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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"

21458 results found.

  1. GRB 250329B: Swift-XRT afterglow detection
  2. GRB 250330A: Swift detection of a burst
  3. Swift GRB250330.26: Global MASTER-Net observations report
  4. GRB 250329B: SVOM/C-GFT optical upper limit
  5. GRB 250329B: SVOM/VT optical upper limit
  6. GRB 250329A: Swift-XRT afterglow detection
  7. GRB 250328A: SVOM/C-GFT optical upper limit
  8. GRB 250328A: SVOM/COLIBRÍ (F-GFT) optical afterglow candidate
  9. GRB 250328A: VLT/HAWK-I near-infrared afterglow candidate
  10. GRB 250327B: LCO optical counterpart detection
  11. GRB 250322A: GRANDMA/TNOT optical upper limits
  12. GRB 250327A: SVOM/VT upper limits on the XRT position
  13. GRB 250327B: Swift-XRT detection of the X-ray afterglow
  14. GRB 250327A: Swift-XRT refined Analysis
  15. FRB 20250316A: The sub-arcsecond localization of FRB 20250316A using CHIME/FRB Outriggers coincides with reported X-ray counterparts
  16. GRB 250327A: J-band observations with WINTER
  17. GRB 250327A: SVOM/VT optical candidate
  18. GRB 250327A: Fermi GBM observation
  19. Swift GRB 250327A: Global MASTER-Net observations report
  20. GRB 250327A: DDOTI Optical Observations
  21. GRB 250327A: COLIBRÍ optical upper limit
  22. GRB 250327A: Swift detection of a burst
  23. Konus-Wind detection of GRB 250322A (short)
  24. IPN triangulation of GRB 250322B
  25. Swift follow-up observations of FRB250316A and EP J120944.2+585060
  26. GRB 250322A: Swift-BAT refined analysis
  27. GRB 250322A: further NOT optical observations
  28. GRB 250322A: Swift/UVOT Upper Limits
  29. GRB 250322A: VLT/X-shooter redshift confirmation of the putative host galaxy
  30. GRB 250321B: Swift-XRT observations
  31. GRB 250322A: Swift-XRT refined Analysis
  32. GRB 250322A: Gemini-North redshift of candidate host galaxy
  33. GRB 250322A: AstroSat CZTI detection of a short burst
  34. GRB250322A: STEP/T80S optical limits
  35. GRB 250322A: Gemini-South optical observations
  36. GRB 250322A: VLT optical observations
  37. GRB 250322A: VLT near-infrared observations
  38. GRB 250322A: NOT optical upper limits
  39. GRB 250322A: Enhanced Swift-XRT position
  40. GRB 250322A: MASTER optical observation
  41. GRB 250322A: Swift detection of a short burst
  42. EP250321a: refined analysis of the EP-WXT and EP-FXT observations
  43. GRB 250225B: GECAM-A detection
  44. GRB 250312A: GECAM-A detection
  45. GRB 250321B: Swift ToO observations
  46. GRB 250321A: Swift-BAT refined analysis
  47. GRB 250321A: Swift-XRT refined Analysis
  48. GRB 250320B: Fermi-LAT detection
  49. GRB 250321A: Swift/UVOT Upper Limits
  50. EP250321a: LCO optical counterpart detection
  51. EP250321a: Swift-XRT detection of an X-ray source
  52. Swift GRB 250321A: Global MASTER-Net observations report
  53. GRB 250321A: GOTO optical upper limits
  54. GRB 250321A: Swift-XRT localisation
  55. GRB 250321A: Fermi GBM Observation
  56. GRB 250321A: Swift detection of a burst
  57. GRB250312A: Swift/UVOT Upper Limits
  58. GRB 250317B: Swift-XRT observations
  59. GRB 250316A: Swift/UVOT Upper Limits
  60. GRB 250314A: REM optical/NIR upper limits
  61. GRB 250316A: AbAO AS-32 Optical Upper Limit
  62. GRB 250316A: Swift-XRT afterglow detection
  63. GRB 250316A: Fermi GBM Observation
  64. GRB 250316A: Swift-XRT observations
  65. GRB 250316A: Swift ToO observations
  66. GRB 250316A: Swift/BAT-GUANO arcminute localization of a burst
  67. GRB 250314A: EP-FXT afterglow detection
  68. GRB 250314A: Swift/UVOT Upper Limits
  69. GRB 250312B: GRBAlpha detection
  70. GRB 250314A: Swift XRT Detection
  71. GRB 250314A: NOT near-infrared candidate counterpart
  72. GRB 250312B: Fermi GBM Observation
  73. GRB 250313A: Swift-XRT observations
  74. Konus-Wind detection of GRB 250308A
  75. GRB 250313A: Fermi-LAT detection
  76. GRB 250313A: Swift ToO observations
  77. GRB 250312B: Swift/BAT-GUANO localization skymap of a burst
  78. EP250304a: SVOM/VT optical observation
  79. EP250302a: Chandra X-ray Detection
  80. GRB 250312A: Swift-XRT refined Analysis
  81. GRB 250312A: Enhanced Swift-XRT position
  82. LIGO/Virgo/KAGRA S250304cb: Upper limits from Swift/BAT-GUANO
  83. GRB 250226B: Fermi GBM Observation
  84. Swift GRB 250312A: Global MASTER-Net observations report
  85. GRB 250302A: Fermi GBM Observation
  86. GRB 250312A: Swift detection of a burst
  87. GRB 241213A: VIRT Optical Upper Limit
  88. GRB 241228A: VIRT Optical Upper Limit
  89. GRB 250223B: Fermi GBM Observation
  90. GRB 250311A: Swift-XRT observations
  91. GRB 250228A: Fermi GBM Observation
  92. GRB 250309B: 1.3m DFOT Optical observations
  93. GRB 250308A: Swift/BAT-GUANO localization skymap of a short burst
  94. GRB 250302A: Swift/BAT-GUANO localization skymap of a burst
  95. GRB 250228A: Swift/BAT-GUANO localization skymap of a likely short burst
  96. GRB 250226B: Swift/BAT-GUANO localization skymap of a likely long GRB
  97. GRB 250226A: Swift/BAT-GUANO localization skymap of a long GRB
  98. GRB 250223B: Swift/BAT-GUANO localization skymap of a short burst
  99. EP250304a: Chandra detection
  100. GRB 250225B: Swift-BAT refined analysis

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