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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"

14824 results found.

  1. GRB 250903A: Swift-XRT afterglow detection
  2. SVOM/sb25090605: detection of an X-ray transient from the LMXB 4U 0513-40
  3. EP250905a: Liverpool Telescope i-band upper limits
  4. EP250905b: EP-FXT follow-up observation
  5. EP250905a: Liverpool Telescope observations
  6. EP250905b: EP-WXT detection of a fast X-ray transient
  7. EP250905a: FTW one optical and multiple NIR counterpart candidates
  8. EP250905a: JinShan likely optical counterpart detection
  9. IceCube-250905A - IceCube observation of a high-energy neutrino candidate track-like event
  10. EP250905a: Einstein Probe detection of an X-ray transient
  11. GRB 250905B: Fermi GBM Final Localization
  12. GRB 250904A: Swift/UVOT Detection
  13. GRB 250903A: Swift/UVOT detection
  14. EP detected a brightening of LMXB 1ES 1735-26.9
  15. GRB 250905A: Swift detection of a burst
  16. GRB 250904A: TRT optical counterpart detection
  17. GRB 250902B: CALET Gamma-Ray Burst Monitor detection
  18. EP250827b: Gemini Spectroscopic Confirmation of AT2025wkm as a Ic-BL Supernova
  19. GRB 250904A: Swift detection of a burst
  20. GRB 250902A: CALET Gamma-Ray Burst Monitor detection
  21. GRB 250902A: VZLUSAT-2 detection
  22. EP250903a: retraction of the LCO candidate, and discovery of the likely counterpart
  23. EP-WXT trigger 01709201209: Liverpool Telescope upper limits
  24. GRB 250830C: VZLUSAT-2 detection
  25. GRB 250903A: VLT X-shooter spectroscopic redshift z = 1.590
  26. GRB 250903A: EP-FXT counterpart detection
  27. GRB 250902A: GECAM-B detection
  28. GRB 250903A: LCO optical afterglow detection
  29. Subject GRB 250903A: SVOM/MXT afterglow detection
  30. GRB 250903A: TRT optical counterpart detection
  31. GRB 250902B: AstroSat CZTI detection
  32. GRB 250903A: SVOM detection of a burst
  33. EP250903a: TRT optical observations
  34. EP250903a: Einstein Probe detection of an X-ray transient
  35. EP 250827B: Detection of supernova counterpart by LCO.
  36. EP250827b / AT 2025wkm: TRT optical observations
  37. EP250827b: continued Liverpool Telescope observations
  38. EP250827b: SVOM/VT observation of AT 2025wkm
  39. GRB 250902A: Fermi GBM Detection
  40. GRB 250902B: Fermi GBM Final Real-time Localization
  41. GRB 250830B: Swift-XRT afterglow detection
  42. EP250827b: Liverpool Telescope observations
  43. EP250828a: Early near-infrared follow-up with MIRAGE on the MDM 1.3m telescope
  44. EP250901a: refined analysis of the EP-WXT and EP-FXT observations
  45. GRB 250901A: EP-FXT follow-up observation
  46. GRB 250902A: Fermi GBM Final Real-time Localization
  47. GRB 250901A: Swift-XRT afterglow detection
  48. EP250831a: NOT optical observations and tentative afterglow candidate
  49. EP250827b: Contemporaneous detection of EP X-ray flare EP250827b and ZTF transient ZTF25abmpngy/AT2025wkm
  50. GRB 250901A: SVOM detection of a burst
  51. GRB 250830C: Insight-HXMT detection
  52. GRB 250830C: GECAM-B detection
  53. GRB 250830C: AstroSat CZTI detection of a long burst
  54. EP250901a: Einstein Probe detection of an X-ray transient
  55. EP250831a: EP-FXT follow-up observation
  56. IceCube-250831A - IceCube observation of a high-energy neutrino candidate track-like event
  57. EP250831a: EP-WXT detection of a fast X-ray transient
  58. GRB 250831A: Swift-XRT counterpart detection
  59. GRB 250831A: SVOM detection of a soft burst
  60. EP250830a/GRB 250830B: Einstein Probe detection of an X-ray transient and Swift/XRT follow-up
  61. EP-WXT trigger 01709200994: Liverpool Telescope upper limits
  62. EP-WXT trigger 01709200994: confirmation of a stellar flare by BOOTES-6
  63. GRB 250830B: MAXI/GSC detection
  64. GRB 250830A / MAXI J0853+337: MAXI/GSC detection
  65. EP250827a: very early ATLAS detections, starting 43 sec after the EP trigger
  66. LIGO/Virgo/KAGRA S250818k: MeerKAT detection of an increase in radio flux from AT2025ulz
  67. GRB 250808B: SVOM detection of a burst through offline search
  68. EP250828a: Optical counterpart detection with Kinder observations
  69. EP250828a: Liverpool Telescope upper limits
  70. EP250827a: Swift/UVOT Detection
  71. EP250828a: NOT optical counterpart confirmation
  72. EP250828a: Seimei/TriCCS optical counterpart detection
  73. GRB 250828B: Swift detection of a burst
  74. EP250827a: STEP/T80S Confirmation of fading optical counterpart
  75. LIGO/Virgo/KAGRA S250818k: uGMRT 1.3 GHz observations of AT2025ulz
  76. GRB 250828A: Fermi GBM Final Localization
  77. EP250828a: Einstein Probe detection of an X-ray transient
  78. GRID detection of GRB 250824A
  79. GRB 250827A: Fermi GBM Final Real-time Localization
  80. EP250827a: Swift-XRT counterpart detection
  81. EP250827a: TRT optical observations
  82. EP250827a: BOOTES-7 early optical dectection
  83. EP250827a / GRB 250827A: MASTER-OAFA OT observation
  84. EP250827a: Las Cumbres independent detection of the optical counterpart
  85. EP250827a: Gemini-South optical counterpart detection
  86. EP250827a: Einstein Probe detection of an X-ray transient
  87. GRB 250806A: HiPERCAM/GTC limits on a possible supernova
  88. GRB 250826A: Fermi GBM Final Real-time Localization
  89. LIGO/Virgo/KAGRA S250818k: VLA upper limits on AT2025ulz
  90. GRB 250821B: AstroSat CZTI detection
  91. GRB 250819A: AstroSat CZTI detection
  92. GRB 250821B: Insight-HXMT detection
  93. LIGO/Virgo/KAGRA S250818k: Swift Observations of AT 2025ulz - Second Epoch
  94. GRB 250824B: Fermi GBM Final Real-time Localization
  95. GRB 250824A: Fermi GBM Final Real-time Localization
  96. GRB 250823A: Swift/UVOT Detection
  97. GRB 250818B: MeerKAT Detection
  98. GRB 250823A: LCOGT Optical Detection
  99. GRB 250823A: BOOTES6/DPRT early optical detection
  100. GRB 250823A: Liverpool Telescope optical detection

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