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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"

44279 results found.

  1. IceCube-Cascade 250903A: Upper limits from a search for additional neutrino events in IceCube
  2. GRB 250904A: TRT optical counterpart detection
  3. EP250827a and EP250827b: Upper limit from Fermi-GBM Observations
  4. GRB 250902B: CALET Gamma-Ray Burst Monitor detection
  5. GRB 250904A: Prompt enhanced Swift-XRT position
  6. EP250827b: Gemini Spectroscopic Confirmation of AT2025wkm as a Ic-BL Supernova
  7. GRB 250904A: Swift detection of a burst
  8. GRB 250902A: CALET Gamma-Ray Burst Monitor detection
  9. LIGO/Virgo/KAGRA S250904ae: Updated Sky localization
  10. GRB 250902A: VZLUSAT-2 detection
  11. LIGO/Virgo/KAGRA S250904cv: Identification of a GW compact binary merger candidate
  12. GRB 250903A: Swift-XRT observations
  13. EP250903a: Swift-XRT observations
  14. EP#01709201209: Swift-XRT observations
  15. EP250903a: retraction of the LCO candidate, and discovery of the likely counterpart
  16. EP-WXT trigger 01709201209: Liverpool Telescope upper limits
  17. GRB 250830C: VZLUSAT-2 detection
  18. EP250903a: refined analysis of the EP-WXT and EP-FXT observations
  19. LIGO/Virgo/KAGRA S250904br: Identification of a GW compact binary merger candidate
  20. GRB 250903A: VLT X-shooter spectroscopic redshift z = 1.590
  21. The EP-WXT trigger 01709201209 is likely a flaring star
  22. LIGO/Virgo/KAGRA S250904ae: Identification of a GW compact binary merger candidate
  23. GRB 250903A: EP-FXT counterpart detection
  24. GRB 250902A: GECAM-B detection
  25. GRB 250903A: LCO optical observation
  26. GRB 250903A: LCO optical afterglow detection
  27. GRB 250903A: SVOM/VT optical confirmation with VHF data
  28. EP250903a: SVOM/VT optical confirmation
  29. EP250901a: Mondy, Assy and SAO RAS optical limits
  30. Subject GRB 250903A: SVOM/MXT afterglow detection
  31. EP250903a: LCO candidate counterpart discovery
  32. GRB 250903A: TRT optical counterpart detection
  33. GRB 250902B: AstroSat CZTI detection
  34. GRB 250903A: SVOM detection of a burst
  35. EP250903a: Global MASTER-Net observations report
  36. EP250903a: TRT optical observations
  37. EP250903a: Einstein Probe detection of an X-ray transient
  38. EP 250827B: Detection of supernova counterpart by LCO.
  39. EP/WXT01709201159: GOTO optical follow-up
  40. EP250827b / AT 2025wkm: TRT optical observations
  41. EP250827b: NOT spectroscopic observations and AT 2025wkm classification as a broad-lined type-Ic supernova
  42. EP250827b: continued Liverpool Telescope observations
  43. GRB 250902B: SVOM/GRM observation
  44. EP250827b: SVOM/VT observation of AT 2025wkm
  45. LIGO/VIRGO/KAGRA S250818k: No evidence for radio variability of AT2025ulz in MeerKAT 3 GHz data
  46. GRB 250831A (SVOM trigger sb25083102): KAIT confirmation of stellar flare
  47. Fermi GRB 250902B: Global MASTER-Net observations report
  48. Fermi-LAT Gamma-ray Observations of IceCube-250831A
  49. GRB 250902A: Fermi GBM Detection
  50. GRB 250901A: Swift/UVOT Upper Limit
  51. GRB 250902B: Fermi GBM Final Real-time Localization
  52. IceCube-250831A: Upper limits from a search for additional neutrino events in IceCube
  53. GRB 250830B: Swift-XRT afterglow detection
  54. LIGO/Virgo/KAGRA S250902av: 1 counterpart neutrino candidate event from an IceCube neutrino search
  55. LIGO/Virgo/KAGRA S250901cb: Updated Sky localization
  56. EP250827b: Liverpool Telescope observations
  57. GRB 250831A (SVOM trigger sb25083102): confirmation of a stellar flare by SVOM/VT
  58. GRB 250902A: SVOM/GRM observation
  59. EP250828a: Early near-infrared follow-up with MIRAGE on the MDM 1.3m telescope
  60. EP250901a: refined analysis of the EP-WXT and EP-FXT observations
  61. GRB 250901A: EP-FXT follow-up observation
  62. GRB 250901A: NOT optical observations
  63. GRB 250902A: Fermi GBM Final Real-time Localization
  64. IceCube-Cascade 250828A: Upper limits from a search for additional neutrino events in IceCube
  65. GRB 250901A: SVOM/VT optical afterglow with VHF data
  66. GRB 250901A: Swift-XRT afterglow detection
  67. EP250901a: Swift-XRT observations
  68. LIGO/Virgo/KAGRA S250830bp: DECam GW-MMADS candidates
  69. GRB 250901A: LCO optical upper limit
  70. EP250827b: Swift observations of AT 2025wkm
  71. LIGO/Virgo/KAGRA S250830bp: DECam DESGW Epoch 1 Candidates
  72. EP250827b: Gemini Spectroscopy of AT 2025wkm
  73. LIGO/Virgo/KAGRA S250901cb: Identification of a GW compact binary merger candidate
  74. EP250831a: NOT optical observations and tentative afterglow candidate
  75. EP250827b: FTW Observations of AT 2025wkm
  76. EP250827b: Contemporaneous detection of EP X-ray flare EP250827b and ZTF transient ZTF25abmpngy/AT2025wkm
  77. GRB 250901A: SVOM detection of a burst
  78. GRB 250831B: SVOM/GRM observation
  79. GRB 250830C: Insight-HXMT detection
  80. EP250901a: Mephisto optical upper limits
  81. GRB 250830C: GECAM-B detection
  82. EP250901a: Global MASTER-Net observations report
  83. GRB 250830C: AstroSat CZTI detection of a long burst
  84. EP250901a: Einstein Probe detection of an X-ray transient
  85. LIGO/Virgo/KAGRA S250830m: Updated Sky localization
  86. EP250831a: EP-FXT follow-up observation
  87. EP250831a: Swift-XRT observations
  88. LIGO/Virgo/KAGRA S250831cc: Coverage and upper limits from MAXI/GSC observations
  89. IceCube Alert 250831.75: Global MASTER-Net observations report
  90. EP250831a: Global MASTER-Net observations report
  91. IceCube-250831A - IceCube observation of a high-energy neutrino candidate track-like event
  92. EP250831a: EP-WXT detection of a fast X-ray transient
  93. GRB 250831A (SVOM trigger sb25083102) is likely an outburst from star G 272-61
  94. GRB 250831A: Swift-XRT counterpart detection
  95. GRB 250831A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  96. GRB 250831A: SVOM/VT upper limit with VHF data
  97. GRB 250831A: SVOM detection of a soft burst
  98. GRB 250830B: Swift-XRT observations
  99. EP250830a: Global MASTER-Net observations report
  100. EP250830a/GRB 250830B: Einstein Probe detection of an X-ray transient and Swift/XRT follow-up

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