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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').

19136 results found.

  1. AMON Coincidence Alert from the sub-threshold IceCube-HAWC search NuEm-250409A
  2. EP250407a: Global MASTER-Net observations report
  3. GRB 250407A: LCO detection of a fading optical counterpart
  4. Fermi-LAT gamma-ray observations of IceCube-250406A
  5. EP250407a: Swift-XRT observations
  6. EP250407a: EP-WXT detection of a fast X-ray transient
  7. GRB 250407A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  8. GRB 250407A: KAIT Optical Afterglow Candidate
  9. IceCube-250406A: No candidates from the Zwicky Transient Facility
  10. GRB 250407A: Swift-XRT afterglow detection
  11. Fermi GRB 250407A: Global MASTER-Net observations report
  12. GRB 250407A: Swift ToO observations
  13. LIGO/Virgo/KAGRA S250331o: Upper limits from Swift/BAT-GUANO
  14. IceCube 250406A: DDOTI Optical Observations of the Refined Position
  15. IceCube 250406.951: COLIBRÍ/DDRAGO Optical Upper Limit
  16. IceCube 250406.951: DDOTI Optical Observations
  17. IceCube Alert 250406.95: Global MASTER-Net observations report
  18. Fermi trigger No 765663719: Global MASTER-Net observations report
  19. EP250404a: Multi-band Optical Observations from UCAS-70 and XL-C14
  20. Fermi GRB 250406A: Global MASTER-Net observations report
  21. GRB 250404A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  22. EP250404a / GRB 250404A: Montarrenti Observatory optical observations
  23. Fermi trigger No 765619921: Global MASTER-Net observations report
  24. GRB 250404A / EP250404a: SVOM/GWAC-F60 and F50 observations
  25. EP250404a / GRB 250404A: J band observations by SYSU 80cm telescope
  26. GRB 250404A / EP250404a: Mondy optical observations
  27. EP250404a: refined analysis of the EP-WXT and EP-FXT observations
  28. GRB 250404A / EP250404a: Leavitt Observatory optical counterpart detection
  29. GRB 250402A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  30. EP250402a: Optical upper limit with PD 1.3m observations
  31. GRB 250404A / EP250404a: NOT optical observations
  32. GRB 250331D: Swift-XRT afterglow detection
  33. EP250404a: Osservatorio Astronomico "Nastro Verde" optical observations: detection of an optical counterpart
  34. EP250404a: REM optical/NIR observations
  35. EP250404a: Seimei/TriCCS optical counterpart detection
  36. EP250404A: COLIBRÍ/DDRAGO Optical Observations
  37. EP250404A / GRB250404A: Ondrejov D50 optical afterglow detection
  38. EP250404a: LCO optical counterpart detection
  39. Fermi GRB 250404A: Global MASTER-Net observations report
  40. EP250404a: Xinglong decaying optical counterpart
  41. GRB 250403A: Montarrenti Observatory optical detection
  42. EP250404a: Global MASTER-Net observations report
  43. GRB 250403A: KAIT optical observations
  44. EP250404a: LAST detection of optical counterpart
  45. GRB 250402A: Swift/BAT-GUANO localization skymap of a burst
  46. GRB 250403A: Fermi GBM observations
  47. EP250404a: Mephisto multi-band optical detection
  48. EP250321A: J band upper limit by SYSU 80cm telescope
  49. EP250404a: Nanshan/HMT optical counterpart detection
  50. GRB 250402A: Mondy optical observations
  51. EP250402a: Optical upper limit with Kinder observations
  52. GRB 250403A: REM NIR afterglow detection
  53. GRB 250403A: LCO optical counterpart detection
  54. GRB 250403A: JinShan optical observations
  55. GRB 250403A: Optical counterpart detection by LCO.
  56. EP250402a: EP-FXT follow-up observations
  57. GRB 250403A: Swift-XRT observations
  58. GRB 250322A: 10 GHz VLA radio upper limits
  59. Fermi GRB 250403A: Global MASTER-Net observations report
  60. GRB 250403A: GOTO optical counterpart follow-up observations
  61. GRB 250402A: NUTTelA-TAO Early Optical Limits
  62. GRB 250403A: 1.6m Mephisto multi-band optical detection
  63. GRB 250403A: SVOM/C-GFT optical observations
  64. GRB 250403A: GOTO detection of the optical afterglow
  65. GRB 250402A: Swift-XRT observations
  66. GRB 250225B: VLT host galaxy redshift z = 0.950
  67. GRB250402A: SVOM/COLIBRÍ (FM-GFT) Detection of the Optical Counterpart
  68. GRB 250402A: VLT/FORS2 spectroscopic redshift z = 2.823
  69. GRB 250402A: REM optical/NIR upper limits
  70. GRB 250402A: LCO optical counterpart detection
  71. GRB 250402A: refined SVOM/MXT data analysis
  72. EP250402a: Einstein Probe detection of a fast X-ray transient
  73. GRB 250331C: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  74. GRB 250314A: ALMA detection
  75. GRB 250329B: Swift/UVOT Upper Limit
  76. GRB 250329A: Swift/UVOT Upper Limit
  77. GRB 250327B: Swift/UVOT Detection
  78. GRB 250327A: Swift/UVOT Upper Limits
  79. GRB 250327B: Kilonova-Catcher Observations
  80. GRB250331D: AbAO optical observations
  81. GRB 250331C: Swift/UVOT Upper Limits
  82. GRB 250331B: Swift/UVOT Upper Limits
  83. GRB 250328A: AbAO AS-32 Optical Observations
  84. GRB 250219A: NOT candidate host galaxy detection
  85. GRB 250331D: Swift-XRT observations
  86. LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Epoch 2)
  87. Fermi GRB 250331E: Global MASTER-Net observations report
  88. Fermi GRB 250331D: Global MASTER-Net observations report
  89. Fermi trigger No 765078057: Global MASTER-Net observations report
  90. GRB 250331D: Swift ToO observations
  91. Swift GRB 250331C: Global MASTER-Net observations report
  92. Swift GRB 250331B: Global MASTER-Net observations report
  93. GRB 250331D: Swift/BAT-GUANO arcminute localization of a burst during slew
  94. LIGO/Virgo/KAGRA S250331o: NED Galaxies in the 3-Initial Localization Volume
  95. LIGO/Virgo/KAGRA S250328ae: Swift XRT observations, 34 possible X-ray sources
  96. GRB 250330A: VLT/FORS2 Afterglow Detection
  97. GRB20250327B: 45th Parallel Observatory upper limit
  98. GRB 250328A: Swift/UVOT Detection
  99. Fermi-LAT gamma-ray observations of IceCube-250330A
  100. GRB 250330A: SVOM/VT optical upper limit

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