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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"

28051 results found.

  1. GRB 250510A: Swift-XRT observations
  2. GRB 250509A: Fermi GBM Observation
  3. IceCube-250506A: No Transient Candidates from the Zwicky Transient Facility
  4. GRB 250510B: Swift/BAT-GUANO localization skymap of a burst
  5. GRB 250510A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  6. GRB 250509A: Swift-XRT refined Analysis
  7. GRB 250510A: SVOM possible detection of a burst
  8. GRB 250507A: J-band observations with WINTER
  9. GRB 250509A: Enhanced Swift-XRT position
  10. GRB 250509A: Swift detection of a burst
  11. GRB 250506A: NOT optical upper limits
  12. EP250508a: Liverpool Telescope optical upper limits
  13. EP250508a: KAIT optical upper limit
  14. GRB 250507A: KAIT optical upper limit
  15. EP250508a: refined analysis of the EP-WXT and EP-FXT observations
  16. GRB 250505B: SVOM/GRM observation of a short burst
  17. GRB 250502A: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  18. EP250508a: REM optical/NIR observations
  19. GRB 250506A: Swift-XRT afterglow detection
  20. EP250508a: COLIBRÍ Optical Limit
  21. EP250508a: Einstein Probe detection of an X-ray transient
  22. GRB 250507A: Swift-XRT refined Analysis
  23. IceCube-250506A: Upper limits from a search for additional neutrino events in IceCube
  24. GRB 250506A: Swift/UVOT Upper Limits
  25. GRB 250507A: follow-up observation with EP-FXT
  26. GRB 250506A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  27. GRB 250507A: REM optical/NIR observations
  28. GRB 250507A: SVOM/VT optical upper limit
  29. GRB 250506A: Swift-XRT observations
  30. Fermi-LAT Gamma-ray Observations of IceCube-250506A
  31. GRB 250507A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  32. EP-WXT trigger 01709175213: a new X-ray outburst of LMXB MAXI J1957+032
  33. GRB 250507A: SVOM detection of a long burst
  34. GRB 250506A: Mephisto optical upper limits
  35. GRB 250504A: EIRSAT-1 GMOD Detection
  36. GRB 250502A: Bassano Bresciano Observatory upper limit
  37. GRB 250506A: Xinglong 2.16m optical upper limit
  38. SVOM/sb25050601: EP-FXT observations
  39. GRB 250506A: SVOM improved position and MXT detection of a fading X-ray afterglow
  40. GRB 250506A: REM optical/NIR upper limits
  41. GRB 250506A: Fermi GBM Observation
  42. GRB 250506A: Swift XRT observations and possible counterpart detection
  43. GRB 250506A: TRT optical observations
  44. GRB 250506A: SVOM/COLIBRÍ (FM-GFT) Upper Limits on the Optical Counterpart
  45. GRB 250506A: SVOM detection of a burst
  46. GRB 250504A: Swift-BAT refined analysis
  47. GRB 250430A: Swift-BAT refined analysis
  48. GRB 250504A: Swift-XRT refined Analysis
  49. GRB 250504A: VLT/X-shooter upper limits
  50. GRB 250504A: REM optical/NIR observations
  51. GRB 250502A: REM optical/NIR observations
  52. GRB 250504A: MeerLICHT optical afterglow detection
  53. GRB 250504A: Fermi GBM Observation
  54. GRB 250504A: Enhanced Swift-XRT position
  55. Fermi GRB 250504A: Global MASTER-Net observations report
  56. GRB 250504A: Swift detection of a burst
  57. GRB 250502A: Swift/UVOT Follow up
  58. GRB 250502A: Mondy and Tien-Shan Optical Observations
  59. GRB 250502A: KAIT optical observations
  60. GRB 250502A: Montarrenti Observatory optical detection
  61. GRB 250502A: Swift-XRT afterglow detection
  62. GRB 250502A: NOT optical observations
  63. GRB 250502B: AstroSat CZTI detection
  64. GRB 250502A: AKO Optical Afterglow Detection
  65. GRB 250502A: LCO optical counterpart detection
  66. GRB 250502A: Redshift from OSIRIS+/GTC z = 2.163
  67. GRB 250407A: VZLUSAT-2 detection
  68. Fermi-LAT Gamma-ray Observations of IceCube-250429A
  69. GRB 250502B: DDOTI Optical Observations
  70. GRB 250430A: Swift-XRT refined Analysis
  71. GRB 250502A: Early optical counterpart detection by LCO.
  72. GRB 250430A: Swift/UVOT Detection
  73. GRB 250502A: TRT optical afterglow confirmation
  74. GRB 250430A: Enhanced Swift-XRT position
  75. GRB 250502A: SVOM/COLIBRÍ (FM-GFT) Detection of a Bright Optical Counterpart Candidate
  76. GRB 250502A: SVOM detection of a burst
  77. GRB 250430A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  78. GRB 250430A: KAIT optical observations
  79. GRB 250430A / EP250430a: J-band upper limits with WINTER
  80. GRB 250430A: NUTTelA-TAO Early Measurements
  81. GRB 250430A: DDOTI Optical Observations
  82. GRB 250430A: Leavitt Observatory optical upper limit
  83. GRB 250430A: Bassano Bresciano Observatory upper limit
  84. GRB 250430A : MITSuME Akeno optical upper limits
  85. SVOM/sb25043004: EP-FXT observations
  86. EP250430a/GRB 250430A: Einstein Probe WXT detection of the X-ray prompt emission
  87. GRB 250424A: CALET Gamma-Ray Burst Monitor detection
  88. IceCube-250429A: Upper limits from a search for additional neutrino events in IceCube
  89. IceCube-250426A: Upper limits from a search for additional neutrino events in IceCube
  90. GRB 250430A: AKO Optical Afterglow Detection
  91. GRB 250430A: Kanata optical upper limit
  92. EP 250427A: Optical counterpart detection by LCO.
  93. GRB 250430A: Swift detection of a burst with optical counterpart
  94. EP250427a/GRB250427A: HCT optical follow-up
  95. SVOM/sb25043004: SVOM detection of a X-ray transient
  96. EP250428b: GROWTH-India telescope optical upper limit
  97. EP250428b: SAO RAS optical upper limit
  98. EP250428b: LAST optical upper limit
  99. GRB 250427A: Swift/UVOT Detection
  100. EP250428b: Global MASTER-Net observations report

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