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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"

31667 results found.

  1. EP260314a: Xinglong optical upper limit
  2. EP260314a: optical upper limit with Kinder observations
  3. IceCube Alert-260315A/AT2026fpm Automatic MASTER optical blue counterpart candidate
  4. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
  5. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS optical observations
  6. GRB 260310A / AT 2026fgk: iTelescope optical observations
  7. EP260314a: COLIBRÍ optical upper limit
  8. GRID detection of GRB 260312B
  9. IceCube-260315A - IceCube observation of a high-energy neutrino candidate track-like event
  10. EP260314a: refined analysis of the EP-WXT and EP-FXT observations
  11. EP260314a: Global MASTER-Net observations report
  12. EP260314a: SVOM/VT optical candidate
  13. GRB 260314A: GECAM-B observation of a burst
  14. GRB 260310A / AT2026fgk: SAO RAS optical observations
  15. GRB 260310A/AT2026fgk: radio detection at 15GHz
  16. GRB 260310A / AT2026fgk: TNG NIR detection
  17. GRB 260310A / AT2026fgk: OASDG optical observations
  18. GRB 260310A / AT2026fgk: Multiband optical follow-up with Kinder observations
  19. GRB 260310A / AT 2026fgk: COLIBRÍ continuing optical observations
  20. GRB 260310A / AT2026fgk: further CAHA 1.23m telescope optical observations suggest shallow decay
  21. Fermi GRB 260314A: Global MASTER-Net observations report
  22. Fermi GRB 260313A: Global MASTER-Net observations report
  23. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  24. GRB 260313A: A Correction to the Fermi GBM Final Localization
  25. GRB 260310A: Einstein Probe Follow-up X-ray Telescope (FXT) Detection
  26. GRB 260310A/AT 2026fgk: J-band observations by the SYSU 80 cm infrared telescope
  27. GRB 260310B: Insight-HXMT/HE detection
  28. GRB 260310A/AT 2026fgk: DDOTI Optical Detection
  29. GRB 260310A: NOT optical polarimetry
  30. GRB 260312B: AstroSat CZTI detection
  31. GRB 260310A/AT 2026fgk: Bok spectroscopic observation
  32. GRB 260310A / AT2026fgk: OSIRIS+/GTC spectroscopy confirms redshift z = 0.153
  33. GRB 260308A: Insight-HXMT/HE detection
  34. GRB 260307A: CALET Gamma-Ray Burst Monitor detection
  35. GRB 260310A / AT 2026fgk: Location in the Epeak - Eiso diagram
  36. GRB 260310A / AT 2026fgk: COLIBRÍ optical observations
  37. GRB 260310A / AT2026fgk: CAHA 1.23m telescope optical observations
  38. GRB 260310A / AT2026fgk : MASTER OT rebrightening during 7h observations
  39. GRB260310A / AT2026fgk: P200 Spectroscopy
  40. GRB 260312B: Glowbug gamma-ray detection
  41. GRB 260310A: Fermi GBM Observation
  42. GRB 260310A: potential optical counterpart
  43. Fermi GRB 260312B: Global MASTER-Net observations report
  44. Fermi GRB 260311B: Global MASTER-Net observations report
  45. GRB 260310B: GECAM-B observation of a burst
  46. Retraction of GCN 43965: GRB is actually solar flare
  47. GRB 260131A/B: radio detection with the VLA
  48. EP260302a: MeerKAT radio counterpart
  49. GRB260307A: GECAM-B observation of a burst
  50. GRB 260308A: SVOM/GRM observation of a short GRB
  51. EP260306a: Mondy optical upper limit
  52. GRB 260310A: AstroSat CZTI detection of a long burst
  53. Fermi GRB 260310B: Global MASTER-Net observations report
  54. Fermi GRB 260310A: Global MASTER-Net observations report
  55. GRB 260307B: SVOM/ECLAIRs refined analysis
  56. GRB 260208A: radio detection with the VLA
  57. GRB 260307A: Glowbug gamma-ray detection
  58. Fermi GBM Sub-Threshold Detection of GRB 260307B
  59. GRB 260307B: Mephisto optical upper limits
  60. GRB 260307B: possible NOT optical counterpart
  61. GRB 260307B: SVOM/VT upper limit with X band data analysis
  62. Fermi GRB 260307A: Global MASTER-Net observations report
  63. GRB260307B: GROWTH-India Telescope optical upper limit
  64. GRB 260307B: SVOM/VT optical candidate
  65. GRB 260307B: SVOM/C-GFT upper limit
  66. GRB 260211A: late-time NOT i-band observations consistent with archival flux
  67. EP260306a: refined analysis of the EP-WXT and EP-FXT observations
  68. GRB 260207A: TESS Detection and Possible VLA Counterpart
  69. EP260302a: SVOM/VT optical observation
  70. EP260306a: Gemini-North redshift z = 4.773
  71. EP260306a: SVOM/VT optical observation
  72. EP260302a: Gemini-South redshift z = 1.535
  73. EP260306a: COLIBRÍ optical observations of the fading and red counterpart
  74. EP260306a: Einstein Probe detection of an X-ray transient
  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 (duplicate submission)
  78. GRB 260303A: 1.3m DFOT optical upper limit
  79. EP260214b: ATCA 6 GHz observations
  80. GRB 260211A: SVOM/VT optical rebrightening at 20 days after the burst, SN candidate
  81. GRB 260303A: SVOM/ECLAIRs refined analysis
  82. Fermi GRB 260305A: Global MASTER-Net observations report
  83. GRB 260303B: AstroSat CZTI detection
  84. GRB 260303A: SVOM/VT optical observations
  85. GRB 260303A: J-band observations with WINTER
  86. GRB 260303B: NuSTAR detection of prompt emission
  87. EP260302a: Global MASTER-Net observations report
  88. Fermi GRB 260303B: Global MASTER-Net observations report
  89. IceCube-260217A: No Candidate Transients from the Zwicky Transient Facility
  90. GRB 260228A: SVOM/ECLAIRs refined analysis
  91. GRB 260225A: SVOM/ECLAIRs refined analysis
  92. EP260302a: analysis of the follow-up EP-FXT observation
  93. EP260227a: Gemini-South optical observations
  94. EP260302a: LCO observations
  95. EP260302a: BOOTES-7 optical counterpart detection at early times
  96. GRB 260303A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  97. GRB 260228A: EP-FXT follow-up observation
  98. GRB 251130B: TERI Gamma-ray detection
  99. GRB 260208A: TERI Gamma-ray detection
  100. EP260227a: Mondy optical observations

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