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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"

20367 results found.

  1. GRB 250916A: further SAO RAS optical observations
  2. GRB 250912A: SVOM/ECLAIRs refined analysis
  3. GRB 250917B: Swift/UVOT Upper Limits
  4. GRB 250916A: OSIRIS+/GTC redshift z = 2.015
  5. GRB 250916A: MAO/AZT-22 optical observations
  6. GRB 250916A: SAO RAS optical observations
  7. GRB 250916A : GIT optical observations
  8. LIGO/Virgo/KAGRA S250917aq: Three counterpart neutrino candidates from IceCube neutrino searches
  9. GRB250917B: WFST optical observations
  10. GRB 250917B: Swift-XRT observations
  11. GRB 250917B: Swift detection of a short burst
  12. GRB 250916A: GOTO optical counterpart candidate
  13. GRB 250916A: AstroSat CZTI detection of a bright long burst
  14. GRB 250910A: SVOM/ECLAIRs refined analysis
  15. EP250916a: Einstein Probe detection of an X-ray transient
  16. EP250827b: VLA Observations
  17. SVOM/sb25091517: SVOM detection of an X-ray transient
  18. GRB 250912A: Swift/BAT-GUANO localization skymap of a possibly short burst
  19. GRB 250912A: SVOM/COLIBRÍ (FM-GFT) optical observations
  20. GRB250912A: VLT/HAWK-I follow-up observations
  21. GRB 250912A: Fermi GBM Observation
  22. GRB 250912A:SVOM/VT optical upper limit
  23. GRB 250912A: LCO optical upper limit
  24. GRB 250912A: SVOM detection of a burst
  25. IceCube-Cascade 250911A: Upper limits from a search for additional neutrino events in IceCube
  26. EP250911a: GTC/OSIRIS+ spectroscopic redshift z = 3.84
  27. LIGO/Virgo/KAGRA S250912f: Identification of a GW compact binary merger candidate
  28. EP250911a: refined analysis of the EP-WXT and EP-FXT observations
  29. GRB 250910B: SVOM/GRM observation
  30. EP250911a: SVOM/VT optical observation
  31. EP250911a: SAO RAS optical observations
  32. EP250911a: Optical detection with Kinder observations
  33. GRB 250911A: Swift/UVOT Detection
  34. GRB 250910A / EP250910a: Swift-XRT afterglow detection
  35. GRB 250910A / EP250910a: SVOM/VT afterglow confirmation
  36. LIGO/Virgo/KAGRA S250911ac: Updated Sky localization and Source Classification
  37. GRB 250910A / EP250910a : VLT/HAWK-I NIR counterpart discovery
  38. EP250911a: COLIBRÍ optical observations
  39. EP250911a: Einstein Probe detection of an X-ray transient
  40. LIGO/Virgo/KAGRA S250911ac: Identification of a GW compact binary merger candidate
  41. GRB 250903A: SVOM/ECLAIRs refined analysis
  42. GRB 250911A: Enhanced Swift-XRT position
  43. GRB 250911A: Swift-XRT observations
  44. GRB 250911A: COLIBRÍ optical counterpart candidate
  45. GRB 250910A / EP250910a: VLT/HAWK-I near-infrared observations
  46. EP250910a/GRB 250910A: EP-WXT detection of a fast X-ray transient
  47. GRB 250909B: AstroSat CZTI detection of a long burst
  48. GRB 250910A: SVOM/VT optical upper limit
  49. GRB 250910A: LCO optical upper limit
  50. GRB 250702B: Late time Chandra observations
  51. EP250908b/EP#01709240653: Swift/UVOT Detection
  52. EP250908c: refined analysis of the EP-WXT and EP-FXT observations
  53. EP250908c: SVOM/VT optical observation
  54. EP250908c: VLT/FORS2 optical counterpart identification
  55. EP250908b: SVOM/VT optical candidate (Coordinate supplement for GCN 41758)
  56. EP250908b: SVOM/VT optical candidate
  57. EP250908c: Einstein Probe detection of an X-ray transient
  58. EP250908b: EP-WXT detection of a fast X-ray transient and EP-FXT observation
  59. Fermi-LAT Gamma-ray Observations of IceCube-250905A
  60. GRB 250903A: Swift-XRT afterglow detection
  61. LIGO/Virgo/KAGRA S250906ca: Identification of a GW compact binary merger candidate
  62. IceCube-250905A: Upper limits from a search for additional neutrino events in IceCube
  63. SVOM/sb25090605: detection of an X-ray transient from the LMXB 4U 0513-40
  64. EP250905a: Liverpool Telescope i-band upper limits
  65. LIGO/Virgo/KAGRA S250830bp: DECam/SOAR GW-MMADS updates
  66. EP250905a: Liverpool Telescope observations
  67. EP250905a: refined analysis of the EP-WXT and EP-FXT observations
  68. EP250905b: EP-WXT detection of a fast X-ray transient
  69. EP250905a: JinShan likely optical counterpart detection
  70. GRB 250905A: Swift/UVOT Upper Limits
  71. GRB 250901A - SVOM/ECLAIRs refined analysis
  72. EP250905a: Einstein Probe detection of an X-ray transient
  73. GRB250904A: Liverpool Telescope upper limits
  74. GRB 250905A: Enhanced Swift-XRT position
  75. GRB 250904A: Swift/UVOT Detection
  76. GRB 250903A: Swift/UVOT detection
  77. EP detected a brightening of LMXB 1ES 1735-26.9
  78. GRB 250905A: KAIT optical upper limit
  79. GRB 250905A: Swift detection of a burst
  80. GRB 250904A: Enhanced Swift-XRT position
  81. IceCube-Cascade 250903A: Upper limits from a search for additional neutrino events in IceCube
  82. GRB 250904A: TRT optical counterpart detection
  83. GRB 250904A: Swift detection of a burst
  84. LIGO/Virgo/KAGRA S250904cv: Identification of a GW compact binary merger candidate
  85. EP250903a: retraction of the LCO candidate, and discovery of the likely counterpart
  86. EP-WXT trigger 01709201209: Liverpool Telescope upper limits
  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. LIGO/Virgo/KAGRA S250904ae: Identification of a GW compact binary merger candidate
  91. GRB 250903A: LCO optical observation
  92. GRB 250903A: LCO optical afterglow detection
  93. GRB 250903A: SVOM/VT optical confirmation with VHF data
  94. EP250901a: Mondy, Assy and SAO RAS optical limits
  95. GRB 250903A: TRT optical counterpart detection
  96. GRB 250903A: SVOM detection of a burst
  97. EP250903a: TRT optical observations
  98. EP250903a: Einstein Probe detection of an X-ray transient
  99. EP 250827B: Detection of supernova counterpart by LCO.
  100. EP250827b: NOT spectroscopic observations and AT 2025wkm classification as a broad-lined type-Ic supernova

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