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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"

45440 results found.

  1. GRB 250910B: BALROG localization (Fermi Trigger 779223130 / GRB 250910786)
  2. GRB 250910B: Fermi GBM Final Real-time Localization
  3. GRB 250910A / EP250910a: VLT/HAWK-I near-infrared observations
  4. EP250910a/GRB 250910A: EP-WXT detection of a fast X-ray transient
  5. GRB 250909B: AstroSat CZTI detection of a long burst
  6. GRB 250910A: SVOM/VT optical upper limit
  7. EP250908C: GROND observation of the fading optical counterpart
  8. GRB 250910A: LCO optical upper limit
  9. GRB 250909A: AstroSat CZTI detection
  10. GRB 250910A: SVOM/MXT possible afterglow detection
  11. GRB 250910A: SVOM detection of a faint burst
  12. LIGO/Virgo/KAGRA S250910b: Retraction of GW compact binary merger candidate
  13. GRB 250702B: Late time Chandra observations
  14. EP250908b/EP#01709240653: Swift/UVOT Detection
  15. EP#01709240653: Swift-XRT observations
  16. The EP-WXT trigger 01709240674 is triggered by the known source SS Cyg
  17. EP250908c: refined analysis of the EP-WXT and EP-FXT observations
  18. GRB 250907A: CALET Gamma-Ray Burst Monitor detection
  19. EP250908c: SVOM/VT optical observation
  20. EP250908c: VLT/FORS2 optical counterpart identification
  21. EP250908b: SVOM/VT optical candidate (Coordinate supplement for GCN 41758)
  22. EP250908b: SVOM/VT optical candidate
  23. The EP-WXT trigger EP250908a/01709240652 is not a real source
  24. EP250908c: Global MASTER-Net observations report
  25. Fermi GRB 250909A: Global MASTER-Net observations report
  26. EP250908c: Einstein Probe detection of an X-ray transient
  27. GRB 250909A: Fermi GBM Final Real-time Localization
  28. EP250908b: EP-WXT detection of a fast X-ray transient and EP-FXT observation
  29. EP#01709240652 (possibly EP250908a): FTW optical and NIR observations
  30. LIGO/Virgo/KAGRA S250908y: Identification of a GW compact binary merger candidate
  31. GRB 250907A: GECAM-B detection
  32. GRB 250905A: Swift-BAT refined analysis
  33. Fermi-LAT Gamma-ray Observations of IceCube-250905A
  34. GRB 250903A: Swift-XRT afterglow detection
  35. LIGO/Virgo/KAGRA S250906ca: Identification of a GW compact binary merger candidate
  36. IceCube-250905A: Upper limits from a search for additional neutrino events in IceCube
  37. SVOM/sb25090605: detection of an X-ray transient from the LMXB 4U 0513-40
  38. EP250905a: Liverpool Telescope i-band upper limits
  39. LIGO/Virgo/KAGRA S250830bp: DECam/SOAR GW-MMADS updates
  40. EP250905b: EP-FXT follow-up observation
  41. LIGO/Virgo/KAGRA S250830bp: DECam DESGW Epoch 2 Candidates
  42. EP250905a: Liverpool Telescope observations
  43. EP250905a: refined analysis of the EP-WXT and EP-FXT observations
  44. EP250905b: Global MASTER-Net observations report
  45. EP250905b: EP-WXT detection of a fast X-ray transient
  46. EP250905a: FTW one optical and multiple NIR counterpart candidates
  47. GRB 250905A: Swift-XRT refined Analysis
  48. EP250905a: JinShan likely optical counterpart detection
  49. IceCube-250905A - IceCube observation of a high-energy neutrino candidate track-like event
  50. GRB 250904A: Swift-BAT refined analysis
  51. IceCube Alert 250905.84: Global MASTER-Net observations report
  52. GRB 250905A: Swift/UVOT Upper Limits
  53. EP250905a: Global MASTER-Net observations report
  54. GRB 250901A - SVOM/ECLAIRs refined analysis
  55. EP250905a: Einstein Probe detection of an X-ray transient
  56. GRB 250905B: Fermi GBM Final Localization
  57. GRB250904A: Liverpool Telescope upper limits
  58. GRB 250905A: Enhanced Swift-XRT position
  59. GRB 250904A: Swift/UVOT Detection
  60. GRB 250903A: Swift/UVOT detection
  61. GRB 250904A: Swift-XRT refined Analysis
  62. LIGO/Virgo/KAGRA S250904cv: Updated Sky localization
  63. LIGO/Virgo/KAGRA S250904br: Updated Sky localization
  64. EP detected a brightening of LMXB 1ES 1735-26.9
  65. GRB 250905A: KAIT optical upper limit
  66. GRB 250905A: Swift detection of a burst
  67. Swift GRB250905.09: Global MASTER-Net observations report
  68. Swift GRB 250904A: Global MASTER-Net observations report
  69. GRB 250904A: Enhanced Swift-XRT position
  70. IceCube-Cascade 250903A: Upper limits from a search for additional neutrino events in IceCube
  71. GRB 250904A: TRT optical counterpart detection
  72. EP250827a and EP250827b: Upper limit from Fermi-GBM Observations
  73. GRB 250902B: CALET Gamma-Ray Burst Monitor detection
  74. GRB 250904A: Prompt enhanced Swift-XRT position
  75. EP250827b: Gemini Spectroscopic Confirmation of AT2025wkm as a Ic-BL Supernova
  76. GRB 250904A: Swift detection of a burst
  77. GRB 250902A: CALET Gamma-Ray Burst Monitor detection
  78. LIGO/Virgo/KAGRA S250904ae: Updated Sky localization
  79. GRB 250902A: VZLUSAT-2 detection
  80. LIGO/Virgo/KAGRA S250904cv: Identification of a GW compact binary merger candidate
  81. GRB 250903A: Swift-XRT observations
  82. EP250903a: Swift-XRT observations
  83. EP#01709201209: Swift-XRT observations
  84. EP250903a: retraction of the LCO candidate, and discovery of the likely counterpart
  85. EP-WXT trigger 01709201209: Liverpool Telescope upper limits
  86. GRB 250830C: VZLUSAT-2 detection
  87. EP250903a: refined analysis of the EP-WXT and EP-FXT observations
  88. LIGO/Virgo/KAGRA S250904br: Identification of a GW compact binary merger candidate
  89. GRB 250903A: VLT X-shooter spectroscopic redshift z = 1.590
  90. The EP-WXT trigger 01709201209 is likely a flaring star
  91. LIGO/Virgo/KAGRA S250904ae: Identification of a GW compact binary merger candidate
  92. GRB 250903A: EP-FXT counterpart detection
  93. GRB 250902A: GECAM-B detection
  94. GRB 250903A: LCO optical observation
  95. GRB 250903A: LCO optical afterglow detection
  96. GRB 250903A: SVOM/VT optical confirmation with VHF data
  97. EP250903a: SVOM/VT optical confirmation
  98. EP250901a: Mondy, Assy and SAO RAS optical limits
  99. Subject GRB 250903A: SVOM/MXT afterglow detection
  100. EP250903a: LCO candidate counterpart discovery

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