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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"

3400 results found.

  1. EP260131a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  2. GRB 260127B: Swift-XRT observations
  3. GRB 260127A: Swift-XRT refined Analysis
  4. GRB 260127A: Prompt enhanced Swift-XRT position
  5. GRB 260125A: Swift-XRT observations
  6. EP260126a: EP-FXT follow-up observation
  7. GRB 260120B: Swift-XRT refined Analysis
  8. EP260119a: update of EP-FXT follow-up observation
  9. GRB 260117A: Swift-XRT afterglow detection
  10. Swift GRB260118.48: Global MASTER-Net observations report
  11. GRB 260117A: Swift-XRT observations
  12. GRB 260114A: VLT/HAWK-I near-infrared upper limits
  13. GRB 260114A: Swift-XRT refined Analysis
  14. GRB 260111A: Swift-XRT observations
  15. Swift Trigger 1439093: is probably not GRB 260113A
  16. Swift Trigger 1434591: possible GRB 260109C
  17. GRB 260102A: Swift-XRT afterglow detection
  18. GRB 260104A: Swift-XRT refined Analysis
  19. GRB 260102A: Swift-XRT observations
  20. GRB 260101A: Swift-XRT refined Analysis
  21. GRB 251230A: Swift-XRT refined Analysis
  22. GRB 251222A: NUTTelA-TAO Early Measurements
  23. GRB 251222A: Swift-XRT afterglow detection
  24. GRB 251221A: Swift-XRT refined Analysis
  25. EP251220a: EP-FXT follow-up observation
  26. GRB 251215A: Swift-XRT afterglow detection
  27. GRB 251215A: Swift/UVOT Upper LImits
  28. GRB 251215A: Swift-XRT observations
  29. GRB 251214B: Swift-XRT refined Analysis
  30. GRB 251214B : MASTER optical afterglow detection
  31. EP251212a: EP-FXT follow-up observation
  32. GRB 251208B: Swift-XRT afterglow detection
  33. GRB 251208D: Swift-XRT observations
  34. GRB 251208B: Fermi-LAT detection
  35. GRB 251205A: FTW optical and NIR observations
  36. GRB 251205A: Swift-XRT refined Analysis
  37. GRB 251203C: Swift/UVOT Upper Limit
  38. Swift GRB 251205A : MASTER OT detection with host galaxy
  39. GRB 251203B: Swift-XRT observations
  40. GRB251129A/EP251129a: Swift UVOT detection
  41. GRB 251202A: Swift-XRT afterglow detection
  42. GRB 251201B: Swift-XRT refined Analysis
  43. Swift GRB 251201B : MASTER optical counterpart detection
  44. EP251130a: Swift-XRT counterpart detection
  45. SVOM GRB 251129A : MASTER optical counterpart detection
  46. GRB 251129A: Swift-XRT afterglow detection
  47. GRB 251126A: Swift-XRT refined Analysis
  48. GRB 251126A: Prompt enhanced Swift-XRT position
  49. Fermi GRB 251125B : MASTER OT J155558.56+581224.1 optical counterpart discovery
  50. EP251124a: Swift-XRT observations
  51. LIGO/Virgo/KAGRA S251105aj: EP-FXT follow-up observations and preliminary results on SVOM J2320.0-2901
  52. GRB 251116C: Swift-XRT confirmation of fading
  53. GRB 251118A: Swift/UVOT Detection
  54. GRB 251118A: Swift-XRT afterglow detection
  55. GRB 251117A: Swift-XRT observations
  56. GRB 251118A: Fermi-LAT detection
  57. GRB 251115A: Swift-XRT observations
  58. LIGO/Virgo/KAGRA S251112cm: J-GEM follow-up observations
  59. GRB 251116C: Swift-XRT observations
  60. LIGO/Virgo/KAGRA S251116en: Identification of a GW compact binary merger candidate
  61. LIGO/Virgo/KAGRA S251112cm: Swift XRT observations, 20 X-ray sources
  62. GRB 251111A: Swift-XRT afterglow detection
  63. GRB 251111A: Swift-XRT observations
  64. GRB 251013C: Chandra X-ray observations and jet break detection
  65. GRB 251106A: Swift/UVOT Upper Limits
  66. SVOM GRB251108.54: Global MASTER-Net observations report
  67. GRB 251106A: Swift-XRT afterglow detection
  68. GRB 251106A: MASTER optical observations
  69. EP251102a: update of EP-FXT follow-up observation
  70. GRB 251103B: Swift-XRT refined Analysis
  71. GRB 251103B: Prompt enhanced Swift-XRT position
  72. GRB 251103A: Swift-XRT afterglow detection
  73. GRB 251022A: Swift-XRT confirmation of fading
  74. GRB 251026A/EP251026a: EP-FXT follow-up observation
  75. GRB 251025B: Swift-XRT confirmation of fading
  76. GRB 251026B: Swift-XRT observations of GOTO25jgl/AT2025absf
  77. GRB 251023B: Swift-UVOT Upper Limits
  78. GRB 251027A: Swift-XRT observations
  79. Konus-Wind detection of GRB 251016A (short/hard)
  80. GRB 251026A: Swift-XRT observations
  81. GRB 251025B: Swift-XRT afterglow detection
  82. GRB 251024A: Swift-XRT refined Analysis
  83. GRB 251025B: MASTER OT detection
  84. GRB 251022A: Swift-XRT detection of GOTO25iym
  85. EP#01709247298: Swift-XRT counterpart detection
  86. GRB 251022A: MASTER OT detection
  87. GRB 251018A: Swift-XRT refined Analysis
  88. GRB 251016A: Swift-XRT afterglow detection
  89. GRB 251016A: Swift/UVOT Detection
  90. GRB 251017A: Swift-XRT refined Analysis
  91. GRB 251018A: MASTER OT detection
  92. sb25101602: Swift-XRT counterpart detection
  93. GRB 251014A: Swift-XRT observations
  94. GRB 251013D: Swift/UVOT Observations
  95. GRB 251013C: Swift/UVOT Detection
  96. GRB 251013D: Swift-XRT observations
  97. GRB 251014B: Swift-XRT observations
  98. GRB 251014D: Swift-XRT afterglow detection
  99. GRB 251013C: Swift-XRT counterpart detection
  100. GRB 251011B inspection: MASTER orphan GRB detection

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