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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 250902A: VZLUSAT-2 detection
  2. LIGO/Virgo/KAGRA S250904cv: Identification of a GW compact binary merger candidate
  3. GRB 250903A: Swift-XRT observations
  4. EP250903a: Swift-XRT observations
  5. EP#01709201209: Swift-XRT observations
  6. EP250903a: retraction of the LCO candidate, and discovery of the likely counterpart
  7. EP-WXT trigger 01709201209: Liverpool Telescope upper limits
  8. GRB 250830C: VZLUSAT-2 detection
  9. EP250903a: refined analysis of the EP-WXT and EP-FXT observations
  10. LIGO/Virgo/KAGRA S250904br: Identification of a GW compact binary merger candidate
  11. GRB 250903A: VLT X-shooter spectroscopic redshift z = 1.590
  12. The EP-WXT trigger 01709201209 is likely a flaring star
  13. LIGO/Virgo/KAGRA S250904ae: Identification of a GW compact binary merger candidate
  14. GRB 250903A: EP-FXT counterpart detection
  15. GRB 250902A: GECAM-B detection
  16. GRB 250903A: LCO optical observation
  17. GRB 250903A: LCO optical afterglow detection
  18. GRB 250903A: SVOM/VT optical confirmation with VHF data
  19. EP250903a: SVOM/VT optical confirmation
  20. EP250901a: Mondy, Assy and SAO RAS optical limits
  21. Subject GRB 250903A: SVOM/MXT afterglow detection
  22. EP250903a: LCO candidate counterpart discovery
  23. GRB 250903A: TRT optical counterpart detection
  24. GRB 250902B: AstroSat CZTI detection
  25. GRB 250903A: SVOM detection of a burst
  26. EP250903a: Global MASTER-Net observations report
  27. EP250903a: TRT optical observations
  28. EP250903a: Einstein Probe detection of an X-ray transient
  29. EP 250827B: Detection of supernova counterpart by LCO.
  30. EP/WXT01709201159: GOTO optical follow-up
  31. EP250827b / AT 2025wkm: TRT optical observations
  32. EP250827b: NOT spectroscopic observations and AT 2025wkm classification as a broad-lined type-Ic supernova
  33. EP250827b: continued Liverpool Telescope observations
  34. GRB 250902B: SVOM/GRM observation
  35. EP250827b: SVOM/VT observation of AT 2025wkm
  36. LIGO/VIRGO/KAGRA S250818k: No evidence for radio variability of AT2025ulz in MeerKAT 3 GHz data
  37. GRB 250831A (SVOM trigger sb25083102): KAIT confirmation of stellar flare
  38. Fermi GRB 250902B: Global MASTER-Net observations report
  39. Fermi-LAT Gamma-ray Observations of IceCube-250831A
  40. GRB 250902A: Fermi GBM Detection
  41. GRB 250901A: Swift/UVOT Upper Limit
  42. GRB 250902B: Fermi GBM Final Real-time Localization
  43. IceCube-250831A: Upper limits from a search for additional neutrino events in IceCube
  44. GRB 250830B: Swift-XRT afterglow detection
  45. LIGO/Virgo/KAGRA S250902av: 1 counterpart neutrino candidate event from an IceCube neutrino search
  46. LIGO/Virgo/KAGRA S250901cb: Updated Sky localization
  47. EP250827b: Liverpool Telescope observations
  48. GRB 250831A (SVOM trigger sb25083102): confirmation of a stellar flare by SVOM/VT
  49. GRB 250902A: SVOM/GRM observation
  50. EP250828a: Early near-infrared follow-up with MIRAGE on the MDM 1.3m telescope
  51. EP250901a: refined analysis of the EP-WXT and EP-FXT observations
  52. GRB 250901A: EP-FXT follow-up observation
  53. GRB 250901A: NOT optical observations
  54. GRB 250902A: Fermi GBM Final Real-time Localization
  55. IceCube-Cascade 250828A: Upper limits from a search for additional neutrino events in IceCube
  56. GRB 250901A: SVOM/VT optical afterglow with VHF data
  57. GRB 250901A: Swift-XRT afterglow detection
  58. EP250901a: Swift-XRT observations
  59. LIGO/Virgo/KAGRA S250830bp: DECam GW-MMADS candidates
  60. GRB 250901A: LCO optical upper limit
  61. EP250827b: Swift observations of AT 2025wkm
  62. LIGO/Virgo/KAGRA S250830bp: DECam DESGW Epoch 1 Candidates
  63. EP250827b: Gemini Spectroscopy of AT 2025wkm
  64. LIGO/Virgo/KAGRA S250901cb: Identification of a GW compact binary merger candidate
  65. EP250831a: NOT optical observations and tentative afterglow candidate
  66. EP250827b: FTW Observations of AT 2025wkm
  67. EP250827b: Contemporaneous detection of EP X-ray flare EP250827b and ZTF transient ZTF25abmpngy/AT2025wkm
  68. GRB 250901A: SVOM detection of a burst
  69. GRB 250831B: SVOM/GRM observation
  70. GRB 250830C: Insight-HXMT detection
  71. EP250901a: Mephisto optical upper limits
  72. GRB 250830C: GECAM-B detection
  73. EP250901a: Global MASTER-Net observations report
  74. GRB 250830C: AstroSat CZTI detection of a long burst
  75. EP250901a: Einstein Probe detection of an X-ray transient
  76. LIGO/Virgo/KAGRA S250830m: Updated Sky localization
  77. EP250831a: EP-FXT follow-up observation
  78. EP250831a: Swift-XRT observations
  79. LIGO/Virgo/KAGRA S250831cc: Coverage and upper limits from MAXI/GSC observations
  80. IceCube Alert 250831.75: Global MASTER-Net observations report
  81. EP250831a: Global MASTER-Net observations report
  82. IceCube-250831A - IceCube observation of a high-energy neutrino candidate track-like event
  83. EP250831a: EP-WXT detection of a fast X-ray transient
  84. GRB 250831A (SVOM trigger sb25083102) is likely an outburst from star G 272-61
  85. GRB 250831A: Swift-XRT counterpart detection
  86. GRB 250831A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  87. GRB 250831A: SVOM/VT upper limit with VHF data
  88. GRB 250831A: SVOM detection of a soft burst
  89. GRB 250830B: Swift-XRT observations
  90. EP250830a: Global MASTER-Net observations report
  91. EP250830a/GRB 250830B: Einstein Probe detection of an X-ray transient and Swift/XRT follow-up
  92. LIGO/Virgo/KAGRA S250830bp: Coverage and upper limits from MAXI/GSC observations
  93. LIGO/Virgo/KAGRA S250830bp GLADEnet Completeness: Potential Host Galaxies in the 90% Credible Volume
  94. LIGO/Virgo/KAGRA S250830bp: NED Galaxies in the 4-Update Localization Volume
  95. LIGO/Virgo/KAGRA S250830bp: Updated Sky localization, EM Bright Classification, and Source Classification
  96. LIGO/Virgo/KAGRA S250830bp: Identification of a GW compact binary merger candidate
  97. EP-WXT trigger 01709200994: Liverpool Telescope upper limits
  98. GRB 250830B: Swift ToO observations
  99. EP-WXT trigger 01709200994: confirmation of a stellar flare by BOOTES-6
  100. GRB 250830B: MAXI/GSC detection

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