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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"

19594 results found.

  1. GRB 251201B: Kilonova-Catcher optical afterglow detection
  2. GRB 251201B: Swift/UVOT Detection
  3. GRB 251126A: SAO RAS optical marginal detection
  4. GRB 251202A: Swift-XRT afterglow detection
  5. GRB 251126A: SVOM/VT optical observation
  6. EP251130a: SVOM/VT optical observation
  7. GRB 251201B: Swift-XRT refined Analysis
  8. GRB 251201B: SVOM/VT optical fading
  9. Swift GRB 251201B : MASTER optical counterpart detection
  10. GRB 251201B: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at Sutherland Observatory
  11. Swift GRB 251201B: Global MASTER-Net observations report
  12. GRB 251201B: Enhanced Swift-XRT position
  13. GRB 251201B: Swift detection of a burst with an optical counterpart
  14. EP251130a: Mondy optical observations
  15. EP251130a: Optical detections with Kinder observations
  16. EP251130a: SAO RAS optical observations
  17. EP251130A: Optical observation from 1.3m DFOT
  18. EP251130a: Swift-XRT counterpart detection
  19. GRB 251129A / EP251129a: GTC/OSIRIS+ spectroscopic redshift z = 1.460
  20. GRB 251128A: AstroSat CZTI detection
  21. GRB 251129A / EP251129a: SAO RAS optical observations
  22. GRB 251126A: SAO RAS optical observations
  23. GRB 251129A: Swift-XRT afterglow detection
  24. Swift trigger 1418333 is not an astrophysical source
  25. GRB 251129A: Swift ToO observations
  26. GRB 251128A: Fermi GBM Observation
  27. SVOM GRB251129A: Global MASTER-Net observations report
  28. GRB 251126A: Swift-BAT refined analysis
  29. GRB 251126A: TShAO, Mondy, and AbAO optical observations
  30. GRB 251128A: Swift/BAT-GUANO localization skymap of a burst
  31. GRB 251126A: OHP/T193 optical observations and tentative spectroscopic redshift
  32. GRB 251126A: further SAO RAS optical observations
  33. GRB 251126A NUTTelA-TAO Early Measurements
  34. GRB251126A: MAO/AZT-22 optical observations
  35. GRB251126A: Continued optical observation from 1.3m DFOT
  36. GRB 251126A: Swift/UVOT Detection
  37. GRB 251126A: Mondy and SAO RAS optical observations
  38. GRB 251126A: Swift-XRT refined Analysis
  39. GRB 251126A : MITSuME Akeno optical afterglow candidate detection
  40. GRB 251126A: NOT optical observations
  41. GRB 251126A: 1.3m DFOT optical afterglow detection
  42. GRB 251126A: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at McDonald Observatory
  43. GRB 251126A: COLIBRÍ photometric redshift z = 3.5
  44. GRB 251126A: Enhanced Swift-XRT position
  45. GRB 251126A: Kilonova-Catcher optical afterglow detection
  46. GRB 251126A: Asiago i-band detection
  47. GRB 251126A: Nanshan/HMT optical afterglow detection
  48. Swift GRB 251126A: Global MASTER-Net observations report
  49. GRB 251121A: Fermi GBM Observation
  50. GRB 251126A: Prompt enhanced Swift-XRT position
  51. GRB 251126A: GIT discovery of the likely optical afterglow
  52. GRB 251126A: Swift detection of a burst
  53. EP251124a: Xinglong GWAC-F60A optical observation
  54. EP251124a: NOT r- and z-band optical upper limits
  55. EP251124a: Swift-XRT observations
  56. GRB 251116C: Swift-XRT confirmation of fading
  57. GRB 251121A: Swift/BAT-GUANO localization skymap of a short burst
  58. GRB 251118A: Swift/UVOT Detection
  59. GRB 251118A: Fermi GBM Observation
  60. GRB 251118A: Swift-XRT afterglow detection
  61. GRB 251103A: SVOM/ECLAIRs and SVOM/GRM joint refined analysis
  62. EP251118a / GRB 251118C: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at CTIO
  63. GRB 251116C: NOT optical observations
  64. GRB 251118C: Glowbug gamma-ray detection of the fast X-ray transient EP251118A
  65. GRB 251118C: Swift/BAT rates detection of a burst with a possible association with EP 251118A
  66. GRB 251018A: FRAM-Auger optical detection
  67. GRB 251117A: Swift-XRT observations
  68. GRB 251118A: Fermi-LAT detection
  69. GRB 251118A: Swift ToO observations
  70. GRB 251117A: FTW Observations of Swift candidate X-ray sources
  71. GRB 251116C: SVOM/ECLAIRs refined analysis
  72. GRB 251117A: AstroSat CZTI detection
  73. GRB 251117A: Fermi GBM observation
  74. GRB 251115A: Swift-XRT observations
  75. GRB 251117A: Swift/BAT-GUANO localization skymap of a short burst
  76. GRB 251117A: Tiled Swift observations
  77. GRB 251117A: Fermi-LAT detection
  78. GRB 251116C: Swift/BAT arcminute localization of a burst
  79. GRB 251116C: Swift-XRT observations
  80. GRB 251116C: SVOM/VT optical upper limit
  81. GRB 251115A: Tiled Swift observations
  82. GRB 251115A: Fermi-LAT detection
  83. GRB 251112A: Swift-BAT refined analysis
  84. LIGO/Virgo/KAGRA S251112cm: Swift XRT observations, 20 X-ray sources
  85. GRB 251112A: Swift/UVOT Upper Limits
  86. GRB 251112A: Swift-XRT refined Analysis
  87. Swift Trigger 1413695: a possible GRB 251112A
  88. GRB251111A: 1.3m DFOT optical upper limit
  89. GRB 251111A: Swift-XRT afterglow detection
  90. GRB 251111A: Swift-XRT observations
  91. GRB 251013C: Chandra X-ray observations and jet break detection
  92. GRB 251103B: Swift-BAT refined analysis
  93. GRB 251106A: Swift/UVOT Upper Limits
  94. GRB 251105A: AstroSat CZTI detection
  95. GRB 251106A: Swift-XRT afterglow detection
  96. GRB 251106A: Kilonova-Catcher optical upper limit
  97. GRB 251106A: Swift/BAT arcminute localization of a burst
  98. GRB 251103B: AstroSat CZTI detection
  99. GRB 250920C: TERI Gamma-ray detection
  100. GRB 251105A: Fermi GBM Observation

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