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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"

27834 results found.

  1. GRB 250902A: Fermi GBM Final Real-time Localization
  2. GRB 250901A: SVOM/VT optical afterglow with VHF data
  3. GRB 250901A: Swift-XRT afterglow detection
  4. EP250901a: Swift-XRT observations
  5. GRB 250901A: LCO optical upper limit
  6. EP250827b: Swift observations of AT 2025wkm
  7. EP250831a: NOT optical observations and tentative afterglow candidate
  8. EP250827b: Contemporaneous detection of EP X-ray flare EP250827b and ZTF transient ZTF25abmpngy/AT2025wkm
  9. GRB 250901A: SVOM detection of a burst
  10. GRB 250830C: Insight-HXMT detection
  11. GRB 250830C: GECAM-B detection
  12. GRB 250830C: AstroSat CZTI detection of a long burst
  13. EP250901a: Einstein Probe detection of an X-ray transient
  14. EP250831a: EP-FXT follow-up observation
  15. EP250831a: Swift-XRT observations
  16. IceCube-250831A - IceCube observation of a high-energy neutrino candidate track-like event
  17. EP250831a: EP-WXT detection of a fast X-ray transient
  18. GRB 250831A: Swift-XRT counterpart detection
  19. GRB 250831A: SVOM detection of a soft burst
  20. GRB 250830B: Swift-XRT observations
  21. EP250830a/GRB 250830B: Einstein Probe detection of an X-ray transient and Swift/XRT follow-up
  22. EP-WXT trigger 01709200994: Liverpool Telescope upper limits
  23. GRB 250830B: Swift ToO observations
  24. EP-WXT trigger 01709200994: confirmation of a stellar flare by BOOTES-6
  25. GRB 250830B: MAXI/GSC detection
  26. GRB 250830A / MAXI J0853+337: MAXI/GSC detection
  27. GRB 250828B: Swift-BAT refined analysis
  28. EP250827a: very early ATLAS detections, starting 43 sec after the EP trigger
  29. LIGO/Virgo/KAGRA S250818k: MeerKAT detection of an increase in radio flux from AT2025ulz
  30. GRB 250808B: SVOM detection of a burst through offline search
  31. EP250828a: Optical counterpart detection with Kinder observations
  32. EP250828a: Liverpool Telescope upper limits
  33. Swift GRB 250828B: Global MASTER-Net observations report
  34. EP250827a: Swift/UVOT Detection
  35. EP250828a: Seimei/TriCCS optical counterpart detection
  36. GRB 250828B: Swift detection of a burst
  37. EP250827a: STEP/T80S Confirmation of fading optical counterpart
  38. LIGO/Virgo/KAGRA S250818k: uGMRT 1.3 GHz observations of AT2025ulz
  39. GRB 250828A: Fermi GBM Final Localization
  40. EP250828a: Einstein Probe detection of an X-ray transient
  41. GRID detection of GRB 250824A
  42. EP250827a: confirmation of optical rebrightening with LCO
  43. GRB 250827A: Fermi GBM Final Real-time Localization
  44. EP250827a: Swift-XRT counterpart detection
  45. EP250827a: BOOTES-7 early optical dectection
  46. EP250827a / GRB 250827A: MASTER-OAFA OT observation
  47. EP250827a: Las Cumbres independent detection of the optical counterpart
  48. EP250827a: Gemini-South optical counterpart detection
  49. EP250827a: Einstein Probe detection of an X-ray transient
  50. GRB 250806A: HiPERCAM/GTC limits on a possible supernova
  51. GRB 250826A: Fermi GBM Final Real-time Localization
  52. LIGO/Virgo/KAGRA S250818k: VLA upper limits on AT2025ulz
  53. GRB 250823A: Swift-BAT refined analysis
  54. GRB 250821B: AstroSat CZTI detection
  55. GRB 250819A: AstroSat CZTI detection
  56. GRB 250821B: Insight-HXMT detection
  57. GRB 250823A: Swift-XRT refined Analysis
  58. LIGO/Virgo/KAGRA S250818k: Swift Observations of AT 2025ulz - Second Epoch
  59. GRB 250824B: Fermi GBM Final Real-time Localization
  60. GRB 250823A: COLIBRÍ optical observations
  61. GRB 250823A: SVOM/VT optical observation
  62. GRB 250824A: Fermi GBM Final Real-time Localization
  63. GRB 250823A: Swift/UVOT Detection
  64. GRB 250823A: NOT optical observations
  65. GRB 250823A: Fermi GBM Observation
  66. GRB 250818B: MeerKAT Detection
  67. GRB 250823A: Enhanced Swift-XRT position
  68. GRB 250823A: LCOGT Optical Detection
  69. GRB 250823A: BOOTES6/DPRT early optical detection
  70. GRB 250823A: Liverpool Telescope optical detection
  71. GRB 250823A: Swift detection of a burst
  72. GRB 250823A: Fermi GBM Final Real-time Localization
  73. Swift GRB250823.84: Global MASTER-Net observations report
  74. Konus-Wind detection of GRB 250821B
  75. LIGO/Virgo/KAGRA S250818k: Rebrightening detected with Gemini/GMOS
  76. LIGO/Virgo/KAGRA S250818k: HST nIR detection of AT 2025ulz
  77. LIGO/Virgo/KAGRA S250818k: GTC/OSIRIS Optical Detection of AT2025ulz
  78. LIGO/Virgo/KAGRA S250818k: 3 GHz MeerKAT observations of AT2025ulz
  79. IPN triangulation of GRB 250821B (long/bright)
  80. GRB 250821A: Kilonova-Catcher optical upper limits
  81. EP250821a: Swift/XRT counterpart fading
  82. GRB 250821A: Swift-BAT refined analysis
  83. EP250821a: Swift/UVOT further observations.
  84. GRB 250821A: VLT/FORS2 Optical Observation
  85. GRB 250821A: GECAM-B detection
  86. EP250821a: SVOM/VT optical observation
  87. GRB 250821A: NOT z-band upper limit
  88. GRB 250821C: Fermi GBM Final Real-time Localization
  89. LIGO/Virgo/KAGRA S250818k: Continued fading and reddening of AT2025ulz from Keck/LRIS imaging observations
  90. GRB 250821A: Swift-XRT refined Analysis
  91. Swift GRB 250821A: Global MASTER-Net observations report
  92. GRB 250821B: Fermi GBM Detection
  93. LIGO/Virgo/KAGRA S250818k: ENGRAVE observations of AT 2025ulz
  94. GRB 250821B: Fermi GBM Final Localization of a Bright Burst
  95. GRB 250821A: Enhanced Swift-XRT position
  96. GRB 250821A: Swift/UVOT Upper Limits
  97. EP250821a: Rapidly fading optical source detected in Las Cumbres followup
  98. EP250821a: Swift XRT and UVOT counterpart detection
  99. GRB 250821A: LCOGT Optical Upper Limits
  100. GRB 250814A: CMO SAI and SAO RAS izJ observations.

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