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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. Fermi-LAT Gamma-ray Observations of IceCube-250426A
  2. EP250427a / GRB 250427A: OHP/T193 photometric observations
  3. EP250427a: EP-FXT follow-up observations
  4. EP250427a/GRB 250427A: FTW optical and NIR observations of the counterpart
  5. EP250427a: Lesedi optical counterpart detection
  6. EP250427A: COLIBRÍ Continuing Optical Observations
  7. GRB250427A/EP250427a GIT optical afterglow detection:
  8. EP250427a: LT optical counterpart detection
  9. GRB 250427A: Swift-XRT refined Analysis
  10. EP250427a / GRB 250427A: LCO optical counterpart detection
  11. EP250427A/GRB250427A: Keck/LRIS redshift
  12. EP250427a: REM optical/NIR afterglow detection
  13. GRB 250424A: LCO optical observation
  14. GRB 250427A/ EP250427a: Fermi-GBM Sub-Threshold Detection
  15. EP250427A: COLIBRÍ Optical Detection
  16. EP250427a: TRT optical counterpart detection
  17. EP 250427a: BOOTES-7 optical afterglow candidate
  18. EP250427a: Global MASTER-Net observations report
  19. IceCube Alert 250426.74: Global MASTER-Net observations report
  20. GRB 250424A: PRIME near-infrared detection
  21. GRB 250424A: WINTER J-band detection
  22. GRB 250424A: EIRSAT-1 GMOD Detection
  23. GRB 250424A: SVOM/VT optical observation
  24. GRB 250419A: Mondy Optical Observations
  25. GRB 250424A: Swift/UVOT Detection
  26. Fermi-LAT gamma-ray observations of IceCube-250421A
  27. GRB 250424A: Skynet Optical Observations
  28. GRB 250424A: Kilonova-Catcher optical afterglow detection
  29. GRB 250419a: Continued Liverpool Telescope observations
  30. GRB 250419A: Liverpool Telescope optical upper limit
  31. GRB 250419A: SVOM/ECLAIRs refined analysis
  32. GRB 250424A: COLIBRÍ Detection of a Bright Optical Counterpart
  33. GRB 250424A: VLT/X-shooter spectroscopic redshift z = 0.310
  34. GRB 250424A: likely host galaxy
  35. GRB 250424A: DDOTI Afterglow Detection
  36. GRB 250424A: REM optical/NIR afterglow detection
  37. Swift GRB250424A: Global MASTER-Net observations report
  38. LIGO/Virgo/KAGRA S250328ae: Subaru/PFS Spectroscopic Follow up and Candidates
  39. EP250421a: Nickel optical upper limit
  40. EP250416a / GRB 250416C: Gemini GMOS-S likely host galaxy redshift z = 0.963
  41. EP250421a: Upper limits from Fermi-GBM Observations
  42. SVOM/sb25042207: XRT observations
  43. SVOM/sb25042207: BOOTES-2 early optical upper limit
  44. SVOM/sb25042207: GOTO optical upper limits
  45. SVOM/sb25042207: SVOM detection of an X-ray transient
  46. GRB250419A: VLA radio detection
  47. IceCube-250421A: DDOTI Detection of the LAST Candidate
  48. GRB 250419A: Mephisto Multi-band Optical Detection
  49. GRB 250419A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  50. IC-250421A: LAST optical observations of the IceCube neutrino candidate
  51. EP250421a: NOT optical observations
  52. GRB 250419A: Optical Observations via Virtual Telescope Project
  53. EP250421a: REM optical upper limit
  54. EP250421a: Swift/XRT counterpart detection
  55. EP250421A: COLIBRÍ Optical Upper Limit
  56. GRB 250419A: Mondy Continued Optical Observations
  57. Fermi GRB 250421A: Global MASTER-Net observations report
  58. EP250421a: Global MASTER-Net observations report
  59. EP250421a: Mephisto optical counterpart confirmation
  60. IceCube Alert 250421.71: Global MASTER-Net observations report
  61. EP250421a: JinShan likely optical counterpart
  62. The EP-WXT trigger 01709135179: Kinder optical counterpart candidate
  63. GRB 250419A: Liverpool Telescope observations
  64. GRB 250419A: LCO optical observation
  65. GRB 250419A: JinShan optical observations
  66. GRB 250419A: SVOM/VT optical continuous observations
  67. GRB 250419A: SVOM/C-GFT optical observations
  68. GRB 250419A: Swift/UVOT Follow up
  69. GRB 250419A: LCO optical afterglow multi-band observations
  70. GRB 250419A: Mondy and AbAO Optical Observations
  71. GRB 250419A: Liverpool Telescope observations
  72. GRB 250419A: MASTER optical afterglow observation
  73. Fermi-LAT Gamma-ray Observations of IceCube-250416A
  74. GRB 250407A: GTC/OSIRIS+ spectroscopic redshift z = 1.36
  75. GRB 250419A: VLT/X-shooter spectroscopic redshift z = 0.845
  76. GRB 250419A: GOTO optical counterpart detection
  77. GRB 250419A: KAIT optical afterglow observations
  78. GRB 250419A: SVOM/COLIBRÍ (FM-GFT) Detection of the Optical Counterpart
  79. EP250416a: Swift/XRT counterpart fading
  80. EP250416a: refined EP-WXT and EP-FXT analysis
  81. EP20250416a: Swift/XRT counterpart detection
  82. GRB 250403A: VLT/FORS2 spectroscopic redshift z = 1.847
  83. IceCube-250416A: DDOTI Optical Observations
  84. EP250416a: Gemini South-GMOS optical counterpart
  85. EP250225a: SVOM/VT optical brightening
  86. EP250416a: GSP optical upper limit
  87. EP250416a: Global MASTER-Net observations report
  88. IceCube-250416A: Global MASTER-Net observations report
  89. IceCube 250414.324: DDOTI Optical Observations
  90. EP250304a: ATCA radio observations
  91. EP250404a: Nanshan 0.43m Telescope optical observatios
  92. Fermi trigger No 766148493: Global MASTER-Net observations report
  93. Fermi trigger No 766173972: Global MASTER-Net observations report
  94. GRB 250411A: DDOTI Optical Observations
  95. Fermi GRB 250411A: Global MASTER-Net observations report
  96. GRB 250407A: Continued KAIT/Nickel optical observations
  97. GRB 250314A: e-MERLIN observations
  98. GRB 250407A: Mondy and AbAO Optical Observations
  99. EP250227a: Further NOT optical observations
  100. IceCube-250406A: Swift-XRT observations

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