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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"

3999 results found.

  1. IceCube-250429A - IceCube observation of a high-energy neutrino candidate track-like event
  2. EP250428b: Global MASTER-Net observations report
  3. EP250427a/GRB 250427A: FTW optical and NIR observations of the counterpart
  4. EP250427a: TRT optical counterpart detection
  5. EP 250427a: BOOTES-7 optical afterglow candidate
  6. GRB 250424A: SVOM/VT optical observation
  7. GRB 250419A: Mondy Optical Observations
  8. GRB 250424A: Swift/UVOT Detection
  9. GRB250419A: VLA radio detection
  10. GRB 250419A: Mephisto Multi-band Optical Detection
  11. GRB 250419A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  12. GRB 250419A: Optical Observations via Virtual Telescope Project
  13. IceCube Alert 250421.71: Global MASTER-Net observations report
  14. EP250421a: JinShan likely optical counterpart
  15. The EP-WXT trigger 01709135179: Kinder optical counterpart candidate
  16. GRB 250419A: Swift/UVOT Follow up
  17. GRB 250419A: AKO Optical Afterglow Detection
  18. GRB 250419A: SVOM/VT optical bright counterpart confirmation
  19. GRB 250419A: SVOM detection of a soft burst
  20. GRB 250412A: AstroSat CZTI detection
  21. EP250404a: Nanshan 0.43m Telescope optical observatios
  22. Fermi trigger No 766148493: Global MASTER-Net observations report
  23. Fermi trigger No 766173972: Global MASTER-Net observations report
  24. Fermi GRB 250407A: Global MASTER-Net observations report
  25. Fermi GRB 250406A: Global MASTER-Net observations report
  26. GRB 250402A: Mondy optical observations
  27. EP250402a: Einstein Probe detection of a fast X-ray transient
  28. Fermi GRB 250331E: Global MASTER-Net observations report
  29. GRB 250329A: AbAO, Mondy and SAO RAS optical upper limits
  30. IceCube-250330A: Upper limits from a search for additional neutrino events in IceCube
  31. SVOM/sb25033102: SVOM detection of an X-ray transient
  32. GRB 250328A: 1.6m Mephisto optical observations
  33. GRB 250327B: ALMA detection
  34. GRB 250327B: VLA detection
  35. GRB 250327B: SVOM/COLIBRÍ (F-GFT) Further Observations
  36. GRB 250329B: 1.6m Mephisto Optical Upper Limits
  37. GRB250329A: REM optical afterglow detection
  38. GRB 250329A: Swift-XRT afterglow detection
  39. GRB 250329A: Fading optical counterpart detection by LCO.
  40. GRB 250328A: SVOM/COLIBRÍ (F-GFT) optical afterglow candidate
  41. GRB 250328A: VLT/HAWK-I near-infrared afterglow candidate
  42. GRB 250329A: SVOM/VT optical counterpart confirmation
  43. GRB 250329A: SVOM/COLIBRÍ (F-GFT) Detection of a Bright Optical Counterpart Candidate
  44. GRB 250327B: further optical observations by LCOGT
  45. GRB 250327B: SVOM/VT optically bright counterpart
  46. GRB 250327B: SAO RAS optical candidate
  47. IPN triangulation of GRB 250322B
  48. EP-WXT trigger 01709133021: Optical upper limit through Kinder observations
  49. FRB 250316A: DDOTI Continued Optical Observations
  50. GRB 250322A: MASTER optical observation
  51. FRB 20250316A: detection of a candidate associated X-ray source EP J120944.2+585060 by Einstein Probe
  52. EP250321a: SVOM/VT optical observation
  53. GRB 250320B: AstroSat CZTI detection
  54. Fermi GRB 250320B: Global MASTER-Net observations report
  55. GRB 250321A: GOTO optical upper limits
  56. GRB 250319B: Fermi GBM Final Localization
  57. Fermi trigger No 763933627: Global MASTER-Net observations report
  58. GRB 250316A: Swift/UVOT Upper Limits
  59. GRB 250317A: Fermi GBM Final Real-time Localization
  60. Fermi GRB 250313A: Global MASTER-Net observations report
  61. EP250311a/GRB 250311A: EP-FXT follow-up observation
  62. Fermi GRB 250312B: Global MASTER-Net observations report
  63. IceCube-250309A: MITSuME Akeno and Seimei/TriCCS optical observations
  64. GRB 250309B / AT2025dws: SAO RAS optical observations
  65. IceCube Alert 250309.32: Global MASTER-Net observations report
  66. EP250304A: Upper limits from Fermi-GBM Observations
  67. GRB 250219A: SVOM/C-GFT optical upper limit at early phase
  68. IceCube-250302A: Upper limits from a search for additional neutrino events in IceCube
  69. EP250304a: refined analysis of the EP-WXT and EP-FXT observations
  70. EP250302a: Mondy Continued Optical Observations
  71. Fermi GRB 250302A: Global MASTER-Net observations report
  72. Fermi GRB 250225A: Global MASTER-Net observations report
  73. GRB 250225B: Swift detection of a burst
  74. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: AstroSat CZTI non-detection and upper limits
  75. EP250223a: REM NIR upper limit
  76. GRB 250223B: Fermi GBM Final Localization
  77. Fermi trigger No 762020305: Global MASTER-Net observations report
  78. GRB 250221A: continued Assy optical observations, brightening afterglow confirmation
  79. GRB 250221A: continued Mondy optical observations, brightening afterglow
  80. GRB 250213A: Swift-XRT observations
  81. Fermi GRB 250217A: Global MASTER-Net observations report
  82. EP250215a: Global MASTER-Net observations report
  83. Fermi trigger No 761206993: Global MASTER-Net observations report
  84. EP250212a: Xinglong optical upper limit
  85. EP250207b: VLA radio upper limits
  86. Fermi GRB 250212A: Global MASTER-Net observations report
  87. Fermi trigger No 760945500: Global MASTER-Net observations report
  88. LIGO/Virgo/KAGRA S250206dm: continued in SOAR galaxy targeted observations and identification of one possible transient
  89. LIGO/VIRGO/KAGRA S250206dm: AT 2025bbo spectroscopic observations with NIRES on Keck II
  90. GRB 241128A: VIRT Optical Upper Limit
  91. GRB 250210A: AstroSat CZTI detection
  92. GRB 250209A: MAXI/GSC detection (possible detection of an X-ray flare from 1RXS J145110.3+310648)
  93. Fermi GRB 250210A: Global MASTER-Net observations report
  94. LIGO/Virgo/KAGRA S250206dm: Global MASTER-Net observations report
  95. IceCube Alert 250207.09: Global MASTER-Net observations report
  96. LIGO/Virgo/KAGRA S250206dm & FRB 20250206A: MASTER observations and possible mother galaxy
  97. LIGO/Virgo/KAGRA S250206dm: GECKO Observation with 7DT and KMTNet
  98. LIGO/Virgo/KAGRA S250206dm: Candidates from the Zwicky Transient Facility
  99. EP250207a: EP-WXT detection and XRT follow-up observation
  100. LIGO/Virgo/KAGRA S250206dm: DDOTI Upper Limits

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