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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"

19315 results found.

  1. GRB 251205A: ZTF and ATLAS optical afterglow detections
  2. GRB 251205A: GROWTH-India Telescope optical observations
  3. GRB 251205A: Swift-BAT refined analysis
  4. GRB 251205A: Swift-XRT refined Analysis
  5. GRB 251205A: Swift/UVOT Detection
  6. GRB 251203C: Swift/UVOT Upper Limit
  7. GRB 251205A: COLIBRÍ optical observations
  8. GRB 251205A: Enhanced Swift-XRT position
  9. Swift GRB 251205A : MASTER OT detection with host galaxy
  10. GRB 251205A: Swift detection of a burst with an optical afterglow
  11. Swift GRB251205A: Global MASTER-Net observations report
  12. GRB 251202A / EP251202a: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 40-cm and 1-m telescopes at McDonald Observatory
  13. GRB 251202A: SVOM/GRM observation
  14. GRB 251201B: SALT spectroscopic redshift z = 1.599
  15. GRB 251129B: Glowbug gamma-ray detection of a short burst
  16. GRB 251203B: Swift-XRT observations
  17. GRB 251203B: LCO optical upper limits
  18. EP251130a: MAO/AZT-22 optical observations
  19. GRB 251202A / EP251202a: SVOM/VT optical observation
  20. GRB 251201B: Fermi GBM Observation
  21. EP251130a: ULL-ASTRO-MASTER late detection of the optical afterglow with LCO 1-m telescope at Teide Observatory
  22. IPN triangulation of GRB 251129B (short/hard)
  23. GRB251129A/EP251129a: Swift UVOT detection
  24. GRB 251202A: Fermi GBM Observation
  25. GRB 251202A: Swift/UVOT Detection
  26. GRB 251201B: Kilonova-Catcher optical afterglow detection
  27. GRB 251201B: Swift/UVOT Detection
  28. GRB 251126A: SAO RAS optical marginal detection
  29. GRB 251202A: Swift-XRT afterglow detection
  30. GRB 251126A: SVOM/VT optical observation
  31. EP251130a: SVOM/VT optical observation
  32. GRB 251201B: Swift-XRT refined Analysis
  33. GRB 251201B: SVOM/VT optical fading
  34. Swift GRB 251201B : MASTER optical counterpart detection
  35. GRB 251201B: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at Sutherland Observatory
  36. Swift GRB 251201B: Global MASTER-Net observations report
  37. GRB 251201B: Enhanced Swift-XRT position
  38. GRB 251201B: Swift detection of a burst with an optical counterpart
  39. EP251130a: Mondy optical observations
  40. EP251130a: Optical detections with Kinder observations
  41. EP251130a: SAO RAS optical observations
  42. EP251130A: Optical observation from 1.3m DFOT
  43. EP251130a: Swift-XRT counterpart detection
  44. GRB 251129A / EP251129a: GTC/OSIRIS+ spectroscopic redshift z = 1.460
  45. GRB 251128A: AstroSat CZTI detection
  46. GRB 251129A / EP251129a: SAO RAS optical observations
  47. GRB 251126A: SAO RAS optical observations
  48. GRB 251129A: Swift-XRT afterglow detection
  49. Swift trigger 1418333 is not an astrophysical source
  50. GRB 251129A: Swift ToO observations
  51. GRB 251128A: Fermi GBM Observation
  52. GRB 251126A: Swift-BAT refined analysis
  53. GRB 251126A: TShAO, Mondy, and AbAO optical observations
  54. GRB 251128A: Swift/BAT-GUANO localization skymap of a burst
  55. GRB 251126A: OHP/T193 optical observations and tentative spectroscopic redshift
  56. GRB 251126A: further SAO RAS optical observations
  57. GRB 251126A NUTTelA-TAO Early Measurements
  58. GRB251126A: MAO/AZT-22 optical observations
  59. GRB251126A: Continued optical observation from 1.3m DFOT
  60. GRB 251126A: Swift/UVOT Detection
  61. GRB 251126A: Mondy and SAO RAS optical observations
  62. GRB 251126A: Swift-XRT refined Analysis
  63. GRB 251126A : MITSuME Akeno optical afterglow candidate detection
  64. GRB 251126A: NOT optical observations
  65. GRB 251126A: 1.3m DFOT optical afterglow detection
  66. GRB 251126A: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at McDonald Observatory
  67. GRB 251126A: COLIBRÍ photometric redshift z = 3.5
  68. GRB 251126A: Enhanced Swift-XRT position
  69. GRB 251126A: Kilonova-Catcher optical afterglow detection
  70. GRB 251126A: Asiago i-band detection
  71. GRB 251126A: Nanshan/HMT optical afterglow detection
  72. Swift GRB 251126A: Global MASTER-Net observations report
  73. GRB 251121A: Fermi GBM Observation
  74. GRB 251126A: Prompt enhanced Swift-XRT position
  75. GRB 251126A: GIT discovery of the likely optical afterglow
  76. GRB 251126A: Swift detection of a burst
  77. EP251124a: Xinglong GWAC-F60A optical observation
  78. EP251124a: NOT r- and z-band optical upper limits
  79. EP251124a: Swift-XRT observations
  80. GRB 251116C: Swift-XRT confirmation of fading
  81. GRB 251121A: Swift/BAT-GUANO localization skymap of a short burst
  82. GRB 251118A: Swift/UVOT Detection
  83. GRB 251118A: Fermi GBM Observation
  84. GRB 251118A: Swift-XRT afterglow detection
  85. GRB 251103A: SVOM/ECLAIRs and SVOM/GRM joint refined analysis
  86. EP251118a / GRB 251118C: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at CTIO
  87. GRB 251116C: NOT optical observations
  88. GRB 251118C: Glowbug gamma-ray detection of the fast X-ray transient EP251118A
  89. GRB 251118C: Swift/BAT rates detection of a burst with a possible association with EP 251118A
  90. GRB 251018A: FRAM-Auger optical detection
  91. GRB 251117A: Swift-XRT observations
  92. GRB 251118A: Fermi-LAT detection
  93. GRB 251118A: Swift ToO observations
  94. GRB 251117A: FTW Observations of Swift candidate X-ray sources
  95. GRB 251116C: SVOM/ECLAIRs refined analysis
  96. GRB 251117A: AstroSat CZTI detection
  97. GRB 251117A: Fermi GBM observation
  98. GRB 251115A: Swift-XRT observations
  99. GRB 251117A: Swift/BAT-GUANO localization skymap of a short burst
  100. GRB 251117A: Tiled Swift observations

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