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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"

40636 results found.

  1. EP260314a: Einstein Probe detection of an X-ray transient
  2. The EP-WXT trigger 01709258851: Las Cumbres upper limit
  3. GRB 260310A / AT2026fgk: SAO RAS optical observations
  4. GRB 260310A/AT2026fgk: radio detection at 15GHz
  5. GRB 260310A / AT2026fgk: TNG NIR detection
  6. GRB 260310A / AT2026fgk: OASDG optical observations
  7. GRB 260310A / AT2026fgk: Multiband optical follow-up with Kinder observations
  8. GRB 260310A / AT 2026fgk: COLIBRÍ continuing optical observations
  9. GRB 260310A / AT2026fgk: further CAHA 1.23m telescope optical observations suggest shallow decay
  10. Fermi GRB 260314A: Global MASTER-Net observations report
  11. Fermi GRB 260313A: Global MASTER-Net observations report
  12. GRB 260314A: Fermi GBM Final Real-time Localization
  13. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  14. GRB 260313A: A Correction to the Fermi GBM Final Localization
  15. GRB 260310A: Einstein Probe Follow-up X-ray Telescope (FXT) Detection
  16. GRB 260310A/AT 2026fgk: J-band observations by the SYSU 80 cm infrared telescope
  17. GRB 260310B: Insight-HXMT/HE detection
  18. GRB 260310A/AT 2026fgk: DDOTI Optical Detection
  19. GRB 260310A: NOT optical polarimetry
  20. GRB 260312B: AstroSat CZTI detection
  21. GRB 260313A: Fermi GBM Final Real-time Localization
  22. GRB 260310A/AT 2026fgk: Bok spectroscopic observation
  23. GRB 260310A / AT2026fgk: OSIRIS+/GTC spectroscopy confirms redshift z = 0.153
  24. GRB 260308A: Insight-HXMT/HE detection
  25. GRB 260310A / AT 2026fgk: Location in the Epeak - Eiso diagram
  26. GRB 260310A / AT 2026fgk: COLIBRÍ optical observations
  27. GRB 260310A / AT2026fgk: CAHA 1.23m telescope optical observations
  28. GRB 260310A / AT2026fgk : MASTER OT rebrightening during 7h observations
  29. GRB260310A / AT2026fgk: P200 Spectroscopy
  30. GRB 260312B: Glowbug gamma-ray detection
  31. GRB 260310A: Fermi GBM Observation
  32. GRB 260310A: potential optical counterpart
  33. Fermi GRB 260312B: Global MASTER-Net observations report
  34. Fermi GRB 260311B: Global MASTER-Net observations report
  35. GRB 260312B: BALROG localization (Fermi Trigger 795001611 / GRB 260312407)
  36. GRB 260312B: Fermi GBM Final Real-time Localization
  37. GRB 260310B: GECAM-B observation of a burst
  38. Retraction of GCN 43965: GRB is actually solar flare
  39. GRB 260312A: Swift detection of a burst
  40. GRB 260311B: Fermi GBM Final Real-time Localization
  41. GRB 260131A/B: radio detection with the VLA
  42. EP260302a: MeerKAT radio counterpart
  43. GRB260307A: GECAM-B observation of a burst
  44. GRB 260308A: SVOM/GRM observation of a short GRB
  45. GRB 260310A: AstroSat CZTI detection of a long burst
  46. GRB 260311A: Fermi GBM Final Real-time Localization
  47. Fermi GRB 260310B: Global MASTER-Net observations report
  48. GRB 260310B: Fermi GBM Final Real-time Localization
  49. Fermi GRB 260310A: Global MASTER-Net observations report
  50. GRB 260307B: SVOM/ECLAIRs refined analysis
  51. GRB 260208A: radio detection with the VLA
  52. GRB 260310A: Fermi GBM Final Real-time Localization
  53. GRB 260307A: Glowbug gamma-ray detection
  54. GRB 260308A: Fermi GBM Final Real-time Localization
  55. Fermi GBM Sub-Threshold Detection of GRB 260307B
  56. GRB 260307B: Mephisto optical upper limits
  57. GRB 260307B: possible NOT optical counterpart
  58. GRB 260307B: SVOM/VT upper limit with X band data analysis
  59. Fermi GRB 260307A: Global MASTER-Net observations report
  60. GRB260307B: GROWTH-India Telescope optical upper limit
  61. GRB 260307B: SVOM/VT optical candidate
  62. GRB 260307B: SVOM/C-GFT upper limit
  63. GRB 260307B: SVOM detection of a burst
  64. GRB 260307A: Fermi GBM Final Localization
  65. GRB 260211A: late-time NOT i-band observations consistent with archival flux
  66. EP260306a: refined analysis of the EP-WXT and EP-FXT observations
  67. GRB 260207A: TESS Detection and Possible VLA Counterpart
  68. EP260302a: SVOM/VT optical observation
  69. EP260306a: Gemini-North redshift z = 4.773
  70. EP260306a: SVOM/VT optical observation
  71. EP260302a: Gemini-South redshift z = 1.535
  72. EP260306a: COLIBRÍ optical observations of the fading and red counterpart
  73. EP260306a: Einstein Probe detection of an X-ray transient
  74. The EP-WXT trigger 01709258759: Las Cumbres discovery of the optical counterpart
  75. EP260302a: Optical afterglow rebrightening
  76. GRB 260228A: further EP-FXT observations and X-ray afterglow confirmation
  77. GRB 260303A: 1.3m DFOT optical upper limit
  78. EP260214b: ATCA 6 GHz observations
  79. GRB 260211A: SVOM/VT optical rebrightening at 20 days after the burst, SN candidate
  80. GRB 260303A: SVOM/ECLAIRs refined analysis
  81. Fermi GRB 260305A: Global MASTER-Net observations report
  82. GRB 260305A: Fermi GBM Final Real-time Localization
  83. GRB 260303B: AstroSat CZTI detection
  84. GRB 260304A: AstroSat CZTI detection of a long burst
  85. SVOM/sb26030408: SVOM detection of an X-ray transient likely associated with Beta Persei
  86. GRB 260303A: SVOM/VT optical observations
  87. GRB 260303A: J-band observations with WINTER
  88. GRB 260303B: NuSTAR detection of prompt emission
  89. EP260302a: Global MASTER-Net observations report
  90. Fermi GRB 260303B: Global MASTER-Net observations report
  91. IceCube-260217A: No Candidate Transients from the Zwicky Transient Facility
  92. GRB 260228A: SVOM/ECLAIRs refined analysis
  93. GRB 260225A: SVOM/ECLAIRs refined analysis
  94. GRB 260303B: BALROG localization (Fermi Trigger 794237065 / GRB 260303559)
  95. GRB 260303B: Fermi GBM Final Real-time Localization
  96. EP260302a: analysis of the follow-up EP-FXT observation
  97. EP260227a: Gemini-South optical observations
  98. EP260302a: LCO observations
  99. EP260302a: BOOTES-7 optical counterpart detection at early times
  100. GRB 260303A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate

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