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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"

45718 results found.

  1. EP250905b: EP-FXT follow-up observation
  2. LIGO/Virgo/KAGRA S250830bp: DECam DESGW Epoch 2 Candidates
  3. EP250905a: Liverpool Telescope observations
  4. EP250905a: refined analysis of the EP-WXT and EP-FXT observations
  5. EP250905b: Global MASTER-Net observations report
  6. EP250905b: EP-WXT detection of a fast X-ray transient
  7. EP250905a: FTW one optical and multiple NIR counterpart candidates
  8. GRB 250905A: Swift-XRT refined Analysis
  9. EP250905a: JinShan likely optical counterpart detection
  10. IceCube-250905A - IceCube observation of a high-energy neutrino candidate track-like event
  11. GRB 250904A: Swift-BAT refined analysis
  12. IceCube Alert 250905.84: Global MASTER-Net observations report
  13. GRB 250905A: Swift/UVOT Upper Limits
  14. EP250905a: Global MASTER-Net observations report
  15. GRB 250901A - SVOM/ECLAIRs refined analysis
  16. EP250905a: Einstein Probe detection of an X-ray transient
  17. GRB 250905B: Fermi GBM Final Localization
  18. GRB250904A: Liverpool Telescope upper limits
  19. GRB 250905A: Enhanced Swift-XRT position
  20. GRB 250904A: Swift/UVOT Detection
  21. GRB 250903A: Swift/UVOT detection
  22. GRB 250904A: Swift-XRT refined Analysis
  23. LIGO/Virgo/KAGRA S250904cv: Updated Sky localization
  24. LIGO/Virgo/KAGRA S250904br: Updated Sky localization
  25. EP detected a brightening of LMXB 1ES 1735-26.9
  26. GRB 250905A: KAIT optical upper limit
  27. GRB 250905A: Swift detection of a burst
  28. Swift GRB250905.09: Global MASTER-Net observations report
  29. Swift GRB 250904A: Global MASTER-Net observations report
  30. GRB 250904A: Enhanced Swift-XRT position
  31. IceCube-Cascade 250903A: Upper limits from a search for additional neutrino events in IceCube
  32. GRB 250904A: TRT optical counterpart detection
  33. EP250827a and EP250827b: Upper limit from Fermi-GBM Observations
  34. GRB 250902B: CALET Gamma-Ray Burst Monitor detection
  35. GRB 250904A: Prompt enhanced Swift-XRT position
  36. EP250827b: Gemini Spectroscopic Confirmation of AT2025wkm as a Ic-BL Supernova
  37. GRB 250904A: Swift detection of a burst
  38. GRB 250902A: CALET Gamma-Ray Burst Monitor detection
  39. LIGO/Virgo/KAGRA S250904ae: Updated Sky localization
  40. GRB 250902A: VZLUSAT-2 detection
  41. LIGO/Virgo/KAGRA S250904cv: Identification of a GW compact binary merger candidate
  42. GRB 250903A: Swift-XRT observations
  43. EP250903a: Swift-XRT observations
  44. EP#01709201209: Swift-XRT observations
  45. EP250903a: retraction of the LCO candidate, and discovery of the likely counterpart
  46. EP-WXT trigger 01709201209: Liverpool Telescope upper limits
  47. GRB 250830C: VZLUSAT-2 detection
  48. EP250903a: refined analysis of the EP-WXT and EP-FXT observations
  49. LIGO/Virgo/KAGRA S250904br: Identification of a GW compact binary merger candidate
  50. GRB 250903A: VLT X-shooter spectroscopic redshift z = 1.590
  51. The EP-WXT trigger 01709201209 is likely a flaring star
  52. LIGO/Virgo/KAGRA S250904ae: Identification of a GW compact binary merger candidate
  53. GRB 250903A: EP-FXT counterpart detection
  54. GRB 250902A: GECAM-B detection
  55. GRB 250903A: LCO optical observation
  56. GRB 250903A: LCO optical afterglow detection
  57. GRB 250903A: SVOM/VT optical confirmation with VHF data
  58. EP250903a: SVOM/VT optical confirmation
  59. EP250901a: Mondy, Assy and SAO RAS optical limits
  60. Subject GRB 250903A: SVOM/MXT afterglow detection
  61. EP250903a: LCO candidate counterpart discovery
  62. GRB 250903A: TRT optical counterpart detection
  63. GRB 250902B: AstroSat CZTI detection
  64. GRB 250903A: SVOM detection of a burst
  65. EP250903a: Global MASTER-Net observations report
  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. EP/WXT01709201159: GOTO optical follow-up
  70. EP250827b / AT 2025wkm: TRT optical observations
  71. EP250827b: NOT spectroscopic observations and AT 2025wkm classification as a broad-lined type-Ic supernova
  72. EP250827b: continued Liverpool Telescope observations
  73. GRB 250902B: SVOM/GRM observation
  74. EP250827b: SVOM/VT observation of AT 2025wkm
  75. LIGO/VIRGO/KAGRA S250818k: No evidence for radio variability of AT2025ulz in MeerKAT 3 GHz data
  76. GRB 250831A (SVOM trigger sb25083102): KAIT confirmation of stellar flare
  77. Fermi GRB 250902B: Global MASTER-Net observations report
  78. Fermi-LAT Gamma-ray Observations of IceCube-250831A
  79. GRB 250902A: Fermi GBM Detection
  80. GRB 250901A: Swift/UVOT Upper Limit
  81. GRB 250902B: Fermi GBM Final Real-time Localization
  82. IceCube-250831A: Upper limits from a search for additional neutrino events in IceCube
  83. GRB 250830B: Swift-XRT afterglow detection
  84. LIGO/Virgo/KAGRA S250902av: 1 counterpart neutrino candidate event from an IceCube neutrino search
  85. LIGO/Virgo/KAGRA S250901cb: Updated Sky localization
  86. EP250827b: Liverpool Telescope observations
  87. GRB 250831A (SVOM trigger sb25083102): confirmation of a stellar flare by SVOM/VT
  88. GRB 250902A: SVOM/GRM observation
  89. EP250828a: Early near-infrared follow-up with MIRAGE on the MDM 1.3m telescope
  90. EP250901a: refined analysis of the EP-WXT and EP-FXT observations
  91. GRB 250901A: EP-FXT follow-up observation
  92. GRB 250901A: NOT optical observations
  93. GRB 250902A: Fermi GBM Final Real-time Localization
  94. IceCube-Cascade 250828A: Upper limits from a search for additional neutrino events in IceCube
  95. GRB 250901A: SVOM/VT optical afterglow with VHF data
  96. GRB 250901A: Swift-XRT afterglow detection
  97. EP250901a: Swift-XRT observations
  98. LIGO/Virgo/KAGRA S250830bp: DECam GW-MMADS candidates
  99. GRB 250901A: LCO optical upper limit
  100. EP250827b: Swift observations of AT 2025wkm

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