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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"

23575 results found.

  1. GRB 250407A: GTC/OSIRIS+ spectroscopic redshift z = 1.36
  2. GRB 250419A: VLT/X-shooter spectroscopic redshift z = 0.845
  3. GRB 250419A: Swift-XRT refined Analysis
  4. GRB 250419A: GOTO optical counterpart detection
  5. GRB 250419A: KAIT optical afterglow observations
  6. Konus-Wind detection of GRB 250416C (a counterpart of EP250416a)
  7. EP250416a: Swift/XRT counterpart fading
  8. Konus-Wind detection of GRB 250403A
  9. EP20250416a: Swift/XRT counterpart detection
  10. IceCube-250416A: DDOTI Optical Observations
  11. SVOM/sb25041603 is not a GRB
  12. EP250416a: GSP optical upper limit
  13. SVOM/sb25041603: SVOM detection of an X-ray transient
  14. Fermi Gamma-ray Burst Monitor trigger 766474855/250416237 is not a GRB
  15. IceCube 250414.324: DDOTI Optical Observations
  16. GRB 250413A: AstroSat CZTI detection
  17. GRB 250412A: AstroSat CZTI detection
  18. GRB 250411A: DDOTI Optical Observations
  19. GRB 250407A: Continued KAIT/Nickel optical observations
  20. EP250227a: Further NOT optical observations
  21. GRB 250320B: cubesat Avion detection
  22. IPN triangulation of GRB 250407A
  23. GRB 250407A: LCO detection of a fading optical counterpart
  24. Fermi-LAT gamma-ray observations of IceCube-250406A
  25. EP250407a: Swift-XRT observations
  26. Konus-Wind detection of GRB 250407A
  27. GRB 250407A: KAIT Optical Afterglow Candidate
  28. GRB 250407A: Swift-XRT afterglow detection
  29. IceCube 250406A: DDOTI Optical Observations of the Refined Position
  30. Konus-Wind detection of GRB 250406B (short/hard)
  31. IceCube 250406.951: DDOTI Optical Observations
  32. GRB 250406A: AstroSat CZTI detection
  33. EP250404a: Multi-band Optical Observations from UCAS-70 and XL-C14
  34. GRB 250406A: Fermi GBM Final Real-time Localization
  35. EP250404a / GRB 250404A: Montarrenti Observatory optical observations
  36. GRB 250404A / EP250404a: SVOM/GWAC-F60 and F50 observations
  37. Konus-Wind detection of GRB 250404A / EP250404a
  38. GRB 250404A / EP250404a: GMG spectroscopic redshift at z ~ 2.627
  39. GRB 250404A / EP250404a: NOT optical observations
  40. GRB 250403A: AstroSat CZTI detection
  41. EP250404a: Osservatorio Astronomico "Nastro Verde" optical observations: detection of an optical counterpart
  42. EP250404a: REM optical/NIR observations
  43. EP250404a: Seimei/TriCCS optical counterpart detection
  44. EP250404A / GRB250404A: Ondrejov D50 optical afterglow detection
  45. EP250404a: LCO optical counterpart detection
  46. EP250404a: Xinglong decaying optical counterpart
  47. GRB 250403A: Montarrenti Observatory optical detection
  48. GRB 250404A: Fermi GBM Detection
  49. GRB 250403A: KAIT optical observations
  50. EP250404a: LAST detection of optical counterpart
  51. EP250404a: Xinglong-2.16m spectroscopic redshift
  52. GRB 250403A: Fermi GBM observations
  53. EP250404a: Mephisto multi-band optical detection
  54. GRB 250331C Swift-BAT refined analysis
  55. GRB 250331B Swift-BAT refined analysis
  56. GRB 250330A Swift-BAT refined analysis
  57. EP250404a: BOOTES-4/JGT optical afterglow detection
  58. EP250402a: Optical upper limit with Kinder observations
  59. GRB 250403A: REM NIR afterglow detection
  60. GRB 250403A: LCO optical counterpart detection
  61. IceCube-250330A: MASTER detection of PKS 2032+107 blazar flare with Zhirkov effect
  62. GRB 250403A: Optical counterpart detection by LCO.
  63. GRB 250403A: GOTO optical counterpart follow-up observations
  64. GRB 250402A: NUTTelA-TAO Early Optical Limits
  65. GRB 250403A: GMG Optical Observation
  66. GRB 250403A: 1.6m Mephisto multi-band optical detection
  67. GRB 250403A: GOTO detection of the optical afterglow
  68. GRB 250403A : SVOM detection of a burst
  69. GRB 250402A: REM optical/NIR upper limits
  70. GRB 250402A: LCO optical counterpart detection
  71. GRB 250402A: refined SVOM/MXT data analysis
  72. GRB 250402B: AstroSat CZTI detection of a short burst
  73. GRB 250327A: Swift/UVOT Upper Limits
  74. GRB 250327B: Kilonova-Catcher Observations
  75. GRB 250331C: Swift/UVOT Upper Limits
  76. GRB 250331B: Swift/UVOT Upper Limits
  77. GRB 250322B: GRBAlpha detection
  78. GRB 250331C: Swift-XRT refined Analysis
  79. GRB 250331B: Swift-XRT refined Analysis
  80. GRB 250331B: Swift-XRT refined Analysis
  81. GRB 250322B possible detection by the AstroSat Satellite
  82. LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Epoch 2)
  83. GRB 250327A Swift-BAT refined analysis
  84. GRB 250329B: CAHA 2.2m telescope optical limit
  85. Konus-Wind detection of GRB 250327B
  86. LIGO/Virgo/KAGRA S250331o: NED Galaxies in the 3-Initial Localization Volume
  87. GRB 250320C : SVOM detection of a burst through offline search
  88. LIGO/Virgo/KAGRA S250328ae: Swift XRT observations, 34 possible X-ray sources
  89. GRB20250327B: 45th Parallel Observatory upper limit
  90. GRB 250328A: Swift-XRT refined Analysis
  91. GRB 250331C: Swift detection of a burst
  92. GRB 250331B: Swift detection of a burst
  93. GRB 250331A: MAXI/GSC detection
  94. LIGO/Virgo/KAGRA S250331o: Identification of a GW compact binary merger candidate
  95. GRB 250330A: BOOTES-7 early optical upper limit
  96. GRB 250330A: Swift/UVOT Upper Limits
  97. GRB 250330A: Swift-XRT afterglow detection
  98. GRB 250328A: 1.6m Mephisto optical observations
  99. GRB 250329B: Swift-XRT afterglow detection
  100. GRB 250330A: Swift detection of a burst

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