A: AstroSat CZTI detection of a long burst
  69. SVOM/sb26030408: SVOM detection of an X-ray transient likely associated with Beta Persei
  70. GRB 260303B: NuSTAR detection of prompt emission
  71. GRB 260228A: SVOM/ECLAIRs refined analysis
  72. GRB 260225A: SVOM/ECLAIRs refined analysis
  73. GRB 260303B: BALROG localization (Fermi Trigger 794237065 / GRB 260303559)
  74. GRB 260303B: Fermi GBM Final Real-time Localization
  75. EP260302a: analysis of the follow-up EP-FXT observation
  76. EP260302a: LCO observations
  77. EP260302a: BOOTES-7 optical counterpart detection at early times
  78. GRB 260303A: SVOM detection of a burst
  79. EP260302a: Einstein Probe detection of an X-ray transient
  80. EP260227a: Mondy optical observations
  81. EP260227a: Mephisto optical detection
  82. EP260227a: SVOM/VT optical observation
  83. GRB 260228A: SVOM detection of a burst
  84. EP260227a: NOT optical observations
  85. EP260227a: Global MASTER-Net observations report
  86. EP260227a: Einstein Probe detection of an X-ray transient and refined analysis
  87. Konus-Wind detection of GRB 260226A
  88. GRB 260223A: 7DT detection and Medium-band SED of Afterglow
  89. GRB 260226A: COLIBRÍ optical upper limits
  90. GRB 260226A: NuSTAR detection of bright prompt emission
  91. GRB 260226A: Fermi-LAT refined analysis
  92. The EP-WXT trigger 01709258652 is likely a flaring star
  93. LAT GRB260226.44: Global MASTER-Net observations report
  94. GRB 260226A: AstroSat CZTI detection of bright long burst
  95. GRB 260226A: Fermi-LAT detection of a bright burst
  96. EP260223a: Xinglong optical upper limit
  97. sb26021801: SVOM/C-GFT upper limit
  98. EP260223a: Einstein Probe detection of an X-ray transient
  99. EP260221a: Optical upper limit with Kinder observations
  100. Fermi GRB 260223A: Global MASTER-Net observations report

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