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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"

23682 results found.

  1. GRB 250911A: GECAM-B detection
  2. GRB 250911A: Swift-BAT refined analysis
  3. EP250911a: GTC/OSIRIS+ spectroscopic redshift z = 3.84
  4. LIGO/Virgo/KAGRA S250912f: Identification of a GW compact binary merger candidate
  5. EP250911a: refined analysis of the EP-WXT and EP-FXT observations
  6. GRB 250910B: SVOM/GRM observation
  7. EP250911a: SVOM/VT optical observation
  8. GRB 250910C: Fermi GBM Final Localization Correction
  9. GRB 250910A / EP250910a: Swift-XRT afterglow detection
  10. GRB 250909B: SVOM/GRM observation
  11. LIGO/Virgo/KAGRA S250911ac: Updated Sky localization and Source Classification
  12. LIGO/Virgo/KAGRA S250908y: Updated Sky localization
  13. Fermi GRB 250910B: Global MASTER-Net observations report
  14. EP250911a: LCO optical counterpart discovery
  15. EP250910a: Global MASTER-Net observations report
  16. LIGO/Virgo/KAGRA S250911ac: Identification of a GW compact binary merger candidate
  17. GRB 250903A: SVOM/ECLAIRs refined analysis
  18. GRB 250911A: Swift detection of a burst
  19. LIGO/Virgo/KAGRA S250906ca: Updated Sky localization
  20. GRB 250910B: BALROG localization (Fermi Trigger 779223130 / GRB 250910786)
  21. GRB 250910B: Fermi GBM Final Real-time Localization
  22. EP250910a/GRB 250910A: EP-WXT detection of a fast X-ray transient
  23. GRB 250910A: SVOM/VT optical upper limit
  24. GRB 250910A: SVOM/MXT possible afterglow detection
  25. GRB 250910A: SVOM detection of a faint burst
  26. LIGO/Virgo/KAGRA S250910b: Retraction of GW compact binary merger candidate
  27. GRB 250702B: Late time Chandra observations
  28. The EP-WXT trigger 01709240674 is triggered by the known source SS Cyg
  29. EP250908c: SVOM/VT optical observation
  30. EP250908c: VLT/FORS2 optical counterpart identification
  31. EP250908b: SVOM/VT optical candidate (Coordinate supplement for GCN 41758)
  32. EP250908b: SVOM/VT optical candidate
  33. The EP-WXT trigger EP250908a/01709240652 is not a real source
  34. EP250908c: Global MASTER-Net observations report
  35. Fermi GRB 250909A: Global MASTER-Net observations report
  36. GRB 250909A: Fermi GBM Final Real-time Localization
  37. EP#01709240652 (possibly EP250908a): FTW optical and NIR observations
  38. LIGO/Virgo/KAGRA S250908y: Identification of a GW compact binary merger candidate
  39. GRB 250907A: GECAM-B detection
  40. GRB 250905A: Swift-BAT refined analysis
  41. Fermi-LAT Gamma-ray Observations of IceCube-250905A
  42. LIGO/Virgo/KAGRA S250906ca: Identification of a GW compact binary merger candidate
  43. IceCube-250905A: Upper limits from a search for additional neutrino events in IceCube
  44. SVOM/sb25090605: detection of an X-ray transient from the LMXB 4U 0513-40
  45. EP250905b: EP-FXT follow-up observation
  46. EP250905b: Global MASTER-Net observations report
  47. EP250905a: FTW one optical and multiple NIR counterpart candidates
  48. IceCube-250905A - IceCube observation of a high-energy neutrino candidate track-like event
  49. GRB 250904A: Swift-BAT refined analysis
  50. IceCube Alert 250905.84: Global MASTER-Net observations report
  51. EP250905a: Global MASTER-Net observations report
  52. GRB 250901A - SVOM/ECLAIRs refined analysis
  53. GRB 250905B: Fermi GBM Final Localization
  54. LIGO/Virgo/KAGRA S250904cv: Updated Sky localization
  55. LIGO/Virgo/KAGRA S250904br: Updated Sky localization
  56. EP detected a brightening of LMXB 1ES 1735-26.9
  57. GRB 250905A: KAIT optical upper limit
  58. GRB 250905A: Swift detection of a burst
  59. Swift GRB250905.09: Global MASTER-Net observations report
  60. Swift GRB 250904A: Global MASTER-Net observations report
  61. IceCube-Cascade 250903A: Upper limits from a search for additional neutrino events in IceCube
  62. EP250827a and EP250827b: Upper limit from Fermi-GBM Observations
  63. GRB 250902B: CALET Gamma-Ray Burst Monitor detection
  64. GRB 250902A: CALET Gamma-Ray Burst Monitor detection
  65. LIGO/Virgo/KAGRA S250904ae: Updated Sky localization
  66. GRB 250902A: VZLUSAT-2 detection
  67. LIGO/Virgo/KAGRA S250904cv: Identification of a GW compact binary merger candidate
  68. EP250903a: retraction of the LCO candidate, and discovery of the likely counterpart
  69. GRB 250830C: VZLUSAT-2 detection
  70. LIGO/Virgo/KAGRA S250904br: Identification of a GW compact binary merger candidate
  71. The EP-WXT trigger 01709201209 is likely a flaring star
  72. LIGO/Virgo/KAGRA S250904ae: Identification of a GW compact binary merger candidate
  73. GRB 250903A: EP-FXT counterpart detection
  74. GRB 250902A: GECAM-B detection
  75. EP250903a: SVOM/VT optical confirmation
  76. EP250901a: Mondy, Assy and SAO RAS optical limits
  77. EP250903a: LCO candidate counterpart discovery
  78. GRB 250903A: SVOM detection of a burst
  79. EP250903a: Global MASTER-Net observations report
  80. EP250903a: Einstein Probe detection of an X-ray transient
  81. EP/WXT01709201159: GOTO optical follow-up
  82. GRB 250902B: SVOM/GRM observation
  83. EP250827b: SVOM/VT observation of AT 2025wkm
  84. Fermi GRB 250902B: Global MASTER-Net observations report
  85. Fermi-LAT Gamma-ray Observations of IceCube-250831A
  86. GRB 250902A: Fermi GBM Detection
  87. GRB 250902B: Fermi GBM Final Real-time Localization
  88. IceCube-250831A: Upper limits from a search for additional neutrino events in IceCube
  89. GRB 250830B: Swift-XRT afterglow detection
  90. LIGO/Virgo/KAGRA S250902av: 1 counterpart neutrino candidate event from an IceCube neutrino search
  91. LIGO/Virgo/KAGRA S250901cb: Updated Sky localization
  92. GRB 250831A (SVOM trigger sb25083102): confirmation of a stellar flare by SVOM/VT
  93. GRB 250902A: SVOM/GRM observation
  94. EP250828a: Early near-infrared follow-up with MIRAGE on the MDM 1.3m telescope
  95. GRB 250901A: EP-FXT follow-up observation
  96. GRB 250902A: Fermi GBM Final Real-time Localization
  97. IceCube-Cascade 250828A: Upper limits from a search for additional neutrino events in IceCube
  98. EP250827b: Swift observations of AT 2025wkm
  99. LIGO/Virgo/KAGRA S250830bp: DECam DESGW Epoch 1 Candidates
  100. LIGO/Virgo/KAGRA S250901cb: Identification of a GW compact binary merger candidate

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