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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"

28209 results found.

  1. EP250828a: Early near-infrared follow-up with MIRAGE on the MDM 1.3m telescope
  2. EP250901a: refined analysis of the EP-WXT and EP-FXT observations
  3. GRB 250901A: EP-FXT follow-up observation
  4. GRB 250901A: NOT optical observations
  5. GRB 250902A: Fermi GBM Final Real-time Localization
  6. GRB 250901A: SVOM/VT optical afterglow with VHF data
  7. GRB 250901A: Swift-XRT afterglow detection
  8. EP250901a: Swift-XRT observations
  9. GRB 250901A: LCO optical upper limit
  10. EP250827b: Swift observations of AT 2025wkm
  11. EP250831a: NOT optical observations and tentative afterglow candidate
  12. EP250827b: Contemporaneous detection of EP X-ray flare EP250827b and ZTF transient ZTF25abmpngy/AT2025wkm
  13. GRB 250901A: SVOM detection of a burst
  14. GRB 250830C: Insight-HXMT detection
  15. GRB 250830C: GECAM-B detection
  16. GRB 250830C: AstroSat CZTI detection of a long burst
  17. EP250901a: Einstein Probe detection of an X-ray transient
  18. EP250831a: EP-FXT follow-up observation
  19. EP250831a: Swift-XRT observations
  20. IceCube-250831A - IceCube observation of a high-energy neutrino candidate track-like event
  21. EP250831a: EP-WXT detection of a fast X-ray transient
  22. GRB 250831A (SVOM trigger sb25083102) is likely an outburst from star G 272-61
  23. GRB 250831A: Swift-XRT counterpart detection
  24. GRB 250831A: SVOM detection of a soft burst
  25. GRB 250830B: Swift-XRT observations
  26. EP250830a/GRB 250830B: Einstein Probe detection of an X-ray transient and Swift/XRT follow-up
  27. EP-WXT trigger 01709200994: Liverpool Telescope upper limits
  28. GRB 250830B: Swift ToO observations
  29. EP-WXT trigger 01709200994: confirmation of a stellar flare by BOOTES-6
  30. GRB 250830B: MAXI/GSC detection
  31. GRB 250830A / MAXI J0853+337: MAXI/GSC detection
  32. EP250827a: very early ATLAS detections, starting 43 sec after the EP trigger
  33. LIGO/Virgo/KAGRA S250818k: MeerKAT detection of an increase in radio flux from AT2025ulz
  34. GRB 250808B: SVOM detection of a burst through offline search
  35. EP250828a: Optical counterpart detection with Kinder observations
  36. EP250828a: Liverpool Telescope upper limits
  37. EP250828a: KAIT optical upper limit
  38. EP250827a: Swift/UVOT Detection
  39. EP250828a: Seimei/TriCCS optical counterpart detection
  40. GRB 250828B: Swift detection of a burst
  41. EP250827a: STEP/T80S Confirmation of fading optical counterpart
  42. LIGO/Virgo/KAGRA S250818k: uGMRT 1.3 GHz observations of AT2025ulz
  43. GRB 250828A: Fermi GBM Final Localization
  44. EP250828a: Einstein Probe detection of an X-ray transient
  45. GRID detection of GRB 250824A
  46. EP250827a: confirmation of optical rebrightening with LCO
  47. EP250827a: GOTO observation of the optical afterglow
  48. GRB 250827A: Fermi GBM Final Real-time Localization
  49. EP250827a: Swift-XRT counterpart detection
  50. EP250827a: BOOTES-7 early optical dectection
  51. EP250827a / GRB 250827A: MASTER-OAFA OT observation
  52. EP250827a: Las Cumbres independent detection of the optical counterpart
  53. EP250827a: Gemini-South optical counterpart detection
  54. EP250827a: Einstein Probe detection of an X-ray transient
  55. GRB 250806A: HiPERCAM/GTC limits on a possible supernova
  56. GRB 250826A: Fermi GBM Final Real-time Localization
  57. LIGO/Virgo/KAGRA S250818k: VLA upper limits on AT2025ulz
  58. GRB 250821B: AstroSat CZTI detection
  59. GRB 250819A: AstroSat CZTI detection
  60. GRB 250821B: Insight-HXMT detection
  61. GRB 250823A: Swift-XRT refined Analysis
  62. LIGO/Virgo/KAGRA S250818k: Swift Observations of AT 2025ulz - Second Epoch
  63. GRB 250824B: Fermi GBM Final Real-time Localization
  64. GRB 250823A: SVOM/VT optical observation
  65. GRB 250824A: Fermi GBM Final Real-time Localization
  66. GRB 250823A: Swift/UVOT Detection
  67. GRB 250818B: MeerKAT Detection
  68. GRB 250823A: Enhanced Swift-XRT position
  69. GRB 250823A: LCOGT Optical Detection
  70. GRB 250823A: BOOTES6/DPRT early optical detection
  71. GRB 250823A: Liverpool Telescope optical detection
  72. GRB 250823A: Swift detection of a burst
  73. GRB 250823A: Fermi GBM Final Real-time Localization
  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. EP250821a: Swift/UVOT further observations.
  83. GRB 250821A: VLT/FORS2 Optical Observation
  84. GRB 250821A: GECAM-B detection
  85. EP250821a: SVOM/VT optical observation
  86. GRB 250821A: NOT z-band upper limit
  87. GRB 250821C: Fermi GBM Final Real-time Localization
  88. GRB 250821A: KAIT optical upper limit
  89. LIGO/Virgo/KAGRA S250818k: Continued fading and reddening of AT2025ulz from Keck/LRIS imaging observations
  90. GRB 250821A: Swift-XRT refined Analysis
  91. GRB 250821B: Fermi GBM Detection
  92. LIGO/Virgo/KAGRA S250818k: ENGRAVE observations of AT 2025ulz
  93. GRB 250821B: Fermi GBM Final Localization of a Bright Burst
  94. GRB 250821A: Enhanced Swift-XRT position
  95. GRB 250821A: Swift/UVOT Upper Limits
  96. EP250821a: Swift XRT and UVOT counterpart detection
  97. GRB 250821A: LCOGT Optical Upper Limits
  98. LIGO/Virgo/KAGRA S250818k: 10 GHz VLA observations of AT2025ulz
  99. GRB 250821A: Prompt enhanced Swift-XRT position
  100. GRB 250821A: Swift detection of a burst

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