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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"

28095 results found.

  1. GRB 250330A: Swift-XRT afterglow detection
  2. GRB 250328A: 1.6m Mephisto optical observations
  3. GRB 250329B: SVOM/COLIBRÍ (F-GFT) optical upper limit
  4. GRB 250330A: Fermi GBM Final Localization
  5. IceCube-250330A - IceCube observation of a high-energy neutrino candidate track-like event
  6. GRB 250330A: VLT/FORS2 Optical Observations
  7. GRB 250330A: Prompt Swift-XRT position
  8. GRB 250329B: Swift-XRT afterglow detection
  9. GRB 250330A: Swift detection of a burst
  10. GRB 250328A: A fading optical afterglow confirmed by SVOM/VT
  11. GRB 250329B: SVOM/C-GFT optical upper limit
  12. GRB 250327B: ALMA detection
  13. GRB 250327B: VLA detection
  14. GRB 250329B: SVOM/VT optical upper limit
  15. GRB250329A: REM optical afterglow detection
  16. GRB 250329B: SVOM detection of a faint transient
  17. GRB 250329A: Swift-XRT afterglow detection
  18. GRB 250329A: Fading optical counterpart detection by LCO.
  19. GRB 250328A: SVOM/C-GFT optical upper limit
  20. GRB 250328A: SVOM/COLIBRÍ (F-GFT) optical afterglow candidate
  21. GRB 250328A: VLT/HAWK-I near-infrared afterglow candidate
  22. GRB 250329A: VLT/X-shooter redshift z = 2.921
  23. GRB 250329A: SVOM detection of a burst
  24. GRB 250329A: SVOM/COLIBRÍ (F-GFT) Detection of a Bright Optical Counterpart Candidate
  25. GRB 250327B: MASTER detection of OT rebrightening
  26. GRB 250327B: LCO optical counterpart detection
  27. GRB 250328A: SVOM detection of a burst
  28. GRB 250327B: CrAO and SAO RAS Optical Observations
  29. GRB 250327B: OHP/T193 spectroscopic observations and redshift confirmation
  30. EP250315a: Pan-STARRS r and i-band imaging and photometry
  31. GRB 250327b: Liverpool Telescope optical observations
  32. GRB 250322A: GRANDMA/TNOT optical upper limits
  33. GRB 250327A: SVOM/VT upper limits on the XRT position
  34. GRB 250327B: SVOM/COLIBRÍ (F-GFT) follow-up observations
  35. GRB 250327B: Las Cumbres optical counterpart detection
  36. GRB 250327B: Swift-XRT detection of the X-ray afterglow
  37. GRB 250327B: 1.6m Mephisto optical observations
  38. GRB 250327B: NOT spectroscopic redshift z = 3.035
  39. GRB 250327A: Swift-XRT refined Analysis
  40. GRB 250327B: GOTO optical counterpart detection
  41. GRB 250327B: SVOM detection of a burst
  42. FRB 20250316A: The sub-arcsecond localization of FRB 20250316A using CHIME/FRB Outriggers coincides with reported X-ray counterparts
  43. FRB 20250316A: Pan-STARRS r and i-band imaging and photometry
  44. GRB 250327A: DDOTI Optical Observations
  45. GRB 250327A: Swift detection of a burst
  46. GRB 250327A: Fermi GBM Final Real-time Localization
  47. Konus-Wind detection of GRB 250322A (short)
  48. IPN triangulation of GRB 250322B
  49. EP250321a: Mondy AZT-33IK Continued Optical Observations
  50. Swift follow-up observations of FRB250316A and EP J120944.2+585060
  51. GRB 250321B: ISON-Kitab RC-36 Optical Upper Limit
  52. FRB 250316A: NOT optical upper limit for the X ray source EP J120944.2+585060
  53. GRB 250322A: further NOT optical observations
  54. EP-WXT trigger 01709133021: Optical upper limit through Kinder observations
  55. GRB 250322A: Swift/UVOT Upper Limits
  56. GRB 250322A: VLT/X-shooter redshift confirmation of the putative host galaxy
  57. GRB 250322B: NuSTAR detection of the prompt emission and regular dips during the burst
  58. GRB 250321B: Swift-XRT observations
  59. GRB 250322A: Swift-XRT refined Analysis
  60. EP250321a: TNOT Observation of Optical Counterpart
  61. FRB 250316A: DDOTI Continued Optical Observations (Third Epoch)
  62. GRB 250322A: Gemini-North redshift of candidate host galaxy
  63. SVOM/sb25032302: SVOM detection of a long X-ray transient
  64. GRB 250322A: AstroSat CZTI detection of a short burst
  65. GRB 250322B: AstroSat CZTI detection of a bright long burst
  66. GRB250322A: STEP/T80S optical limits
  67. GRB 250322A: Gemini-South optical observations
  68. GRB 250322A: VLT optical observations
  69. GRB 250322A: VLT near-infrared observations
  70. GRB 250322A: NOT optical upper limits
  71. GRB 250322A: Enhanced Swift-XRT position
  72. FRB 20250316A: Kinder optical upper limits of the Einstein Probe candidate X-ray source EP J120944.2+585060
  73. EP250321a: Liverpool Telescope optical follow-up
  74. EP250321a: Mondy AZT-33IK Optical Observations
  75. GRB 250322A: Swift detection of a short burst
  76. FRB 20250316A: detection of a candidate associated X-ray source EP J120944.2+585060 by Einstein Probe
  77. EP250321a: refined analysis of the EP-WXT and EP-FXT observations
  78. EP250321a: KAIT optical observations
  79. GRB 250225B: GECAM-A detection
  80. GRB 250312A: GECAM-A detection
  81. GRB 250321B: Swift ToO observations
  82. EP250321a: WFST optical observations
  83. GRB 250320B: NuSTAR detection of the prompt emission from two broad bursts and preliminary analysis
  84. GRB 250321C: Fermi GBM Final Real-time Localization
  85. GRB 250320A: NuSTAR Detection of the Prompt Emission and Preliminary Results
  86. GRB 250321A: Swift-XRT refined Analysis
  87. GRB 250320B: Fermi-LAT detection
  88. GRB 250321B: SVOM detection of a sub-threshold transient event
  89. EP 250321A: Optical counterpart detection by LCO.
  90. GRB 250321A: Swift/UVOT Upper Limits
  91. EP250321a: LCO optical counterpart detection
  92. EP250321a: Swift-XRT detection of an X-ray source
  93. EP250321a: VLT/X-shooter redshift z = 4.368
  94. GRB 250320B: AstroSat CZTI detection
  95. EP250321a: REM optical/NIR afterglow detection
  96. EP250321a: BOOTES-5/JGT optical afterglow detection
  97. EP250321a: TRT optical counterpart detection
  98. EP250321a: Einstein Probe detection of an X-ray transient
  99. GRB 250321A: GOTO optical upper limits
  100. GRB 250321A: Swift-XRT localisation

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