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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"

3029 results found.

  1. Fermi GRB 250601A: Global MASTER-Net observations report
  2. GRB 250602A: Fermi GBM Final Real-time Localization
  3. Fermi trigger No 770470765: Global MASTER-Net observations report
  4. GRB 250527B / MAXI J1450-527 : MAXI/GSC detection
  5. GRB 250521D: LAST tentative optical counterpart candidate
  6. Fermi GRB 250516A: Global MASTER-Net observations report
  7. GRB 250515A: 1.6m Mephisto optical detection
  8. EP250512a: Global MASTER-Net observations report
  9. Fermi GRB 250510C: Global MASTER-Net observations report
  10. Fermi GRB 250510B: Global MASTER-Net observations report
  11. IceCube-250506A: No Transient Candidates from the Zwicky Transient Facility
  12. EP250508a: Global MASTER-Net observations report
  13. EP250508a: Einstein Probe detection of an X-ray transient
  14. IceCube Alert 250506.59: Global MASTER-Net observations report
  15. GRB 250504A: Swift-XRT refined Analysis
  16. EP250428b: SAO RAS optical upper limit
  17. EP250427a / GRB 250427A: LCO optical counterpart detection
  18. GRB 250424A: BlackGEM optical afterglow detection
  19. IceCube-250421A: DDOTI Detection of the LAST Candidate
  20. IceCube Alert 250421.71: Global MASTER-Net observations report
  21. IceCube-Cascade 250414A: Upper limits from a search for additional neutrino events in IceCube
  22. GRB 250419A: MASTER optical afterglow observation
  23. Konus-Wind detection of GRB 250416C (a counterpart of EP250416a)
  24. EP250416a: Global MASTER-Net observations report
  25. EP250404a: Nanshan 0.43m Telescope optical observatios
  26. Fermi trigger No 766173972: Global MASTER-Net observations report
  27. GRB 250407A: KAIT Optical Afterglow Candidate
  28. IceCube-250406A: No candidates from the Zwicky Transient Facility
  29. GRB 250407A: Swift-XRT afterglow detection
  30. Fermi GRB 250407A: Global MASTER-Net observations report
  31. IceCube 250406.951: COLIBRÍ/DDRAGO Optical Upper Limit
  32. Fermi GRB 250406A: Global MASTER-Net observations report
  33. GRB 250404A / EP250404a: Leavitt Observatory optical counterpart detection
  34. Fermi GRB 250404A: Global MASTER-Net observations report
  35. EP250404a: Xinglong decaying optical counterpart
  36. GRB 250404A: Fermi GBM Detection
  37. EP250404a: AKO Optical Afterglow Detection
  38. GRB 250331B Swift-BAT refined analysis
  39. Fermi GRB 250331E: Global MASTER-Net observations report
  40. LIGO/Virgo/KAGRA S250328ae: Swift XRT observations, 34 possible X-ray sources
  41. Fermi GRB 250330A: Global MASTER-Net observations report
  42. GRB 250330A: Prompt Swift-XRT position
  43. Swift GRB250330.26: Global MASTER-Net observations report
  44. GRB 250327B: ALMA detection
  45. GRB 250327B: VLA detection
  46. GRB 250329A: Fading optical counterpart detection by LCO.
  47. GRB 250327B: SVOM/VT optically bright counterpart
  48. GRB 250327B: SAO RAS optical candidate
  49. GRB 250327A: Fermi GBM observation
  50. GRB 250321C: Fermi GBM Final Real-time Localization
  51. GRB 250317B: Mondy AZT-33IK Continued Optical Observations
  52. FRB 20250316A: Upper limits for gamma-ray transient from Insight-HXMT/HE observations
  53. GRB 250317D: EIRSAT-1 GMOD Detection
  54. EP250315a: Einstein Probe detection of an X-ray transient
  55. GRB 250226A: Mondy AZT-33IK and Koshka Zeiss-1000 Optical Upper Limits
  56. Fermi trigger No 763581136: Global MASTER-Net observations report
  57. Fermi GRB 250313A: Global MASTER-Net observations report
  58. GRB 250313A: Fermi GBM Final Real-time Localization
  59. EP250302a: Chandra X-ray Detection
  60. Fermi trigger No 763509110: Global MASTER-Net observations report
  61. GRB 250311A: Swift-XRT observations
  62. EP250311a: Global MASTER-Net observations report
  63. GRB 250225B: Swift-BAT refined analysis
  64. GRB 250309B / AT2025dws: SAO RAS optical observations
  65. Fermi GRB 250309A: Global MASTER-Net observations report
  66. GRB250309B: One candidate counterpart from the Zwicky Transient Facility
  67. IceCube-250309A: No candidates from the Zwicky Transient Facility
  68. IceCube Alert 250309.32: Global MASTER-Net observations report
  69. Fermi trigger No 762963055: Global MASTER-Net observations report
  70. Fermi GRB 250305A: Global MASTER-Net observations report
  71. IPN triangulation of GRB 250222A
  72. EP250302a : GIT optical follow-up
  73. Fermi GRB 250302A: Global MASTER-Net observations report
  74. EP250302a: Nanshan/HMT optical counterpart detection
  75. LIGO/Virgo/KAGRA S250206dm: early X-ray upper limits from Einstein Probe WXT and preliminary results of FXT observations
  76. EP250227a: Global MASTER-Net observations report
  77. EP250227a: Optical upper limits with Kinder observations
  78. GRB 250205A / EP250205A: further radio observations with the VLA
  79. Fermi GRB 250226A: Global MASTER-Net observations report
  80. Fermi GRB 250225A: Global MASTER-Net observations report
  81. The EP-WXT trigger 01709131882 is likely a flaring star
  82. EP250223a: LCO detection of the afterglow
  83. Konus-Wind detection of GRB 250217C (short)
  84. Fermi GRB 250217A: Global MASTER-Net observations report
  85. GRB 250217A: Fermi GBM Final Real-time Localization
  86. Fermi GRB 250216A: Global MASTER-Net observations report
  87. EP250215a: Global MASTER-Net observations report
  88. EP250207b: Xinglong optical upper limit
  89. EP250212a: Global MASTER-Net observations report
  90. Fermi trigger No 760945500: Global MASTER-Net observations report
  91. GRB 250211A: SVOM trigger sb25021103 is not a GRB
  92. GRB 250212A: Fermi GBM Final Real-time Localization
  93. IceCube-250207A: One candidate from the Zwicky Transient Facility
  94. EP250207b: Global MASTER-Net observations report
  95. GRB 241128A: VIRT Optical Upper Limit
  96. EP250207b: a new X-ray transient detected by Einstein Probe
  97. LIGO/Virgo/KAGRA S250206dm: Global MASTER-Net observations report
  98. LIGO/Virgo/KAGRA S250206dm: COLIBRÍ/DDRAGO Observations of AT2025bbo and Galaxies in the Localization Volume
  99. LIGO/Virgo/KAGRA S250206dm: GECKO Observation with 7DT and KMTNet
  100. LIGO/Virgo/KAGRA S250206dm: NEWFIRM NIR Observations

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