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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"

2907 results found.

  1. IceCube 250406.951: COLIBRÍ/DDRAGO Optical Upper Limit
  2. Fermi GRB 250406A: Global MASTER-Net observations report
  3. GRB 250404A / EP250404a: Leavitt Observatory optical counterpart detection
  4. Fermi GRB 250404A: Global MASTER-Net observations report
  5. EP250404a: Xinglong decaying optical counterpart
  6. GRB 250404A: Fermi GBM Detection
  7. EP250404a: AKO Optical Afterglow Detection
  8. GRB 250331B Swift-BAT refined analysis
  9. Fermi GRB 250331E: Global MASTER-Net observations report
  10. LIGO/Virgo/KAGRA S250328ae: Swift XRT observations, 34 possible X-ray sources
  11. Fermi GRB 250330A: Global MASTER-Net observations report
  12. GRB 250330A: Prompt Swift-XRT position
  13. Swift GRB250330.26: Global MASTER-Net observations report
  14. GRB 250327B: ALMA detection
  15. GRB 250327B: VLA detection
  16. GRB 250329A: Fading optical counterpart detection by LCO.
  17. GRB 250327B: SVOM/VT optically bright counterpart
  18. GRB 250327B: SAO RAS optical candidate
  19. GRB 250327A: Fermi GBM observation
  20. GRB 250321C: Fermi GBM Final Real-time Localization
  21. GRB 250317B: Mondy AZT-33IK Continued Optical Observations
  22. FRB 20250316A: Upper limits for gamma-ray transient from Insight-HXMT/HE observations
  23. GRB 250317D: EIRSAT-1 GMOD Detection
  24. EP250315a: Einstein Probe detection of an X-ray transient
  25. GRB 250226A: Mondy AZT-33IK and Koshka Zeiss-1000 Optical Upper Limits
  26. Fermi trigger No 763581136: Global MASTER-Net observations report
  27. Fermi GRB 250313A: Global MASTER-Net observations report
  28. GRB 250313A: Fermi GBM Final Real-time Localization
  29. EP250302a: Chandra X-ray Detection
  30. Fermi trigger No 763509110: Global MASTER-Net observations report
  31. GRB 250311A: Swift-XRT observations
  32. EP250311a: Global MASTER-Net observations report
  33. GRB 250225B: Swift-BAT refined analysis
  34. GRB 250309B / AT2025dws: SAO RAS optical observations
  35. Fermi GRB 250309A: Global MASTER-Net observations report
  36. GRB250309B: One candidate counterpart from the Zwicky Transient Facility
  37. IceCube-250309A: No candidates from the Zwicky Transient Facility
  38. IceCube Alert 250309.32: Global MASTER-Net observations report
  39. Fermi trigger No 762963055: Global MASTER-Net observations report
  40. Fermi GRB 250305A: Global MASTER-Net observations report
  41. IPN triangulation of GRB 250222A
  42. EP250302a : GIT optical follow-up
  43. Fermi GRB 250302A: Global MASTER-Net observations report
  44. EP250302a: Nanshan/HMT optical counterpart detection
  45. LIGO/Virgo/KAGRA S250206dm: early X-ray upper limits from Einstein Probe WXT and preliminary results of FXT observations
  46. EP250227a: Global MASTER-Net observations report
  47. EP250227a: Optical upper limits with Kinder observations
  48. GRB 250205A / EP250205A: further radio observations with the VLA
  49. Fermi GRB 250226A: Global MASTER-Net observations report
  50. Fermi GRB 250225A: Global MASTER-Net observations report
  51. The EP-WXT trigger 01709131882 is likely a flaring star
  52. EP250223a: LCO detection of the afterglow
  53. Konus-Wind detection of GRB 250217C (short)
  54. Fermi GRB 250217A: Global MASTER-Net observations report
  55. GRB 250217A: Fermi GBM Final Real-time Localization
  56. Fermi GRB 250216A: Global MASTER-Net observations report
  57. EP250215a: Global MASTER-Net observations report
  58. EP250207b: Xinglong optical upper limit
  59. EP250212a: Global MASTER-Net observations report
  60. Fermi trigger No 760945500: Global MASTER-Net observations report
  61. GRB 250211A: SVOM trigger sb25021103 is not a GRB
  62. GRB 250212A: Fermi GBM Final Real-time Localization
  63. IceCube-250207A: One candidate from the Zwicky Transient Facility
  64. EP250207b: Global MASTER-Net observations report
  65. GRB 241128A: VIRT Optical Upper Limit
  66. EP250207b: a new X-ray transient detected by Einstein Probe
  67. LIGO/Virgo/KAGRA S250206dm: Global MASTER-Net observations report
  68. LIGO/Virgo/KAGRA S250206dm: COLIBRÍ/DDRAGO Observations of AT2025bbo and Galaxies in the Localization Volume
  69. LIGO/Virgo/KAGRA S250206dm: GECKO Observation with 7DT and KMTNet
  70. LIGO/Virgo/KAGRA S250206dm: NEWFIRM NIR Observations
  71. IceCube-250203A: No transient candidates from the Zwicky Transient Facility
  72. LIGO/Virgo/KAGRA S250206dm: Candidates from the Zwicky Transient Facility
  73. EP trigger 01709131361 (possible EP250207a): NOT optical observations and flaring star
  74. IPN triangulation of GRB 250201A
  75. GRB 250202B: Fermi GBM Detection
  76. The EP-WXT trigger 01709131153 is not a real source
  77. GRB 250128B: VLA radio upper limit
  78. GRB 250129A: REM optical/NIR afterglow detection
  79. GRB 250129A: GOTO optical observations show brightening afterglow
  80. Fermi GRB 250128B: Global MASTER-Net observations report
  81. GRB 250129A: Swift detection of a burst with an optical counterpart
  82. GRB 250117A: Fermi GBM Observation
  83. Fermi GRB 250127B: Global MASTER-Net observations report
  84. IPN triangulation of GRB 250119C
  85. GECAM-A detection of a bright burst from SGR 1E1841-045
  86. EP250125a: Optical upper limit with Kinder observations
  87. Konus-Wind detection of a bright burst from SGR 1E1841-045 on 2025 January 23
  88. IPN triangulation of a bright burst from SGR 1E1841-045
  89. GRB 250119B: Fermi GBM Observation
  90. GRB 250118A: Fermi GBM Final Real-time Localization
  91. GRB 250101A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations and rebrightening.
  92. Integral GRB250114.55: Global MASTER-Net observations report
  93. EP250108a / AT 2025kg: SAO RAS optical observations
  94. GRB 250101B: Fermi GBM Observation
  95. Fermi GRB 250107B: Global MASTER-Net observations report
  96. GRB 250103B: REM optical/NIR upper limits
  97. GRB 250101A: REM optical/NIR counterpart detection
  98. GRB 250106A: Swift-XRT observations
  99. GRB 250101A: Swift-BAT refined analysis
  100. GRB 250101A: Montarrenti Observatory optical observations and rebrightening

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