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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/VT optical upper limit
  2. GRB 250912A: LCO optical upper limit
  3. The EP-WXT trigger 01709240768 is likely a flaring star
  4. Fermi GRB 250912A: Global MASTER-Net observations report
  5. EP250911a: Global MASTER-Net observations report
  6. GRB 250912A: SVOM detection of a burst
  7. GRB 250912A: Fermi GBM Final Real-time Localization
  8. IceCube-Cascade 250911A: Upper limits from a search for additional neutrino events in IceCube
  9. LIGO/Virgo/KAGRA S250912s: 2 counterpart neutrino candidate events from an IceCube neutrino search
  10. EP250908c: tentative VLT/FORS2 redshift z = 2.87
  11. EP250911a: Upper limit from Fermi-GBM Observations
  12. LIGO/Virgo/KAGRA S250912f: Updated Sky localization
  13. GRB 250911A: GECAM-B detection
  14. GRB 250911A: Swift-BAT refined analysis
  15. EP250911a: GTC/OSIRIS+ spectroscopic redshift z = 3.84
  16. LIGO/Virgo/KAGRA S250912f: Identification of a GW compact binary merger candidate
  17. EP250911a: refined analysis of the EP-WXT and EP-FXT observations
  18. GRB 250910B: SVOM/GRM observation
  19. EP250911a: SVOM/VT optical observation
  20. GRB 250911A: MASTER optical counterpart observations
  21. EP250911a: SAO RAS optical observations
  22. GRB 250911A: Swift-XRT refined Analysis
  23. GRB 250910C: Fermi GBM Final Localization Correction
  24. EP250911a: Swift-XRT observations
  25. EP250911a: Optical detection with Kinder observations
  26. GRB 250911A: Swift/UVOT Detection
  27. GRB 250910A / EP250910a: Swift-XRT afterglow detection
  28. GRB 250910A / EP250910a: SVOM/VT afterglow confirmation
  29. GRB 250909B: Insight-HXMT detection
  30. GRB 250909B: SVOM/GRM observation
  31. LIGO/Virgo/KAGRA S250911ac: Updated Sky localization and Source Classification
  32. GRB 250910A / EP250910a : VLT/HAWK-I NIR counterpart discovery
  33. EP250911a: COLIBRÍ optical observations
  34. LIGO/Virgo/KAGRA S250908y: Updated Sky localization
  35. Fermi GRB 250910B: Global MASTER-Net observations report
  36. EP250911a: LCO optical counterpart discovery
  37. EP250910a: Global MASTER-Net observations report
  38. EP250911a: Einstein Probe detection of an X-ray transient
  39. GRB 250404A / EP250404a: spectroscopic redshift at z = 1.88 (correction to GCN 40084)
  40. LIGO/Virgo/KAGRA S250911ac: Identification of a GW compact binary merger candidate
  41. GRB 250903A: SVOM/ECLAIRs refined analysis
  42. GRB 250911A: Enhanced Swift-XRT position
  43. GRB 250911A: Swift-XRT observations
  44. GRB 250911A: COLIBRÍ optical counterpart candidate
  45. GRB 250911A: Swift detection of a burst
  46. LIGO/Virgo/KAGRA S250906ca: Updated Sky localization
  47. GRB 250910B: BALROG localization (Fermi Trigger 779223130 / GRB 250910786)
  48. GRB 250910B: Fermi GBM Final Real-time Localization
  49. GRB 250910A / EP250910a: VLT/HAWK-I near-infrared observations
  50. EP250910a/GRB 250910A: EP-WXT detection of a fast X-ray transient
  51. GRB 250909B: AstroSat CZTI detection of a long burst
  52. GRB 250910A: SVOM/VT optical upper limit
  53. EP250908C: GROND observation of the fading optical counterpart
  54. GRB 250910A: LCO optical upper limit
  55. GRB 250909A: AstroSat CZTI detection
  56. GRB 250910A: SVOM/MXT possible afterglow detection
  57. GRB 250910A: SVOM detection of a faint burst
  58. LIGO/Virgo/KAGRA S250910b: Retraction of GW compact binary merger candidate
  59. GRB 250702B: Late time Chandra observations
  60. EP250908b/EP#01709240653: Swift/UVOT Detection
  61. EP#01709240653: Swift-XRT observations
  62. The EP-WXT trigger 01709240674 is triggered by the known source SS Cyg
  63. EP250908c: refined analysis of the EP-WXT and EP-FXT observations
  64. GRB 250907A: CALET Gamma-Ray Burst Monitor detection
  65. EP250908c: SVOM/VT optical observation
  66. EP250908c: VLT/FORS2 optical counterpart identification
  67. EP250908b: SVOM/VT optical candidate (Coordinate supplement for GCN 41758)
  68. EP250908b: SVOM/VT optical candidate
  69. The EP-WXT trigger EP250908a/01709240652 is not a real source
  70. EP250908c: Global MASTER-Net observations report
  71. Fermi GRB 250909A: Global MASTER-Net observations report
  72. EP250908c: Einstein Probe detection of an X-ray transient
  73. GRB 250909A: Fermi GBM Final Real-time Localization
  74. EP250908b: EP-WXT detection of a fast X-ray transient and EP-FXT observation
  75. EP#01709240652 (possibly EP250908a): FTW optical and NIR observations
  76. LIGO/Virgo/KAGRA S250908y: Identification of a GW compact binary merger candidate
  77. GRB 250907A: GECAM-B detection
  78. GRB 250905A: Swift-BAT refined analysis
  79. Fermi-LAT Gamma-ray Observations of IceCube-250905A
  80. GRB 250903A: Swift-XRT afterglow detection
  81. LIGO/Virgo/KAGRA S250906ca: Identification of a GW compact binary merger candidate
  82. IceCube-250905A: Upper limits from a search for additional neutrino events in IceCube
  83. SVOM/sb25090605: detection of an X-ray transient from the LMXB 4U 0513-40
  84. EP250905a: Liverpool Telescope i-band upper limits
  85. LIGO/Virgo/KAGRA S250830bp: DECam/SOAR GW-MMADS updates
  86. EP250905b: EP-FXT follow-up observation
  87. LIGO/Virgo/KAGRA S250830bp: DECam DESGW Epoch 2 Candidates
  88. EP250905a: Liverpool Telescope observations
  89. EP250905a: refined analysis of the EP-WXT and EP-FXT observations
  90. EP250905b: Global MASTER-Net observations report
  91. EP250905b: EP-WXT detection of a fast X-ray transient
  92. EP250905a: FTW one optical and multiple NIR counterpart candidates
  93. GRB 250905A: Swift-XRT refined Analysis
  94. EP250905a: JinShan likely optical counterpart detection
  95. IceCube-250905A - IceCube observation of a high-energy neutrino candidate track-like event
  96. GRB 250904A: Swift-BAT refined analysis
  97. IceCube Alert 250905.84: Global MASTER-Net observations report
  98. GRB 250905A: Swift/UVOT Upper Limits
  99. EP250905a: Global MASTER-Net observations report
  100. GRB 250901A - SVOM/ECLAIRs refined analysis

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