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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"

27092 results found.

  1. LIGO/Virgo/KAGRA S250818k: HCT optical follow-up
  2. SVOM/sb25091517: Confirmation of a stellar flare by SVOM/VT
  3. SVOM/sb25091517: FRAM-ORM stellar flare - transient observation
  4. SVOM/sb25091517: SVOM detection of an X-ray transient
  5. GRB 250912A: Swift/BAT-GUANO localization skymap of a possibly short burst
  6. GRB 250912A: SVOM/COLIBRÍ (FM-GFT) optical observations
  7. GRB 250912A: Swift-XRT observations
  8. GRB250912A: VLT/HAWK-I follow-up observations
  9. GRB 250912A: VLT observations
  10. GRB 250912A: Fermi GBM Observation
  11. GRB 250912A: SVOM/GRM analysis suggests a possible short GRB with extended emission
  12. GRB 250912A:SVOM/VT optical upper limit
  13. GRB 250912A: LCO optical upper limit
  14. The EP-WXT trigger 01709240768 is likely a flaring star
  15. Fermi GRB 250912A: Global MASTER-Net observations report
  16. EP250911a: Global MASTER-Net observations report
  17. GRB 250912A: SVOM detection of a burst
  18. GRB 250912A: Fermi GBM Final Real-time Localization
  19. LIGO/Virgo/KAGRA S250912s: 2 counterpart neutrino candidate events from an IceCube neutrino search
  20. EP250908c: tentative VLT/FORS2 redshift z = 2.87
  21. EP250911a: Upper limit from Fermi-GBM Observations
  22. GRB 250911A: GECAM-B detection
  23. GRB 250911A: Swift-BAT refined analysis
  24. EP250911a: GTC/OSIRIS+ spectroscopic redshift z = 3.84
  25. EP250911a: refined analysis of the EP-WXT and EP-FXT observations
  26. GRB 250910B: SVOM/GRM observation
  27. EP250911a: SVOM/VT optical observation
  28. GRB 250911A: Swift-XRT refined Analysis
  29. GRB 250910C: Fermi GBM Final Localization Correction
  30. EP250911a: Swift-XRT observations
  31. EP250911a: Optical detection with Kinder observations
  32. GRB 250911A: Swift/UVOT Detection
  33. GRB 250910A / EP250910a: SVOM/VT afterglow confirmation
  34. GRB 250909B: SVOM/GRM observation
  35. GRB 250910A / EP250910a : VLT/HAWK-I NIR counterpart discovery
  36. EP250911a: COLIBRÍ optical observations
  37. Fermi GRB 250910B: Global MASTER-Net observations report
  38. EP250911a: LCO optical counterpart discovery
  39. EP250910a: Global MASTER-Net observations report
  40. EP250911a: Einstein Probe detection of an X-ray transient
  41. GRB 250903A: SVOM/ECLAIRs refined analysis
  42. GRB 250911A: Swift-XRT observations
  43. GRB 250911A: COLIBRÍ optical counterpart candidate
  44. GRB 250911A: Swift detection of a burst
  45. GRB 250910B: BALROG localization (Fermi Trigger 779223130 / GRB 250910786)
  46. GRB 250910B: Fermi GBM Final Real-time Localization
  47. GRB 250910A / EP250910a: VLT/HAWK-I near-infrared observations
  48. EP250910a/GRB 250910A: EP-WXT detection of a fast X-ray transient
  49. GRB 250910A: SVOM/VT optical upper limit
  50. EP250908C: GROND observation of the fading optical counterpart
  51. GRB 250910A: LCO optical upper limit
  52. GRB 250910A: SVOM/MXT possible afterglow detection
  53. GRB 250910A: SVOM detection of a faint burst
  54. LIGO/Virgo/KAGRA S250910b: Retraction of GW compact binary merger candidate
  55. GRB 250702B: Late time Chandra observations
  56. EP250908b/EP#01709240653: Swift/UVOT Detection
  57. EP#01709240653: Swift-XRT observations
  58. The EP-WXT trigger 01709240674 is triggered by the known source SS Cyg
  59. EP250908c: refined analysis of the EP-WXT and EP-FXT observations
  60. GRB 250907A: CALET Gamma-Ray Burst Monitor detection
  61. EP250908c: SVOM/VT optical observation
  62. EP250908c: VLT/FORS2 optical counterpart identification
  63. EP250908b: SVOM/VT optical candidate (Coordinate supplement for GCN 41758)
  64. EP250908b: SVOM/VT optical candidate
  65. The EP-WXT trigger EP250908a/01709240652 is not a real source
  66. EP250908c: Global MASTER-Net observations report
  67. Fermi GRB 250909A: Global MASTER-Net observations report
  68. EP250908c: Einstein Probe detection of an X-ray transient
  69. GRB 250909A: Fermi GBM Final Real-time Localization
  70. EP250908b: EP-WXT detection of a fast X-ray transient and EP-FXT observation
  71. EP#01709240652 (possibly EP250908a): FTW optical and NIR observations
  72. GRB 250907A: GECAM-B detection
  73. GRB 250905A: Swift-BAT refined analysis
  74. SVOM/sb25090605: detection of an X-ray transient from the LMXB 4U 0513-40
  75. EP250905a: Liverpool Telescope i-band upper limits
  76. EP250905b: EP-FXT follow-up observation
  77. EP250905a: refined analysis of the EP-WXT and EP-FXT observations
  78. EP250905b: Global MASTER-Net observations report
  79. EP250905b: EP-WXT detection of a fast X-ray transient
  80. GRB 250905A: Swift-XRT refined Analysis
  81. EP250905a: JinShan likely optical counterpart detection
  82. GRB 250904A: Swift-BAT refined analysis
  83. IceCube Alert 250905.84: Global MASTER-Net observations report
  84. GRB 250905A: Swift/UVOT Upper Limits
  85. EP250905a: Global MASTER-Net observations report
  86. GRB 250901A - SVOM/ECLAIRs refined analysis
  87. EP250905a: Einstein Probe detection of an X-ray transient
  88. GRB 250905B: Fermi GBM Final Localization
  89. GRB250904A: Liverpool Telescope upper limits
  90. GRB 250904A: Swift/UVOT Detection
  91. GRB 250904A: Swift-XRT refined Analysis
  92. EP detected a brightening of LMXB 1ES 1735-26.9
  93. GRB 250905A: Swift detection of a burst
  94. Swift GRB250905.09: Global MASTER-Net observations report
  95. Swift GRB 250904A: Global MASTER-Net observations report
  96. GRB 250904A: TRT optical counterpart detection
  97. EP250827a and EP250827b: Upper limit from Fermi-GBM Observations
  98. GRB 250902B: CALET Gamma-Ray Burst Monitor detection
  99. GRB 250904A: Swift detection of a burst
  100. GRB 250902A: CALET Gamma-Ray Burst Monitor detection

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