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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"

26057 results found.

  1. Swift GRB 250331B: Global MASTER-Net observations report
  2. GRB 250331D: Swift/BAT-GUANO arcminute localization of a burst during slew
  3. GRB 250331C: Enhanced Swift-XRT position
  4. GRB 250331B: Enhanced Swift-XRT position
  5. LIGO/Virgo/KAGRA S250328ae: Swift XRT observations, 34 possible X-ray sources
  6. GRB 250329B: Swift-XRT confirmation of fading
  7. GRB 250330A: VLT/FORS2 Afterglow Detection
  8. GRB20250327B: 45th Parallel Observatory upper limit
  9. GRB 250328A: Swift/UVOT Detection
  10. GRB 250328A: Swift-XRT refined Analysis
  11. GRB 250330A: Fermi GBM Observation
  12. GRB 250331C: COLIBRÍ/DDRAGO optical upper limit
  13. GRB 250331B: COLIBRÍ/DDRAGO optical upper limit
  14. GRB 250331C: Prompt enhanced Swift-XRT position
  15. GRB 250331C: Swift detection of a burst
  16. GRB 250331B: Swift detection of a burst
  17. GRB 250330A: SVOM/VT optical upper limit
  18. GRB 250330A: BOOTES-7 early optical upper limit
  19. GRB 250330A: Swift/UVOT Upper Limits
  20. GRB 250330A: Swift-XRT afterglow detection
  21. GRB 250328A: 1.6m Mephisto optical observations
  22. GRB 250329B: SVOM/COLIBRÍ (F-GFT) optical upper limit
  23. GRB 250330A: Fermi GBM Final Localization
  24. GRB 250330A: VLT/FORS2 Optical Observations
  25. GRB 250330A: Prompt Swift-XRT position
  26. GRB 250329B: Swift-XRT afterglow detection
  27. GRB 250330A: Swift detection of a burst
  28. Swift GRB250330.26: Global MASTER-Net observations report
  29. GRB 250328A: A fading optical afterglow confirmed by SVOM/VT
  30. GRB 250329B: SVOM/C-GFT optical upper limit
  31. GRB 250329B: SVOM/VT optical upper limit
  32. GRB250329A: REM optical afterglow detection
  33. GRB 250329A: Swift-XRT afterglow detection
  34. GRB 250328A: SVOM/C-GFT optical upper limit
  35. GRB 250328A: SVOM/COLIBRÍ (F-GFT) optical afterglow candidate
  36. GRB 250328A: VLT/HAWK-I near-infrared afterglow candidate
  37. GRB 250327B: LCO optical counterpart detection
  38. GRB 250327B: CrAO and SAO RAS Optical Observations
  39. GRB 250327B: OHP/T193 spectroscopic observations and redshift confirmation
  40. GRB 250322A: GRANDMA/TNOT optical upper limits
  41. GRB 250327A: SVOM/VT upper limits on the XRT position
  42. GRB 250327B: SVOM/COLIBRÍ (F-GFT) follow-up observations
  43. GRB 250327B: Swift-XRT detection of the X-ray afterglow
  44. GRB 250327B: 1.6m Mephisto optical observations
  45. GRB 250327B: NOT spectroscopic redshift z = 3.035
  46. GRB 250327A: Swift-XRT refined Analysis
  47. FRB 20250316A: The sub-arcsecond localization of FRB 20250316A using CHIME/FRB Outriggers coincides with reported X-ray counterparts
  48. GRB 250327A: J-band observations with WINTER
  49. GRB 250327A: SVOM/VT optical candidate
  50. GRB 250327A: Fermi GBM observation
  51. Swift GRB 250327A: Global MASTER-Net observations report
  52. GRB 250327A: DDOTI Optical Observations
  53. GRB 250327A: COLIBRÍ optical upper limit
  54. GRB 250327A: Swift detection of a burst
  55. Konus-Wind detection of GRB 250322A (short)
  56. IPN triangulation of GRB 250322B
  57. EP250321a: Mondy AZT-33IK Continued Optical Observations
  58. Swift follow-up observations of FRB250316A and EP J120944.2+585060
  59. GRB 250322A: Swift-BAT refined analysis
  60. GRB 250321B: ISON-Kitab RC-36 Optical Upper Limit
  61. GRB 250322A: further NOT optical observations
  62. EP-WXT trigger 01709133021: Optical upper limit through Kinder observations
  63. GRB 250322A: Swift/UVOT Upper Limits
  64. GRB 250322A: VLT/X-shooter redshift confirmation of the putative host galaxy
  65. GRB 250321B: Swift-XRT observations
  66. GRB 250322A: Swift-XRT refined Analysis
  67. EP250321a: TNOT Observation of Optical Counterpart
  68. GRB 250322A: Gemini-North redshift of candidate host galaxy
  69. GRB 250322A: AstroSat CZTI detection of a short burst
  70. GRB250322A: STEP/T80S optical limits
  71. GRB 250322A: Gemini-South optical observations
  72. GRB 250322A: VLT optical observations
  73. GRB 250322A: VLT near-infrared observations
  74. GRB 250322A: NOT optical upper limits
  75. GRB 250322A: Enhanced Swift-XRT position
  76. FRB 20250316A: Kinder optical upper limits of the Einstein Probe candidate X-ray source EP J120944.2+585060
  77. GRB 250322A: MASTER optical observation
  78. EP250321a: Mondy AZT-33IK Optical Observations
  79. GRB 250322A: Swift detection of a short burst
  80. EP250321a: refined analysis of the EP-WXT and EP-FXT observations
  81. EP250321a: KAIT optical observations
  82. GRB 250225B: GECAM-A detection
  83. GRB 250312A: GECAM-A detection
  84. GRB 250321B: Swift ToO observations
  85. EP250321a: WFST optical observations
  86. GRB 250321A: Swift-BAT refined analysis
  87. GRB 250321A: Swift-XRT refined Analysis
  88. GRB 250320B: Fermi-LAT detection
  89. GRB 250321A: Swift/UVOT Upper Limits
  90. EP250321a: LCO optical counterpart detection
  91. EP250321a: Swift-XRT detection of an X-ray source
  92. EP250321a: VLT/X-shooter redshift z = 4.368
  93. EP250321a: REM optical/NIR afterglow detection
  94. EP250321a: BOOTES-5/JGT optical afterglow detection
  95. Swift GRB 250321A: Global MASTER-Net observations report
  96. GRB 250321A: GOTO optical upper limits
  97. GRB 250321A: Swift-XRT localisation
  98. GRB 250314A: Keck/NIRC2 J-band upper limit
  99. EP250226a/GRB 250226A: KAIT optical observations
  100. GRB 250321A: Fermi GBM Observation

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