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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"
  1. EP250905a: Global MASTER-Net observations report
  2. GRB 250901A - SVOM/ECLAIRs refined analysis
  3. EP250905a: Einstein Probe detection of an X-ray transient
  4. GRB 250905B: Fermi GBM Final Localization
  5. GRB250904A: Liverpool Telescope upper limits
  6. GRB 250905A: Enhanced Swift-XRT position
  7. GRB 250904A: Swift/UVOT Detection
  8. GRB 250903A: Swift/UVOT detection
  9. GRB 250904A: Swift-XRT refined Analysis
  10. LIGO/Virgo/KAGRA S250904cv: Updated Sky localization
  11. LIGO/Virgo/KAGRA S250904br: Updated Sky localization
  12. EP detected a brightening of LMXB 1ES 1735-26.9
  13. GRB 250905A: KAIT optical upper limit
  14. GRB 250905A: Swift detection of a burst
  15. Swift GRB250905.09: Global MASTER-Net observations report
  16. Swift GRB 250904A: Global MASTER-Net observations report
  17. GRB 250904A: Enhanced Swift-XRT position
  18. IceCube-Cascade 250903A: Upper limits from a search for additional neutrino events in IceCube
  19. GRB 250904A: TRT optical counterpart detection
  20. EP250827a and EP250827b: Upper limit from Fermi-GBM Observations
  21. GRB 250902B: CALET Gamma-Ray Burst Monitor detection
  22. GRB 250904A: Prompt enhanced Swift-XRT position
  23. EP250827b: Gemini Spectroscopic Confirmation of AT2025wkm as a Ic-BL Supernova
  24. GRB 250904A: Swift detection of a burst
  25. GRB 250902A: CALET Gamma-Ray Burst Monitor detection
  26. LIGO/Virgo/KAGRA S250904ae: Updated Sky localization
  27. GRB 250902A: VZLUSAT-2 detection
  28. LIGO/Virgo/KAGRA S250904cv: Identification of a GW compact binary merger candidate
  29. GRB 250903A: Swift-XRT observations
  30. EP250903a: Swift-XRT observations
  31. EP#01709201209: Swift-XRT observations
  32. EP250903a: retraction of the LCO candidate, and discovery of the likely counterpart
  33. EP-WXT trigger 01709201209: Liverpool Telescope upper limits
  34. GRB 250830C: VZLUSAT-2 detection
  35. EP250903a: refined analysis of the EP-WXT and EP-FXT observations
  36. LIGO/Virgo/KAGRA S250904br: Identification of a GW compact binary merger candidate
  37. GRB 250903A: VLT X-shooter spectroscopic redshift z = 1.590
  38. The EP-WXT trigger 01709201209 is likely a flaring star
  39. LIGO/Virgo/KAGRA S250904ae: Identification of a GW compact binary merger candidate
  40. GRB 250903A: EP-FXT counterpart detection
  41. GRB 250902A: GECAM-B detection
  42. GRB 250903A: LCO optical observation
  43. GRB 250903A: LCO optical afterglow detection
  44. GRB 250903A: SVOM/VT optical confirmation with VHF data
  45. EP250903a: SVOM/VT optical confirmation
  46. EP250901a: Mondy, Assy and SAO RAS optical limits
  47. Subject GRB 250903A: SVOM/MXT afterglow detection
  48. EP250903a: LCO candidate counterpart discovery
  49. GRB 250903A: TRT optical counterpart detection
  50. GRB 250902B: AstroSat CZTI detection
  51. GRB 250903A: SVOM detection of a burst
  52. EP250903a: Global MASTER-Net observations report
  53. EP250903a: TRT optical observations
  54. EP250903a: Einstein Probe detection of an X-ray transient
  55. EP 250827B: Detection of supernova counterpart by LCO.
  56. EP/WXT01709201159: GOTO optical follow-up
  57. EP250827b / AT 2025wkm: TRT optical observations
  58. EP250827b: NOT spectroscopic observations and AT 2025wkm classification as a broad-lined type-Ic supernova
  59. EP250827b: continued Liverpool Telescope observations
  60. GRB 250902B: SVOM/GRM observation
  61. EP250827b: SVOM/VT observation of AT 2025wkm
  62. LIGO/VIRGO/KAGRA S250818k: No evidence for radio variability of AT2025ulz in MeerKAT 3 GHz data
  63. GRB 250831A (SVOM trigger sb25083102): KAIT confirmation of stellar flare
  64. Fermi GRB 250902B: Global MASTER-Net observations report
  65. Fermi-LAT Gamma-ray Observations of IceCube-250831A
  66. GRB 250902A: Fermi GBM Detection
  67. GRB 250901A: Swift/UVOT Upper Limit
  68. GRB 250902B: Fermi GBM Final Real-time Localization
  69. IceCube-250831A: Upper limits from a search for additional neutrino events in IceCube
  70. GRB 250830B: Swift-XRT afterglow detection
  71. LIGO/Virgo/KAGRA S250902av: 1 counterpart neutrino candidate event from an IceCube neutrino search
  72. LIGO/Virgo/KAGRA S250901cb: Updated Sky localization
  73. EP250827b: Liverpool Telescope observations
  74. GRB 250831A (SVOM trigger sb25083102): confirmation of a stellar flare by SVOM/VT
  75. GRB 250902A: SVOM/GRM observation
  76. EP250828a: Early near-infrared follow-up with MIRAGE on the MDM 1.3m telescope
  77. EP250901a: refined analysis of the EP-WXT and EP-FXT observations
  78. GRB 250901A: EP-FXT follow-up observation
  79. GRB 250901A: NOT optical observations
  80. GRB 250902A: Fermi GBM Final Real-time Localization
  81. IceCube-Cascade 250828A: Upper limits from a search for additional neutrino events in IceCube
  82. GRB 250901A: SVOM/VT optical afterglow with VHF data
  83. GRB 250901A: Swift-XRT afterglow detection
  84. EP250901a: Swift-XRT observations
  85. LIGO/Virgo/KAGRA S250830bp: DECam GW-MMADS candidates
  86. GRB 250901A: LCO optical upper limit
  87. EP250827b: Swift observations of AT 2025wkm
  88. LIGO/Virgo/KAGRA S250830bp: DECam DESGW Epoch 1 Candidates
  89. EP250827b: Gemini Spectroscopy of AT 2025wkm
  90. LIGO/Virgo/KAGRA S250901cb: Identification of a GW compact binary merger candidate
  91. EP250831a: NOT optical observations and tentative afterglow candidate
  92. EP250827b: FTW Observations of AT 2025wkm
  93. EP250827b: Contemporaneous detection of EP X-ray flare EP250827b and ZTF transient ZTF25abmpngy/AT2025wkm
  94. GRB 250901A: SVOM detection of a burst
  95. GRB 250831B: SVOM/GRM observation
  96. GRB 250830C: Insight-HXMT detection
  97. EP250901a: Mephisto optical upper limits
  98. GRB 250830C: GECAM-B detection
  99. EP250901a: Global MASTER-Net observations report
  100. GRB 250830C: AstroSat CZTI detection of a long burst

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