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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"

6667 results found.

  1. EP250428b: refined analysis of the EP-FXT follow-up observation
  2. EP250428b: SAO RAS optical upper limit
  3. GRB 250427A: Swift/UVOT Detection
  4. Fermi-LAT Gamma-ray Observations of IceCube-250426A
  5. EP250427a: EP-FXT follow-up observations
  6. GRB 250427A: Swift-XRT refined Analysis
  7. Konus-Wind detection of GRB 250424A
  8. Fermi-LAT gamma-ray observations of IceCube-250421A
  9. GRB 250424A: Swift-XRT refined Analysis
  10. GRB 250424A: VLT/X-shooter spectroscopic redshift z = 0.310
  11. SVOM/sb25042207: XRT observations
  12. GRB 250419A: Optical Observations via Virtual Telescope Project
  13. EP250421a: Swift/XRT counterpart detection
  14. EP250421a: Mephisto optical counterpart confirmation
  15. The EP-WXT trigger 01709135179: Kinder optical counterpart candidate
  16. GRB 250419A: LCO optical afterglow multi-band observations
  17. Fermi-LAT Gamma-ray Observations of IceCube-250416A
  18. GRB 250407A: rest-frame energetics from Konus-Wind observation
  19. GRB 250419A: Swift-XRT refined Analysis
  20. EP250416a: Swift/XRT counterpart fading
  21. Konus-Wind detection of GRB 250403A
  22. EP20250416a: Swift/XRT counterpart detection
  23. SVOM/sb25041603 is not a GRB
  24. EP250227a: Further NOT optical observations
  25. IceCube-250406A: Swift-XRT observations
  26. GRB 250407A: LCO detection of a fading optical counterpart
  27. Fermi-LAT gamma-ray observations of IceCube-250406A
  28. EP250407a: Swift-XRT observations
  29. GRB 250407A: Fermi GBM Detection
  30. GRB 250407A: Swift-XRT afterglow detection
  31. Konus-Wind detection of GRB 250404A / EP250404a
  32. EP250404a: refined analysis of the EP-WXT and EP-FXT observations
  33. GRB 250331D: Swift-XRT afterglow detection
  34. EP250404a: LCO optical counterpart detection
  35. EP250404a: Xinglong decaying optical counterpart
  36. GRB 250404A: Fermi GBM Detection
  37. GRB 250403A: Fermi GBM observations
  38. EP250404a: Nanshan/HMT optical counterpart detection
  39. EP250402a: Optical upper limit with Kinder observations
  40. GRB 250403A: LCO optical counterpart detection
  41. EP250402a: EP-FXT follow-up observations
  42. GRB 250403A: Swift-XRT observations
  43. GRB 250402A: Fermi GBM Observation
  44. GRB 250402A: Swift-XRT observations
  45. GRB 250402A: LCO optical counterpart detection
  46. GRB 250402A: refined SVOM/MXT data analysis
  47. GRB 250329B: Swift/UVOT Upper Limit
  48. GRB 250327A: Swift/UVOT Upper Limits
  49. GRB 250331D: Fermi GBM observation
  50. GRB 250331D: Swift-XRT observations
  51. GRB 250331C: Swift-XRT refined Analysis
  52. GRB 250331B: Swift-XRT refined Analysis
  53. GRB 250331B: Swift-XRT refined Analysis
  54. GRB 250329A: AbAO, Mondy and SAO RAS optical upper limits
  55. Konus-Wind detection of GRB 250327B
  56. LIGO/Virgo/KAGRA S250328ae: Swift XRT observations, 34 possible X-ray sources
  57. GRB 250328A: Swift-XRT refined Analysis
  58. Fermi-LAT gamma-ray observations of IceCube-250330A
  59. GRB 250330A: Fermi GBM Observation
  60. GRB 250331C: Prompt enhanced Swift-XRT position
  61. GRB 250330A: Swift-XRT afterglow detection
  62. GRB 250330A: Prompt Swift-XRT position
  63. GRB 250329B: Swift-XRT afterglow detection
  64. GRB 250329B: 1.6m Mephisto Optical Upper Limits
  65. GRB 250329A: Swift-XRT afterglow detection
  66. GRB 250329A: Fading optical counterpart detection by LCO.
  67. GRB 250327B: LCO optical counterpart detection
  68. GRB 250327B: CrAO and SAO RAS Optical Observations
  69. GRB 250327B: further optical observations by LCOGT
  70. GRB 250327A: SVOM/VT upper limits on the XRT position
  71. GRB 250327B: Swift-XRT detection of the X-ray afterglow
  72. GRB 250327A: Swift-XRT refined Analysis
  73. GRB 250327B: SVOM detection of a burst
  74. GRB 250327A: Fermi GBM observation
  75. Konus-Wind detection of GRB 250322A (short)
  76. Swift follow-up observations of FRB250316A and EP J120944.2+585060
  77. FRB 250316A: NOT optical upper limit for the X ray source EP J120944.2+585060
  78. EP-WXT trigger 01709133021: Optical upper limit through Kinder observations
  79. GRB 250321B: Swift-XRT observations
  80. GRB 250322A: Swift-XRT refined Analysis
  81. GRB 250322A: NOT optical upper limits
  82. FRB 20250316A: Kinder optical upper limits of the Einstein Probe candidate X-ray source EP J120944.2+585060
  83. FRB 20250316A: detection of a candidate associated X-ray source EP J120944.2+585060 by Einstein Probe
  84. EP250321a: refined analysis of the EP-WXT and EP-FXT observations
  85. GRB 250320B: Fermi GBM Observation
  86. GRB 250321A: Swift-XRT refined Analysis
  87. GRB 250320B: Fermi-LAT detection
  88. EP250321a: Kinder optical follow-up observations
  89. EP250321a: Swift-XRT detection of an X-ray source
  90. EP250321a: TRT optical counterpart detection
  91. GRB 250321A: Swift-XRT localisation
  92. GRB 250321A: Fermi GBM Observation
  93. GRB 250309B: Proof-of-concept for Joint ZTF+EP Experiment
  94. GRB 250317B: NOT optical observations suggest an optical plateau phase
  95. GRB 250317B: Swift-XRT observations
  96. GRB 250316A: Swift/UVOT Upper Limits
  97. EP 250317B: Fading optical counterpart detection by LCO
  98. GRB 250316A: Swift-XRT afterglow detection
  99. GRB 250317B: LCO detection of the fading optical afterglow
  100. GRB 250316A: Fermi GBM Observation

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