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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"

28057 results found.

  1. LIGO/Virgo/KAGRA S250911ac: Identification of a GW compact binary merger candidate
  2. GRB 250903A: SVOM/ECLAIRs refined analysis
  3. GRB 250911A: Enhanced Swift-XRT position
  4. GRB 250911A: Swift-XRT observations
  5. GRB 250911A: COLIBRÍ optical counterpart candidate
  6. LIGO/Virgo/KAGRA S250906ca: Updated Sky localization
  7. GRB 250910B: BALROG localization (Fermi Trigger 779223130 / GRB 250910786)
  8. GRB 250910A / EP250910a: VLT/HAWK-I near-infrared observations
  9. EP250910a/GRB 250910A: EP-WXT detection of a fast X-ray transient
  10. GRB 250910A: SVOM/VT optical upper limit
  11. GRB 250910A: LCO optical upper limit
  12. EP250908b/EP#01709240653: Swift/UVOT Detection
  13. EP#01709240653: Swift-XRT observations
  14. EP250908c: refined analysis of the EP-WXT and EP-FXT observations
  15. EP250908c: SVOM/VT optical observation
  16. EP250908c: VLT/FORS2 optical counterpart identification
  17. EP250908b: SVOM/VT optical candidate (Coordinate supplement for GCN 41758)
  18. EP250908b: SVOM/VT optical candidate
  19. Fermi GRB 250909A: Global MASTER-Net observations report
  20. EP250908c: Einstein Probe detection of an X-ray transient
  21. EP250908b: EP-WXT detection of a fast X-ray transient and EP-FXT observation
  22. LIGO/Virgo/KAGRA S250908y: Identification of a GW compact binary merger candidate
  23. GRB 250907A: GECAM-B detection
  24. GRB 250905A: Swift-BAT refined analysis
  25. Fermi-LAT Gamma-ray Observations of IceCube-250905A
  26. GRB 250903A: Swift-XRT afterglow detection
  27. LIGO/Virgo/KAGRA S250906ca: Identification of a GW compact binary merger candidate
  28. IceCube-250905A: Upper limits from a search for additional neutrino events in IceCube
  29. SVOM/sb25090605: detection of an X-ray transient from the LMXB 4U 0513-40
  30. EP250905a: Liverpool Telescope i-band upper limits
  31. LIGO/Virgo/KAGRA S250830bp: DECam/SOAR GW-MMADS updates
  32. LIGO/Virgo/KAGRA S250830bp: DECam DESGW Epoch 2 Candidates
  33. EP250905a: Liverpool Telescope observations
  34. EP250905a: refined analysis of the EP-WXT and EP-FXT observations
  35. EP250905b: EP-WXT detection of a fast X-ray transient
  36. GRB 250905A: Swift-XRT refined Analysis
  37. EP250905a: JinShan likely optical counterpart detection
  38. GRB 250904A: Swift-BAT refined analysis
  39. GRB 250905A: Swift/UVOT Upper Limits
  40. GRB 250901A - SVOM/ECLAIRs refined analysis
  41. EP250905a: Einstein Probe detection of an X-ray transient
  42. GRB250904A: Liverpool Telescope upper limits
  43. GRB 250905A: Enhanced Swift-XRT position
  44. GRB 250904A: Swift/UVOT Detection
  45. GRB 250903A: Swift/UVOT detection
  46. GRB 250904A: Swift-XRT refined Analysis
  47. LIGO/Virgo/KAGRA S250904cv: Updated Sky localization
  48. LIGO/Virgo/KAGRA S250904br: Updated Sky localization
  49. EP detected a brightening of LMXB 1ES 1735-26.9
  50. GRB 250905A: KAIT optical upper limit
  51. GRB 250905A: Swift detection of a burst
  52. GRB 250904A: Enhanced Swift-XRT position
  53. IceCube-Cascade 250903A: Upper limits from a search for additional neutrino events in IceCube
  54. GRB 250904A: TRT optical counterpart detection
  55. EP250827a and EP250827b: Upper limit from Fermi-GBM Observations
  56. GRB 250904A: Swift detection of a burst
  57. LIGO/Virgo/KAGRA S250904ae: Updated Sky localization
  58. GRB 250902A: VZLUSAT-2 detection
  59. LIGO/Virgo/KAGRA S250904cv: Identification of a GW compact binary merger candidate
  60. GRB 250903A: Swift-XRT observations
  61. EP250903a: Swift-XRT observations
  62. EP#01709201209: Swift-XRT observations
  63. EP250903a: retraction of the LCO candidate, and discovery of the likely counterpart
  64. EP-WXT trigger 01709201209: Liverpool Telescope upper limits
  65. GRB 250830C: VZLUSAT-2 detection
  66. EP250903a: refined analysis of the EP-WXT and EP-FXT observations
  67. LIGO/Virgo/KAGRA S250904br: Identification of a GW compact binary merger candidate
  68. LIGO/Virgo/KAGRA S250904ae: Identification of a GW compact binary merger candidate
  69. GRB 250903A: EP-FXT counterpart detection
  70. GRB 250902A: GECAM-B detection
  71. GRB 250903A: LCO optical observation
  72. GRB 250903A: LCO optical afterglow detection
  73. GRB 250903A: SVOM/VT optical confirmation with VHF data
  74. EP250901a: Mondy, Assy and SAO RAS optical limits
  75. EP250903a: LCO candidate counterpart discovery
  76. GRB 250903A: TRT optical counterpart detection
  77. EP250903a: TRT optical observations
  78. EP250903a: Einstein Probe detection of an X-ray transient
  79. EP 250827B: Detection of supernova counterpart by LCO.
  80. GRB 250902B: SVOM/GRM observation
  81. EP250827b: SVOM/VT observation of AT 2025wkm
  82. LIGO/VIRGO/KAGRA S250818k: No evidence for radio variability of AT2025ulz in MeerKAT 3 GHz data
  83. GRB 250831A (SVOM trigger sb25083102): KAIT confirmation of stellar flare
  84. Fermi-LAT Gamma-ray Observations of IceCube-250831A
  85. GRB 250902A: Fermi GBM Detection
  86. GRB 250901A: Swift/UVOT Upper Limit
  87. IceCube-250831A: Upper limits from a search for additional neutrino events in IceCube
  88. GRB 250830B: Swift-XRT afterglow detection
  89. LIGO/Virgo/KAGRA S250902av: 1 counterpart neutrino candidate event from an IceCube neutrino search
  90. LIGO/Virgo/KAGRA S250901cb: Updated Sky localization
  91. GRB 250831A (SVOM trigger sb25083102): confirmation of a stellar flare by SVOM/VT
  92. GRB 250902A: SVOM/GRM observation
  93. EP250828a: Early near-infrared follow-up with MIRAGE on the MDM 1.3m telescope
  94. EP250901a: refined analysis of the EP-WXT and EP-FXT observations
  95. IceCube-Cascade 250828A: Upper limits from a search for additional neutrino events in IceCube
  96. GRB 250901A: SVOM/VT optical afterglow with VHF data
  97. GRB 250901A: Swift-XRT afterglow detection
  98. EP250901a: Swift-XRT observations
  99. LIGO/Virgo/KAGRA S250830bp: DECam GW-MMADS candidates
  100. GRB 250901A: LCO optical upper limit

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