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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"

24373 results found.

  1. GRB 250909B: SVOM/GRM observation
  2. LIGO/Virgo/KAGRA S250911ac: Updated Sky localization and Source Classification
  3. LIGO/Virgo/KAGRA S250908y: Updated Sky localization
  4. Fermi GRB 250910B: Global MASTER-Net observations report
  5. EP250911a: LCO optical counterpart discovery
  6. EP250910a: Global MASTER-Net observations report
  7. LIGO/Virgo/KAGRA S250911ac: Identification of a GW compact binary merger candidate
  8. GRB 250903A: SVOM/ECLAIRs refined analysis
  9. GRB 250911A: Swift detection of a burst
  10. LIGO/Virgo/KAGRA S250906ca: Updated Sky localization
  11. GRB 250910B: BALROG localization (Fermi Trigger 779223130 / GRB 250910786)
  12. GRB 250910B: Fermi GBM Final Real-time Localization
  13. EP250910a/GRB 250910A: EP-WXT detection of a fast X-ray transient
  14. GRB 250910A: SVOM/VT optical upper limit
  15. GRB 250910A: SVOM/MXT possible afterglow detection
  16. GRB 250910A: SVOM detection of a faint burst
  17. LIGO/Virgo/KAGRA S250910b: Retraction of GW compact binary merger candidate
  18. GRB 250702B: Late time Chandra observations
  19. The EP-WXT trigger 01709240674 is triggered by the known source SS Cyg
  20. EP250908c: SVOM/VT optical observation
  21. EP250908c: VLT/FORS2 optical counterpart identification
  22. EP250908b: SVOM/VT optical candidate (Coordinate supplement for GCN 41758)
  23. EP250908b: SVOM/VT optical candidate
  24. The EP-WXT trigger EP250908a/01709240652 is not a real source
  25. EP250908c: Global MASTER-Net observations report
  26. Fermi GRB 250909A: Global MASTER-Net observations report
  27. GRB 250909A: Fermi GBM Final Real-time Localization
  28. EP#01709240652 (possibly EP250908a): FTW optical and NIR observations
  29. LIGO/Virgo/KAGRA S250908y: Identification of a GW compact binary merger candidate
  30. GRB 250907A: GECAM-B detection
  31. GRB 250905A: Swift-BAT refined analysis
  32. Fermi-LAT Gamma-ray Observations of IceCube-250905A
  33. LIGO/Virgo/KAGRA S250906ca: Identification of a GW compact binary merger candidate
  34. IceCube-250905A: Upper limits from a search for additional neutrino events in IceCube
  35. SVOM/sb25090605: detection of an X-ray transient from the LMXB 4U 0513-40
  36. EP250905b: EP-FXT follow-up observation
  37. EP250905b: Global MASTER-Net observations report
  38. EP250905a: FTW one optical and multiple NIR counterpart candidates
  39. IceCube-250905A - IceCube observation of a high-energy neutrino candidate track-like event
  40. GRB 250904A: Swift-BAT refined analysis
  41. IceCube Alert 250905.84: Global MASTER-Net observations report
  42. EP250905a: Global MASTER-Net observations report
  43. GRB 250901A - SVOM/ECLAIRs refined analysis
  44. GRB 250905B: Fermi GBM Final Localization
  45. LIGO/Virgo/KAGRA S250904cv: Updated Sky localization
  46. LIGO/Virgo/KAGRA S250904br: Updated Sky localization
  47. EP detected a brightening of LMXB 1ES 1735-26.9
  48. GRB 250905A: KAIT optical upper limit
  49. GRB 250905A: Swift detection of a burst
  50. Swift GRB250905.09: Global MASTER-Net observations report
  51. Swift GRB 250904A: Global MASTER-Net observations report
  52. IceCube-Cascade 250903A: Upper limits from a search for additional neutrino events in IceCube
  53. EP250827a and EP250827b: Upper limit from Fermi-GBM Observations
  54. GRB 250902B: CALET Gamma-Ray Burst Monitor detection
  55. GRB 250902A: CALET Gamma-Ray Burst Monitor detection
  56. LIGO/Virgo/KAGRA S250904ae: Updated Sky localization
  57. GRB 250902A: VZLUSAT-2 detection
  58. LIGO/Virgo/KAGRA S250904cv: Identification of a GW compact binary merger candidate
  59. EP250903a: retraction of the LCO candidate, and discovery of the likely counterpart
  60. GRB 250830C: VZLUSAT-2 detection
  61. LIGO/Virgo/KAGRA S250904br: Identification of a GW compact binary merger candidate
  62. The EP-WXT trigger 01709201209 is likely a flaring star
  63. LIGO/Virgo/KAGRA S250904ae: Identification of a GW compact binary merger candidate
  64. GRB 250903A: EP-FXT counterpart detection
  65. GRB 250902A: GECAM-B detection
  66. EP250903a: SVOM/VT optical confirmation
  67. EP250901a: Mondy, Assy and SAO RAS optical limits
  68. EP250903a: LCO candidate counterpart discovery
  69. GRB 250903A: SVOM detection of a burst
  70. EP250903a: Global MASTER-Net observations report
  71. EP250903a: Einstein Probe detection of an X-ray transient
  72. EP/WXT01709201159: GOTO optical follow-up
  73. GRB 250902B: SVOM/GRM observation
  74. EP250827b: SVOM/VT observation of AT 2025wkm
  75. Fermi GRB 250902B: Global MASTER-Net observations report
  76. Fermi-LAT Gamma-ray Observations of IceCube-250831A
  77. GRB 250902A: Fermi GBM Detection
  78. GRB 250902B: Fermi GBM Final Real-time Localization
  79. IceCube-250831A: Upper limits from a search for additional neutrino events in IceCube
  80. GRB 250830B: Swift-XRT afterglow detection
  81. LIGO/Virgo/KAGRA S250902av: 1 counterpart neutrino candidate event from an IceCube neutrino search
  82. LIGO/Virgo/KAGRA S250901cb: Updated Sky localization
  83. GRB 250831A (SVOM trigger sb25083102): confirmation of a stellar flare by SVOM/VT
  84. GRB 250902A: SVOM/GRM observation
  85. EP250828a: Early near-infrared follow-up with MIRAGE on the MDM 1.3m telescope
  86. GRB 250901A: EP-FXT follow-up observation
  87. GRB 250902A: Fermi GBM Final Real-time Localization
  88. IceCube-Cascade 250828A: Upper limits from a search for additional neutrino events in IceCube
  89. EP250827b: Swift observations of AT 2025wkm
  90. LIGO/Virgo/KAGRA S250830bp: DECam DESGW Epoch 1 Candidates
  91. LIGO/Virgo/KAGRA S250901cb: Identification of a GW compact binary merger candidate
  92. EP250827b: FTW Observations of AT 2025wkm
  93. EP250827b: Contemporaneous detection of EP X-ray flare EP250827b and ZTF transient ZTF25abmpngy/AT2025wkm
  94. GRB 250901A: SVOM detection of a burst
  95. GRB 250831B: SVOM/GRM observation
  96. EP250901a: Mephisto optical upper limits
  97. GRB 250830C: GECAM-B detection
  98. EP250901a: Global MASTER-Net observations report
  99. LIGO/Virgo/KAGRA S250830m: Updated Sky localization
  100. EP250831a: EP-FXT follow-up observation

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