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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').
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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"

2730 results found.

  1. EP250512a: Global MASTER-Net observations report
  2. Fermi GRB 250510C: Global MASTER-Net observations report
  3. Fermi GRB 250510B: Global MASTER-Net observations report
  4. IceCube-250506A: No Transient Candidates from the Zwicky Transient Facility
  5. EP250508a: Global MASTER-Net observations report
  6. EP250508a: Einstein Probe detection of an X-ray transient
  7. IceCube Alert 250506.59: Global MASTER-Net observations report
  8. GRB 250504A: Swift-XRT refined Analysis
  9. EP250428b: SAO RAS optical upper limit
  10. EP250427a / GRB 250427A: LCO optical counterpart detection
  11. GRB 250424A: BlackGEM optical afterglow detection
  12. IceCube-250421A: DDOTI Detection of the LAST Candidate
  13. IceCube Alert 250421.71: Global MASTER-Net observations report
  14. IceCube-Cascade 250414A: Upper limits from a search for additional neutrino events in IceCube
  15. GRB 250419A: MASTER optical afterglow observation
  16. Konus-Wind detection of GRB 250416C (a counterpart of EP250416a)
  17. EP250416a: Global MASTER-Net observations report
  18. EP250404a: Nanshan 0.43m Telescope optical observatios
  19. Fermi trigger No 766173972: Global MASTER-Net observations report
  20. GRB 250407A: KAIT Optical Afterglow Candidate
  21. IceCube-250406A: No candidates from the Zwicky Transient Facility
  22. GRB 250407A: Swift-XRT afterglow detection
  23. Fermi GRB 250407A: Global MASTER-Net observations report
  24. IceCube 250406.951: COLIBRÍ/DDRAGO Optical Upper Limit
  25. Fermi GRB 250406A: Global MASTER-Net observations report
  26. GRB 250404A / EP250404a: Leavitt Observatory optical counterpart detection
  27. Fermi GRB 250404A: Global MASTER-Net observations report
  28. EP250404a: Xinglong decaying optical counterpart
  29. GRB 250404A: Fermi GBM Detection
  30. EP250404a: AKO Optical Afterglow Detection
  31. GRB 250331B Swift-BAT refined analysis
  32. Fermi GRB 250331E: Global MASTER-Net observations report
  33. LIGO/Virgo/KAGRA S250328ae: Swift XRT observations, 34 possible X-ray sources
  34. Fermi GRB 250330A: Global MASTER-Net observations report
  35. GRB 250330A: Prompt Swift-XRT position
  36. Swift GRB250330.26: Global MASTER-Net observations report
  37. GRB 250327B: ALMA detection
  38. GRB 250327B: VLA detection
  39. GRB 250329A: Fading optical counterpart detection by LCO.
  40. GRB 250327B: SVOM/VT optically bright counterpart
  41. GRB 250327B: SAO RAS optical candidate
  42. GRB 250327A: Fermi GBM observation
  43. GRB 250321C: Fermi GBM Final Real-time Localization
  44. GRB 250317B: Mondy AZT-33IK Continued Optical Observations
  45. FRB 20250316A: Upper limits for gamma-ray transient from Insight-HXMT/HE observations
  46. GRB 250317D: EIRSAT-1 GMOD Detection
  47. EP250315a: Einstein Probe detection of an X-ray transient
  48. GRB 250226A: Mondy AZT-33IK and Koshka Zeiss-1000 Optical Upper Limits
  49. Fermi trigger No 763581136: Global MASTER-Net observations report
  50. Fermi GRB 250313A: Global MASTER-Net observations report
  51. GRB 250313A: Fermi GBM Final Real-time Localization
  52. EP250302a: Chandra X-ray Detection
  53. Fermi trigger No 763509110: Global MASTER-Net observations report
  54. GRB 250311A: Swift-XRT observations
  55. EP250311a: Global MASTER-Net observations report
  56. GRB 250225B: Swift-BAT refined analysis
  57. GRB 250309B / AT2025dws: SAO RAS optical observations
  58. Fermi GRB 250309A: Global MASTER-Net observations report
  59. GRB250309B: One candidate counterpart from the Zwicky Transient Facility
  60. IceCube-250309A: No candidates from the Zwicky Transient Facility
  61. IceCube Alert 250309.32: Global MASTER-Net observations report
  62. Fermi trigger No 762963055: Global MASTER-Net observations report
  63. Fermi GRB 250305A: Global MASTER-Net observations report
  64. IPN triangulation of GRB 250222A
  65. EP250302a : GIT optical follow-up
  66. Fermi GRB 250302A: Global MASTER-Net observations report
  67. EP250302a: Nanshan/HMT optical counterpart detection
  68. LIGO/Virgo/KAGRA S250206dm: early X-ray upper limits from Einstein Probe WXT and preliminary results of FXT observations
  69. EP250227a: Global MASTER-Net observations report
  70. EP250227a: Optical upper limits with Kinder observations
  71. GRB 250205A / EP250205A: further radio observations with the VLA
  72. Fermi GRB 250226A: Global MASTER-Net observations report
  73. Fermi GRB 250225A: Global MASTER-Net observations report
  74. The EP-WXT trigger 01709131882 is likely a flaring star
  75. EP250223a: LCO detection of the afterglow
  76. Konus-Wind detection of GRB 250217C (short)
  77. Fermi GRB 250217A: Global MASTER-Net observations report
  78. GRB 250217A: Fermi GBM Final Real-time Localization
  79. Fermi GRB 250216A: Global MASTER-Net observations report
  80. EP250215a: Global MASTER-Net observations report
  81. EP250207b: Xinglong optical upper limit
  82. EP250212a: Global MASTER-Net observations report
  83. Fermi trigger No 760945500: Global MASTER-Net observations report
  84. GRB 250211A: SVOM trigger sb25021103 is not a GRB
  85. GRB 250212A: Fermi GBM Final Real-time Localization
  86. IceCube-250207A: One candidate from the Zwicky Transient Facility
  87. EP250207b: Global MASTER-Net observations report
  88. GRB 241128A: VIRT Optical Upper Limit
  89. EP250207b: a new X-ray transient detected by Einstein Probe
  90. LIGO/Virgo/KAGRA S250206dm: Global MASTER-Net observations report
  91. LIGO/Virgo/KAGRA S250206dm: COLIBRÍ/DDRAGO Observations of AT2025bbo and Galaxies in the Localization Volume
  92. LIGO/Virgo/KAGRA S250206dm: GECKO Observation with 7DT and KMTNet
  93. LIGO/Virgo/KAGRA S250206dm: NEWFIRM NIR Observations
  94. IceCube-250203A: No transient candidates from the Zwicky Transient Facility
  95. LIGO/Virgo/KAGRA S250206dm: Candidates from the Zwicky Transient Facility
  96. EP trigger 01709131361 (possible EP250207a): NOT optical observations and flaring star
  97. IPN triangulation of GRB 250201A
  98. GRB 250202B: Fermi GBM Detection
  99. The EP-WXT trigger 01709131153 is not a real source
  100. GRB 250128B: VLA radio upper limit

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