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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"

24988 results found.

  1. GRB 250516A: COLIBRÍ optical upper limit
  2. EP-WXT trigger (ID: 01709176312): a new X-ray outburst of HMXB RX J0111.2-7317
  3. GRB 250515A: Swift-XRT observations
  4. GRB 250515A:COLIBRÍ optical observations of the GOTO candidate
  5. GRB 250515A: 1.6m Mephisto optical detection
  6. GRB 250516A: Fermi GBM Observation
  7. GRB 250516A: Swift-XRT refined Analysis
  8. GRB 250516A: Swift/UVOT Detection
  9. GRB 250516B: GECAM-B detection of a bright long burst
  10. GRB 250516A: Enhanced Swift-XRT position
  11. GRB 250516A: Swift detection of a burst
  12. MAXI GRB250515.65: Global MASTER-Net observations report
  13. GRB 250424A: COLIBRÍ detection of the associated supernova
  14. GRB 250502A: TESS observations
  15. GRB 250509A: Swift-BAT refined analysis
  16. Fermi GRB 250512A: Global MASTER-Net observations report
  17. EP250512a/GRB 250512B: REM optical/NIR observations
  18. EP250511a: Koshka Zeiss-1000 Optical Upper Limit
  19. GRB 250507B: AstroSat CZTI detection
  20. EP250511a: Gemini optical counterpart observation
  21. EP250512a/GRB 250512B refined analysis of the EP-WXT and EP-FXT observations
  22. EP250511a: Mephisto optical upper limits
  23. GRB 250512B: SVOM detection of a burst
  24. EP250512a: Einstein Probe detection of an X-ray transient
  25. EP250511a: REM optical/NIR observations
  26. EP250511a: Einstein Probe follow-up obsevation and refined analysis
  27. EP250511a: COLIBRÍ optical counterpart candidate
  28. EP250511a: BOOTES-5 optical upper limit
  29. EP250511a: Einstein Probe detection of an X-ray transient
  30. EP250508a: Gemini NIR upper limits
  31. GRB 250510B: Fermi GBM Observation
  32. GRB 250510A: Swift-XRT observations
  33. GRB 250509A: Fermi GBM Observation
  34. IceCube-250506A: No Transient Candidates from the Zwicky Transient Facility
  35. GRB 250510B: Swift/BAT-GUANO localization skymap of a burst
  36. GRB 250510A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  37. GRB 250509A: Swift-XRT refined Analysis
  38. GRB 250510A: SVOM possible detection of a burst
  39. GRB 250507A: J-band observations with WINTER
  40. GRB 250509A: Enhanced Swift-XRT position
  41. GRB 250509A: Swift detection of a burst
  42. GRB 250506A: NOT optical upper limits
  43. EP250508a: Liverpool Telescope optical upper limits
  44. EP250508a: KAIT optical upper limit
  45. GRB 250507A: KAIT optical upper limit
  46. EP250508a: refined analysis of the EP-WXT and EP-FXT observations
  47. GRB 250505B: SVOM/GRM observation of a short burst
  48. GRB 250502A: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  49. EP250508a: REM optical/NIR observations
  50. GRB 250506A: Swift-XRT afterglow detection
  51. EP250508a: COLIBRÍ Optical Limit
  52. EP250508a: Einstein Probe detection of an X-ray transient
  53. GRB 250507A: Swift-XRT refined Analysis
  54. IceCube-250506A: Upper limits from a search for additional neutrino events in IceCube
  55. GRB 250506A: Swift/UVOT Upper Limits
  56. GRB 250507A: follow-up observation with EP-FXT
  57. GRB 250506A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  58. GRB 250507A: REM optical/NIR observations
  59. GRB 250507A: SVOM/VT optical upper limit
  60. GRB 250506A: Swift-XRT observations
  61. Fermi-LAT Gamma-ray Observations of IceCube-250506A
  62. GRB 250507A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  63. EP-WXT trigger 01709175213: a new X-ray outburst of LMXB MAXI J1957+032
  64. GRB 250507A: SVOM detection of a long burst
  65. GRB 250506A: Mephisto optical upper limits
  66. GRB 250504A: EIRSAT-1 GMOD Detection
  67. GRB 250502A: Bassano Bresciano Observatory upper limit
  68. GRB 250506A: Xinglong 2.16m optical upper limit
  69. SVOM/sb25050601: EP-FXT observations
  70. GRB 250506A: SVOM improved position and MXT detection of a fading X-ray afterglow
  71. GRB 250506A: REM optical/NIR upper limits
  72. GRB 250506A: Fermi GBM Observation
  73. GRB 250506A: Swift XRT observations and possible counterpart detection
  74. GRB 250506A: TRT optical observations
  75. GRB 250506A: SVOM/COLIBRÍ (FM-GFT) Upper Limits on the Optical Counterpart
  76. GRB 250506A: SVOM detection of a burst
  77. GRB 250504A: Swift-BAT refined analysis
  78. GRB 250430A: Swift-BAT refined analysis
  79. GRB 250504A: Swift-XRT refined Analysis
  80. GRB 250504A: VLT/X-shooter upper limits
  81. GRB 250504A: REM optical/NIR observations
  82. GRB 250502A: REM optical/NIR observations
  83. GRB 250504A: MeerLICHT optical afterglow detection
  84. GRB 250504A: Fermi GBM Observation
  85. GRB 250504A: Enhanced Swift-XRT position
  86. Fermi GRB 250504A: Global MASTER-Net observations report
  87. GRB 250504A: Swift detection of a burst
  88. GRB 250502A: Swift/UVOT Follow up
  89. GRB 250502A: Mondy and Tien-Shan Optical Observations
  90. GRB 250502A: KAIT optical observations
  91. GRB 250502A: Montarrenti Observatory optical detection
  92. GRB 250502A: Swift-XRT afterglow detection
  93. GRB 250502A: NOT optical observations
  94. GRB 250502B: AstroSat CZTI detection
  95. GRB 250502A: AKO Optical Afterglow Detection
  96. GRB 250502A: LCO optical counterpart detection
  97. GRB 250502A: Redshift from OSIRIS+/GTC z = 2.163
  98. GRB 250407A: VZLUSAT-2 detection
  99. Fermi-LAT Gamma-ray Observations of IceCube-250429A
  100. GRB 250502B: DDOTI Optical Observations

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