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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"

19323 results found.

  1. Fermi GBM Sub-Threshold Detection of GRB 251205A
  2. GRB 251208B: COLIBRÍ optical upper limits
  3. EP251118a / GRB 251118C: VLT/MUSE redshift confirmation
  4. GRB 251208B: Swift-XRT afterglow detection
  5. GRB 251208D: LCO analysis of the XRT sources
  6. GRB 251208B: Fermi GBM Observation
  7. GRB 251208B: GROWTH-India Telescope optical upper limits
  8. GRB 251208D: Swift-XRT observations
  9. GRB 251208B: Swift ToO observations
  10. GRB 251208B: Fermi-LAT detection
  11. GRB 251208B: Swift/BAT-GUANO arcminute localization of a burst
  12. GRB 251205A : MITSuME Akeno optical afterglow candidate detection
  13. GRB 251205A: ZTF and ATLAS optical afterglow detections
  14. GRB 251205A: GROWTH-India Telescope optical observations
  15. GRB 251205A: Swift-BAT refined analysis
  16. GRB 251205A: Swift-XRT refined Analysis
  17. GRB 251205A: Swift/UVOT Detection
  18. GRB 251203C: Swift/UVOT Upper Limit
  19. GRB 251205A: COLIBRÍ optical observations
  20. GRB 251205A: Enhanced Swift-XRT position
  21. Swift GRB 251205A : MASTER OT detection with host galaxy
  22. GRB 251205A: Swift detection of a burst with an optical afterglow
  23. Swift GRB251205A: Global MASTER-Net observations report
  24. GRB 251202A / EP251202a: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 40-cm and 1-m telescopes at McDonald Observatory
  25. GRB 251202A: SVOM/GRM observation
  26. GRB 251201B: SALT spectroscopic redshift z = 1.599
  27. GRB 251129B: Glowbug gamma-ray detection of a short burst
  28. GRB 251203B: Swift-XRT observations
  29. GRB 251203B: LCO optical upper limits
  30. EP251130a: MAO/AZT-22 optical observations
  31. GRB 251202A / EP251202a: SVOM/VT optical observation
  32. GRB 251201B: Fermi GBM Observation
  33. EP251130a: ULL-ASTRO-MASTER late detection of the optical afterglow with LCO 1-m telescope at Teide Observatory
  34. IPN triangulation of GRB 251129B (short/hard)
  35. GRB251129A/EP251129a: Swift UVOT detection
  36. GRB 251202A: Fermi GBM Observation
  37. GRB 251202A: Swift/UVOT Detection
  38. GRB 251201B: Kilonova-Catcher optical afterglow detection
  39. GRB 251201B: Swift/UVOT Detection
  40. GRB 251126A: SAO RAS optical marginal detection
  41. GRB 251202A: Swift-XRT afterglow detection
  42. GRB 251126A: SVOM/VT optical observation
  43. EP251130a: SVOM/VT optical observation
  44. GRB 251201B: Swift-XRT refined Analysis
  45. GRB 251201B: SVOM/VT optical fading
  46. Swift GRB 251201B : MASTER optical counterpart detection
  47. GRB 251201B: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at Sutherland Observatory
  48. Swift GRB 251201B: Global MASTER-Net observations report
  49. GRB 251201B: Enhanced Swift-XRT position
  50. GRB 251201B: Swift detection of a burst with an optical counterpart
  51. EP251130a: Mondy optical observations
  52. EP251130a: Optical detections with Kinder observations
  53. EP251130a: SAO RAS optical observations
  54. EP251130A: Optical observation from 1.3m DFOT
  55. EP251130a: Swift-XRT counterpart detection
  56. GRB 251129A / EP251129a: GTC/OSIRIS+ spectroscopic redshift z = 1.460
  57. GRB 251128A: AstroSat CZTI detection
  58. GRB 251129A / EP251129a: SAO RAS optical observations
  59. GRB 251126A: SAO RAS optical observations
  60. GRB 251129A: Swift-XRT afterglow detection
  61. Swift trigger 1418333 is not an astrophysical source
  62. GRB 251129A: Swift ToO observations
  63. GRB 251128A: Fermi GBM Observation
  64. GRB 251126A: Swift-BAT refined analysis
  65. GRB 251126A: TShAO, Mondy, and AbAO optical observations
  66. GRB 251128A: Swift/BAT-GUANO localization skymap of a burst
  67. GRB 251126A: OHP/T193 optical observations and tentative spectroscopic redshift
  68. GRB 251126A: further SAO RAS optical observations
  69. GRB 251126A NUTTelA-TAO Early Measurements
  70. GRB251126A: MAO/AZT-22 optical observations
  71. GRB251126A: Continued optical observation from 1.3m DFOT
  72. GRB 251126A: Swift/UVOT Detection
  73. GRB 251126A: Mondy and SAO RAS optical observations
  74. GRB 251126A: Swift-XRT refined Analysis
  75. GRB 251126A : MITSuME Akeno optical afterglow candidate detection
  76. GRB 251126A: NOT optical observations
  77. GRB 251126A: 1.3m DFOT optical afterglow detection
  78. GRB 251126A: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at McDonald Observatory
  79. GRB 251126A: COLIBRÍ photometric redshift z = 3.5
  80. GRB 251126A: Enhanced Swift-XRT position
  81. GRB 251126A: Kilonova-Catcher optical afterglow detection
  82. GRB 251126A: Asiago i-band detection
  83. GRB 251126A: Nanshan/HMT optical afterglow detection
  84. Swift GRB 251126A: Global MASTER-Net observations report
  85. GRB 251121A: Fermi GBM Observation
  86. GRB 251126A: Prompt enhanced Swift-XRT position
  87. GRB 251126A: GIT discovery of the likely optical afterglow
  88. GRB 251126A: Swift detection of a burst
  89. EP251124a: Xinglong GWAC-F60A optical observation
  90. EP251124a: NOT r- and z-band optical upper limits
  91. EP251124a: Swift-XRT observations
  92. GRB 251116C: Swift-XRT confirmation of fading
  93. GRB 251121A: Swift/BAT-GUANO localization skymap of a short burst
  94. GRB 251118A: Swift/UVOT Detection
  95. GRB 251118A: Fermi GBM Observation
  96. GRB 251118A: Swift-XRT afterglow detection
  97. GRB 251103A: SVOM/ECLAIRs and SVOM/GRM joint refined analysis
  98. EP251118a / GRB 251118C: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at CTIO
  99. GRB 251116C: NOT optical observations
  100. GRB 251118C: Glowbug gamma-ray detection of the fast X-ray transient EP251118A

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