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GCN Circulars

GCN Circulars are rapid bulletins submitted by and distributed to the community. 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"

27919 results found.

  1. IceCube-250831A - IceCube observation of a high-energy neutrino candidate track-like event
  2. EP250831a: EP-WXT detection of a fast X-ray transient
  3. GRB 250831A: Swift-XRT counterpart detection
  4. GRB 250831A: SVOM detection of a soft burst
  5. GRB 250830B: Swift-XRT observations
  6. EP250830a/GRB 250830B: Einstein Probe detection of an X-ray transient and Swift/XRT follow-up
  7. EP-WXT trigger 01709200994: Liverpool Telescope upper limits
  8. GRB 250830B: Swift ToO observations
  9. EP-WXT trigger 01709200994: confirmation of a stellar flare by BOOTES-6
  10. GRB 250830B: MAXI/GSC detection
  11. GRB 250830A / MAXI J0853+337: MAXI/GSC detection
  12. GRB 250828B: Swift-BAT refined analysis
  13. EP250827a: very early ATLAS detections, starting 43 sec after the EP trigger
  14. LIGO/Virgo/KAGRA S250818k: MeerKAT detection of an increase in radio flux from AT2025ulz
  15. GRB 250808B: SVOM detection of a burst through offline search
  16. EP250828a: Optical counterpart detection with Kinder observations
  17. EP250828a: Liverpool Telescope upper limits
  18. Swift GRB 250828B: Global MASTER-Net observations report
  19. EP250827a: Swift/UVOT Detection
  20. EP250828a: Seimei/TriCCS optical counterpart detection
  21. GRB 250828B: Swift detection of a burst
  22. EP250827a: STEP/T80S Confirmation of fading optical counterpart
  23. LIGO/Virgo/KAGRA S250818k: uGMRT 1.3 GHz observations of AT2025ulz
  24. GRB 250828A: Fermi GBM Final Localization
  25. EP250828a: Einstein Probe detection of an X-ray transient
  26. GRID detection of GRB 250824A
  27. EP250827a: confirmation of optical rebrightening with LCO
  28. GRB 250827A: Fermi GBM Final Real-time Localization
  29. EP250827a: Swift-XRT counterpart detection
  30. EP250827a: BOOTES-7 early optical dectection
  31. EP250827a / GRB 250827A: MASTER-OAFA OT observation
  32. EP250827a: Las Cumbres independent detection of the optical counterpart
  33. EP250827a: Gemini-South optical counterpart detection
  34. EP250827a: Einstein Probe detection of an X-ray transient
  35. GRB 250806A: HiPERCAM/GTC limits on a possible supernova
  36. GRB 250826A: Fermi GBM Final Real-time Localization
  37. LIGO/Virgo/KAGRA S250818k: VLA upper limits on AT2025ulz
  38. GRB 250823A: Swift-BAT refined analysis
  39. GRB 250821B: AstroSat CZTI detection
  40. GRB 250819A: AstroSat CZTI detection
  41. GRB 250821B: Insight-HXMT detection
  42. GRB 250823A: Swift-XRT refined Analysis
  43. LIGO/Virgo/KAGRA S250818k: Swift Observations of AT 2025ulz - Second Epoch
  44. GRB 250824B: Fermi GBM Final Real-time Localization
  45. GRB 250823A: COLIBRÍ optical observations
  46. GRB 250823A: SVOM/VT optical observation
  47. GRB 250824A: Fermi GBM Final Real-time Localization
  48. GRB 250823A: Swift/UVOT Detection
  49. GRB 250823A: NOT optical observations
  50. GRB 250823A: Fermi GBM Observation
  51. GRB 250818B: MeerKAT Detection
  52. GRB 250823A: Enhanced Swift-XRT position
  53. GRB 250823A: LCOGT Optical Detection
  54. GRB 250823A: BOOTES6/DPRT early optical detection
  55. GRB 250823A: Liverpool Telescope optical detection
  56. GRB 250823A: Swift detection of a burst
  57. GRB 250823A: Fermi GBM Final Real-time Localization
  58. Swift GRB250823.84: Global MASTER-Net observations report
  59. Konus-Wind detection of GRB 250821B
  60. LIGO/Virgo/KAGRA S250818k: Rebrightening detected with Gemini/GMOS
  61. LIGO/Virgo/KAGRA S250818k: HST nIR detection of AT 2025ulz
  62. LIGO/Virgo/KAGRA S250818k: GTC/OSIRIS Optical Detection of AT2025ulz
  63. LIGO/Virgo/KAGRA S250818k: 3 GHz MeerKAT observations of AT2025ulz
  64. IPN triangulation of GRB 250821B (long/bright)
  65. GRB 250821A: Kilonova-Catcher optical upper limits
  66. EP250821a: Swift/XRT counterpart fading
  67. GRB 250821A: Swift-BAT refined analysis
  68. EP250821a: Swift/UVOT further observations.
  69. GRB 250821A: VLT/FORS2 Optical Observation
  70. GRB 250821A: GECAM-B detection
  71. EP250821a: SVOM/VT optical observation
  72. GRB 250821A: NOT z-band upper limit
  73. GRB 250821C: Fermi GBM Final Real-time Localization
  74. LIGO/Virgo/KAGRA S250818k: Continued fading and reddening of AT2025ulz from Keck/LRIS imaging observations
  75. GRB 250821A: Swift-XRT refined Analysis
  76. Swift GRB 250821A: Global MASTER-Net observations report
  77. GRB 250821B: Fermi GBM Detection
  78. LIGO/Virgo/KAGRA S250818k: ENGRAVE observations of AT 2025ulz
  79. GRB 250821B: Fermi GBM Final Localization of a Bright Burst
  80. GRB 250821A: Enhanced Swift-XRT position
  81. GRB 250821A: Swift/UVOT Upper Limits
  82. EP250821a: Rapidly fading optical source detected in Las Cumbres followup
  83. EP250821a: Swift XRT and UVOT counterpart detection
  84. GRB 250821A: LCOGT Optical Upper Limits
  85. GRB 250814A: CMO SAI and SAO RAS izJ observations.
  86. LIGO/Virgo/KAGRA S250818k: 10 GHz VLA observations of AT2025ulz
  87. GRB 250821A: Prompt enhanced Swift-XRT position
  88. GRB 250821A: Swift detection of a burst
  89. LIGO/Virgo/KAGRA S250818k: WFST pre-discovery limits and follow-up observations of AT 2025ulz
  90. EP250821a: Einstein Probe detection of an X-ray transient
  91. GRB 250819A: SVOM/GRM observation of a possible “long” duration type I burst
  92. GRB 250819A: Insight-HXMT detection
  93. GRB 250818B: 10 GHz VLA detection
  94. LIGO/Virgo/KAGRA S250818k: Swift observations of AT 2025ulz
  95. LIGO/Virgo/KAGRA S250818k: Multi-band Gemini GMOS Detections
  96. GRB 250814A: Swift/UVOT Upper Limits
  97. GRB 250813B: Swift/UVOT Upper Limit
  98. IPN triangulation of GRB 250816A (short)
  99. IPN triangulation of GRB 250814C (short)
  100. IPN triangulation of GRB 250804B (short)

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