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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.

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subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"

24603 results found.

  1. GRB 250504A: REM optical/NIR observations
  2. GRB 250502A: REM optical/NIR observations
  3. GRB 250504A: MeerLICHT optical afterglow detection
  4. GRB 250504A: Fermi GBM Observation
  5. GRB 250504A: Enhanced Swift-XRT position
  6. Fermi GRB 250504A: Global MASTER-Net observations report
  7. GRB 250504A: Swift detection of a burst
  8. GRB 250502A: Swift/UVOT Follow up
  9. GRB 250502A: Mondy and Tien-Shan Optical Observations
  10. GRB 250502A: KAIT optical observations
  11. GRB 250502A: Montarrenti Observatory optical detection
  12. GRB 250502A: Swift-XRT afterglow detection
  13. GRB 250502A: NOT optical observations
  14. GRB 250502B: AstroSat CZTI detection
  15. GRB 250502A: AKO Optical Afterglow Detection
  16. GRB 250502A: LCO optical counterpart detection
  17. GRB 250502A: Redshift from OSIRIS+/GTC z = 2.163
  18. GRB 250407A: VZLUSAT-2 detection
  19. Fermi-LAT Gamma-ray Observations of IceCube-250429A
  20. GRB 250502B: DDOTI Optical Observations
  21. GRB 250430A: Swift-XRT refined Analysis
  22. GRB 250502A: Early optical counterpart detection by LCO.
  23. GRB 250430A: Swift/UVOT Detection
  24. GRB 250502A: TRT optical afterglow confirmation
  25. GRB 250430A: Enhanced Swift-XRT position
  26. GRB 250502A: SVOM/COLIBRÍ (FM-GFT) Detection of a Bright Optical Counterpart Candidate
  27. GRB 250502A: SVOM detection of a burst
  28. GRB 250430A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  29. GRB 250430A: KAIT optical observations
  30. GRB 250430A / EP250430a: J-band upper limits with WINTER
  31. GRB 250430A: NUTTelA-TAO Early Measurements
  32. GRB 250430A: DDOTI Optical Observations
  33. GRB 250430A: Leavitt Observatory optical upper limit
  34. GRB 250430A: Bassano Bresciano Observatory upper limit
  35. GRB 250430A : MITSuME Akeno optical upper limits
  36. SVOM/sb25043004: EP-FXT observations
  37. EP250430a/GRB 250430A: Einstein Probe WXT detection of the X-ray prompt emission
  38. GRB 250424A: CALET Gamma-Ray Burst Monitor detection
  39. IceCube-250429A: Upper limits from a search for additional neutrino events in IceCube
  40. IceCube-250426A: Upper limits from a search for additional neutrino events in IceCube
  41. GRB 250430A: AKO Optical Afterglow Detection
  42. GRB 250430A: Kanata optical upper limit
  43. EP 250427A: Optical counterpart detection by LCO.
  44. GRB 250430A: Swift detection of a burst with optical counterpart
  45. EP250427a/GRB250427A: HCT optical follow-up
  46. SVOM/sb25043004: SVOM detection of a X-ray transient
  47. EP250428b: GROWTH-India telescope optical upper limit
  48. EP250428b: SAO RAS optical upper limit
  49. EP250428b: LAST optical upper limit
  50. GRB 250427A: Swift/UVOT Detection
  51. EP250428b: Global MASTER-Net observations report
  52. EP250428b: Einstein Probe detection of a fast X-ray transient
  53. Fermi-LAT Gamma-ray Observations of IceCube-250426A
  54. EP250427a: Lesedi optical counterpart detection
  55. EP250427A: COLIBRÍ Continuing Optical Observations
  56. GRB250427A/EP250427a GIT optical afterglow detection:
  57. EP250427a: LT optical counterpart detection
  58. GRB 250427A: Swift-XRT refined Analysis
  59. EP250427a / GRB 250427A: LCO optical counterpart detection
  60. EP250427a: REM optical/NIR afterglow detection
  61. GRB 250424A: LCO optical observation
  62. GRB 250427A/ EP250427a: Fermi-GBM Sub-Threshold Detection
  63. EP250427A: COLIBRÍ Optical Detection
  64. EP250427a: TRT optical counterpart detection
  65. EP250427a: Einstein Probe detection of a fast X-ray transient
  66. GRB 250424A: Swift-BAT refined analysis
  67. GRB 250424A: SVOM/GRM observation of a long burst
  68. GRB 250424A: PRIME near-infrared detection
  69. GRB 250424A: WINTER J-band detection
  70. GRB 250424A: EIRSAT-1 GMOD Detection
  71. IceCube-250416A: Upper limits from a search for additional neutrino events in IceCube
  72. IceCube-250421A: Upper limits from a search for additional neutrino events in IceCube
  73. GRB 250419A: Mondy Optical Observations
  74. GRB 250424A: Swift/UVOT Detection
  75. Fermi-LAT gamma-ray observations of IceCube-250421A
  76. GRB 250424A: Skynet Optical Observations
  77. GRB 250424A: Kilonova-Catcher optical afterglow detection
  78. GRB 250330B: GRBAlpha detection
  79. GRB 250424A: Swift-XRT refined Analysis
  80. GRB 250424A: Enhanced Swift-XRT position
  81. GRB 250424A: AstroSat CZTI detection of a bright long burst
  82. GRB 250424A: COLIBRÍ Detection of a Bright Optical Counterpart
  83. GRB 250424A: BlackGEM optical afterglow detection
  84. GRB 250424A: DDOTI Afterglow Detection
  85. GRB 250424A: REM optical/NIR afterglow detection
  86. GRB 250424A: Swift detection of a burst with an optical counterpart
  87. Swift GRB250424A: Global MASTER-Net OT detection
  88. LIGO/Virgo/KAGRA S250328ae: Subaru/PFS Spectroscopic Follow up and Candidates
  89. EP250421a: Nickel optical upper limit
  90. EP250421a: Upper limits from Fermi-GBM Observations
  91. SVOM/sb25042207: SVOM detection of an X-ray transient
  92. IceCube-250421A: DDOTI Detection of the LAST Candidate
  93. GRB 250419A: Mephisto Multi-band Optical Detection
  94. GRB 250419A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  95. IC-250421A: LAST optical observations of the IceCube neutrino candidate
  96. EP250421a: NOT optical observations
  97. GRB 250419A: Optical Observations via Virtual Telescope Project
  98. EP250421a: REM optical upper limit
  99. EP250421A: COLIBRÍ Optical Upper Limit
  100. GRB 250419A: Mondy Continued Optical Observations

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