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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"
  1. GRB 250912A: SVOM detection of a burst
  2. GRB 250912A: Fermi GBM Final Real-time Localization
  3. IceCube-Cascade 250911A: Upper limits from a search for additional neutrino events in IceCube
  4. LIGO/Virgo/KAGRA S250912s: 2 counterpart neutrino candidate events from an IceCube neutrino search
  5. EP250908c: tentative VLT/FORS2 redshift z = 2.87
  6. EP250911a: Upper limit from Fermi-GBM Observations
  7. LIGO/Virgo/KAGRA S250912f: Updated Sky localization
  8. GRB 250911A: GECAM-B detection
  9. GRB 250911A: Swift-BAT refined analysis
  10. EP250911a: GTC/OSIRIS+ spectroscopic redshift z = 3.84
  11. LIGO/Virgo/KAGRA S250912f: Identification of a GW compact binary merger candidate
  12. EP250911a: refined analysis of the EP-WXT and EP-FXT observations
  13. GRB 250910B: SVOM/GRM observation
  14. EP250911a: SVOM/VT optical observation
  15. GRB 250911A: MASTER optical counterpart observations
  16. EP250911a: SAO RAS optical observations
  17. GRB 250911A: Swift-XRT refined Analysis
  18. GRB 250910C: Fermi GBM Final Localization Correction
  19. EP250911a: Swift-XRT observations
  20. EP250911a: Optical detection with Kinder observations
  21. GRB 250911A: Swift/UVOT Detection
  22. GRB 250910A / EP250910a: Swift-XRT afterglow detection
  23. GRB 250910A / EP250910a: SVOM/VT afterglow confirmation
  24. GRB 250909B: Insight-HXMT detection
  25. GRB 250909B: SVOM/GRM observation
  26. LIGO/Virgo/KAGRA S250911ac: Updated Sky localization and Source Classification
  27. GRB 250910A / EP250910a : VLT/HAWK-I NIR counterpart discovery
  28. EP250911a: COLIBRÍ optical observations
  29. LIGO/Virgo/KAGRA S250908y: Updated Sky localization
  30. Fermi GRB 250910B: Global MASTER-Net observations report
  31. EP250911a: LCO optical counterpart discovery
  32. EP250910a: Global MASTER-Net observations report
  33. EP250911a: Einstein Probe detection of an X-ray transient
  34. GRB 250404A / EP250404a: spectroscopic redshift at z = 1.88 (correction to GCN 40084)
  35. LIGO/Virgo/KAGRA S250911ac: Identification of a GW compact binary merger candidate
  36. GRB 250903A: SVOM/ECLAIRs refined analysis
  37. GRB 250911A: Enhanced Swift-XRT position
  38. GRB 250911A: Swift-XRT observations
  39. GRB 250911A: COLIBRÍ optical counterpart candidate
  40. GRB 250911A: Swift detection of a burst
  41. LIGO/Virgo/KAGRA S250906ca: Updated Sky localization
  42. GRB 250910B: BALROG localization (Fermi Trigger 779223130 / GRB 250910786)
  43. GRB 250910B: Fermi GBM Final Real-time Localization
  44. GRB 250910A / EP250910a: VLT/HAWK-I near-infrared observations
  45. EP250910a/GRB 250910A: EP-WXT detection of a fast X-ray transient
  46. GRB 250909B: AstroSat CZTI detection of a long burst
  47. GRB 250910A: SVOM/VT optical upper limit
  48. EP250908C: GROND observation of the fading optical counterpart
  49. GRB 250910A: LCO optical upper limit
  50. GRB 250909A: AstroSat CZTI detection
  51. GRB 250910A: SVOM/MXT possible afterglow detection
  52. GRB 250910A: SVOM detection of a faint burst
  53. LIGO/Virgo/KAGRA S250910b: Retraction of GW compact binary merger candidate
  54. GRB 250702B: Late time Chandra observations
  55. EP250908b/EP#01709240653: Swift/UVOT Detection
  56. EP#01709240653: Swift-XRT observations
  57. The EP-WXT trigger 01709240674 is triggered by the known source SS Cyg
  58. EP250908c: refined analysis of the EP-WXT and EP-FXT observations
  59. GRB 250907A: CALET Gamma-Ray Burst Monitor detection
  60. EP250908c: SVOM/VT optical observation
  61. EP250908c: VLT/FORS2 optical counterpart identification
  62. EP250908b: SVOM/VT optical candidate (Coordinate supplement for GCN 41758)
  63. EP250908b: SVOM/VT optical candidate
  64. The EP-WXT trigger EP250908a/01709240652 is not a real source
  65. EP250908c: Global MASTER-Net observations report
  66. Fermi GRB 250909A: Global MASTER-Net observations report
  67. EP250908c: Einstein Probe detection of an X-ray transient
  68. GRB 250909A: Fermi GBM Final Real-time Localization
  69. EP250908b: EP-WXT detection of a fast X-ray transient and EP-FXT observation
  70. EP#01709240652 (possibly EP250908a): FTW optical and NIR observations
  71. LIGO/Virgo/KAGRA S250908y: Identification of a GW compact binary merger candidate
  72. GRB 250907A: GECAM-B detection
  73. GRB 250905A: Swift-BAT refined analysis
  74. Fermi-LAT Gamma-ray Observations of IceCube-250905A
  75. GRB 250903A: Swift-XRT afterglow detection
  76. LIGO/Virgo/KAGRA S250906ca: Identification of a GW compact binary merger candidate
  77. IceCube-250905A: Upper limits from a search for additional neutrino events in IceCube
  78. SVOM/sb25090605: detection of an X-ray transient from the LMXB 4U 0513-40
  79. EP250905a: Liverpool Telescope i-band upper limits
  80. LIGO/Virgo/KAGRA S250830bp: DECam/SOAR GW-MMADS updates
  81. EP250905b: EP-FXT follow-up observation
  82. LIGO/Virgo/KAGRA S250830bp: DECam DESGW Epoch 2 Candidates
  83. EP250905a: Liverpool Telescope observations
  84. EP250905a: refined analysis of the EP-WXT and EP-FXT observations
  85. EP250905b: Global MASTER-Net observations report
  86. EP250905b: EP-WXT detection of a fast X-ray transient
  87. EP250905a: FTW one optical and multiple NIR counterpart candidates
  88. GRB 250905A: Swift-XRT refined Analysis
  89. EP250905a: JinShan likely optical counterpart detection
  90. IceCube-250905A - IceCube observation of a high-energy neutrino candidate track-like event
  91. GRB 250904A: Swift-BAT refined analysis
  92. IceCube Alert 250905.84: Global MASTER-Net observations report
  93. GRB 250905A: Swift/UVOT Upper Limits
  94. EP250905a: Global MASTER-Net observations report
  95. GRB 250901A - SVOM/ECLAIRs refined analysis
  96. EP250905a: Einstein Probe detection of an X-ray transient
  97. GRB 250905B: Fermi GBM Final Localization
  98. GRB250904A: Liverpool Telescope upper limits
  99. GRB 250905A: Enhanced Swift-XRT position
  100. GRB 250904A: Swift/UVOT Detection

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