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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"
  1. EP251130a: Mondy and AbAO optical observations
  2. GRB 251208A: AstroSat CZTI detection
  3. Fermi GBM Sub-Threshold Detection of GRB 251205A
  4. GRB 251208A: Glowbug gamma-ray detection
  5. GRB 251208B: COLIBRÍ optical upper limits
  6. EP251118a / GRB 251118C: VLT/MUSE redshift confirmation
  7. GRB 251208C: GECAM-B observation of a short burst
  8. GRB 251208A: GECAM-B observation of a short burst
  9. Fermi GRB 251209A: Global MASTER-Net observations report
  10. Fermi GRB 251208C: Global MASTER-Net observations report
  11. GRB 251206A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  12. GRB 251208B: Swift-XRT afterglow detection
  13. GRB 251208D: LAST optical upper limit
  14. GRB 251209A: Fermi GBM Final Real-time Localization
  15. GRB 251208D: LCO analysis of the XRT sources
  16. GRB 251208B: Fermi GBM Observation
  17. GRB 251208B: GROWTH-India Telescope optical upper limits
  18. GRB 251205A: J-band detection with WINTER
  19. GRB 251208D: Swift-XRT observations
  20. GRB 251208A: SVOM/GRM observation of a short burst
  21. GRB 251208C: SVOM/GRM observation of a short burst
  22. GRB 251129A: e-MERLIN C-band observations
  23. LAT GRB251208.43: Global MASTER-Net observations report
  24. GRB 251205A: Liverpool Telescope further optical follow-up observations
  25. GRB 251208D: LCO optical upper limits
  26. SVOM GRB251208D: Global MASTER-Net observations report
  27. GRB 251208B: Swift ToO observations
  28. GRB 251208B: Fermi-LAT detection
  29. GRB 251208B: Swift/BAT-GUANO arcminute localization of a burst
  30. GRB 251208D: SVOM possible detection of a faint burst
  31. GRB 251206A: SVOM detection of a burst through offline search
  32. GRB 251208C: Fermi GBM Final Real-time Localization
  33. GRB 251205A : MITSuME Akeno optical afterglow candidate detection
  34. GRB 251208B: Fermi GBM Final Real-time Localization
  35. GRB 251208A: Fermi GBM Final Real-time Localization
  36. GRB 251205A: FTW optical and NIR observations
  37. EP-WXT trigger 01709249380: KAIT confirmation of a stellar flare
  38. GRB 251205A: Liverpool Telescope further optical follow-up observations
  39. SVOM GRB251206.86: Global MASTER-Net observations report
  40. EP-WXT trigger 01709249380: confirmation of a stellar flare by BOOTES-5
  41. The EP-WXT trigger 01709249380 is likely a flaring star
  42. GRB 251205A: ZTF and ATLAS optical afterglow detections
  43. GRB 251205A: GROWTH-India Telescope optical observations
  44. GRB 251205A: Swift-BAT refined analysis
  45. GRB 251205A: Swift-XRT refined Analysis
  46. GRB 251205A: Swift/UVOT Detection
  47. GRB 251205A: Liverpool Telescope optical follow-up observations
  48. GRB 251203C: Swift/UVOT Upper Limit
  49. Konus-Wind detection of GRB 251118A
  50. GRB 251205A: Zeiss-1000 Koshka observatory optical observations
  51. GRB 251205A: COLIBRÍ optical observations
  52. GRB 251205A: GOTO optical afterglow detection
  53. GRB 251205A: NOT optical observations
  54. GRB 251205A: GTC/OSIRIS+ redshift z = 1.100
  55. GRB 251205A: Enhanced Swift-XRT position
  56. Swift GRB 251205A : MASTER OT detection with host galaxy
  57. GRB 251205A: Swift detection of a burst with an optical afterglow
  58. Swift GRB251205A: Global MASTER-Net observations report
  59. GRB 251126B: Fermi GBM Final Localization
  60. GRB 251203A: Insight-HXMT/HE detection
  61. GRB 251203C: SVOM/ECLAIRs refined analysis
  62. SVOM/sb25120502: SVOM detection of a faint X-ray transient candidate
  63. GRB 251202A / EP251202a: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 40-cm and 1-m telescopes at McDonald Observatory
  64. GRB 251203C: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  65. GRB 251202A: SVOM/GRM observation
  66. GRB 251203A: GECAM-B observation of a burst
  67. GRB 251203A: SVOM/GRM observation
  68. GRB 251201B: SALT spectroscopic redshift z = 1.599
  69. GRB 251203C: J-band observations with WINTER
  70. GRB 251129B: Glowbug gamma-ray detection of a short burst
  71. GRB 251203A: AstroSat CZTI detection
  72. EP251130a: JinShan near-infrared observations
  73. Fermi Gamma-ray Burst Monitor trigger 786496343/251203967 is not a GRB
  74. GRB 251203C: LCO optical afterglow confirmation
  75. GRB 251203C: SVOM/VT optical counterpart
  76. GRB 251203C: EP-FXT follow-up observation
  77. GRB 251129A/EP251129a : SVOM/ECLAIRs refined analysis
  78. GRB 251129B: GECAM-B observation of a burst
  79. GRB 251203B: Swift-XRT observations
  80. GRB 251203B: confirmation of a stellar flare by BOOTES-2
  81. GRB 251203B : SVOM trigger sb25120304 is not a GRB
  82. GRB 251203C: LCO optical upper limits
  83. GRB 251203B: LCO optical upper limits
  84. GRB 251203B: SVOM/VT optical observation
  85. GRB 251202A / EP251202a: Liverpool Telescope optical follow-up observations
  86. GRB 251203C: SVOM detection of a burst
  87. SVOM GRB251203.77: Global MASTER-Net observations report
  88. SVOM GRB251203B: Global MASTER-Net observations report
  89. GRB 251203B: SVOM detection of a burst
  90. GRB 251129A / EP251129a: SVOM/VT optical color bluer
  91. GRB 251201B: Insight-HXMT/HE detection
  92. EP251202a / GRB 251202A: Insight-HXMT/HE detection
  93. EP251130a: MAO/AZT-22 optical observations
  94. GRB 251203A: Fermi GBM Final Real-time Localization
  95. EP251202a / GRB251202A: AstroSat CZTI detection
  96. GRB 251202A / EP251202a: SVOM/VT optical observation
  97. GRB 251201B: Fermi GBM Observation
  98. EP251202a/GRB 251202A: KAIT optical observations
  99. EP251130a: ULL-ASTRO-MASTER late detection of the optical afterglow with LCO 1-m telescope at Teide Observatory
  100. Fermi GRB 251202B: Global MASTER-Net observations report

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