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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"

6791 results found.

  1. GRB 250721A: Swift-XRT observations
  2. GRB 250717B: Swift-XRT observations
  3. GRB 250717B: Fermi GBM Observation
  4. GRB 250716A: Swift-XRT afterglow detection
  5. GRB 250716A: Fermi GBM Observation
  6. GRB 250706B/C: 7DT Follow-up Observations
  7. GRB 250713A: Swift-XRT observations
  8. GRB250702 B,D,E / EP250702a: MOSFIRE imaging of the afterglow
  9. LIGO/Virgo/KAGRA S250701bp: Updated Sky localization
  10. GRB 250706B/C: Konus-Wind analysis of the prompt emission
  11. IceCube-250706A: EP-FXT follow-up observations
  12. Fermi-LAT Gamma-ray Observations of IceCube-250706A
  13. GRB 250706B/C: Fermi-LAT detection
  14. GRB 250706B: Swift/UVOT Detection
  15. EP250702a/ GRB 250702B: NuSTAR X-ray Observations
  16. GRB 250706A: Swift-XRT refined Analysis
  17. GRB 250706B: refined SVOM/MXT data analysis
  18. GRB 250706A: SAO RAS optical observations
  19. GRB250706B: Swift-XRT counterpart detection
  20. GRB 250706B: iTelescope optical observations
  21. GRB 250706A: GROWTH-India Telescope optical upper limit
  22. GRB 250704B: Swift-XRT refined Analysis
  23. EP250702a/GRB 250702B,C,D,E: Archival radio observations from ASKAP VAST
  24. GRB 250704B: Swift/UVOT Upper Limits
  25. GRB 250704A: Swift/UVOT Detection
  26. EP250704a/GRB 250704B VLT/HAWK-I NIR afterglow detection
  27. EP250704a / GRB 250704B: JinShan optical observations
  28. EP250704a / GRB 250704B: SAO RAS optical observations
  29. EP250704a / GRB 250704B : GROWTH-India Telescope optical observations
  30. GRBs 250702B/C/D/E / EP250702a: Swift/UVOT Upper Limits
  31. EP250704a / GRB250704B: Swift-XRT counterpart detection
  32. GRB 250704A: Swift-XRT afterglow detection
  33. Konus-Wind detection of GRB 250702F
  34. GRB 250702F: GROWTH-India Telescope optical observations
  35. GRB 250702F: optical photometry from Konkoly
  36. Fermi GBM Analysis of GRB 250702B (formerly B,D,E); dissociation of C burst
  37. GRB 250702F: Swift-XRT refined Analysis
  38. GRB 250702F: Fermi GBM Observation
  39. GRBs 250702B,C,D,E / EP250702a: Konus-Wind detection of a hard X-ray transient activity
  40. Fermi GBM Triggers 250702B, C, D and E are likely from the same source
  41. GRB 250702A: Fermi GBM Detection
  42. LIGO/Virgo/KAGRA S250701bp: Identification of a GW compact binary merger candidate
  43. GRB 250628B: Swift-XRT observations
  44. GRB 250628A: Swift-XRT refined Analysis
  45. GRB 250625A: Fermi-LAT detection
  46. GRB 250625A: Swift-XRT refined Analysis
  47. GRB250625A: Fermi GBM Observation
  48. GRB 250620B: Fermi GBM Observation
  49. GRB 250625A: SAO RAS possible optical afterglow
  50. GRB 250617B: Mondy and SAO RAS optical observations on 2025-06-23, 2025-06-24
  51. GRB250620A: Fermi GBM Observation
  52. GRB 250619B: Fermi GBM Observation
  53. GRB250620C: Fermi GBM Observation
  54. GRB 250506A - SVOM/ECLAIRs Refined analysis
  55. EP-WXT trigger 01709179036: a new outburst of GRS 1739-278
  56. GRB 250612A / Swift J1643.6−3854: Swift-BAT refined analysis
  57. GRB 250617B: Swift-XRT refined Analysis
  58. GRB 250617B: Fermi GBM Observation
  59. GRB 250617B: SAO RAS optical observations
  60. EP#01709178975: Swift-XRT counterpart detection
  61. GRB 250615A: Swift-XRT refined Analysis
  62. GRB 250615A: Prompt enhanced Swift-XRT position
  63. sb25061207: Mephisto optical upper limits
  64. sb25061218: Swift-XRT observations
  65. sb25061207: EP-FXT follow-up observation and afterglow candidate
  66. GRB 250612B: Fermi GBM Observation
  67. GRB 250612C: Fermi GBM Observation
  68. sb25061207: Swift-XRT observations
  69. GRB 250610B: Swift-XRT refined Analysis
  70. GRB 250610B: Swift/UVOT Detection
  71. EP250610A: Swift/UVOT Upper limits
  72. GRB 250610B: Fermi/GBM sub-threshold detection of a possibly hard burst
  73. GRB 250610B: EP-FXT follow-up observation and afterglow counterpart
  74. GRB 250610B: Swift-XRT counterpart detection
  75. GRB 250609A: Fermi GBM Observation
  76. EP250610a: Swift-XRT counterpart detection
  77. GRB 250605A: Swift-XRT refined Analysis
  78. GRB 250601A: Fermi GBM Observation
  79. GRB 250603A: Swift-XRT refined Analysis
  80. GRB 250602A: Fermi GBM Observation
  81. GRB 250602A: Fermi-LAT detection
  82. GRB 250601A: EP-FXT follow-up observation and afterglow candidates
  83. GRB 250601A: Swift-XRT observations
  84. EP#01709177494: Swift-XRT counterpart detection of known source
  85. GRB 250530C: Swift-XRT refined Analysis
  86. GRB 250530A: Swift-XRT counterpart detection
  87. GRB 250527C: Swift/UVOT Upper Limits
  88. EP J1350.0-8622: EP-FXT follow-up observation
  89. GRB 250527B: Swift-XRT observations
  90. GRB 250521B: EP-FXT follow-up observation and afterglow candidates
  91. EP#01709176612: Swift-XRT counterpart detection of flaring star
  92. GRB 250520A: Swift-XRT refined Analysis
  93. GRB 250520A: Prompt enhanced Swift-XRT position
  94. EP-WXT trigger (ID: 01709176312): a new X-ray outburst of HMXB RX J0111.2-7317
  95. GRB 250515A: Swift-XRT observations
  96. GRB 250516A: Fermi GBM Observation
  97. GRB 250516A: Swift-XRT refined Analysis
  98. EP250508a: Gemini NIR upper limits
  99. GRB 250510B: Fermi GBM Observation
  100. GRB 250510A: Swift-XRT observations

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