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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"

45426 results found.

  1. The EP-WXT trigger EP250908a/01709240652 is not a real source
  2. EP250908c: Global MASTER-Net observations report
  3. Fermi GRB 250909A: Global MASTER-Net observations report
  4. EP250908c: Einstein Probe detection of an X-ray transient
  5. GRB 250909A: Fermi GBM Final Real-time Localization
  6. EP250908b: EP-WXT detection of a fast X-ray transient and EP-FXT observation
  7. EP#01709240652 (possibly EP250908a): FTW optical and NIR observations
  8. LIGO/Virgo/KAGRA S250908y: Identification of a GW compact binary merger candidate
  9. GRB 250907A: GECAM-B detection
  10. GRB 250905A: Swift-BAT refined analysis
  11. Fermi-LAT Gamma-ray Observations of IceCube-250905A
  12. GRB 250903A: Swift-XRT afterglow detection
  13. LIGO/Virgo/KAGRA S250906ca: Identification of a GW compact binary merger candidate
  14. IceCube-250905A: Upper limits from a search for additional neutrino events in IceCube
  15. SVOM/sb25090605: detection of an X-ray transient from the LMXB 4U 0513-40
  16. EP250905a: Liverpool Telescope i-band upper limits
  17. LIGO/Virgo/KAGRA S250830bp: DECam/SOAR GW-MMADS updates
  18. EP250905b: EP-FXT follow-up observation
  19. LIGO/Virgo/KAGRA S250830bp: DECam DESGW Epoch 2 Candidates
  20. EP250905a: Liverpool Telescope observations
  21. EP250905a: refined analysis of the EP-WXT and EP-FXT observations
  22. EP250905b: Global MASTER-Net observations report
  23. EP250905b: EP-WXT detection of a fast X-ray transient
  24. EP250905a: FTW one optical and multiple NIR counterpart candidates
  25. GRB 250905A: Swift-XRT refined Analysis
  26. EP250905a: JinShan likely optical counterpart detection
  27. IceCube-250905A - IceCube observation of a high-energy neutrino candidate track-like event
  28. GRB 250904A: Swift-BAT refined analysis
  29. IceCube Alert 250905.84: Global MASTER-Net observations report
  30. GRB 250905A: Swift/UVOT Upper Limits
  31. EP250905a: Global MASTER-Net observations report
  32. GRB 250901A - SVOM/ECLAIRs refined analysis
  33. EP250905a: Einstein Probe detection of an X-ray transient
  34. GRB 250905B: Fermi GBM Final Localization
  35. GRB250904A: Liverpool Telescope upper limits
  36. GRB 250905A: Enhanced Swift-XRT position
  37. GRB 250904A: Swift/UVOT Detection
  38. GRB 250903A: Swift/UVOT detection
  39. GRB 250904A: Swift-XRT refined Analysis
  40. LIGO/Virgo/KAGRA S250904cv: Updated Sky localization
  41. LIGO/Virgo/KAGRA S250904br: Updated Sky localization
  42. EP detected a brightening of LMXB 1ES 1735-26.9
  43. GRB 250905A: KAIT optical upper limit
  44. GRB 250905A: Swift detection of a burst
  45. Swift GRB250905.09: Global MASTER-Net observations report
  46. Swift GRB 250904A: Global MASTER-Net observations report
  47. GRB 250904A: Enhanced Swift-XRT position
  48. IceCube-Cascade 250903A: Upper limits from a search for additional neutrino events in IceCube
  49. GRB 250904A: TRT optical counterpart detection
  50. EP250827a and EP250827b: Upper limit from Fermi-GBM Observations
  51. GRB 250902B: CALET Gamma-Ray Burst Monitor detection
  52. GRB 250904A: Prompt enhanced Swift-XRT position
  53. EP250827b: Gemini Spectroscopic Confirmation of AT2025wkm as a Ic-BL Supernova
  54. GRB 250904A: Swift detection of a burst
  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. GRB 250903A: Swift-XRT observations
  60. EP250903a: Swift-XRT observations
  61. EP#01709201209: Swift-XRT observations
  62. EP250903a: retraction of the LCO candidate, and discovery of the likely counterpart
  63. EP-WXT trigger 01709201209: Liverpool Telescope upper limits
  64. GRB 250830C: VZLUSAT-2 detection
  65. EP250903a: refined analysis of the EP-WXT and EP-FXT observations
  66. LIGO/Virgo/KAGRA S250904br: Identification of a GW compact binary merger candidate
  67. GRB 250903A: VLT X-shooter spectroscopic redshift z = 1.590
  68. The EP-WXT trigger 01709201209 is likely a flaring star
  69. LIGO/Virgo/KAGRA S250904ae: Identification of a GW compact binary merger candidate
  70. GRB 250903A: EP-FXT counterpart detection
  71. GRB 250902A: GECAM-B detection
  72. GRB 250903A: LCO optical observation
  73. GRB 250903A: LCO optical afterglow detection
  74. GRB 250903A: SVOM/VT optical confirmation with VHF data
  75. EP250903a: SVOM/VT optical confirmation
  76. EP250901a: Mondy, Assy and SAO RAS optical limits
  77. Subject GRB 250903A: SVOM/MXT afterglow detection
  78. EP250903a: LCO candidate counterpart discovery
  79. GRB 250903A: TRT optical counterpart detection
  80. GRB 250902B: AstroSat CZTI detection
  81. GRB 250903A: SVOM detection of a burst
  82. EP250903a: Global MASTER-Net observations report
  83. EP250903a: TRT optical observations
  84. EP250903a: Einstein Probe detection of an X-ray transient
  85. EP 250827B: Detection of supernova counterpart by LCO.
  86. EP/WXT01709201159: GOTO optical follow-up
  87. EP250827b / AT 2025wkm: TRT optical observations
  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. LIGO/VIRGO/KAGRA S250818k: No evidence for radio variability of AT2025ulz in MeerKAT 3 GHz data
  93. GRB 250831A (SVOM trigger sb25083102): KAIT confirmation of stellar flare
  94. Fermi GRB 250902B: Global MASTER-Net observations report
  95. Fermi-LAT Gamma-ray Observations of IceCube-250831A
  96. GRB 250902A: Fermi GBM Detection
  97. GRB 250901A: Swift/UVOT Upper Limit
  98. GRB 250902B: Fermi GBM Final Real-time Localization
  99. IceCube-250831A: Upper limits from a search for additional neutrino events in IceCube
  100. GRB 250830B: Swift-XRT afterglow detection

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