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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"

20353 results found.

  1. GRB 250502A: Early optical counterpart detection by LCO.
  2. GRB 250430A: Swift/UVOT Detection
  3. GRB 250502A: TRT optical afterglow confirmation
  4. GRB 250430A: Enhanced Swift-XRT position
  5. GRB 250502A: SVOM/COLIBRÍ (FM-GFT) Detection of a Bright Optical Counterpart Candidate
  6. GRB 250502A: SVOM detection of a burst
  7. GRB 250430A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  8. GRB 250430A: KAIT optical observations
  9. GRB 250430A / EP250430a: J-band upper limits with WINTER
  10. GRB 250430A: NUTTelA-TAO Early Measurements
  11. GRB 250430A: DDOTI Optical Observations
  12. GRB 250430A: Leavitt Observatory optical upper limit
  13. GRB 250430A: Bassano Bresciano Observatory upper limit
  14. GRB 250430A : MITSuME Akeno optical upper limits
  15. GRB 250430A / EP250430a: VLT/X-shooter spectroscopic redshift z = 0.767
  16. EP250430a/GRB 250430A: Einstein Probe WXT detection of the X-ray prompt emission
  17. IceCube-250429A: Upper limits from a search for additional neutrino events in IceCube
  18. IceCube-250426A: Upper limits from a search for additional neutrino events in IceCube
  19. GRB 250430A: AKO Optical Afterglow Detection
  20. GRB 250430A: Kanata optical upper limit
  21. EP 250427A: Optical counterpart detection by LCO.
  22. GRB 250430A: Swift detection of a burst with optical counterpart
  23. EP250427a/GRB250427A: HCT optical follow-up
  24. SVOM/sb25043004: SVOM detection of a X-ray transient
  25. EP250428b: GROWTH-India telescope optical upper limit
  26. EP250428b: SAO RAS optical upper limit
  27. EP250428b: LAST optical upper limit
  28. GRB 250427A: Swift/UVOT Detection
  29. EP250428b: Einstein Probe detection of a fast X-ray transient
  30. EP250427A: COLIBRÍ Continuing Optical Observations
  31. GRB250427A/EP250427a GIT optical afterglow detection:
  32. EP250427a: LT optical counterpart detection
  33. EP250427a / GRB 250427A: LCO optical counterpart detection
  34. EP250427a: REM optical/NIR afterglow detection
  35. GRB 250424A: LCO optical observation
  36. EP250427A: COLIBRÍ Optical Detection
  37. EP250427a: TRT optical counterpart detection
  38. EP 250427a: BOOTES-7 optical afterglow candidate
  39. EP250427a: Einstein Probe detection of a fast X-ray transient
  40. GRB 250424A: SVOM/GRM observation of a long burst
  41. GRB 250424A: PRIME near-infrared detection
  42. GRB 250424A: WINTER J-band detection
  43. IceCube-250416A: Upper limits from a search for additional neutrino events in IceCube
  44. IceCube-250421A: Upper limits from a search for additional neutrino events in IceCube
  45. GRB 250419A: Mondy Optical Observations
  46. GRB 250424A: Swift/UVOT Detection
  47. Konus-Wind detection of GRB 250424A
  48. Fermi-LAT gamma-ray observations of IceCube-250421A
  49. GRB 250424A: Skynet Optical Observations
  50. GRB 250424A: Kilonova-Catcher optical afterglow detection
  51. GRB 250419A: SVOM/ECLAIRs refined analysis
  52. GRB 250424A: Swift-XRT refined Analysis
  53. GRB 250424A: Enhanced Swift-XRT position
  54. GRB 250424A: COLIBRÍ Detection of a Bright Optical Counterpart
  55. GRB 250424A: BlackGEM optical afterglow detection
  56. GRB 250424A: DDOTI Afterglow Detection
  57. GRB 250424A: REM optical/NIR afterglow detection
  58. GRB 250424A: Swift detection of a burst with an optical counterpart
  59. LIGO/Virgo/KAGRA S250328ae: Subaru/PFS Spectroscopic Follow up and Candidates
  60. EP250421a: Nickel optical upper limit
  61. EP250416a / GRB 250416C: Gemini GMOS-S likely host galaxy redshift z = 0.963
  62. SVOM/sb25042207: XRT observations
  63. GRB250419A: VLA radio detection
  64. IceCube-250421A: DDOTI Detection of the LAST Candidate
  65. GRB 250419A: Mephisto Multi-band Optical Detection
  66. GRB 250419A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  67. IC-250421A: LAST optical observations of the IceCube neutrino candidate
  68. EP250421a: NOT optical observations
  69. GRB 250419A: Optical Observations via Virtual Telescope Project
  70. EP250421a: REM optical upper limit
  71. EP250421A: COLIBRÍ Optical Upper Limit
  72. GRB 250419A: Mondy Continued Optical Observations
  73. GRB 250421B: AstroSat CZTI detection of a bright long burst
  74. EP250421a: Einstein Probe detection of an X-ray transient
  75. EP250421a: Mephisto optical counterpart confirmation
  76. IceCube-Cascade 250414A: Upper limits from a search for additional neutrino events in IceCube
  77. EP250421a: JinShan likely optical counterpart
  78. The EP-WXT trigger 01709135179: Kinder optical counterpart candidate
  79. GRB 250419A: LCO optical observation
  80. GRB 250419A: JinShan optical observations
  81. GRB 250419A: SVOM/C-GFT optical observations
  82. GRB 250419A: Swift/UVOT Follow up
  83. GRB 250416C / EP250416a: SVOM/GRM observation of a burst
  84. GRB 250419A: LCO optical afterglow multi-band observations
  85. GRB 250419A: Mondy and AbAO Optical Observations
  86. GRB 250419A: AKO Optical Afterglow Detection
  87. Fermi-LAT Gamma-ray Observations of IceCube-250416A
  88. GRB 250419A: VLT/X-shooter spectroscopic redshift z = 0.845
  89. GRB 250419A: KAIT optical afterglow observations
  90. GRB 250419A: SVOM/VT optical bright counterpart confirmation
  91. GRB 250419A: SVOM/COLIBRÍ (FM-GFT) Detection of the Optical Counterpart
  92. GRB 250419A: SVOM detection of a soft burst
  93. EP250416a: refined EP-WXT and EP-FXT analysis
  94. EP20250416a: Swift/XRT counterpart detection
  95. GRB 250403A: VLT/FORS2 spectroscopic redshift z = 1.847
  96. IceCube-250416A: DDOTI Optical Observations
  97. EP250416a: Gemini South-GMOS optical counterpart
  98. SVOM/sb25041603 is not a GRB
  99. EP250416a: Einstein Probe detection of an X-ray transient
  100. SVOM/sb25041603: SVOM/COLIBRÍ (FM-GFT) Upper Limit on the Optical Counterpart

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