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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"

32532 results found.

  1. GRB 250419A: VLT/X-shooter spectroscopic redshift z = 0.845
  2. GRB 250419A: Swift-XRT refined Analysis
  3. GRB 250419A: GOTO optical counterpart detection
  4. GRB 250419A: KAIT optical afterglow observations
  5. GRB 250419A: SVOM/VT optical bright counterpart confirmation
  6. GRB 250419A: SVOM/COLIBRÍ (FM-GFT) Detection of the Optical Counterpart
  7. Konus-Wind detection of GRB 250416C (a counterpart of EP250416a)
  8. EP250416a: Swift/XRT counterpart fading
  9. EP250416a: refined EP-WXT and EP-FXT analysis
  10. Konus-Wind detection of GRB 250403A
  11. EP20250416a: Swift/XRT counterpart detection
  12. GRB 250403A: VLT/FORS2 spectroscopic redshift z = 1.847
  13. IceCube-250416A: DDOTI Optical Observations
  14. EP250416a: Gemini South-GMOS optical counterpart
  15. EP250225a: SVOM/VT optical brightening
  16. SVOM/sb25041603 is not a GRB
  17. EP250416a: GSP optical upper limit
  18. EP250416a: Global MASTER-Net observations report
  19. SVOM/sb25041603: SVOM/COLIBRÍ (FM-GFT) Upper Limit on the Optical Counterpart
  20. GRB 250413A: AstroSat CZTI detection
  21. EP250304a: ATCA radio observations
  22. EP250404a: Nanshan 0.43m Telescope optical observatios
  23. GRB 250411A: DDOTI Optical Observations
  24. Fermi GRB 250411A: Global MASTER-Net observations report
  25. GRB 250407A: Continued KAIT/Nickel optical observations
  26. GRB 250314A: e-MERLIN observations
  27. GRB 250407A: Mondy and AbAO Optical Observations
  28. EP250227a: Further NOT optical observations
  29. GRB 250320B: cubesat Avion detection
  30. IceCube-250406A: Swift-XRT observations
  31. IPN triangulation of GRB 250321D (consistent with the fast X-ray transient EP250321a)
  32. IPN triangulation of GRB 250407A
  33. EP250407a: Global MASTER-Net observations report
  34. GRB 250407A: LCO detection of a fading optical counterpart
  35. Fermi-LAT gamma-ray observations of IceCube-250406A
  36. EP250407a: Swift-XRT observations
  37. IceCube-250406A: Upper limits from a search for additional neutrino events in IceCube
  38. Konus-Wind detection of GRB 250407A
  39. GRB 250407A: SVOM/GRM observation of a bright long burst
  40. GRB 250407A: EP-WXT afterglow detection
  41. EP250407a: EP-WXT detection of a fast X-ray transient
  42. GRB 250407A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  43. GRB 250407A: KAIT Optical Afterglow Candidate
  44. IceCube-250406A: No candidates from the Zwicky Transient Facility
  45. GRB 250407A: Fermi GBM Detection
  46. GRB 250407A: Swift-XRT afterglow detection
  47. Fermi GRB 250407A: Global MASTER-Net observations report
  48. GRB 250407A: Swift ToO observations
  49. GRB 250407A: SRG/ART-XC afterglow detection
  50. IceCube 250406A: DDOTI Optical Observations of the Refined Position
  51. Konus-Wind detection of GRB 250406B (short/hard)
  52. IPN triangulation of GRB 250406B (short/hard)
  53. IceCube 250406.951: COLIBRÍ/DDRAGO Optical Upper Limit
  54. GRB 250406A: AstroSat CZTI detection
  55. EP250404a: Multi-band Optical Observations from UCAS-70 and XL-C14
  56. Fermi GRB 250406A: Global MASTER-Net observations report
  57. GRB 250404A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  58. EP250404a / GRB 250404A: Montarrenti Observatory optical observations
  59. GRB 250404A / EP250404a: RC500 INASAN-Kislovodsk optical upper limit
  60. GRB 250404A / EP250404a: SVOM/GWAC-F60 and F50 observations
  61. EP250404a / GRB 250404A: J band observations by SYSU 80cm telescope
  62. Konus-Wind detection of GRB 250404A / EP250404a
  63. GRB 250404A / EP250404a: Mondy optical observations
  64. EP250404a: refined analysis of the EP-WXT and EP-FXT observations
  65. GRB 250404A / EP250404a: GMG spectroscopic redshift at z ~ 2.627
  66. GRB 250404A / EP250404a: Leavitt Observatory optical counterpart detection
  67. GRB 250402A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  68. EP250402a: Optical upper limit with PD 1.3m observations
  69. GRB 250404A / EP250404a: NOT optical observations
  70. GRB 250403A: AstroSat CZTI detection
  71. EP250404a: Osservatorio Astronomico "Nastro Verde" optical observations: detection of an optical counterpart
  72. EP250404a: REM optical/NIR observations
  73. EP250404a: Seimei/TriCCS optical counterpart detection
  74. EP250404A: COLIBRÍ/DDRAGO Optical Observations
  75. EP250404A / GRB250404A: Ondrejov D50 optical afterglow detection
  76. EP250404a: LCO optical counterpart detection
  77. Fermi GRB 250404A: Global MASTER-Net observations report
  78. GRB 250403A: Montarrenti Observatory optical detection
  79. EP250404a: Global MASTER-Net observations report
  80. GRB 250403A: KAIT optical observations
  81. EP250404a: AKO Optical Afterglow Detection
  82. EP250404a: LAST detection of optical counterpart
  83. GRB 250402A: Swift/BAT-GUANO localization skymap of a burst
  84. EP250404a: Xinglong-2.16m spectroscopic redshift
  85. GRB 250403A: Fermi GBM observations
  86. GRB 250327B: VIRT Optical Upper Limit
  87. EP250404a: Mephisto multi-band optical detection
  88. GRB 250331C Swift-BAT refined analysis
  89. GRB 250331B Swift-BAT refined analysis
  90. GRB 250330A Swift-BAT refined analysis
  91. EP250321A: J band upper limit by SYSU 80cm telescope
  92. EP250404a: BOOTES-4/JGT optical afterglow detection
  93. EP250404a: Nanshan/HMT optical counterpart detection
  94. EP250404a: Einstein Probe detection of an X-ray transient
  95. GRB 250402A: Mondy optical observations
  96. GRB 250403A: Swift/UVOT Detection
  97. GRB 250402A: Swift/UVOT Upper Limits
  98. EP250402a: Optical upper limit with Kinder observations
  99. GRB 250403A: SVOM/VT optical observation
  100. GRB 250403A: REM NIR afterglow detection

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