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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"

27074 results found.

  1. LIGO/Virgo/KAGRA S250912s: 2 counterpart neutrino candidate events from an IceCube neutrino search
  2. EP250908c: tentative VLT/FORS2 redshift z = 2.87
  3. EP250911a: Upper limit from Fermi-GBM Observations
  4. GRB 250911A: GECAM-B detection
  5. GRB 250911A: Swift-BAT refined analysis
  6. EP250911a: GTC/OSIRIS+ spectroscopic redshift z = 3.84
  7. EP250911a: refined analysis of the EP-WXT and EP-FXT observations
  8. GRB 250910B: SVOM/GRM observation
  9. EP250911a: SVOM/VT optical observation
  10. GRB 250911A: Swift-XRT refined Analysis
  11. GRB 250910C: Fermi GBM Final Localization Correction
  12. EP250911a: Swift-XRT observations
  13. EP250911a: Optical detection with Kinder observations
  14. GRB 250911A: Swift/UVOT Detection
  15. GRB 250910A / EP250910a: SVOM/VT afterglow confirmation
  16. GRB 250909B: SVOM/GRM observation
  17. GRB 250910A / EP250910a : VLT/HAWK-I NIR counterpart discovery
  18. EP250911a: COLIBRÍ optical observations
  19. Fermi GRB 250910B: Global MASTER-Net observations report
  20. EP250911a: LCO optical counterpart discovery
  21. EP250910a: Global MASTER-Net observations report
  22. EP250911a: Einstein Probe detection of an X-ray transient
  23. GRB 250903A: SVOM/ECLAIRs refined analysis
  24. GRB 250911A: Swift-XRT observations
  25. GRB 250911A: COLIBRÍ optical counterpart candidate
  26. GRB 250911A: Swift detection of a burst
  27. GRB 250910B: BALROG localization (Fermi Trigger 779223130 / GRB 250910786)
  28. GRB 250910B: Fermi GBM Final Real-time Localization
  29. GRB 250910A / EP250910a: VLT/HAWK-I near-infrared observations
  30. EP250910a/GRB 250910A: EP-WXT detection of a fast X-ray transient
  31. GRB 250910A: SVOM/VT optical upper limit
  32. EP250908C: GROND observation of the fading optical counterpart
  33. GRB 250910A: LCO optical upper limit
  34. GRB 250910A: SVOM/MXT possible afterglow detection
  35. GRB 250910A: SVOM detection of a faint burst
  36. LIGO/Virgo/KAGRA S250910b: Retraction of GW compact binary merger candidate
  37. GRB 250702B: Late time Chandra observations
  38. EP250908b/EP#01709240653: Swift/UVOT Detection
  39. EP#01709240653: Swift-XRT observations
  40. The EP-WXT trigger 01709240674 is triggered by the known source SS Cyg
  41. EP250908c: refined analysis of the EP-WXT and EP-FXT observations
  42. GRB 250907A: CALET Gamma-Ray Burst Monitor detection
  43. EP250908c: SVOM/VT optical observation
  44. EP250908c: VLT/FORS2 optical counterpart identification
  45. EP250908b: SVOM/VT optical candidate (Coordinate supplement for GCN 41758)
  46. EP250908b: SVOM/VT optical candidate
  47. The EP-WXT trigger EP250908a/01709240652 is not a real source
  48. EP250908c: Global MASTER-Net observations report
  49. Fermi GRB 250909A: Global MASTER-Net observations report
  50. EP250908c: Einstein Probe detection of an X-ray transient
  51. GRB 250909A: Fermi GBM Final Real-time Localization
  52. EP250908b: EP-WXT detection of a fast X-ray transient and EP-FXT observation
  53. EP#01709240652 (possibly EP250908a): FTW optical and NIR observations
  54. GRB 250907A: GECAM-B detection
  55. GRB 250905A: Swift-BAT refined analysis
  56. SVOM/sb25090605: detection of an X-ray transient from the LMXB 4U 0513-40
  57. EP250905a: Liverpool Telescope i-band upper limits
  58. EP250905b: EP-FXT follow-up observation
  59. EP250905a: refined analysis of the EP-WXT and EP-FXT observations
  60. EP250905b: Global MASTER-Net observations report
  61. EP250905b: EP-WXT detection of a fast X-ray transient
  62. GRB 250905A: Swift-XRT refined Analysis
  63. EP250905a: JinShan likely optical counterpart detection
  64. GRB 250904A: Swift-BAT refined analysis
  65. IceCube Alert 250905.84: Global MASTER-Net observations report
  66. GRB 250905A: Swift/UVOT Upper Limits
  67. EP250905a: Global MASTER-Net observations report
  68. GRB 250901A - SVOM/ECLAIRs refined analysis
  69. EP250905a: Einstein Probe detection of an X-ray transient
  70. GRB 250905B: Fermi GBM Final Localization
  71. GRB250904A: Liverpool Telescope upper limits
  72. GRB 250904A: Swift/UVOT Detection
  73. GRB 250904A: Swift-XRT refined Analysis
  74. EP detected a brightening of LMXB 1ES 1735-26.9
  75. GRB 250905A: Swift detection of a burst
  76. Swift GRB250905.09: Global MASTER-Net observations report
  77. Swift GRB 250904A: Global MASTER-Net observations report
  78. GRB 250904A: TRT optical counterpart detection
  79. EP250827a and EP250827b: Upper limit from Fermi-GBM Observations
  80. GRB 250902B: CALET Gamma-Ray Burst Monitor detection
  81. GRB 250904A: Swift detection of a burst
  82. GRB 250902A: CALET Gamma-Ray Burst Monitor detection
  83. GRB 250902A: VZLUSAT-2 detection
  84. GRB 250903A: Swift-XRT observations
  85. EP250903a: Swift-XRT observations
  86. EP#01709201209: Swift-XRT observations
  87. EP250903a: retraction of the LCO candidate, and discovery of the likely counterpart
  88. EP-WXT trigger 01709201209: Liverpool Telescope upper limits
  89. GRB 250830C: VZLUSAT-2 detection
  90. EP250903a: refined analysis of the EP-WXT and EP-FXT observations
  91. GRB 250903A: VLT X-shooter spectroscopic redshift z = 1.590
  92. The EP-WXT trigger 01709201209 is likely a flaring star
  93. GRB 250903A: EP-FXT counterpart detection
  94. GRB 250902A: GECAM-B detection
  95. GRB 250903A: LCO optical observation
  96. GRB 250903A: LCO optical afterglow detection
  97. GRB 250903A: SVOM/VT optical confirmation with VHF data
  98. EP250903a: SVOM/VT optical confirmation
  99. Subject GRB 250903A: SVOM/MXT afterglow detection
  100. EP250903a: LCO candidate counterpart discovery

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