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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"

20968 results found.

  1. SVOM/sb25041603: SVOM/COLIBRÍ (FM-GFT) Upper Limit on the Optical Counterpart
  2. IceCube 250414.324: DDOTI Optical Observations
  3. GRB 250413A: AstroSat CZTI detection
  4. EP250304a: ATCA radio observations
  5. GRB 250412A: AstroSat CZTI detection
  6. EP250404a: Nanshan 0.43m Telescope optical observatios
  7. GRB 250411A: DDOTI Optical Observations
  8. GRB 250314A: e-MERLIN observations
  9. GRB 250407A: Mondy and AbAO Optical Observations
  10. EP250227a: Further NOT optical observations
  11. GRB 250320B: cubesat Avion detection
  12. IceCube-250406A: Swift-XRT observations
  13. IPN triangulation of GRB 250321D (consistent with the fast X-ray transient EP250321a)
  14. IPN triangulation of GRB 250407A
  15. GRB 250407A: LCO detection of a fading optical counterpart
  16. EP250407a: Swift-XRT observations
  17. GRB 250407A: SVOM/GRM observation of a bright long burst
  18. GRB 250407A: EP-WXT afterglow detection
  19. EP250407a: EP-WXT detection of a fast X-ray transient
  20. GRB 250407A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  21. GRB 250407A: KAIT Optical Afterglow Candidate
  22. IceCube-250406A: No candidates from the Zwicky Transient Facility
  23. GRB 250407A: Swift-XRT afterglow detection
  24. IceCube 250406A: DDOTI Optical Observations of the Refined Position
  25. IPN triangulation of GRB 250406B (short/hard)
  26. IceCube 250406.951: COLIBRÍ/DDRAGO Optical Upper Limit
  27. IceCube 250406.951: DDOTI Optical Observations
  28. Fermi trigger No 765663719: Global MASTER-Net observations report
  29. EP250404a: Multi-band Optical Observations from UCAS-70 and XL-C14
  30. GRB 250404A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  31. EP250404a / GRB 250404A: Montarrenti Observatory optical observations
  32. GRB 250404A / EP250404a: SVOM/GWAC-F60 and F50 observations
  33. EP250404a / GRB 250404A: J band observations by SYSU 80cm telescope
  34. EP250404a: refined analysis of the EP-WXT and EP-FXT observations
  35. GRB 250404A / EP250404a: Leavitt Observatory optical counterpart detection
  36. GRB 250402A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  37. EP250402a: Optical upper limit with PD 1.3m observations
  38. GRB 250404A / EP250404a: NOT optical observations
  39. GRB 250331D: Swift-XRT afterglow detection
  40. GRB 250403A: AstroSat CZTI detection
  41. EP250404a: Osservatorio Astronomico "Nastro Verde" optical observations: detection of an optical counterpart
  42. EP250404a: REM optical/NIR observations
  43. EP250404a: Seimei/TriCCS optical counterpart detection
  44. EP250404A: COLIBRÍ/DDRAGO Optical Observations
  45. EP250404A / GRB250404A: Ondrejov D50 optical afterglow detection
  46. EP250404a: LCO optical counterpart detection
  47. EP250404a: Xinglong decaying optical counterpart
  48. GRB 250403A: Montarrenti Observatory optical detection
  49. GRB 250403A: KAIT optical observations
  50. EP250404a: AKO Optical Afterglow Detection
  51. EP250404a: LAST detection of optical counterpart
  52. GRB 250402A: Swift/BAT-GUANO localization skymap of a burst
  53. GRB 250327B: VIRT Optical Upper Limit
  54. EP250404a: Mephisto multi-band optical detection
  55. EP250321A: J band upper limit by SYSU 80cm telescope
  56. EP250404a: Nanshan/HMT optical counterpart detection
  57. EP250404a: Einstein Probe detection of an X-ray transient
  58. GRB 250403A: Swift/UVOT Detection
  59. GRB 250402A: Swift/UVOT Upper Limits
  60. EP250402a: Optical upper limit with Kinder observations
  61. GRB 250403A: REM NIR afterglow detection
  62. GRB 250403A: LCO optical counterpart detection
  63. IceCube-250330A: MASTER detection of PKS 2032+107 blazar flare with Zhirkov effect
  64. GRB 250403A: JinShan optical observations
  65. GRB 250403A: Optical counterpart detection by LCO.
  66. GRB 250322A: 10 GHz VLA radio upper limits
  67. GRB 250403A: GMG Optical Observation
  68. GRB 250403A: 1.6m Mephisto multi-band optical detection
  69. GRB 250403A: SVOM/C-GFT optical observations
  70. GRB 250403A: Fermi GBM Final Real-time Localization
  71. GRB 250225B: VLT host galaxy redshift z = 0.950
  72. GRB250402A: SVOM/COLIBRÍ (FM-GFT) Detection of the Optical Counterpart
  73. GRB 250402A: VLT/FORS2 spectroscopic redshift z = 2.823
  74. GRB 250402A: REM optical/NIR upper limits
  75. GRB 250402A: LCO optical counterpart detection
  76. EP250402a: Einstein Probe detection of a fast X-ray transient
  77. GRB 250402A: SVOM/VT optical counterpart
  78. GRB 250402A: SVOM detection of a burst
  79. GRB 250331C: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  80. GRB 250329B: Swift/UVOT Upper Limit
  81. GRB 250329A: Swift/UVOT Upper Limit
  82. GRB 250327B: Swift/UVOT Detection
  83. GRB 250327A: Swift/UVOT Upper Limits
  84. GRB 250331E: SVOM/GRM observation
  85. GRB 250327B: Kilonova-Catcher Observations
  86. GRB250331D: AbAO optical observations
  87. GRB 250331C: Swift/UVOT Upper Limits
  88. GRB 250331B: Swift/UVOT Upper Limits
  89. GRB 250328A: AbAO AS-32 Optical Observations
  90. GRB 250219A: NOT candidate host galaxy detection
  91. GRB 250331D: Swift-XRT observations
  92. GRB 250322B possible detection by the AstroSat Satellite
  93. GRB 250330B: SVOM/GRM observation of a short burst
  94. GRB 250329A: AbAO, Mondy and SAO RAS optical upper limits
  95. GRB 250331C: Enhanced Swift-XRT position
  96. LIGO/Virgo/KAGRA S250331o: NED Galaxies in the 3-Initial Localization Volume
  97. GRB 250331B: Enhanced Swift-XRT position
  98. LIGO/Virgo/KAGRA S250328ae: Swift XRT observations, 34 possible X-ray sources
  99. GRB 250330A: VLT/FORS2 Afterglow Detection
  100. GRB20250327B: 45th Parallel Observatory upper limit

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