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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"

5402 results found.

  1. Fermi GRB 250510B: Global MASTER-Net observations report
  2. GRB 250510A: Swift-XRT observations
  3. GRB 250509A: Prompt enhanced Swift-XRT position
  4. Fermi GRB 250509A: Global MASTER-Net observations report
  5. EP250508a: follow-up observation with EP-FXT
  6. EP250508a: Einstein Probe detection of an X-ray transient
  7. EP#01709175213/IGR J19566+0326: Swift-XRT detection
  8. GRB 250506A: SVOM/COLIBRÍ (FM-GFT) Upper Limits on the Optical Counterpart
  9. GRB 250504A: VLT/X-shooter upper limits
  10. GRB 250502A: Mondy and Tien-Shan Optical Observations
  11. Fermi trigger No 767975731: Global MASTER-Net observations report
  12. GRB 250430A: Kanata optical upper limit
  13. EP250427a: LT optical counterpart detection
  14. GRB 250330B: GRBAlpha detection
  15. IceCube-250421A: DDOTI Detection of the LAST Candidate
  16. EP250421A: COLIBRÍ Optical Upper Limit
  17. GRB 250419A: Mondy Continued Optical Observations
  18. IceCube Alert 250421.71: Global MASTER-Net observations report
  19. GRB 250419A: LCO optical afterglow multi-band observations
  20. GRB 250419A: MASTER optical afterglow observation
  21. GRB 250407A: GTC/OSIRIS+ spectroscopic redshift z = 1.36
  22. GRB 250419A: GOTO optical counterpart detection
  23. GRB 250419A: SVOM/COLIBRÍ (FM-GFT) Detection of the Optical Counterpart
  24. IceCube-250416A: DDOTI Optical Observations
  25. EP250416a: Gemini South-GMOS optical counterpart
  26. EP250225a: SVOM/VT optical brightening
  27. IceCube 250414.324: DDOTI Optical Observations
  28. EP250404a: Nanshan 0.43m Telescope optical observatios
  29. Fermi trigger No 766148493: Global MASTER-Net observations report
  30. Fermi trigger No 766173972: Global MASTER-Net observations report
  31. GRB 250407A: Continued KAIT/Nickel optical observations
  32. GRB 250320B: cubesat Avion detection
  33. IceCube-250406A: Swift-XRT observations
  34. EP250407a: Global MASTER-Net observations report
  35. GRB 250407A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  36. IceCube-250406A: No candidates from the Zwicky Transient Facility
  37. Fermi GRB 250407A: Global MASTER-Net observations report
  38. IceCube 250406A: DDOTI Optical Observations of the Refined Position
  39. IPN triangulation of GRB 250406B (short/hard)
  40. IceCube 250406.951: COLIBRÍ/DDRAGO Optical Upper Limit
  41. IceCube 250406.951: DDOTI Optical Observations
  42. Fermi GRB 250406A: Global MASTER-Net observations report
  43. Fermi trigger No 765619921: Global MASTER-Net observations report
  44. EP250404a / GRB 250404A: J band observations by SYSU 80cm telescope
  45. GRB 250402A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  46. EP250402a: Optical upper limit with PD 1.3m observations
  47. GRB 250403A: AstroSat CZTI detection
  48. Fermi GRB 250404A: Global MASTER-Net observations report
  49. EP250404a: Xinglong decaying optical counterpart
  50. GRB 250403A: Montarrenti Observatory optical detection
  51. EP250404a: Global MASTER-Net observations report
  52. GRB 250403A: Fermi GBM observations
  53. GRB 250327B: VIRT Optical Upper Limit
  54. EP250404a: Mephisto multi-band optical detection
  55. GRB 250402A: Mondy optical observations
  56. GRB 250403A: Swift/UVOT Detection
  57. GRB 250402A: Swift/UVOT Upper Limits
  58. GRB 250403A: REM NIR afterglow detection
  59. GRB 250403A: LCO optical counterpart detection
  60. IceCube-250330A: MASTER detection of PKS 2032+107 blazar flare with Zhirkov effect
  61. GRB 250403A: JinShan optical observations
  62. GRB 250402A: EP-FXT afterglow detection
  63. Fermi GRB 250403A: Global MASTER-Net observations report
  64. GRB 250403A: GOTO optical counterpart follow-up observations
  65. GRB 250403A: GMG Optical Observation
  66. GRB 250403A: 1.6m Mephisto multi-band optical detection
  67. GRB 250403A: GOTO detection of the optical afterglow
  68. GRB250402A: SVOM/COLIBRÍ (FM-GFT) Detection of the Optical Counterpart
  69. GRB 250402A: REM optical/NIR upper limits
  70. GRB 250402A: LCO optical counterpart detection
  71. GRB 250331C: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  72. GRB 250331E: SVOM/GRM observation
  73. GRB250331D: AbAO optical observations
  74. GRB 250328A: AbAO AS-32 Optical Observations
  75. GRB 250322B: GRBAlpha detection
  76. GRB 250331D: Swift-XRT observations
  77. GRB 250330B: SVOM/GRM observation of a short burst
  78. Fermi GRB 250331E: Global MASTER-Net observations report
  79. Fermi GRB 250331D: Global MASTER-Net observations report
  80. GRB 250330B: EIRSAT-1 GMOD Detection
  81. GRB 250329A: AbAO, Mondy and SAO RAS optical upper limits
  82. Fermi trigger No 765078057: Global MASTER-Net observations report
  83. Swift GRB 250331C: Global MASTER-Net observations report
  84. Swift GRB 250331B: Global MASTER-Net observations report
  85. GRB 250331D: Swift/BAT-GUANO arcminute localization of a burst during slew
  86. GRB 250331C: Enhanced Swift-XRT position
  87. IceCube-250330A: Upper limits from a search for additional neutrino events in IceCube
  88. GRB 250320C : SVOM detection of a burst through offline search
  89. Fermi-LAT gamma-ray observations of IceCube-250330A
  90. SVOM/sb25033102 is a false trigger
  91. GRB 250331C: COLIBRÍ/DDRAGO optical upper limit
  92. GRB 250331B: COLIBRÍ/DDRAGO optical upper limit
  93. GRB 250331C: Prompt enhanced Swift-XRT position
  94. GRB 250331C: Swift detection of a burst
  95. GRB 250330A: SVOM/VT optical upper limit
  96. GRB 250331A: MAXI/GSC detection
  97. SVOM/sb25033102: SVOM detection of an X-ray transient
  98. LIGO/Virgo/KAGRA S250331o: Identification of a GW compact binary merger candidate
  99. Fermi GRB 250330B: Global MASTER-Net observations report
  100. Fermi GRB 250330A: Global MASTER-Net observations report

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