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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"

44473 results found.

  1. GRB 260403A: Fermi GBM Final Real-time Localization
  2. EP260324A / AT 2026hir: Spectroscopic Observations with the Next Generation Palomar Spectrograph
  3. GRB 260402B: Fermi GBM Final Real-time Localization
  4. GRB 260402A: WINTER J-band upper limit
  5. GRB260402A: GROWTH-India Telescope optical upper limit
  6. GRB 260402A / EP260402a: SVOM/VT optical upper limits
  7. EP260402a/GRB 260402A: SVOM/C-GFT upper limit
  8. GRB 260401A: SVOM/GRM observation
  9. GRB 260401A: GECAM-B observation
  10. EP260402a/GRB 260402A: Einstein Probe detection of an X-ray transient
  11. GRB 260402A: Kilonova-Catcher optical upper limit
  12. GRB 260402A: MASTER optical observations
  13. GRB 260402A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  14. GRB 260402A: SVOM/MXT candidate X-ray afterglow
  15. GRB 260402A: SVOM detection of a burst
  16. Fermi GRB 260401A: Global MASTER-Net observations report
  17. GRB 260401A: Fermi GBM Observation
  18. GRB 260401A: NuSTAR detection of prompt emission
  19. GRB 260401A: CALET Gamma-Ray Burst Monitor detection
  20. GRB 260401A: MAXI/GSC detection
  21. GRB 260401A: BALROG localization (Fermi Trigger 796733611 / GRB 260401454)
  22. GRB 260401A: Fermi GBM Final Real-time Localization
  23. EP260329b: Mondy and Assy-Turgen optical upper limits
  24. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  25. EP260321a :Xinglong optical observations
  26. EP260327a: Xinglong optical upper limit
  27. EP260329b: GOTO detection of optical counterpart
  28. GRB 260330B: SVOM/VT optical upper limits
  29. Konus-Wind detection of GRB 260320A
  30. Konus-Wind detection of GRB 260316B (duplicate submission)
  31. Konus-Wind detection of GRB 260316B
  32. GRB 260321A: SVOM/ECLAIRs refined analysis
  33. EP260329b: J-band upper limits with WINTER
  34. EP260329a: J-band upper limit with WINTER
  35. GRB 260330A: Glowbug gamma-ray detection
  36. GRB 260310A: VLA Multi-frequency Radio Observations
  37. Fermi GBM Sub-Threshold Detection of GRB 260330B
  38. GRB 260330B: LCO optical upper limits
  39. GRB 260330B: SVOM detection of a burst
  40. EP260324a / AT2026hir: g- and r-band optical follow-up with the PKU 60cm Telescope
  41. EP260329b: refined analysis of the EP-WXT and EP-FXT observations
  42. EP260329a: COLIBRÍ optical upper limit
  43. EP260329a: EP-FXT follow up observation
  44. EP260329a: NOT optical counterpart candidate
  45. GRB 260330A: Fermi GBM Final Real-time Localization
  46. EP260329b: Global MASTER-Net observations report
  47. Fermi trigger No 796485221: Global MASTER-Net observations report
  48. GRB 260327A: Insight-HXMT/HE detection
  49. EP260329b: Optical follow-up with Kinder observations
  50. EP 260329b: COLIBRÍ optical observations
  51. EP260329a: Optical upper limit with Kinder observations
  52. EP260329b: LCO optical observations of the counterpart
  53. GRB 260326A: Insight-HXMT/HE detection
  54. EP260329b: Einstein Probe detection of an X-ray transient
  55. EP260329a: Einstein Probe detection of an X-ray transient
  56. EP-WXT trigger 01709259209: TRT optical counterpart detection
  57. The EP-WXT trigger 01709259209 (EP260329b?): Las Cumbres discovery of the optical counterpart
  58. GRID detection of GRB 260326A
  59. GRB 260310A: Gemini-North Spectral Confirmation of Supernova Features
  60. EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  61. EP260327a: SVOM/VT optical upper limits
  62. SMA Detection of GRB 260310A / AT 2026fgk
  63. GRB 260307B: ATCA Radio Upper Limits
  64. EP260327a: WINTER J-band upper limit
  65. EP260327a: COLIBRÍ optical upper limits
  66. GRB 260327A: AstroSat CZTI detection of a long burst
  67. EP260327a: Gemini-North optical upper limits
  68. EP260324a: GROWTH-India Telescope optical observation
  69. EP260327a: Global MASTER-Net observations report
  70. EP260327a: Einstein Probe detection of an X-ray transient
  71. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova
  72. GRB 260310A: OSIRIS+/GTC spectroscopic detection of the associated BL-Ic, SN 2026fgk
  73. The EP-WXT trigger 01709259173 is likely a flaring star
  74. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  75. IPN triangulation of GRB 260320A
  76. EP260324a: ZTF discovery of the optical counterpart ZTF26aapviim/AT2026hir
  77. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  78. GRB 260326A: Fermi GBM Detection
  79. EP260321a: JinShan near-infrared observations
  80. GRB 260325A: Fermi GBM Final Localization
  81. GRB 260326A: Fermi GBM Final Real-time Localization
  82. EP260321a: Upper limits from a neutrino search with IceCube
  83. Fermi Gamma-ray Burst Monitor trigger 796145512/260325647 is not a GRB
  84. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  85. IPN triangulation of GRB 260316B
  86. EP260321a: J-band observations by the SYSU 80 cm infrared telescope
  87. GRID detection of GRB 260320A
  88. EP260321a: Gemini-South confirmation of a supernova (duplicate submission)
  89. EP260321a: Gemini-South confirmation of a supernova
  90. Fermi Gamma-ray Burst Monitor trigger 796060650/260324665 is not a GRB
  91. EP260321a: VLT/FORS2 spectroscopy confirmation of an associated type Ic-BL supernova SN 2026gzf
  92. GRB 260310A: LBT optical observations
  93. EP260321A: Mondy optical observations
  94. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  95. EP-WXT trigger 01709259112: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  96. GRB 260316B: CALET Gamma-Ray Burst Monitor detection
  97. The EP-WXT trigger 01709259112 is likely a flaring star
  98. Fermi GRB 260323A: Global MASTER-Net observations report
  99. GRB 260323A: Fermi GBM Final Real-time Localization
  100. GRB260310A: Palomar 60-inch photometry of an extremely bright late-time afterglow with a temporal break at 8 days

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