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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"

20364 results found.

  1. GRB 250916A: OSIRIS+/GTC redshift z = 2.015
  2. GRB 250916A: MAO/AZT-22 optical observations
  3. GRB 250916A: SAO RAS optical observations
  4. GRB 250916A : GIT optical observations
  5. LIGO/Virgo/KAGRA S250917aq: Three counterpart neutrino candidates from IceCube neutrino searches
  6. GRB250917B: WFST optical observations
  7. GRB 250917B: Swift-XRT observations
  8. GRB 250917B: Swift detection of a short burst
  9. GRB 250916A: GOTO optical counterpart candidate
  10. GRB 250916A: AstroSat CZTI detection of a bright long burst
  11. GRB 250910A: SVOM/ECLAIRs refined analysis
  12. EP250916a: Einstein Probe detection of an X-ray transient
  13. EP250827b: VLA Observations
  14. SVOM/sb25091517: SVOM detection of an X-ray transient
  15. GRB 250912A: Swift/BAT-GUANO localization skymap of a possibly short burst
  16. GRB 250912A: SVOM/COLIBRÍ (FM-GFT) optical observations
  17. GRB250912A: VLT/HAWK-I follow-up observations
  18. GRB 250912A: Fermi GBM Observation
  19. GRB 250912A:SVOM/VT optical upper limit
  20. GRB 250912A: LCO optical upper limit
  21. GRB 250912A: SVOM detection of a burst
  22. IceCube-Cascade 250911A: Upper limits from a search for additional neutrino events in IceCube
  23. EP250911a: GTC/OSIRIS+ spectroscopic redshift z = 3.84
  24. LIGO/Virgo/KAGRA S250912f: Identification of a GW compact binary merger candidate
  25. EP250911a: refined analysis of the EP-WXT and EP-FXT observations
  26. GRB 250910B: SVOM/GRM observation
  27. EP250911a: SVOM/VT optical observation
  28. EP250911a: SAO RAS optical observations
  29. EP250911a: Optical detection with Kinder observations
  30. GRB 250911A: Swift/UVOT Detection
  31. GRB 250910A / EP250910a: Swift-XRT afterglow detection
  32. GRB 250910A / EP250910a: SVOM/VT afterglow confirmation
  33. LIGO/Virgo/KAGRA S250911ac: Updated Sky localization and Source Classification
  34. GRB 250910A / EP250910a : VLT/HAWK-I NIR counterpart discovery
  35. EP250911a: COLIBRÍ optical observations
  36. EP250911a: Einstein Probe detection of an X-ray transient
  37. LIGO/Virgo/KAGRA S250911ac: Identification of a GW compact binary merger candidate
  38. GRB 250903A: SVOM/ECLAIRs refined analysis
  39. GRB 250911A: Enhanced Swift-XRT position
  40. GRB 250911A: Swift-XRT observations
  41. GRB 250911A: COLIBRÍ optical counterpart candidate
  42. GRB 250910A / EP250910a: VLT/HAWK-I near-infrared observations
  43. EP250910a/GRB 250910A: EP-WXT detection of a fast X-ray transient
  44. GRB 250909B: AstroSat CZTI detection of a long burst
  45. GRB 250910A: SVOM/VT optical upper limit
  46. GRB 250910A: LCO optical upper limit
  47. GRB 250702B: Late time Chandra observations
  48. EP250908b/EP#01709240653: Swift/UVOT Detection
  49. EP250908c: refined analysis of the EP-WXT and EP-FXT observations
  50. EP250908c: SVOM/VT optical observation
  51. EP250908c: VLT/FORS2 optical counterpart identification
  52. EP250908b: SVOM/VT optical candidate (Coordinate supplement for GCN 41758)
  53. EP250908b: SVOM/VT optical candidate
  54. EP250908c: Einstein Probe detection of an X-ray transient
  55. EP250908b: EP-WXT detection of a fast X-ray transient and EP-FXT observation
  56. Fermi-LAT Gamma-ray Observations of IceCube-250905A
  57. GRB 250903A: Swift-XRT afterglow detection
  58. LIGO/Virgo/KAGRA S250906ca: Identification of a GW compact binary merger candidate
  59. IceCube-250905A: Upper limits from a search for additional neutrino events in IceCube
  60. SVOM/sb25090605: detection of an X-ray transient from the LMXB 4U 0513-40
  61. EP250905a: Liverpool Telescope i-band upper limits
  62. LIGO/Virgo/KAGRA S250830bp: DECam/SOAR GW-MMADS updates
  63. EP250905a: Liverpool Telescope observations
  64. EP250905a: refined analysis of the EP-WXT and EP-FXT observations
  65. EP250905b: EP-WXT detection of a fast X-ray transient
  66. EP250905a: JinShan likely optical counterpart detection
  67. GRB 250905A: Swift/UVOT Upper Limits
  68. GRB 250901A - SVOM/ECLAIRs refined analysis
  69. EP250905a: Einstein Probe detection of an X-ray transient
  70. GRB250904A: Liverpool Telescope upper limits
  71. GRB 250905A: Enhanced Swift-XRT position
  72. GRB 250904A: Swift/UVOT Detection
  73. GRB 250903A: Swift/UVOT detection
  74. EP detected a brightening of LMXB 1ES 1735-26.9
  75. GRB 250905A: KAIT optical upper limit
  76. GRB 250905A: Swift detection of a burst
  77. GRB 250904A: Enhanced Swift-XRT position
  78. IceCube-Cascade 250903A: Upper limits from a search for additional neutrino events in IceCube
  79. GRB 250904A: TRT optical counterpart detection
  80. GRB 250904A: Swift detection of a burst
  81. LIGO/Virgo/KAGRA S250904cv: Identification of a GW compact binary merger candidate
  82. EP250903a: retraction of the LCO candidate, and discovery of the likely counterpart
  83. EP-WXT trigger 01709201209: Liverpool Telescope upper limits
  84. EP250903a: refined analysis of the EP-WXT and EP-FXT observations
  85. LIGO/Virgo/KAGRA S250904br: Identification of a GW compact binary merger candidate
  86. GRB 250903A: VLT X-shooter spectroscopic redshift z = 1.590
  87. LIGO/Virgo/KAGRA S250904ae: Identification of a GW compact binary merger candidate
  88. GRB 250903A: LCO optical observation
  89. GRB 250903A: LCO optical afterglow detection
  90. GRB 250903A: SVOM/VT optical confirmation with VHF data
  91. EP250901a: Mondy, Assy and SAO RAS optical limits
  92. GRB 250903A: TRT optical counterpart detection
  93. GRB 250903A: SVOM detection of a burst
  94. EP250903a: TRT optical observations
  95. EP250903a: Einstein Probe detection of an X-ray transient
  96. EP 250827B: Detection of supernova counterpart by LCO.
  97. EP250827b: NOT spectroscopic observations and AT 2025wkm classification as a broad-lined type-Ic supernova
  98. GRB 250902B: SVOM/GRM observation
  99. EP250827b: SVOM/VT observation of AT 2025wkm
  100. LIGO/VIRGO/KAGRA S250818k: No evidence for radio variability of AT2025ulz in MeerKAT 3 GHz data

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