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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"

6792 results found.

  1. GRB 250510A: Swift-XRT observations
  2. GRB 250509A: Fermi GBM Observation
  3. IceCube-250506A: No Transient Candidates from the Zwicky Transient Facility
  4. GRB 250509A: Swift-XRT refined Analysis
  5. GRB 250506A: Swift-XRT afterglow detection
  6. GRB 250507A: Swift-XRT refined Analysis
  7. GRB 250506A: Swift/UVOT Upper Limits
  8. EP#01709175213/IGR J19566+0326: Swift-XRT detection
  9. GRB 250507A: refined SVOM/MXT data analysis
  10. GRB 250506A: Swift-XRT observations
  11. Fermi-LAT Gamma-ray Observations of IceCube-250506A
  12. EP-WXT trigger 01709175213: a new X-ray outburst of LMXB MAXI J1957+032
  13. GRB 250506A: Mephisto optical upper limits
  14. GRB 250430A: Konus-Wind detection and joint Konus-Wind+Swift-BAT spectral analysis
  15. GRB 250506A: SVOM improved position and MXT detection of a fading X-ray afterglow
  16. GRB 250506A: Fermi GBM Observation
  17. GRB 250506A: Swift XRT observations and possible counterpart detection
  18. GRB 250504A: Swift-XRT refined Analysis
  19. GRB 250504A: Fermi GBM Observation
  20. GRB 250502A: Swift-XRT afterglow detection
  21. GRB 250502A: LCO optical counterpart detection
  22. Fermi-LAT Gamma-ray Observations of IceCube-250429A
  23. GRB 250430A: Swift-XRT refined Analysis
  24. GRB 250430A: Optical Observations via Virtual Telescope Project, Italy
  25. GRB 250430A: NUTTelA-TAO Early Measurements
  26. EP250428b: refined analysis of the EP-FXT follow-up observation
  27. EP250428b: SAO RAS optical upper limit
  28. GRB 250427A: Swift/UVOT Detection
  29. Fermi-LAT Gamma-ray Observations of IceCube-250426A
  30. EP250427a: EP-FXT follow-up observations
  31. GRB 250427A: Swift-XRT refined Analysis
  32. Konus-Wind detection of GRB 250424A
  33. Fermi-LAT gamma-ray observations of IceCube-250421A
  34. GRB 250424A: Swift-XRT refined Analysis
  35. GRB 250424A: VLT/X-shooter spectroscopic redshift z = 0.310
  36. SVOM/sb25042207: XRT observations
  37. GRB 250419A: Optical Observations via Virtual Telescope Project
  38. EP250421a: Swift/XRT counterpart detection
  39. EP250421a: Mephisto optical counterpart confirmation
  40. The EP-WXT trigger 01709135179: Kinder optical counterpart candidate
  41. GRB 250419A: LCO optical afterglow multi-band observations
  42. Fermi-LAT Gamma-ray Observations of IceCube-250416A
  43. GRB 250407A: rest-frame energetics from Konus-Wind observation
  44. GRB 250419A: Swift-XRT refined Analysis
  45. EP250416a: Swift/XRT counterpart fading
  46. Konus-Wind detection of GRB 250403A
  47. EP20250416a: Swift/XRT counterpart detection
  48. SVOM/sb25041603 is not a GRB
  49. EP250227a: Further NOT optical observations
  50. IceCube-250406A: Swift-XRT observations
  51. GRB 250407A: LCO detection of a fading optical counterpart
  52. Fermi-LAT gamma-ray observations of IceCube-250406A
  53. EP250407a: Swift-XRT observations
  54. GRB 250407A: Fermi GBM Detection
  55. GRB 250407A: Swift-XRT afterglow detection
  56. Konus-Wind detection of GRB 250404A / EP250404a
  57. EP250404a: refined analysis of the EP-WXT and EP-FXT observations
  58. GRB 250331D: Swift-XRT afterglow detection
  59. EP250404a: LCO optical counterpart detection
  60. EP250404a: Xinglong decaying optical counterpart
  61. GRB 250404A: Fermi GBM Detection
  62. GRB 250403A: Fermi GBM observations
  63. EP250404a: Nanshan/HMT optical counterpart detection
  64. EP250402a: Optical upper limit with Kinder observations
  65. GRB 250403A: LCO optical counterpart detection
  66. EP250402a: EP-FXT follow-up observations
  67. GRB 250403A: Swift-XRT observations
  68. GRB 250402A: Fermi GBM Observation
  69. GRB 250402A: Swift-XRT observations
  70. GRB 250402A: LCO optical counterpart detection
  71. GRB 250402A: refined SVOM/MXT data analysis
  72. GRB 250329B: Swift/UVOT Upper Limit
  73. GRB 250327A: Swift/UVOT Upper Limits
  74. GRB 250331D: Fermi GBM observation
  75. GRB 250331D: Swift-XRT observations
  76. GRB 250331C: Swift-XRT refined Analysis
  77. GRB 250331B: Swift-XRT refined Analysis
  78. GRB 250331B: Swift-XRT refined Analysis
  79. GRB 250329A: AbAO, Mondy and SAO RAS optical upper limits
  80. Konus-Wind detection of GRB 250327B
  81. LIGO/Virgo/KAGRA S250328ae: Swift XRT observations, 34 possible X-ray sources
  82. GRB 250328A: Swift-XRT refined Analysis
  83. Fermi-LAT gamma-ray observations of IceCube-250330A
  84. GRB 250330A: Fermi GBM Observation
  85. GRB 250331C: Prompt enhanced Swift-XRT position
  86. GRB 250330A: Swift-XRT afterglow detection
  87. GRB 250330A: Prompt Swift-XRT position
  88. GRB 250329B: Swift-XRT afterglow detection
  89. GRB 250329B: 1.6m Mephisto Optical Upper Limits
  90. GRB 250329A: Swift-XRT afterglow detection
  91. GRB 250329A: Fading optical counterpart detection by LCO.
  92. GRB 250327B: LCO optical counterpart detection
  93. GRB 250327B: CrAO and SAO RAS Optical Observations
  94. GRB 250327B: further optical observations by LCOGT
  95. GRB 250327A: SVOM/VT upper limits on the XRT position
  96. GRB 250327B: Swift-XRT detection of the X-ray afterglow
  97. GRB 250327A: Swift-XRT refined Analysis
  98. GRB 250327B: SVOM detection of a burst
  99. GRB 250327A: Fermi GBM observation
  100. Konus-Wind detection of GRB 250322A (short)

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