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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"

2902 results found.

  1. IceCube-250406A: No candidates from the Zwicky Transient Facility
  2. GRB 250407A: Swift-XRT afterglow detection
  3. Fermi GRB 250407A: Global MASTER-Net observations report
  4. IceCube 250406.951: COLIBRÍ/DDRAGO Optical Upper Limit
  5. Fermi GRB 250406A: Global MASTER-Net observations report
  6. GRB 250404A / EP250404a: Leavitt Observatory optical counterpart detection
  7. Fermi GRB 250404A: Global MASTER-Net observations report
  8. EP250404a: Xinglong decaying optical counterpart
  9. GRB 250404A: Fermi GBM Detection
  10. EP250404a: AKO Optical Afterglow Detection
  11. GRB 250331B Swift-BAT refined analysis
  12. Fermi GRB 250331E: Global MASTER-Net observations report
  13. LIGO/Virgo/KAGRA S250328ae: Swift XRT observations, 34 possible X-ray sources
  14. Fermi GRB 250330A: Global MASTER-Net observations report
  15. GRB 250330A: Prompt Swift-XRT position
  16. Swift GRB250330.26: Global MASTER-Net observations report
  17. GRB 250327B: ALMA detection
  18. GRB 250327B: VLA detection
  19. GRB 250329A: Fading optical counterpart detection by LCO.
  20. GRB 250327B: SVOM/VT optically bright counterpart
  21. GRB 250327B: SAO RAS optical candidate
  22. GRB 250327A: Fermi GBM observation
  23. GRB 250321C: Fermi GBM Final Real-time Localization
  24. GRB 250317B: Mondy AZT-33IK Continued Optical Observations
  25. FRB 20250316A: Upper limits for gamma-ray transient from Insight-HXMT/HE observations
  26. GRB 250317D: EIRSAT-1 GMOD Detection
  27. EP250315a: Einstein Probe detection of an X-ray transient
  28. GRB 250226A: Mondy AZT-33IK and Koshka Zeiss-1000 Optical Upper Limits
  29. Fermi trigger No 763581136: Global MASTER-Net observations report
  30. Fermi GRB 250313A: Global MASTER-Net observations report
  31. GRB 250313A: Fermi GBM Final Real-time Localization
  32. EP250302a: Chandra X-ray Detection
  33. Fermi trigger No 763509110: Global MASTER-Net observations report
  34. GRB 250311A: Swift-XRT observations
  35. EP250311a: Global MASTER-Net observations report
  36. GRB 250225B: Swift-BAT refined analysis
  37. GRB 250309B / AT2025dws: SAO RAS optical observations
  38. Fermi GRB 250309A: Global MASTER-Net observations report
  39. GRB250309B: One candidate counterpart from the Zwicky Transient Facility
  40. IceCube-250309A: No candidates from the Zwicky Transient Facility
  41. IceCube Alert 250309.32: Global MASTER-Net observations report
  42. Fermi trigger No 762963055: Global MASTER-Net observations report
  43. Fermi GRB 250305A: Global MASTER-Net observations report
  44. IPN triangulation of GRB 250222A
  45. EP250302a : GIT optical follow-up
  46. Fermi GRB 250302A: Global MASTER-Net observations report
  47. EP250302a: Nanshan/HMT optical counterpart detection
  48. LIGO/Virgo/KAGRA S250206dm: early X-ray upper limits from Einstein Probe WXT and preliminary results of FXT observations
  49. EP250227a: Global MASTER-Net observations report
  50. EP250227a: Optical upper limits with Kinder observations
  51. GRB 250205A / EP250205A: further radio observations with the VLA
  52. Fermi GRB 250226A: Global MASTER-Net observations report
  53. Fermi GRB 250225A: Global MASTER-Net observations report
  54. The EP-WXT trigger 01709131882 is likely a flaring star
  55. EP250223a: LCO detection of the afterglow
  56. Konus-Wind detection of GRB 250217C (short)
  57. Fermi GRB 250217A: Global MASTER-Net observations report
  58. GRB 250217A: Fermi GBM Final Real-time Localization
  59. Fermi GRB 250216A: Global MASTER-Net observations report
  60. EP250215a: Global MASTER-Net observations report
  61. EP250207b: Xinglong optical upper limit
  62. EP250212a: Global MASTER-Net observations report
  63. Fermi trigger No 760945500: Global MASTER-Net observations report
  64. GRB 250211A: SVOM trigger sb25021103 is not a GRB
  65. GRB 250212A: Fermi GBM Final Real-time Localization
  66. IceCube-250207A: One candidate from the Zwicky Transient Facility
  67. EP250207b: Global MASTER-Net observations report
  68. GRB 241128A: VIRT Optical Upper Limit
  69. EP250207b: a new X-ray transient detected by Einstein Probe
  70. LIGO/Virgo/KAGRA S250206dm: Global MASTER-Net observations report
  71. LIGO/Virgo/KAGRA S250206dm: COLIBRÍ/DDRAGO Observations of AT2025bbo and Galaxies in the Localization Volume
  72. LIGO/Virgo/KAGRA S250206dm: GECKO Observation with 7DT and KMTNet
  73. LIGO/Virgo/KAGRA S250206dm: NEWFIRM NIR Observations
  74. IceCube-250203A: No transient candidates from the Zwicky Transient Facility
  75. LIGO/Virgo/KAGRA S250206dm: Candidates from the Zwicky Transient Facility
  76. EP trigger 01709131361 (possible EP250207a): NOT optical observations and flaring star
  77. IPN triangulation of GRB 250201A
  78. GRB 250202B: Fermi GBM Detection
  79. The EP-WXT trigger 01709131153 is not a real source
  80. GRB 250128B: VLA radio upper limit
  81. GRB 250129A: REM optical/NIR afterglow detection
  82. GRB 250129A: GOTO optical observations show brightening afterglow
  83. Fermi GRB 250128B: Global MASTER-Net observations report
  84. GRB 250129A: Swift detection of a burst with an optical counterpart
  85. GRB 250117A: Fermi GBM Observation
  86. Fermi GRB 250127B: Global MASTER-Net observations report
  87. IPN triangulation of GRB 250119C
  88. GECAM-A detection of a bright burst from SGR 1E1841-045
  89. EP250125a: Optical upper limit with Kinder observations
  90. Konus-Wind detection of a bright burst from SGR 1E1841-045 on 2025 January 23
  91. IPN triangulation of a bright burst from SGR 1E1841-045
  92. GRB 250119B: Fermi GBM Observation
  93. GRB 250118A: Fermi GBM Final Real-time Localization
  94. GRB 250101A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations and rebrightening.
  95. Integral GRB250114.55: Global MASTER-Net observations report
  96. EP250108a / AT 2025kg: SAO RAS optical observations
  97. GRB 250101B: Fermi GBM Observation
  98. Fermi GRB 250107B: Global MASTER-Net observations report
  99. GRB 250103B: REM optical/NIR upper limits
  100. GRB 250101A: REM optical/NIR counterpart detection

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