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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"

21319 results found.

  1. Fermi GBM Sub-Threshold Detection of GRB 251205A
  2. Fermi GRB 251209A: Global MASTER-Net observations report
  3. Fermi GRB 251208C: Global MASTER-Net observations report
  4. GRB 251208B: Swift-XRT afterglow detection
  5. GRB 251208D: LAST optical upper limit
  6. GRB 251208D: LCO analysis of the XRT sources
  7. GRB 251208B: GROWTH-India Telescope optical upper limits
  8. GRB 251205A: J-band detection with WINTER
  9. GRB 251208D: Swift-XRT observations
  10. GRB 251129A: e-MERLIN C-band observations
  11. LAT GRB251208.43: Global MASTER-Net observations report
  12. GRB 251205A: Liverpool Telescope further optical follow-up observations
  13. SVOM GRB251208D: Global MASTER-Net observations report
  14. GRB 251208B: Swift ToO observations
  15. GRB 251208B: Swift/BAT-GUANO arcminute localization of a burst
  16. GRB 251205A : MITSuME Akeno optical afterglow candidate detection
  17. GRB 251205A: FTW optical and NIR observations
  18. EP-WXT trigger 01709249380: KAIT confirmation of a stellar flare
  19. GRB 251205A: Liverpool Telescope further optical follow-up observations
  20. SVOM GRB251206.86: Global MASTER-Net observations report
  21. GRB 251205A: ZTF and ATLAS optical afterglow detections
  22. GRB 251205A: GROWTH-India Telescope optical observations
  23. GRB 251205A: Swift/UVOT Detection
  24. GRB 251205A: Liverpool Telescope optical follow-up observations
  25. GRB 251203C: Swift/UVOT Upper Limit
  26. GRB 251205A: Zeiss-1000 Koshka observatory optical observations
  27. GRB 251205A: COLIBRÍ optical observations
  28. GRB 251205A: GOTO optical afterglow detection
  29. GRB 251205A: NOT optical observations
  30. GRB 251205A: GTC/OSIRIS+ redshift z = 1.100
  31. Swift GRB 251205A : MASTER OT detection with host galaxy
  32. Swift GRB251205A: Global MASTER-Net observations report
  33. GRB 251203C: SVOM/ECLAIRs refined analysis
  34. GRB 251202A / EP251202a: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 40-cm and 1-m telescopes at McDonald Observatory
  35. GRB 251203C: J-band observations with WINTER
  36. EP251130a: JinShan near-infrared observations
  37. GRB 251203C: SVOM/VT optical counterpart
  38. GRB 251129A/EP251129a : SVOM/ECLAIRs refined analysis
  39. GRB 251203B: Swift-XRT observations
  40. GRB 251203B : SVOM trigger sb25120304 is not a GRB
  41. GRB 251203B: LCO optical upper limits
  42. GRB 251203B: SVOM/VT optical observation
  43. GRB 251202A / EP251202a: Liverpool Telescope optical follow-up observations
  44. SVOM GRB251203.77: Global MASTER-Net observations report
  45. SVOM GRB251203B: Global MASTER-Net observations report
  46. GRB 251129A / EP251129a: SVOM/VT optical color bluer
  47. EP251130a: MAO/AZT-22 optical observations
  48. GRB 251202A / EP251202a: SVOM/VT optical observation
  49. EP251202a/GRB 251202A: KAIT optical observations
  50. EP251130a: ULL-ASTRO-MASTER late detection of the optical afterglow with LCO 1-m telescope at Teide Observatory
  51. Fermi GRB 251202B: Global MASTER-Net observations report
  52. GRB251129A/EP251129a: Swift UVOT detection
  53. GRB 251202A: Swift/UVOT Detection
  54. GRB 251201B: Kilonova-Catcher optical afterglow detection
  55. GRB 251201B: Swift/UVOT Detection
  56. EP251130a: continued NOT optical observations indicate steep fading phase
  57. GRB 251122A/EP251122a: CrAO ZTSh optical observations
  58. Fermi-LAT Gamma-ray Observations of IceCube-251130A
  59. EP251202a / GRB 251202A: LCO r- and i-band optical detection
  60. GRB 251202A: GOTO optical afterglow detection
  61. EP251202a/GRB 251202A: refined analysis of the EP-WXT observations
  62. GRB 251202A: Swift-XRT afterglow detection
  63. Fermi GRB 251202A: Global MASTER-Net observations report
  64. GRB 251201B: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at Sutherland Observatory
  65. Swift GRB 251201B: Global MASTER-Net observations report
  66. EP251118a: Mondy, CrAO, Assy and SAO RAS/Zeiss-1000 optical observations
  67. EP251130a: Mondy optical observations
  68. EP251130a: Optical detections with Kinder observations
  69. SVOM GRB251201.19: Global MASTER-Net observations report
  70. EP251130a: SAO RAS optical observations
  71. EP251130a: GTC OSIRIS+ redshift z = 4.035 and rebrightening
  72. EP251130a: KAIT optical observations
  73. EP251130A: Optical observation from 1.3m DFOT
  74. EP251130a: refined analysis of the EP-WXT and EP-FXT observations
  75. EP251130a: JinShan optical observations
  76. Fermi GRB 251130B: Global MASTER-Net observations report
  77. IceCube Alert 251130.75: Global MASTER-Net observations report
  78. EP251130a: Swift-XRT counterpart detection
  79. EP251130a: Global MASTER-Net observations report
  80. EP251129a/GRB 251129A: EP-FXT follow-up observations
  81. GRB 251129A / EP251129a: GTC/OSIRIS+ spectroscopic redshift z = 1.460
  82. GRB 251129A / EP251129a: SAO RAS optical observations
  83. GRB 251126A: SAO RAS optical observations
  84. GRB 251129A: Swift-XRT afterglow detection
  85. GRB 251129A: Swift ToO observations
  86. EP251129a: Global MASTER-Net observations report
  87. GRB 251129A: Optical Observations via Virtual Telescope Project, Italy
  88. GRB 251129A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  89. SVOM GRB251129A: Global MASTER-Net observations report
  90. GRB 251126A: TShAO, Mondy, and AbAO optical observations
  91. GRB 251128A: Swift/BAT-GUANO localization skymap of a burst
  92. Fermi GRB 251128A: Global MASTER-Net observations report
  93. GRB 251126A: OHP/T193 optical observations and tentative spectroscopic redshift
  94. GRB 251126A: further SAO RAS optical observations
  95. GRB 250702B: detection of the compact radio counterpart 139 days after the burst
  96. GRB 251126A NUTTelA-TAO Early Measurements
  97. LIGO/Virgo/KAGRA S251112cm: GECKO/KMTNet tiling observations and transient candidates
  98. GRB251126A: MAO/AZT-22 optical observations
  99. GRB251126A: Continued optical observation from 1.3m DFOT
  100. GRB 251126A: Swift/UVOT Detection

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