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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"

21952 results found.

  1. EP250225a: SVOM/VT optical brightening
  2. EP250416a: GSP optical upper limit
  3. EP250416a: Global MASTER-Net observations report
  4. IceCube-250416A: Global MASTER-Net observations report
  5. IceCube 250414.324: DDOTI Optical Observations
  6. EP250304a: ATCA radio observations
  7. EP250404a: Nanshan 0.43m Telescope optical observatios
  8. Fermi trigger No 766148493: Global MASTER-Net observations report
  9. Fermi trigger No 766173972: Global MASTER-Net observations report
  10. GRB 250411A: DDOTI Optical Observations
  11. Fermi GRB 250411A: Global MASTER-Net observations report
  12. GRB 250407A: Continued KAIT/Nickel optical observations
  13. GRB 250314A: e-MERLIN observations
  14. GRB 250407A: Mondy and AbAO Optical Observations
  15. EP250227a: Further NOT optical observations
  16. IceCube-250406A: Swift-XRT observations
  17. AMON Coincidence Alert from the sub-threshold IceCube-HAWC search NuEm-250409A
  18. EP250407a: Global MASTER-Net observations report
  19. GRB 250407A: LCO detection of a fading optical counterpart
  20. Fermi-LAT gamma-ray observations of IceCube-250406A
  21. EP250407a: Swift-XRT observations
  22. EP250407a: EP-WXT detection of a fast X-ray transient
  23. GRB 250407A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  24. GRB 250407A: KAIT Optical Afterglow Candidate
  25. IceCube-250406A: No candidates from the Zwicky Transient Facility
  26. GRB 250407A: Swift-XRT afterglow detection
  27. Fermi GRB 250407A: Global MASTER-Net observations report
  28. GRB 250407A: Swift ToO observations
  29. LIGO/Virgo/KAGRA S250331o: Upper limits from Swift/BAT-GUANO
  30. IceCube 250406A: DDOTI Optical Observations of the Refined Position
  31. IceCube 250406.951: COLIBRÍ/DDRAGO Optical Upper Limit
  32. IceCube 250406.951: DDOTI Optical Observations
  33. IceCube Alert 250406.95: Global MASTER-Net observations report
  34. Fermi trigger No 765663719: Global MASTER-Net observations report
  35. EP250404a: Multi-band Optical Observations from UCAS-70 and XL-C14
  36. Fermi GRB 250406A: Global MASTER-Net observations report
  37. GRB 250404A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  38. EP250404a / GRB 250404A: Montarrenti Observatory optical observations
  39. Fermi trigger No 765619921: Global MASTER-Net observations report
  40. GRB 250404A / EP250404a: SVOM/GWAC-F60 and F50 observations
  41. EP250404a / GRB 250404A: J band observations by SYSU 80cm telescope
  42. GRB 250404A / EP250404a: Mondy optical observations
  43. EP250404a: refined analysis of the EP-WXT and EP-FXT observations
  44. GRB 250404A / EP250404a: Leavitt Observatory optical counterpart detection
  45. GRB 250402A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  46. EP250402a: Optical upper limit with PD 1.3m observations
  47. GRB 250404A / EP250404a: NOT optical observations
  48. GRB 250331D: Swift-XRT afterglow detection
  49. EP250404a: Osservatorio Astronomico "Nastro Verde" optical observations: detection of an optical counterpart
  50. EP250404a: REM optical/NIR observations
  51. EP250404a: Seimei/TriCCS optical counterpart detection
  52. EP250404A: COLIBRÍ/DDRAGO Optical Observations
  53. EP250404A / GRB250404A: Ondrejov D50 optical afterglow detection
  54. EP250404a: LCO optical counterpart detection
  55. Fermi GRB 250404A: Global MASTER-Net observations report
  56. EP250404a: Xinglong decaying optical counterpart
  57. GRB 250403A: Montarrenti Observatory optical detection
  58. EP250404a: Global MASTER-Net observations report
  59. GRB 250403A: KAIT optical observations
  60. EP250404a: LAST detection of optical counterpart
  61. GRB 250402A: Swift/BAT-GUANO localization skymap of a burst
  62. GRB 250403A: Fermi GBM observations
  63. EP250404a: Mephisto multi-band optical detection
  64. EP250321A: J band upper limit by SYSU 80cm telescope
  65. EP250404a: Nanshan/HMT optical counterpart detection
  66. GRB 250402A: Mondy optical observations
  67. EP250402a: Optical upper limit with Kinder observations
  68. GRB 250403A: REM NIR afterglow detection
  69. GRB 250403A: LCO optical counterpart detection
  70. GRB 250403A: JinShan optical observations
  71. GRB 250403A: Optical counterpart detection by LCO.
  72. EP250402a: EP-FXT follow-up observations
  73. GRB 250403A: Swift-XRT observations
  74. GRB 250322A: 10 GHz VLA radio upper limits
  75. Fermi GRB 250403A: Global MASTER-Net observations report
  76. GRB 250403A: GOTO optical counterpart follow-up observations
  77. GRB 250402A: NUTTelA-TAO Early Optical Limits
  78. GRB 250403A: 1.6m Mephisto multi-band optical detection
  79. GRB 250403A: SVOM/C-GFT optical observations
  80. GRB 250403A: GOTO detection of the optical afterglow
  81. GRB 250402A: Swift-XRT observations
  82. GRB 250225B: VLT host galaxy redshift z = 0.950
  83. GRB250402A: SVOM/COLIBRÍ (FM-GFT) Detection of the Optical Counterpart
  84. GRB 250402A: VLT/FORS2 spectroscopic redshift z = 2.823
  85. GRB 250402A: REM optical/NIR upper limits
  86. GRB 250402A: LCO optical counterpart detection
  87. GRB 250402A: refined SVOM/MXT data analysis
  88. EP250402a: Einstein Probe detection of a fast X-ray transient
  89. GRB 250331C: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  90. GRB 250314A: ALMA detection
  91. GRB 250329B: Swift/UVOT Upper Limit
  92. GRB 250329A: Swift/UVOT Upper Limit
  93. GRB 250327B: Swift/UVOT Detection
  94. GRB 250327A: Swift/UVOT Upper Limits
  95. GRB 250327B: Kilonova-Catcher Observations
  96. GRB250331D: AbAO optical observations
  97. GRB 250331C: Swift/UVOT Upper Limits
  98. GRB 250331B: Swift/UVOT Upper Limits
  99. GRB 250328A: AbAO AS-32 Optical Observations
  100. GRB 250219A: NOT candidate host galaxy detection

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