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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"

6791 results found.

  1. GRB 250509A: Fermi GBM Observation
  2. IceCube-250506A: No Transient Candidates from the Zwicky Transient Facility
  3. GRB 250509A: Swift-XRT refined Analysis
  4. GRB 250506A: Swift-XRT afterglow detection
  5. GRB 250507A: Swift-XRT refined Analysis
  6. GRB 250506A: Swift/UVOT Upper Limits
  7. EP#01709175213/IGR J19566+0326: Swift-XRT detection
  8. GRB 250507A: refined SVOM/MXT data analysis
  9. GRB 250506A: Swift-XRT observations
  10. Fermi-LAT Gamma-ray Observations of IceCube-250506A
  11. EP-WXT trigger 01709175213: a new X-ray outburst of LMXB MAXI J1957+032
  12. GRB 250506A: Mephisto optical upper limits
  13. GRB 250430A: Konus-Wind detection and joint Konus-Wind+Swift-BAT spectral analysis
  14. GRB 250506A: SVOM improved position and MXT detection of a fading X-ray afterglow
  15. GRB 250506A: Fermi GBM Observation
  16. GRB 250506A: Swift XRT observations and possible counterpart detection
  17. GRB 250504A: Swift-XRT refined Analysis
  18. GRB 250504A: Fermi GBM Observation
  19. GRB 250502A: Swift-XRT afterglow detection
  20. GRB 250502A: LCO optical counterpart detection
  21. Fermi-LAT Gamma-ray Observations of IceCube-250429A
  22. GRB 250430A: Swift-XRT refined Analysis
  23. GRB 250430A: Optical Observations via Virtual Telescope Project, Italy
  24. GRB 250430A: NUTTelA-TAO Early Measurements
  25. EP250428b: refined analysis of the EP-FXT follow-up observation
  26. EP250428b: SAO RAS optical upper limit
  27. GRB 250427A: Swift/UVOT Detection
  28. Fermi-LAT Gamma-ray Observations of IceCube-250426A
  29. EP250427a: EP-FXT follow-up observations
  30. GRB 250427A: Swift-XRT refined Analysis
  31. Konus-Wind detection of GRB 250424A
  32. Fermi-LAT gamma-ray observations of IceCube-250421A
  33. GRB 250424A: Swift-XRT refined Analysis
  34. GRB 250424A: VLT/X-shooter spectroscopic redshift z = 0.310
  35. SVOM/sb25042207: XRT observations
  36. GRB 250419A: Optical Observations via Virtual Telescope Project
  37. EP250421a: Swift/XRT counterpart detection
  38. EP250421a: Mephisto optical counterpart confirmation
  39. The EP-WXT trigger 01709135179: Kinder optical counterpart candidate
  40. GRB 250419A: LCO optical afterglow multi-band observations
  41. Fermi-LAT Gamma-ray Observations of IceCube-250416A
  42. GRB 250407A: rest-frame energetics from Konus-Wind observation
  43. GRB 250419A: Swift-XRT refined Analysis
  44. EP250416a: Swift/XRT counterpart fading
  45. Konus-Wind detection of GRB 250403A
  46. EP20250416a: Swift/XRT counterpart detection
  47. SVOM/sb25041603 is not a GRB
  48. EP250227a: Further NOT optical observations
  49. IceCube-250406A: Swift-XRT observations
  50. GRB 250407A: LCO detection of a fading optical counterpart
  51. Fermi-LAT gamma-ray observations of IceCube-250406A
  52. EP250407a: Swift-XRT observations
  53. GRB 250407A: Fermi GBM Detection
  54. GRB 250407A: Swift-XRT afterglow detection
  55. Konus-Wind detection of GRB 250404A / EP250404a
  56. EP250404a: refined analysis of the EP-WXT and EP-FXT observations
  57. GRB 250331D: Swift-XRT afterglow detection
  58. EP250404a: LCO optical counterpart detection
  59. EP250404a: Xinglong decaying optical counterpart
  60. GRB 250404A: Fermi GBM Detection
  61. GRB 250403A: Fermi GBM observations
  62. EP250404a: Nanshan/HMT optical counterpart detection
  63. EP250402a: Optical upper limit with Kinder observations
  64. GRB 250403A: LCO optical counterpart detection
  65. EP250402a: EP-FXT follow-up observations
  66. GRB 250403A: Swift-XRT observations
  67. GRB 250402A: Fermi GBM Observation
  68. GRB 250402A: Swift-XRT observations
  69. GRB 250402A: LCO optical counterpart detection
  70. GRB 250402A: refined SVOM/MXT data analysis
  71. GRB 250329B: Swift/UVOT Upper Limit
  72. GRB 250327A: Swift/UVOT Upper Limits
  73. GRB 250331D: Fermi GBM observation
  74. GRB 250331D: Swift-XRT observations
  75. GRB 250331C: Swift-XRT refined Analysis
  76. GRB 250331B: Swift-XRT refined Analysis
  77. GRB 250331B: Swift-XRT refined Analysis
  78. GRB 250329A: AbAO, Mondy and SAO RAS optical upper limits
  79. Konus-Wind detection of GRB 250327B
  80. LIGO/Virgo/KAGRA S250328ae: Swift XRT observations, 34 possible X-ray sources
  81. GRB 250328A: Swift-XRT refined Analysis
  82. Fermi-LAT gamma-ray observations of IceCube-250330A
  83. GRB 250330A: Fermi GBM Observation
  84. GRB 250331C: Prompt enhanced Swift-XRT position
  85. GRB 250330A: Swift-XRT afterglow detection
  86. GRB 250330A: Prompt Swift-XRT position
  87. GRB 250329B: Swift-XRT afterglow detection
  88. GRB 250329B: 1.6m Mephisto Optical Upper Limits
  89. GRB 250329A: Swift-XRT afterglow detection
  90. GRB 250329A: Fading optical counterpart detection by LCO.
  91. GRB 250327B: LCO optical counterpart detection
  92. GRB 250327B: CrAO and SAO RAS Optical Observations
  93. GRB 250327B: further optical observations by LCOGT
  94. GRB 250327A: SVOM/VT upper limits on the XRT position
  95. GRB 250327B: Swift-XRT detection of the X-ray afterglow
  96. GRB 250327A: Swift-XRT refined Analysis
  97. GRB 250327B: SVOM detection of a burst
  98. GRB 250327A: Fermi GBM observation
  99. Konus-Wind detection of GRB 250322A (short)
  100. Swift follow-up observations of FRB250316A and EP J120944.2+585060

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