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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"

5822 results found.

  1. EP250911a: SVOM/VT optical observation
  2. GRB 250911A: MASTER optical counterpart observations
  3. GRB 250910A / EP250910a: SVOM/VT afterglow confirmation
  4. GRB 250909B: Insight-HXMT detection
  5. GRB 250909B: SVOM/GRM observation
  6. GRB 250910A / EP250910a : VLT/HAWK-I NIR counterpart discovery
  7. EP250911a: COLIBRÍ optical observations
  8. Fermi GRB 250910B: Global MASTER-Net observations report
  9. EP250911a: LCO optical counterpart discovery
  10. EP250910a: Global MASTER-Net observations report
  11. EP250911a: Einstein Probe detection of an X-ray transient
  12. LIGO/Virgo/KAGRA S250911ac: Identification of a GW compact binary merger candidate
  13. GRB 250903A: SVOM/ECLAIRs refined analysis
  14. GRB 250911A: COLIBRÍ optical counterpart candidate
  15. GRB 250910A / EP250910a: VLT/HAWK-I near-infrared observations
  16. EP250910a/GRB 250910A: EP-WXT detection of a fast X-ray transient
  17. GRB 250909B: AstroSat CZTI detection of a long burst
  18. GRB 250910A: SVOM/VT optical upper limit
  19. EP250908C: GROND observation of the fading optical counterpart
  20. GRB 250910A: LCO optical upper limit
  21. GRB 250909A: AstroSat CZTI detection
  22. GRB 250910A: SVOM/MXT possible afterglow detection
  23. GRB 250910A: SVOM detection of a faint burst
  24. GRB 250702B: Late time Chandra observations
  25. The EP-WXT trigger 01709240674 is triggered by the known source SS Cyg
  26. EP250908c: refined analysis of the EP-WXT and EP-FXT observations
  27. EP250908c: SVOM/VT optical observation
  28. EP250908b: SVOM/VT optical candidate (Coordinate supplement for GCN 41758)
  29. EP250908b: SVOM/VT optical candidate
  30. The EP-WXT trigger EP250908a/01709240652 is not a real source
  31. EP250908c: Global MASTER-Net observations report
  32. Fermi GRB 250909A: Global MASTER-Net observations report
  33. EP250908c: Einstein Probe detection of an X-ray transient
  34. EP250908b: EP-WXT detection of a fast X-ray transient and EP-FXT observation
  35. EP#01709240652 (possibly EP250908a): FTW optical and NIR observations
  36. LIGO/Virgo/KAGRA S250908y: Identification of a GW compact binary merger candidate
  37. GRB 250907A: GECAM-B detection
  38. Fermi-LAT Gamma-ray Observations of IceCube-250905A
  39. LIGO/Virgo/KAGRA S250906ca: Identification of a GW compact binary merger candidate
  40. IceCube-250905A: Upper limits from a search for additional neutrino events in IceCube
  41. SVOM/sb25090605: detection of an X-ray transient from the LMXB 4U 0513-40
  42. EP250905a: Liverpool Telescope i-band upper limits
  43. LIGO/Virgo/KAGRA S250830bp: DECam/SOAR GW-MMADS updates
  44. EP250905b: EP-FXT follow-up observation
  45. LIGO/Virgo/KAGRA S250830bp: DECam DESGW Epoch 2 Candidates
  46. EP250905a: Liverpool Telescope observations
  47. EP250905a: refined analysis of the EP-WXT and EP-FXT observations
  48. EP250905b: Global MASTER-Net observations report
  49. EP250905b: EP-WXT detection of a fast X-ray transient
  50. EP250905a: FTW one optical and multiple NIR counterpart candidates
  51. EP250905a: JinShan likely optical counterpart detection
  52. IceCube-250905A - IceCube observation of a high-energy neutrino candidate track-like event
  53. IceCube Alert 250905.84: Global MASTER-Net observations report
  54. EP250905a: Global MASTER-Net observations report
  55. GRB 250901A - SVOM/ECLAIRs refined analysis
  56. EP250905a: Einstein Probe detection of an X-ray transient
  57. GRB250904A: Liverpool Telescope upper limits
  58. EP detected a brightening of LMXB 1ES 1735-26.9
  59. GRB 250905A: Swift detection of a burst
  60. Swift GRB250905.09: Global MASTER-Net observations report
  61. Swift GRB 250904A: Global MASTER-Net observations report
  62. IceCube-Cascade 250903A: Upper limits from a search for additional neutrino events in IceCube
  63. GRB 250904A: TRT optical counterpart detection
  64. EP250827b: Gemini Spectroscopic Confirmation of AT2025wkm as a Ic-BL Supernova
  65. GRB 250902A: VZLUSAT-2 detection
  66. LIGO/Virgo/KAGRA S250904cv: Identification of a GW compact binary merger candidate
  67. GRB 250903A: Swift-XRT observations
  68. EP250903a: refined analysis of the EP-WXT and EP-FXT observations
  69. LIGO/Virgo/KAGRA S250904br: Identification of a GW compact binary merger candidate
  70. GRB 250903A: VLT X-shooter spectroscopic redshift z = 1.590
  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. GRB 250903A: LCO optical observation
  76. GRB 250903A: LCO optical afterglow detection
  77. GRB 250903A: SVOM/VT optical confirmation with VHF data
  78. EP250903a: SVOM/VT optical confirmation
  79. Subject GRB 250903A: SVOM/MXT afterglow detection
  80. EP250903a: LCO candidate counterpart discovery
  81. GRB 250903A: TRT optical counterpart detection
  82. GRB 250902B: AstroSat CZTI detection
  83. GRB 250903A: SVOM detection of a burst
  84. EP250903a: Global MASTER-Net observations report
  85. EP250903a: TRT optical observations
  86. EP250903a: Einstein Probe detection of an X-ray transient
  87. EP 250827B: Detection of supernova counterpart by LCO.
  88. EP250827b: NOT spectroscopic observations and AT 2025wkm classification as a broad-lined type-Ic supernova
  89. EP250827b: continued Liverpool Telescope observations
  90. GRB 250902B: SVOM/GRM observation
  91. EP250827b: SVOM/VT observation of AT 2025wkm
  92. GRB 250831A (SVOM trigger sb25083102): KAIT confirmation of stellar flare
  93. Fermi GRB 250902B: Global MASTER-Net observations report
  94. IceCube-250831A: Upper limits from a search for additional neutrino events in IceCube
  95. LIGO/Virgo/KAGRA S250902av: 1 counterpart neutrino candidate event from an IceCube neutrino search
  96. EP250827b: Liverpool Telescope observations
  97. GRB 250902A: SVOM/GRM observation
  98. EP250901a: refined analysis of the EP-WXT and EP-FXT observations
  99. GRB 250901A: EP-FXT follow-up observation
  100. GRB 250901A: SVOM/VT optical afterglow with VHF data

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