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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"

28051 results found.

  1. EP250908b/EP#01709240653: Swift/UVOT Detection
  2. EP#01709240653: Swift-XRT observations
  3. EP250908c: refined analysis of the EP-WXT and EP-FXT observations
  4. EP250908c: SVOM/VT optical observation
  5. EP250908c: VLT/FORS2 optical counterpart identification
  6. EP250908b: SVOM/VT optical candidate (Coordinate supplement for GCN 41758)
  7. EP250908b: SVOM/VT optical candidate
  8. Fermi GRB 250909A: Global MASTER-Net observations report
  9. EP250908c: Einstein Probe detection of an X-ray transient
  10. EP250908b: EP-WXT detection of a fast X-ray transient and EP-FXT observation
  11. LIGO/Virgo/KAGRA S250908y: Identification of a GW compact binary merger candidate
  12. GRB 250907A: GECAM-B detection
  13. GRB 250905A: Swift-BAT refined analysis
  14. Fermi-LAT Gamma-ray Observations of IceCube-250905A
  15. GRB 250903A: Swift-XRT afterglow detection
  16. LIGO/Virgo/KAGRA S250906ca: Identification of a GW compact binary merger candidate
  17. IceCube-250905A: Upper limits from a search for additional neutrino events in IceCube
  18. SVOM/sb25090605: detection of an X-ray transient from the LMXB 4U 0513-40
  19. EP250905a: Liverpool Telescope i-band upper limits
  20. LIGO/Virgo/KAGRA S250830bp: DECam/SOAR GW-MMADS updates
  21. LIGO/Virgo/KAGRA S250830bp: DECam DESGW Epoch 2 Candidates
  22. EP250905a: Liverpool Telescope observations
  23. EP250905a: refined analysis of the EP-WXT and EP-FXT observations
  24. EP250905b: EP-WXT detection of a fast X-ray transient
  25. GRB 250905A: Swift-XRT refined Analysis
  26. EP250905a: JinShan likely optical counterpart detection
  27. GRB 250904A: Swift-BAT refined analysis
  28. GRB 250905A: Swift/UVOT Upper Limits
  29. GRB 250901A - SVOM/ECLAIRs refined analysis
  30. EP250905a: Einstein Probe detection of an X-ray transient
  31. GRB250904A: Liverpool Telescope upper limits
  32. GRB 250905A: Enhanced Swift-XRT position
  33. GRB 250904A: Swift/UVOT Detection
  34. GRB 250903A: Swift/UVOT detection
  35. GRB 250904A: Swift-XRT refined Analysis
  36. LIGO/Virgo/KAGRA S250904cv: Updated Sky localization
  37. LIGO/Virgo/KAGRA S250904br: Updated Sky localization
  38. EP detected a brightening of LMXB 1ES 1735-26.9
  39. GRB 250905A: KAIT optical upper limit
  40. GRB 250905A: Swift detection of a burst
  41. GRB 250904A: Enhanced Swift-XRT position
  42. IceCube-Cascade 250903A: Upper limits from a search for additional neutrino events in IceCube
  43. GRB 250904A: TRT optical counterpart detection
  44. EP250827a and EP250827b: Upper limit from Fermi-GBM Observations
  45. GRB 250904A: Swift detection of a burst
  46. LIGO/Virgo/KAGRA S250904ae: Updated Sky localization
  47. GRB 250902A: VZLUSAT-2 detection
  48. LIGO/Virgo/KAGRA S250904cv: Identification of a GW compact binary merger candidate
  49. GRB 250903A: Swift-XRT observations
  50. EP250903a: Swift-XRT observations
  51. EP#01709201209: Swift-XRT observations
  52. EP250903a: retraction of the LCO candidate, and discovery of the likely counterpart
  53. EP-WXT trigger 01709201209: Liverpool Telescope upper limits
  54. GRB 250830C: VZLUSAT-2 detection
  55. EP250903a: refined analysis of the EP-WXT and EP-FXT observations
  56. LIGO/Virgo/KAGRA S250904br: Identification of a GW compact binary merger candidate
  57. LIGO/Virgo/KAGRA S250904ae: Identification of a GW compact binary merger candidate
  58. GRB 250903A: EP-FXT counterpart detection
  59. GRB 250902A: GECAM-B detection
  60. GRB 250903A: LCO optical observation
  61. GRB 250903A: LCO optical afterglow detection
  62. GRB 250903A: SVOM/VT optical confirmation with VHF data
  63. EP250901a: Mondy, Assy and SAO RAS optical limits
  64. EP250903a: LCO candidate counterpart discovery
  65. GRB 250903A: TRT optical counterpart detection
  66. EP250903a: TRT optical observations
  67. EP250903a: Einstein Probe detection of an X-ray transient
  68. EP 250827B: Detection of supernova counterpart by LCO.
  69. GRB 250902B: SVOM/GRM observation
  70. EP250827b: SVOM/VT observation of AT 2025wkm
  71. LIGO/VIRGO/KAGRA S250818k: No evidence for radio variability of AT2025ulz in MeerKAT 3 GHz data
  72. GRB 250831A (SVOM trigger sb25083102): KAIT confirmation of stellar flare
  73. Fermi-LAT Gamma-ray Observations of IceCube-250831A
  74. GRB 250902A: Fermi GBM Detection
  75. GRB 250901A: Swift/UVOT Upper Limit
  76. IceCube-250831A: Upper limits from a search for additional neutrino events in IceCube
  77. GRB 250830B: Swift-XRT afterglow detection
  78. LIGO/Virgo/KAGRA S250902av: 1 counterpart neutrino candidate event from an IceCube neutrino search
  79. LIGO/Virgo/KAGRA S250901cb: Updated Sky localization
  80. GRB 250831A (SVOM trigger sb25083102): confirmation of a stellar flare by SVOM/VT
  81. GRB 250902A: SVOM/GRM observation
  82. EP250828a: Early near-infrared follow-up with MIRAGE on the MDM 1.3m telescope
  83. EP250901a: refined analysis of the EP-WXT and EP-FXT observations
  84. IceCube-Cascade 250828A: Upper limits from a search for additional neutrino events in IceCube
  85. GRB 250901A: SVOM/VT optical afterglow with VHF data
  86. GRB 250901A: Swift-XRT afterglow detection
  87. EP250901a: Swift-XRT observations
  88. LIGO/Virgo/KAGRA S250830bp: DECam GW-MMADS candidates
  89. GRB 250901A: LCO optical upper limit
  90. LIGO/Virgo/KAGRA S250830bp: DECam DESGW Epoch 1 Candidates
  91. EP250827b: Gemini Spectroscopy of AT 2025wkm
  92. LIGO/Virgo/KAGRA S250901cb: Identification of a GW compact binary merger candidate
  93. EP250831a: NOT optical observations and tentative afterglow candidate
  94. EP250827b: Contemporaneous detection of EP X-ray flare EP250827b and ZTF transient ZTF25abmpngy/AT2025wkm
  95. GRB 250901A: SVOM detection of a burst
  96. EP250901a: Mephisto optical upper limits
  97. GRB 250830C: GECAM-B detection
  98. EP250901a: Einstein Probe detection of an X-ray transient
  99. LIGO/Virgo/KAGRA S250830m: Updated Sky localization
  100. EP250831a: Swift-XRT observations

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