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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"

3402 results found.

  1. GRB 260206A: Swift-XRT observations
  2. GRB 260204A: Swift-XRT observations
  3. EP260131a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  4. GRB 260127B: Swift-XRT observations
  5. GRB 260127A: Swift-XRT refined Analysis
  6. GRB 260127A: Prompt enhanced Swift-XRT position
  7. GRB 260125A: Swift-XRT observations
  8. EP260126a: EP-FXT follow-up observation
  9. GRB 260120B: Swift-XRT refined Analysis
  10. EP260119a: update of EP-FXT follow-up observation
  11. GRB 260117A: Swift-XRT afterglow detection
  12. Swift GRB260118.48: Global MASTER-Net observations report
  13. GRB 260117A: Swift-XRT observations
  14. GRB 260114A: VLT/HAWK-I near-infrared upper limits
  15. GRB 260114A: Swift-XRT refined Analysis
  16. GRB 260111A: Swift-XRT observations
  17. Swift Trigger 1439093: is probably not GRB 260113A
  18. Swift Trigger 1434591: possible GRB 260109C
  19. GRB 260102A: Swift-XRT afterglow detection
  20. GRB 260104A: Swift-XRT refined Analysis
  21. GRB 260102A: Swift-XRT observations
  22. GRB 260101A: Swift-XRT refined Analysis
  23. GRB 251230A: Swift-XRT refined Analysis
  24. GRB 251222A: NUTTelA-TAO Early Measurements
  25. GRB 251222A: Swift-XRT afterglow detection
  26. GRB 251221A: Swift-XRT refined Analysis
  27. EP251220a: EP-FXT follow-up observation
  28. GRB 251215A: Swift-XRT afterglow detection
  29. GRB 251215A: Swift/UVOT Upper LImits
  30. GRB 251215A: Swift-XRT observations
  31. GRB 251214B: Swift-XRT refined Analysis
  32. GRB 251214B : MASTER optical afterglow detection
  33. EP251212a: EP-FXT follow-up observation
  34. GRB 251208B: Swift-XRT afterglow detection
  35. GRB 251208D: Swift-XRT observations
  36. GRB 251208B: Fermi-LAT detection
  37. GRB 251205A: FTW optical and NIR observations
  38. GRB 251205A: Swift-XRT refined Analysis
  39. GRB 251203C: Swift/UVOT Upper Limit
  40. Swift GRB 251205A : MASTER OT detection with host galaxy
  41. GRB 251203B: Swift-XRT observations
  42. GRB251129A/EP251129a: Swift UVOT detection
  43. GRB 251202A: Swift-XRT afterglow detection
  44. GRB 251201B: Swift-XRT refined Analysis
  45. Swift GRB 251201B : MASTER optical counterpart detection
  46. EP251130a: Swift-XRT counterpart detection
  47. SVOM GRB 251129A : MASTER optical counterpart detection
  48. GRB 251129A: Swift-XRT afterglow detection
  49. GRB 251126A: Swift-XRT refined Analysis
  50. GRB 251126A: Prompt enhanced Swift-XRT position
  51. Fermi GRB 251125B : MASTER OT J155558.56+581224.1 optical counterpart discovery
  52. EP251124a: Swift-XRT observations
  53. LIGO/Virgo/KAGRA S251105aj: EP-FXT follow-up observations and preliminary results on SVOM J2320.0-2901
  54. GRB 251116C: Swift-XRT confirmation of fading
  55. GRB 251118A: Swift/UVOT Detection
  56. GRB 251118A: Swift-XRT afterglow detection
  57. GRB 251117A: Swift-XRT observations
  58. GRB 251118A: Fermi-LAT detection
  59. GRB 251115A: Swift-XRT observations
  60. LIGO/Virgo/KAGRA S251112cm: J-GEM follow-up observations
  61. GRB 251116C: Swift-XRT observations
  62. LIGO/Virgo/KAGRA S251116en: Identification of a GW compact binary merger candidate
  63. LIGO/Virgo/KAGRA S251112cm: Swift XRT observations, 20 X-ray sources
  64. GRB 251111A: Swift-XRT afterglow detection
  65. GRB 251111A: Swift-XRT observations
  66. GRB 251013C: Chandra X-ray observations and jet break detection
  67. GRB 251106A: Swift/UVOT Upper Limits
  68. SVOM GRB251108.54: Global MASTER-Net observations report
  69. GRB 251106A: Swift-XRT afterglow detection
  70. GRB 251106A: MASTER optical observations
  71. EP251102a: update of EP-FXT follow-up observation
  72. GRB 251103B: Swift-XRT refined Analysis
  73. GRB 251103B: Prompt enhanced Swift-XRT position
  74. GRB 251103A: Swift-XRT afterglow detection
  75. GRB 251022A: Swift-XRT confirmation of fading
  76. GRB 251026A/EP251026a: EP-FXT follow-up observation
  77. GRB 251025B: Swift-XRT confirmation of fading
  78. GRB 251026B: Swift-XRT observations of GOTO25jgl/AT2025absf
  79. GRB 251023B: Swift-UVOT Upper Limits
  80. GRB 251027A: Swift-XRT observations
  81. Konus-Wind detection of GRB 251016A (short/hard)
  82. GRB 251026A: Swift-XRT observations
  83. GRB 251025B: Swift-XRT afterglow detection
  84. GRB 251024A: Swift-XRT refined Analysis
  85. GRB 251025B: MASTER OT detection
  86. GRB 251022A: Swift-XRT detection of GOTO25iym
  87. EP#01709247298: Swift-XRT counterpart detection
  88. GRB 251022A: MASTER OT detection
  89. GRB 251018A: Swift-XRT refined Analysis
  90. GRB 251016A: Swift-XRT afterglow detection
  91. GRB 251016A: Swift/UVOT Detection
  92. GRB 251017A: Swift-XRT refined Analysis
  93. GRB 251018A: MASTER OT detection
  94. sb25101602: Swift-XRT counterpart detection
  95. GRB 251014A: Swift-XRT observations
  96. GRB 251013D: Swift/UVOT Observations
  97. GRB 251013C: Swift/UVOT Detection
  98. GRB 251013D: Swift-XRT observations
  99. GRB 251014B: Swift-XRT observations
  100. GRB 251014D: Swift-XRT afterglow detection

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