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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"

20259 results found.

  1. LIGO/Virgo/KAGRA S250917aq: Identification of a GW compact binary merger candidate
  2. GRB 250917B: Swift detection of a short burst
  3. GRB 250916A: GOTO optical counterpart candidate
  4. GRB 250916A: AstroSat CZTI detection of a bright long burst
  5. EP250916a: Einstein Probe detection of an X-ray transient
  6. EP250827b: VLA Observations
  7. SVOM/sb25091517: SVOM detection of an X-ray transient
  8. GRB 250912A: Swift/BAT-GUANO localization skymap of a possibly short burst
  9. GRB 250912A: SVOM/COLIBRÍ (FM-GFT) optical observations
  10. GRB250912A: VLT/HAWK-I follow-up observations
  11. GRB 250912A:SVOM/VT optical upper limit
  12. GRB 250912A: LCO optical upper limit
  13. GRB 250912A: SVOM detection of a burst
  14. GRB 250911A: GECAM-B detection
  15. LIGO/Virgo/KAGRA S250912f: Identification of a GW compact binary merger candidate
  16. EP250911a: refined analysis of the EP-WXT and EP-FXT observations
  17. GRB 250910B: SVOM/GRM observation
  18. EP250911a: SVOM/VT optical observation
  19. EP250911a: SAO RAS optical observations
  20. EP250911a: Optical detection with Kinder observations
  21. GRB 250911A: Swift/UVOT Detection
  22. GRB 250910A / EP250910a: Swift-XRT afterglow detection
  23. GRB 250910A / EP250910a: SVOM/VT afterglow confirmation
  24. GRB 250910A / EP250910a : VLT/HAWK-I NIR counterpart discovery
  25. EP250911a: COLIBRÍ optical observations
  26. EP250911a: Einstein Probe detection of an X-ray transient
  27. LIGO/Virgo/KAGRA S250911ac: Identification of a GW compact binary merger candidate
  28. GRB 250911A: Enhanced Swift-XRT position
  29. GRB 250911A: Swift-XRT observations
  30. GRB 250911A: COLIBRÍ optical counterpart candidate
  31. GRB 250910A / EP250910a: VLT/HAWK-I near-infrared observations
  32. EP250910a/GRB 250910A: EP-WXT detection of a fast X-ray transient
  33. GRB 250910A: SVOM/VT optical upper limit
  34. GRB 250910A: LCO optical upper limit
  35. GRB 250909A: AstroSat CZTI detection
  36. GRB 250910A: SVOM detection of a faint burst
  37. EP250908b/EP#01709240653: Swift/UVOT Detection
  38. EP#01709240653: Swift-XRT observations
  39. EP250908c: refined analysis of the EP-WXT and EP-FXT observations
  40. EP250908c: SVOM/VT optical observation
  41. EP250908c: VLT/FORS2 optical counterpart identification
  42. EP250908b: SVOM/VT optical candidate (Coordinate supplement for GCN 41758)
  43. EP250908b: SVOM/VT optical candidate
  44. EP250908c: Einstein Probe detection of an X-ray transient
  45. EP250908b: EP-WXT detection of a fast X-ray transient and EP-FXT observation
  46. LIGO/Virgo/KAGRA S250908y: Identification of a GW compact binary merger candidate
  47. GRB 250907A: GECAM-B detection
  48. GRB 250903A: Swift-XRT afterglow detection
  49. LIGO/Virgo/KAGRA S250906ca: Identification of a GW compact binary merger candidate
  50. SVOM/sb25090605: detection of an X-ray transient from the LMXB 4U 0513-40
  51. EP250905a: Liverpool Telescope i-band upper limits
  52. LIGO/Virgo/KAGRA S250830bp: DECam/SOAR GW-MMADS updates
  53. EP250905a: Liverpool Telescope observations
  54. EP250905a: refined analysis of the EP-WXT and EP-FXT observations
  55. EP250905b: EP-WXT detection of a fast X-ray transient
  56. EP250905a: FTW one optical and multiple NIR counterpart candidates
  57. EP250905a: JinShan likely optical counterpart detection
  58. GRB 250905A: Swift/UVOT Upper Limits
  59. GRB 250901A - SVOM/ECLAIRs refined analysis
  60. EP250905a: Einstein Probe detection of an X-ray transient
  61. GRB250904A: Liverpool Telescope upper limits
  62. GRB 250905A: Enhanced Swift-XRT position
  63. GRB 250904A: Swift/UVOT Detection
  64. GRB 250903A: Swift/UVOT detection
  65. EP detected a brightening of LMXB 1ES 1735-26.9
  66. GRB 250905A: KAIT optical upper limit
  67. GRB 250905A: Swift detection of a burst
  68. GRB 250904A: Enhanced Swift-XRT position
  69. GRB 250904A: TRT optical counterpart detection
  70. GRB 250904A: Swift detection of a burst
  71. GRB 250902A: VZLUSAT-2 detection
  72. LIGO/Virgo/KAGRA S250904cv: Identification of a GW compact binary merger candidate
  73. EP250903a: retraction of the LCO candidate, and discovery of the likely counterpart
  74. EP-WXT trigger 01709201209: Liverpool Telescope upper limits
  75. GRB 250830C: VZLUSAT-2 detection
  76. EP250903a: refined analysis of the EP-WXT and EP-FXT observations
  77. LIGO/Virgo/KAGRA S250904br: Identification of a GW compact binary merger candidate
  78. LIGO/Virgo/KAGRA S250904ae: Identification of a GW compact binary merger candidate
  79. GRB 250903A: LCO optical observation
  80. GRB 250903A: LCO optical afterglow detection
  81. GRB 250903A: SVOM/VT optical confirmation with VHF data
  82. EP250901a: Mondy, Assy and SAO RAS optical limits
  83. GRB 250903A: TRT optical counterpart detection
  84. GRB 250902B: AstroSat CZTI detection
  85. GRB 250903A: SVOM detection of a burst
  86. EP250903a: TRT optical observations
  87. EP250903a: Einstein Probe detection of an X-ray transient
  88. EP 250827B: Detection of supernova counterpart by LCO.
  89. GRB 250902B: SVOM/GRM observation
  90. EP250827b: SVOM/VT observation of AT 2025wkm
  91. LIGO/VIRGO/KAGRA S250818k: No evidence for radio variability of AT2025ulz in MeerKAT 3 GHz data
  92. GRB 250831A (SVOM trigger sb25083102): KAIT confirmation of stellar flare
  93. GRB 250901A: Swift/UVOT Upper Limit
  94. GRB 250830B: Swift-XRT afterglow detection
  95. GRB 250831A (SVOM trigger sb25083102): confirmation of a stellar flare by SVOM/VT
  96. GRB 250902A: SVOM/GRM observation
  97. EP250828a: Early near-infrared follow-up with MIRAGE on the MDM 1.3m telescope
  98. EP250901a: refined analysis of the EP-WXT and EP-FXT observations
  99. GRB 250901A: EP-FXT follow-up observation
  100. GRB 250901A: SVOM/VT optical afterglow with VHF data

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