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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"

44624 results found.

  1. GRB 250903A: Swift-XRT afterglow detection
  2. LIGO/Virgo/KAGRA S250906ca: Identification of a GW compact binary merger candidate
  3. IceCube-250905A: Upper limits from a search for additional neutrino events in IceCube
  4. SVOM/sb25090605: detection of an X-ray transient from the LMXB 4U 0513-40
  5. EP250905a: Liverpool Telescope i-band upper limits
  6. LIGO/Virgo/KAGRA S250830bp: DECam/SOAR GW-MMADS updates
  7. EP250905b: EP-FXT follow-up observation
  8. LIGO/Virgo/KAGRA S250830bp: DECam DESGW Epoch 2 Candidates
  9. EP250905a: Liverpool Telescope observations
  10. EP250905a: refined analysis of the EP-WXT and EP-FXT observations
  11. EP250905b: Global MASTER-Net observations report
  12. EP250905b: EP-WXT detection of a fast X-ray transient
  13. EP250905a: FTW one optical and multiple NIR counterpart candidates
  14. GRB 250905A: Swift-XRT refined Analysis
  15. EP250905a: JinShan likely optical counterpart detection
  16. IceCube-250905A - IceCube observation of a high-energy neutrino candidate track-like event
  17. GRB 250904A: Swift-BAT refined analysis
  18. IceCube Alert 250905.84: Global MASTER-Net observations report
  19. GRB 250905A: Swift/UVOT Upper Limits
  20. EP250905a: Global MASTER-Net observations report
  21. GRB 250901A - SVOM/ECLAIRs refined analysis
  22. EP250905a: Einstein Probe detection of an X-ray transient
  23. GRB 250905B: Fermi GBM Final Localization
  24. GRB250904A: Liverpool Telescope upper limits
  25. GRB 250905A: Enhanced Swift-XRT position
  26. GRB 250904A: Swift/UVOT Detection
  27. GRB 250903A: Swift/UVOT detection
  28. GRB 250904A: Swift-XRT refined Analysis
  29. LIGO/Virgo/KAGRA S250904cv: Updated Sky localization
  30. LIGO/Virgo/KAGRA S250904br: Updated Sky localization
  31. EP detected a brightening of LMXB 1ES 1735-26.9
  32. GRB 250905A: KAIT optical upper limit
  33. GRB 250905A: Swift detection of a burst
  34. Swift GRB250905.09: Global MASTER-Net observations report
  35. Swift GRB 250904A: Global MASTER-Net observations report
  36. GRB 250904A: Enhanced Swift-XRT position
  37. IceCube-Cascade 250903A: Upper limits from a search for additional neutrino events in IceCube
  38. GRB 250904A: TRT optical counterpart detection
  39. EP250827a and EP250827b: Upper limit from Fermi-GBM Observations
  40. GRB 250902B: CALET Gamma-Ray Burst Monitor detection
  41. GRB 250904A: Prompt enhanced Swift-XRT position
  42. EP250827b: Gemini Spectroscopic Confirmation of AT2025wkm as a Ic-BL Supernova
  43. GRB 250904A: Swift detection of a burst
  44. GRB 250902A: CALET Gamma-Ray Burst Monitor detection
  45. LIGO/Virgo/KAGRA S250904ae: Updated Sky localization
  46. GRB 250902A: VZLUSAT-2 detection
  47. LIGO/Virgo/KAGRA S250904cv: Identification of a GW compact binary merger candidate
  48. GRB 250903A: Swift-XRT observations
  49. EP250903a: Swift-XRT observations
  50. EP#01709201209: Swift-XRT observations
  51. EP250903a: retraction of the LCO candidate, and discovery of the likely counterpart
  52. EP-WXT trigger 01709201209: Liverpool Telescope upper limits
  53. GRB 250830C: VZLUSAT-2 detection
  54. EP250903a: refined analysis of the EP-WXT and EP-FXT observations
  55. LIGO/Virgo/KAGRA S250904br: Identification of a GW compact binary merger candidate
  56. GRB 250903A: VLT X-shooter spectroscopic redshift z = 1.590
  57. The EP-WXT trigger 01709201209 is likely a flaring star
  58. LIGO/Virgo/KAGRA S250904ae: Identification of a GW compact binary merger candidate
  59. GRB 250903A: EP-FXT counterpart detection
  60. GRB 250902A: GECAM-B detection
  61. GRB 250903A: LCO optical observation
  62. GRB 250903A: LCO optical afterglow detection
  63. GRB 250903A: SVOM/VT optical confirmation with VHF data
  64. EP250903a: SVOM/VT optical confirmation
  65. EP250901a: Mondy, Assy and SAO RAS optical limits
  66. Subject GRB 250903A: SVOM/MXT afterglow detection
  67. EP250903a: LCO candidate counterpart discovery
  68. GRB 250903A: TRT optical counterpart detection
  69. GRB 250902B: AstroSat CZTI detection
  70. GRB 250903A: SVOM detection of a burst
  71. EP250903a: Global MASTER-Net observations report
  72. EP250903a: TRT optical observations
  73. EP250903a: Einstein Probe detection of an X-ray transient
  74. EP 250827B: Detection of supernova counterpart by LCO.
  75. EP/WXT01709201159: GOTO optical follow-up
  76. EP250827b / AT 2025wkm: TRT optical observations
  77. EP250827b: NOT spectroscopic observations and AT 2025wkm classification as a broad-lined type-Ic supernova
  78. EP250827b: continued Liverpool Telescope observations
  79. GRB 250902B: SVOM/GRM observation
  80. EP250827b: SVOM/VT observation of AT 2025wkm
  81. LIGO/VIRGO/KAGRA S250818k: No evidence for radio variability of AT2025ulz in MeerKAT 3 GHz data
  82. GRB 250831A (SVOM trigger sb25083102): KAIT confirmation of stellar flare
  83. Fermi GRB 250902B: Global MASTER-Net observations report
  84. Fermi-LAT Gamma-ray Observations of IceCube-250831A
  85. GRB 250902A: Fermi GBM Detection
  86. GRB 250901A: Swift/UVOT Upper Limit
  87. GRB 250902B: Fermi GBM Final Real-time Localization
  88. IceCube-250831A: Upper limits from a search for additional neutrino events in IceCube
  89. GRB 250830B: Swift-XRT afterglow detection
  90. LIGO/Virgo/KAGRA S250902av: 1 counterpart neutrino candidate event from an IceCube neutrino search
  91. LIGO/Virgo/KAGRA S250901cb: Updated Sky localization
  92. EP250827b: Liverpool Telescope observations
  93. GRB 250831A (SVOM trigger sb25083102): confirmation of a stellar flare by SVOM/VT
  94. GRB 250902A: SVOM/GRM observation
  95. EP250828a: Early near-infrared follow-up with MIRAGE on the MDM 1.3m telescope
  96. EP250901a: refined analysis of the EP-WXT and EP-FXT observations
  97. GRB 250901A: EP-FXT follow-up observation
  98. GRB 250901A: NOT optical observations
  99. GRB 250902A: Fermi GBM Final Real-time Localization
  100. IceCube-Cascade 250828A: Upper limits from a search for additional neutrino events in IceCube

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