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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"

21458 results found.

  1. GRB 251201B: SALT spectroscopic redshift z = 1.599
  2. GRB 251129B: Glowbug gamma-ray detection of a short burst
  3. GRB 251203B: Swift-XRT observations
  4. GRB 251203B : SVOM trigger sb25120304 is not a GRB
  5. GRB 251203B: LCO optical upper limits
  6. EP251130a: MAO/AZT-22 optical observations
  7. GRB 251202A / EP251202a: SVOM/VT optical observation
  8. GRB 251201B: Fermi GBM Observation
  9. EP251130a: ULL-ASTRO-MASTER late detection of the optical afterglow with LCO 1-m telescope at Teide Observatory
  10. IPN triangulation of GRB 251129B (short/hard)
  11. GRB251129A/EP251129a: Swift UVOT detection
  12. GRB 251202A: Fermi GBM Observation
  13. GRB 251202A: Swift/UVOT Detection
  14. GRB 251201B: Kilonova-Catcher optical afterglow detection
  15. GRB 251201B: Swift/UVOT Detection
  16. GRB 251126A: SAO RAS optical marginal detection
  17. GRB 251202A: Swift-XRT afterglow detection
  18. GRB 251126A: SVOM/VT optical observation
  19. EP251130a: SVOM/VT optical observation
  20. GRB 251201B: Swift-XRT refined Analysis
  21. GRB 251201B: SVOM/VT optical fading
  22. Swift GRB 251201B : MASTER optical counterpart detection
  23. GRB 251201B: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at Sutherland Observatory
  24. Swift GRB 251201B: Global MASTER-Net observations report
  25. GRB 251201B: Enhanced Swift-XRT position
  26. GRB 251201B: Swift detection of a burst with an optical counterpart
  27. EP251130a: Mondy optical observations
  28. EP251130a: Optical detections with Kinder observations
  29. EP251130a: SAO RAS optical observations
  30. EP251130A: Optical observation from 1.3m DFOT
  31. EP251130a: Swift-XRT counterpart detection
  32. GRB 251129A / EP251129a: GTC/OSIRIS+ spectroscopic redshift z = 1.460
  33. GRB 251128A: AstroSat CZTI detection
  34. GRB 251129A / EP251129a: SAO RAS optical observations
  35. GRB 251126A: SAO RAS optical observations
  36. GRB 251129A: Swift-XRT afterglow detection
  37. Swift trigger 1418333 is not an astrophysical source
  38. GRB 251129A: Swift ToO observations
  39. GRB 251128A: Fermi GBM Observation
  40. GRB 251126A: Swift-BAT refined analysis
  41. GRB 251126A: TShAO, Mondy, and AbAO optical observations
  42. GRB 251128A: Swift/BAT-GUANO localization skymap of a burst
  43. GRB 251126A: OHP/T193 optical observations and tentative spectroscopic redshift
  44. GRB 251126A: further SAO RAS optical observations
  45. GRB 251126A NUTTelA-TAO Early Measurements
  46. GRB251126A: MAO/AZT-22 optical observations
  47. GRB251126A: Continued optical observation from 1.3m DFOT
  48. GRB 251126A: Swift/UVOT Detection
  49. GRB 251126A: Mondy and SAO RAS optical observations
  50. GRB 251126A: Swift-XRT refined Analysis
  51. GRB 251126A : MITSuME Akeno optical afterglow candidate detection
  52. GRB 251126A: NOT optical observations
  53. GRB 251126A: 1.3m DFOT optical afterglow detection
  54. GRB 251126A: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at McDonald Observatory
  55. GRB 251126A: COLIBRÍ photometric redshift z = 3.5
  56. GRB 251126A: Enhanced Swift-XRT position
  57. GRB 251126A: Kilonova-Catcher optical afterglow detection
  58. GRB 251126A: Asiago i-band detection
  59. GRB 251126A: Nanshan/HMT optical afterglow detection
  60. Swift GRB 251126A: Global MASTER-Net observations report
  61. GRB 251121A: Fermi GBM Observation
  62. GRB 251126A: Prompt enhanced Swift-XRT position
  63. GRB 251126A: GIT discovery of the likely optical afterglow
  64. GRB 251126A: Swift detection of a burst
  65. EP251124a: Xinglong GWAC-F60A optical observation
  66. EP251124a: NOT r- and z-band optical upper limits
  67. EP251124a: Swift-XRT observations
  68. GRB 251116C: Swift-XRT confirmation of fading
  69. GRB 251121A: Swift/BAT-GUANO localization skymap of a short burst
  70. GRB 251118A: Swift/UVOT Detection
  71. GRB 251118A: Fermi GBM Observation
  72. GRB 251118A: Swift-XRT afterglow detection
  73. GRB 251103A: SVOM/ECLAIRs and SVOM/GRM joint refined analysis
  74. EP251118a / GRB 251118C: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at CTIO
  75. GRB 251116C: NOT optical observations
  76. GRB 251118C: Glowbug gamma-ray detection of the fast X-ray transient EP251118A
  77. GRB 251118C: Swift/BAT rates detection of a burst with a possible association with EP 251118A
  78. GRB 251018A: FRAM-Auger optical detection
  79. GRB 251117A: Swift-XRT observations
  80. GRB 251118A: Fermi-LAT detection
  81. GRB 251118A: Swift ToO observations
  82. GRB 251117A: FTW Observations of Swift candidate X-ray sources
  83. GRB 251116C: SVOM/ECLAIRs refined analysis
  84. GRB 251117A: AstroSat CZTI detection
  85. GRB 251117A: Fermi GBM observation
  86. GRB 251115A: Swift-XRT observations
  87. GRB 251117A: Swift/BAT-GUANO localization skymap of a short burst
  88. GRB 251117A: Tiled Swift observations
  89. GRB 251117A: Fermi-LAT detection
  90. GRB 251116C: Swift/BAT arcminute localization of a burst
  91. GRB 251116C: Swift-XRT observations
  92. GRB 251116C: SVOM/VT optical upper limit
  93. GRB 251115A: Tiled Swift observations
  94. GRB 251115A: Fermi-LAT detection
  95. GRB 251112A: Swift-BAT refined analysis
  96. LIGO/Virgo/KAGRA S251112cm: Swift XRT observations, 20 X-ray sources
  97. GRB 251112A: Swift/UVOT Upper Limits
  98. GRB 251112A: Swift-XRT refined Analysis
  99. Swift Trigger 1413695: a possible GRB 251112A
  100. GRB251111A: 1.3m DFOT optical upper limit

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