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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"

5831 results found.

  1. EP250911a: Global MASTER-Net observations report
  2. GRB 250912A: SVOM detection of a burst
  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. EP250911a: Upper limit from Fermi-GBM Observations
  6. GRB 250911A: GECAM-B detection
  7. LIGO/Virgo/KAGRA S250912f: Identification of a GW compact binary merger candidate
  8. EP250911a: refined analysis of the EP-WXT and EP-FXT observations
  9. GRB 250910B: SVOM/GRM observation
  10. EP250911a: SVOM/VT optical observation
  11. GRB 250911A: MASTER optical counterpart observations
  12. GRB 250910A / EP250910a: SVOM/VT afterglow confirmation
  13. GRB 250909B: Insight-HXMT detection
  14. GRB 250909B: SVOM/GRM observation
  15. GRB 250910A / EP250910a : VLT/HAWK-I NIR counterpart discovery
  16. EP250911a: COLIBRÍ optical observations
  17. Fermi GRB 250910B: Global MASTER-Net observations report
  18. EP250911a: LCO optical counterpart discovery
  19. EP250910a: Global MASTER-Net observations report
  20. EP250911a: Einstein Probe detection of an X-ray transient
  21. LIGO/Virgo/KAGRA S250911ac: Identification of a GW compact binary merger candidate
  22. GRB 250903A: SVOM/ECLAIRs refined analysis
  23. GRB 250911A: COLIBRÍ optical counterpart candidate
  24. GRB 250910A / EP250910a: VLT/HAWK-I near-infrared observations
  25. EP250910a/GRB 250910A: EP-WXT detection of a fast X-ray transient
  26. GRB 250909B: AstroSat CZTI detection of a long burst
  27. GRB 250910A: SVOM/VT optical upper limit
  28. EP250908C: GROND observation of the fading optical counterpart
  29. GRB 250910A: LCO optical upper limit
  30. GRB 250909A: AstroSat CZTI detection
  31. GRB 250910A: SVOM/MXT possible afterglow detection
  32. GRB 250910A: SVOM detection of a faint burst
  33. GRB 250702B: Late time Chandra observations
  34. The EP-WXT trigger 01709240674 is triggered by the known source SS Cyg
  35. EP250908c: refined analysis of the EP-WXT and EP-FXT observations
  36. EP250908c: SVOM/VT optical observation
  37. EP250908b: SVOM/VT optical candidate (Coordinate supplement for GCN 41758)
  38. EP250908b: SVOM/VT optical candidate
  39. The EP-WXT trigger EP250908a/01709240652 is not a real source
  40. EP250908c: Global MASTER-Net observations report
  41. Fermi GRB 250909A: Global MASTER-Net observations report
  42. EP250908c: Einstein Probe detection of an X-ray transient
  43. EP250908b: EP-WXT detection of a fast X-ray transient and EP-FXT observation
  44. EP#01709240652 (possibly EP250908a): FTW optical and NIR observations
  45. LIGO/Virgo/KAGRA S250908y: Identification of a GW compact binary merger candidate
  46. GRB 250907A: GECAM-B detection
  47. Fermi-LAT Gamma-ray Observations of IceCube-250905A
  48. LIGO/Virgo/KAGRA S250906ca: Identification of a GW compact binary merger candidate
  49. IceCube-250905A: Upper limits from a search for additional neutrino events in IceCube
  50. SVOM/sb25090605: detection of an X-ray transient from the LMXB 4U 0513-40
  51. EP250905a: Liverpool Telescope i-band upper limits
  52. LIGO/Virgo/KAGRA S250830bp: DECam/SOAR GW-MMADS updates
  53. EP250905b: EP-FXT follow-up observation
  54. LIGO/Virgo/KAGRA S250830bp: DECam DESGW Epoch 2 Candidates
  55. EP250905a: Liverpool Telescope observations
  56. EP250905a: refined analysis of the EP-WXT and EP-FXT observations
  57. EP250905b: Global MASTER-Net observations report
  58. EP250905b: EP-WXT detection of a fast X-ray transient
  59. EP250905a: FTW one optical and multiple NIR counterpart candidates
  60. EP250905a: JinShan likely optical counterpart detection
  61. IceCube-250905A - IceCube observation of a high-energy neutrino candidate track-like event
  62. IceCube Alert 250905.84: Global MASTER-Net observations report
  63. EP250905a: Global MASTER-Net observations report
  64. GRB 250901A - SVOM/ECLAIRs refined analysis
  65. EP250905a: Einstein Probe detection of an X-ray transient
  66. GRB250904A: Liverpool Telescope upper limits
  67. EP detected a brightening of LMXB 1ES 1735-26.9
  68. GRB 250905A: Swift detection of a burst
  69. Swift GRB250905.09: Global MASTER-Net observations report
  70. Swift GRB 250904A: Global MASTER-Net observations report
  71. IceCube-Cascade 250903A: Upper limits from a search for additional neutrino events in IceCube
  72. GRB 250904A: TRT optical counterpart detection
  73. EP250827b: Gemini Spectroscopic Confirmation of AT2025wkm as a Ic-BL Supernova
  74. GRB 250902A: VZLUSAT-2 detection
  75. LIGO/Virgo/KAGRA S250904cv: Identification of a GW compact binary merger candidate
  76. GRB 250903A: Swift-XRT observations
  77. EP250903a: refined analysis of the EP-WXT and EP-FXT observations
  78. LIGO/Virgo/KAGRA S250904br: Identification of a GW compact binary merger candidate
  79. GRB 250903A: VLT X-shooter spectroscopic redshift z = 1.590
  80. The EP-WXT trigger 01709201209 is likely a flaring star
  81. LIGO/Virgo/KAGRA S250904ae: Identification of a GW compact binary merger candidate
  82. GRB 250903A: EP-FXT counterpart detection
  83. GRB 250902A: GECAM-B detection
  84. GRB 250903A: LCO optical observation
  85. GRB 250903A: LCO optical afterglow detection
  86. GRB 250903A: SVOM/VT optical confirmation with VHF data
  87. EP250903a: SVOM/VT optical confirmation
  88. Subject GRB 250903A: SVOM/MXT afterglow detection
  89. EP250903a: LCO candidate counterpart discovery
  90. GRB 250903A: TRT optical counterpart detection
  91. GRB 250902B: AstroSat CZTI detection
  92. GRB 250903A: SVOM detection of a burst
  93. EP250903a: Global MASTER-Net observations report
  94. EP250903a: TRT optical observations
  95. EP250903a: Einstein Probe detection of an X-ray transient
  96. EP 250827B: Detection of supernova counterpart by LCO.
  97. EP250827b: NOT spectroscopic observations and AT 2025wkm classification as a broad-lined type-Ic supernova
  98. EP250827b: continued Liverpool Telescope observations
  99. GRB 250902B: SVOM/GRM observation
  100. EP250827b: SVOM/VT observation of AT 2025wkm

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