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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"

26053 results found.

  1. GRB 251203C: LCO optical afterglow confirmation
  2. GRB 251203C: SVOM/VT optical counterpart
  3. GRB 251129A/EP251129a : SVOM/ECLAIRs refined analysis
  4. GRB 251203B: Swift-XRT observations
  5. GRB 251203B : SVOM trigger sb25120304 is not a GRB
  6. GRB 251203B: LCO optical upper limits
  7. GRB 251202A / EP251202a: Liverpool Telescope optical follow-up observations
  8. GRB 251129A / EP251129a: SVOM/VT optical color bluer
  9. EP251130a: MAO/AZT-22 optical observations
  10. GRB 251202A / EP251202a: SVOM/VT optical observation
  11. GRB 251201B: Fermi GBM Observation
  12. EP251202a/GRB 251202A: KAIT optical observations
  13. EP251130a: ULL-ASTRO-MASTER late detection of the optical afterglow with LCO 1-m telescope at Teide Observatory
  14. IPN triangulation of GRB 251129B (short/hard)
  15. GRB251129A/EP251129a: Swift UVOT detection
  16. GRB 251202A: Fermi GBM Observation
  17. GRB 251202A: Swift/UVOT Detection
  18. GRB 251201B: Kilonova-Catcher optical afterglow detection
  19. GRB 251201B: Swift/UVOT Detection
  20. GRB 251202A: GOTO optical afterglow detection
  21. GRB 251126A: SAO RAS optical marginal detection
  22. GRB 251202A: Swift-XRT afterglow detection
  23. GRB 251126A: SVOM/VT optical observation
  24. EP251130a: SVOM/VT optical observation
  25. EP251202a / GRB 251202A: NOT spectroscopic redshift z = 2.785
  26. GRB 251201B: Swift-XRT refined Analysis
  27. GRB 251201B: SVOM/VT optical fading
  28. Swift GRB 251201B : MASTER optical counterpart detection
  29. GRB 251201B: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at Sutherland Observatory
  30. Swift GRB 251201B: Global MASTER-Net observations report
  31. GRB 251201B: Enhanced Swift-XRT position
  32. GRB 251201B: Swift detection of a burst with an optical counterpart
  33. EP251130a: Mondy optical observations
  34. EP251130a: Optical detections with Kinder observations
  35. EP251130a: SAO RAS optical observations
  36. EP251130a: KAIT optical observations
  37. EP251130A: Optical observation from 1.3m DFOT
  38. EP251130a: Swift-XRT counterpart detection
  39. GRB 251129A / EP251129a: GTC/OSIRIS+ spectroscopic redshift z = 1.460
  40. GRB 251129A / EP251129a: OSN and CAHA optical follow-up
  41. GRB 251128A: AstroSat CZTI detection
  42. GRB 251129A / EP251129a: SAO RAS optical observations
  43. GRB 251126A: SAO RAS optical observations
  44. GRB 251129A: Swift-XRT afterglow detection
  45. Swift trigger 1418333 is not an astrophysical source
  46. GRB 251129A: Swift ToO observations
  47. GRB 251128A: Fermi GBM Observation
  48. GRB 251126A: Swift-BAT refined analysis
  49. GRB 251126A: TShAO, Mondy, and AbAO optical observations
  50. GRB 251128A: Swift/BAT-GUANO localization skymap of a burst
  51. GRB 251126A: OHP/T193 optical observations and tentative spectroscopic redshift
  52. GRB 251126A: further SAO RAS optical observations
  53. GRB 250702B: detection of the compact radio counterpart 139 days after the burst
  54. GRB 251126A NUTTelA-TAO Early Measurements
  55. GRB251126A: MAO/AZT-22 optical observations
  56. GRB251126A: Continued optical observation from 1.3m DFOT
  57. GRB 251126A: Swift/UVOT Detection
  58. GRB 251126A: Mondy and SAO RAS optical observations
  59. GRB 251126A: Swift-XRT refined Analysis
  60. GRB 251126A : MITSuME Akeno optical afterglow candidate detection
  61. GRB 251126A: NOT optical observations
  62. GRB 251126A: 1.3m DFOT optical afterglow detection
  63. GRB 251126A: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at McDonald Observatory
  64. GRB 251126A: COLIBRÍ photometric redshift z = 3.5
  65. GRB 251126A: Enhanced Swift-XRT position
  66. GRB 251126A: Kilonova-Catcher optical afterglow detection
  67. GRB 251126A: Asiago i-band detection
  68. GRB 251126A: Nanshan/HMT optical afterglow detection
  69. Swift GRB 251126A: Global MASTER-Net observations report
  70. GRB 251121A: Fermi GBM Observation
  71. GRB 251126A: Prompt enhanced Swift-XRT position
  72. GRB 251126A: GIT discovery of the likely optical afterglow
  73. GRB 251126A: Swift detection of a burst
  74. GRB 251125B: COLIBRÍ further observations and photometric redshift upper limit of z < 3
  75. GRB 251125B: COLIBRÍ observations of fading of the MASTER OT candidate
  76. EP251124a: Xinglong GWAC-F60A optical observation
  77. EP251124a: NOT r- and z-band optical upper limits
  78. EP251124a: Swift-XRT observations
  79. GRB 251116C: Swift-XRT confirmation of fading
  80. GRB 251122A/EP251122A: 1.3m DFOT optical detection
  81. EP251118A: 3.6m DOT optical afterglow detection
  82. GRB 251122A / EP251122a: WFST optical observations
  83. GRB 251121A: Swift/BAT-GUANO localization skymap of a short burst
  84. EP251118a: Xinglong-2.16m optical observation
  85. EP251118A: 1.3m DFOT optical afterglow detection
  86. GRB 251118A: Swift/UVOT Detection
  87. GRB 251118A: Fermi GBM Observation
  88. GRB 251118A: Swift-XRT afterglow detection
  89. GRB 251103A: SVOM/ECLAIRs and SVOM/GRM joint refined analysis
  90. EP251118a / GRB 251118C: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at CTIO
  91. GRB 251116C: NOT optical observations
  92. GRB 251118C: Glowbug gamma-ray detection of the fast X-ray transient EP251118A
  93. GRB 251118C: Swift/BAT rates detection of a burst with a possible association with EP 251118A
  94. GRB 251018A: FRAM-Auger optical detection
  95. GRB 251117A: Swift-XRT observations
  96. EP251118a: GOTO optical afterglow detection
  97. EP251118a: NOT spectroscopic redshift of z = 1.216
  98. GRB 251118A: Fermi-LAT detection
  99. EP251118a: NOT candidate optical counterpart
  100. GRB 251118A: Swift ToO observations

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