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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"

20612 results found.

  1. EP250404a / GRB 250404A: J band observations by SYSU 80cm telescope
  2. GRB 250404A / EP250404a: Mondy optical observations
  3. EP250404a: refined analysis of the EP-WXT and EP-FXT observations
  4. GRB 250404A / EP250404a: Leavitt Observatory optical counterpart detection
  5. GRB 250402A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  6. EP250402a: Optical upper limit with PD 1.3m observations
  7. GRB 250404A / EP250404a: NOT optical observations
  8. GRB 250331D: Swift-XRT afterglow detection
  9. EP250404a: Osservatorio Astronomico "Nastro Verde" optical observations: detection of an optical counterpart
  10. EP250404a: REM optical/NIR observations
  11. EP250404a: Seimei/TriCCS optical counterpart detection
  12. EP250404A: COLIBRÍ/DDRAGO Optical Observations
  13. EP250404A / GRB250404A: Ondrejov D50 optical afterglow detection
  14. EP250404a: LCO optical counterpart detection
  15. Fermi GRB 250404A: Global MASTER-Net observations report
  16. EP250404a: Xinglong decaying optical counterpart
  17. GRB 250403A: Montarrenti Observatory optical detection
  18. EP250404a: Global MASTER-Net observations report
  19. GRB 250403A: KAIT optical observations
  20. EP250404a: LAST detection of optical counterpart
  21. GRB 250402A: Swift/BAT-GUANO localization skymap of a burst
  22. GRB 250403A: Fermi GBM observations
  23. EP250404a: Mephisto multi-band optical detection
  24. EP250321A: J band upper limit by SYSU 80cm telescope
  25. EP250404a: Nanshan/HMT optical counterpart detection
  26. GRB 250402A: Mondy optical observations
  27. EP250402a: Optical upper limit with Kinder observations
  28. GRB 250403A: REM NIR afterglow detection
  29. GRB 250403A: LCO optical counterpart detection
  30. GRB 250403A: JinShan optical observations
  31. GRB 250403A: Optical counterpart detection by LCO.
  32. EP250402a: EP-FXT follow-up observations
  33. GRB 250403A: Swift-XRT observations
  34. GRB 250322A: 10 GHz VLA radio upper limits
  35. Fermi GRB 250403A: Global MASTER-Net observations report
  36. GRB 250403A: GOTO optical counterpart follow-up observations
  37. GRB 250402A: NUTTelA-TAO Early Optical Limits
  38. GRB 250403A: 1.6m Mephisto multi-band optical detection
  39. GRB 250403A: SVOM/C-GFT optical observations
  40. GRB 250403A: GOTO detection of the optical afterglow
  41. GRB 250402A: Swift-XRT observations
  42. GRB 250225B: VLT host galaxy redshift z = 0.950
  43. GRB250402A: SVOM/COLIBRÍ (FM-GFT) Detection of the Optical Counterpart
  44. GRB 250402A: VLT/FORS2 spectroscopic redshift z = 2.823
  45. GRB 250402A: REM optical/NIR upper limits
  46. GRB 250402A: LCO optical counterpart detection
  47. GRB 250402A: refined SVOM/MXT data analysis
  48. EP250402a: Einstein Probe detection of a fast X-ray transient
  49. GRB 250331C: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  50. GRB 250314A: ALMA detection
  51. GRB 250329B: Swift/UVOT Upper Limit
  52. GRB 250329A: Swift/UVOT Upper Limit
  53. GRB 250327B: Swift/UVOT Detection
  54. GRB 250327A: Swift/UVOT Upper Limits
  55. GRB 250327B: Kilonova-Catcher Observations
  56. GRB250331D: AbAO optical observations
  57. GRB 250331C: Swift/UVOT Upper Limits
  58. GRB 250331B: Swift/UVOT Upper Limits
  59. GRB 250328A: AbAO AS-32 Optical Observations
  60. GRB 250219A: NOT candidate host galaxy detection
  61. GRB 250331D: Swift-XRT observations
  62. LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Epoch 2)
  63. Fermi GRB 250331E: Global MASTER-Net observations report
  64. Fermi GRB 250331D: Global MASTER-Net observations report
  65. Fermi trigger No 765078057: Global MASTER-Net observations report
  66. GRB 250331D: Swift ToO observations
  67. Swift GRB 250331C: Global MASTER-Net observations report
  68. Swift GRB 250331B: Global MASTER-Net observations report
  69. GRB 250331D: Swift/BAT-GUANO arcminute localization of a burst during slew
  70. LIGO/Virgo/KAGRA S250331o: NED Galaxies in the 3-Initial Localization Volume
  71. LIGO/Virgo/KAGRA S250328ae: Swift XRT observations, 34 possible X-ray sources
  72. GRB 250330A: VLT/FORS2 Afterglow Detection
  73. GRB20250327B: 45th Parallel Observatory upper limit
  74. GRB 250328A: Swift/UVOT Detection
  75. Fermi-LAT gamma-ray observations of IceCube-250330A
  76. GRB 250330A: SVOM/VT optical upper limit
  77. GRB 250314A: VLA detection
  78. Fermi GRB 250330B: Global MASTER-Net observations report
  79. Fermi GRB 250330A: Global MASTER-Net observations report
  80. GRB 250330A: BOOTES-7 early optical upper limit
  81. GRB 250330A: Swift/UVOT Upper Limits
  82. GRB 250330A: Swift-XRT afterglow detection
  83. GRB 250328A: 1.6m Mephisto optical observations
  84. IceCube Alert 250330.35: Global MASTER-Net observations report
  85. GRB 250330A: VLT/FORS2 Optical Observations
  86. Swift GRB250330.26: Global MASTER-Net observations report
  87. GRB 250329B: SVOM/C-GFT optical upper limit
  88. LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Epoch 1)
  89. GRB 250327B: ALMA detection
  90. GRB 250327B: VLA detection
  91. GRB 250327B: SVOM/COLIBRÍ (F-GFT) Further Observations
  92. GRB 250329B: 1.6m Mephisto Optical Upper Limits
  93. GRB250329A: REM optical afterglow detection
  94. GRB 250329B: GWAC-F50A optical upper limit
  95. GRB 250328A: SVOM/VT optical observation
  96. GRB 250329A: Fading optical counterpart detection by LCO.
  97. GRB 250328A: SVOM/C-GFT optical upper limit
  98. GRB 250328A: SVOM/COLIBRÍ (F-GFT) optical afterglow candidate
  99. GRB 250328A: VLT/HAWK-I near-infrared afterglow candidate
  100. GRB 250329A: SVOM/COLIBRÍ (F-GFT) Detection of a Bright Optical Counterpart Candidate

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