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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"

19673 results found.

  1. GRB 251214B: Enhanced Swift-XRT position
  2. GRB 251214B: Xinglong-2.16m optical observation
  3. GRB 251214B : MASTER optical afterglow detection
  4. GRB 251214B: SVOM/C-GFT optical observations
  5. Swift GRB 251214B: Global MASTER-Net observations report
  6. GRB 251214B: Swift detection of a burst with an optical counterpart
  7. GRB 251205A: 1.3m DFOT optical upper limit
  8. GRB 251129A/EP251129a: AbAO and Mondy optical observations
  9. EP251130a: Mondy and AbAO optical observations
  10. Fermi GBM Sub-Threshold Detection of GRB 251205A
  11. GRB 251208B: COLIBRÍ optical upper limits
  12. EP251118a / GRB 251118C: VLT/MUSE redshift confirmation
  13. GRB 251208B: Swift-XRT afterglow detection
  14. GRB 251208D: LCO analysis of the XRT sources
  15. GRB 251208B: Fermi GBM Observation
  16. GRB 251208B: GROWTH-India Telescope optical upper limits
  17. GRB 251208D: Swift-XRT observations
  18. GRB 251208B: Swift ToO observations
  19. GRB 251208B: Fermi-LAT detection
  20. GRB 251208B: Swift/BAT-GUANO arcminute localization of a burst
  21. GRB 251205A : MITSuME Akeno optical afterglow candidate detection
  22. GRB 251205A: ZTF and ATLAS optical afterglow detections
  23. GRB 251205A: GROWTH-India Telescope optical observations
  24. GRB 251205A: Swift-BAT refined analysis
  25. GRB 251205A: Swift-XRT refined Analysis
  26. GRB 251205A: Swift/UVOT Detection
  27. GRB 251203C: Swift/UVOT Upper Limit
  28. GRB 251205A: COLIBRÍ optical observations
  29. GRB 251205A: Enhanced Swift-XRT position
  30. Swift GRB 251205A : MASTER OT detection with host galaxy
  31. GRB 251205A: Swift detection of a burst with an optical afterglow
  32. Swift GRB251205A: Global MASTER-Net observations report
  33. GRB 251202A / EP251202a: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 40-cm and 1-m telescopes at McDonald Observatory
  34. GRB 251202A: SVOM/GRM observation
  35. GRB 251201B: SALT spectroscopic redshift z = 1.599
  36. GRB 251129B: Glowbug gamma-ray detection of a short burst
  37. GRB 251203B: Swift-XRT observations
  38. GRB 251203B: LCO optical upper limits
  39. EP251130a: MAO/AZT-22 optical observations
  40. GRB 251202A / EP251202a: SVOM/VT optical observation
  41. GRB 251201B: Fermi GBM Observation
  42. EP251130a: ULL-ASTRO-MASTER late detection of the optical afterglow with LCO 1-m telescope at Teide Observatory
  43. IPN triangulation of GRB 251129B (short/hard)
  44. GRB251129A/EP251129a: Swift UVOT detection
  45. GRB 251202A: Fermi GBM Observation
  46. GRB 251202A: Swift/UVOT Detection
  47. GRB 251201B: Kilonova-Catcher optical afterglow detection
  48. GRB 251201B: Swift/UVOT Detection
  49. GRB 251126A: SAO RAS optical marginal detection
  50. GRB 251202A: Swift-XRT afterglow detection
  51. GRB 251126A: SVOM/VT optical observation
  52. EP251130a: SVOM/VT optical observation
  53. GRB 251201B: Swift-XRT refined Analysis
  54. GRB 251201B: SVOM/VT optical fading
  55. Swift GRB 251201B : MASTER optical counterpart detection
  56. GRB 251201B: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at Sutherland Observatory
  57. Swift GRB 251201B: Global MASTER-Net observations report
  58. GRB 251201B: Enhanced Swift-XRT position
  59. GRB 251201B: Swift detection of a burst with an optical counterpart
  60. EP251130a: Mondy optical observations
  61. EP251130a: Optical detections with Kinder observations
  62. EP251130a: SAO RAS optical observations
  63. EP251130A: Optical observation from 1.3m DFOT
  64. EP251130a: Swift-XRT counterpart detection
  65. GRB 251129A / EP251129a: GTC/OSIRIS+ spectroscopic redshift z = 1.460
  66. GRB 251128A: AstroSat CZTI detection
  67. GRB 251129A / EP251129a: SAO RAS optical observations
  68. GRB 251126A: SAO RAS optical observations
  69. GRB 251129A: Swift-XRT afterglow detection
  70. Swift trigger 1418333 is not an astrophysical source
  71. GRB 251129A: Swift ToO observations
  72. GRB 251128A: Fermi GBM Observation
  73. GRB 251126A: Swift-BAT refined analysis
  74. GRB 251126A: TShAO, Mondy, and AbAO optical observations
  75. GRB 251128A: Swift/BAT-GUANO localization skymap of a burst
  76. GRB 251126A: OHP/T193 optical observations and tentative spectroscopic redshift
  77. GRB 251126A: further SAO RAS optical observations
  78. GRB 251126A NUTTelA-TAO Early Measurements
  79. GRB251126A: MAO/AZT-22 optical observations
  80. GRB251126A: Continued optical observation from 1.3m DFOT
  81. GRB 251126A: Swift/UVOT Detection
  82. GRB 251126A: Mondy and SAO RAS optical observations
  83. GRB 251126A: Swift-XRT refined Analysis
  84. GRB 251126A : MITSuME Akeno optical afterglow candidate detection
  85. GRB 251126A: NOT optical observations
  86. GRB 251126A: 1.3m DFOT optical afterglow detection
  87. GRB 251126A: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at McDonald Observatory
  88. GRB 251126A: COLIBRÍ photometric redshift z = 3.5
  89. GRB 251126A: Enhanced Swift-XRT position
  90. GRB 251126A: Kilonova-Catcher optical afterglow detection
  91. GRB 251126A: Asiago i-band detection
  92. GRB 251126A: Nanshan/HMT optical afterglow detection
  93. Swift GRB 251126A: Global MASTER-Net observations report
  94. GRB 251121A: Fermi GBM Observation
  95. GRB 251126A: Prompt enhanced Swift-XRT position
  96. GRB 251126A: GIT discovery of the likely optical afterglow
  97. GRB 251126A: Swift detection of a burst
  98. EP251124a: Xinglong GWAC-F60A optical observation
  99. EP251124a: NOT r- and z-band optical upper limits
  100. EP251124a: Swift-XRT observations

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