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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').
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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.

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subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"

32490 results found.

  1. LIGO/Virgo/KAGRA S250908y: Updated Sky localization
  2. Fermi GRB 250910B: Global MASTER-Net observations report
  3. EP250911a: LCO optical counterpart discovery
  4. EP250910a: Global MASTER-Net observations report
  5. GRB 250404A / EP250404a: spectroscopic redshift at z = 1.88 (correction to GCN 40084)
  6. LIGO/Virgo/KAGRA S250911ac: Identification of a GW compact binary merger candidate
  7. GRB 250903A: SVOM/ECLAIRs refined analysis
  8. GRB 250911A: COLIBRÍ optical counterpart candidate
  9. LIGO/Virgo/KAGRA S250906ca: Updated Sky localization
  10. GRB 250910A / EP250910a: VLT/HAWK-I near-infrared observations
  11. EP250910a/GRB 250910A: EP-WXT detection of a fast X-ray transient
  12. GRB 250910A: SVOM/VT optical upper limit
  13. EP250908C: GROND observation of the fading optical counterpart
  14. GRB 250910A: LCO optical upper limit
  15. GRB 250909A: AstroSat CZTI detection
  16. GRB 250910A: SVOM/MXT possible afterglow detection
  17. GRB 250702B: Late time Chandra observations
  18. EP250908b/EP#01709240653: Swift/UVOT Detection
  19. EP250908c: refined analysis of the EP-WXT and EP-FXT observations
  20. GRB 250907A: CALET Gamma-Ray Burst Monitor detection
  21. EP250908c: SVOM/VT optical observation
  22. EP250908c: VLT/FORS2 optical counterpart identification
  23. EP250908b: SVOM/VT optical candidate (Coordinate supplement for GCN 41758)
  24. EP250908b: SVOM/VT optical candidate
  25. EP250908c: Global MASTER-Net observations report
  26. Fermi GRB 250909A: Global MASTER-Net observations report
  27. LIGO/Virgo/KAGRA S250908y: Identification of a GW compact binary merger candidate
  28. GRB 250905A: Swift-BAT refined analysis
  29. Fermi-LAT Gamma-ray Observations of IceCube-250905A
  30. GRB 250903A: Swift-XRT afterglow detection
  31. LIGO/Virgo/KAGRA S250906ca: Identification of a GW compact binary merger candidate
  32. IceCube-250905A: Upper limits from a search for additional neutrino events in IceCube
  33. EP250905a: Liverpool Telescope i-band upper limits
  34. LIGO/Virgo/KAGRA S250830bp: DECam/SOAR GW-MMADS updates
  35. EP250905b: EP-FXT follow-up observation
  36. LIGO/Virgo/KAGRA S250830bp: DECam DESGW Epoch 2 Candidates
  37. EP250905a: Liverpool Telescope observations
  38. EP250905a: refined analysis of the EP-WXT and EP-FXT observations
  39. EP250905b: Global MASTER-Net observations report
  40. EP250905a: FTW one optical and multiple NIR counterpart candidates
  41. EP250905a: JinShan likely optical counterpart detection
  42. GRB 250904A: Swift-BAT refined analysis
  43. GRB 250905A: Swift/UVOT Upper Limits
  44. EP250905a: Global MASTER-Net observations report
  45. GRB 250901A - SVOM/ECLAIRs refined analysis
  46. GRB250904A: Liverpool Telescope upper limits
  47. GRB 250904A: Swift/UVOT Detection
  48. GRB 250903A: Swift/UVOT detection
  49. LIGO/Virgo/KAGRA S250904cv: Updated Sky localization
  50. LIGO/Virgo/KAGRA S250904br: Updated Sky localization
  51. GRB 250905A: KAIT optical upper limit
  52. Swift GRB 250904A: Global MASTER-Net observations report
  53. GRB 250904A: TRT optical counterpart detection
  54. EP250827a and EP250827b: Upper limit from Fermi-GBM Observations
  55. GRB 250902B: CALET Gamma-Ray Burst Monitor detection
  56. EP250827b: Gemini Spectroscopic Confirmation of AT2025wkm as a Ic-BL Supernova
  57. GRB 250902A: CALET Gamma-Ray Burst Monitor detection
  58. LIGO/Virgo/KAGRA S250904ae: Updated Sky localization
  59. GRB 250902A: VZLUSAT-2 detection
  60. LIGO/Virgo/KAGRA S250904cv: Identification of a GW compact binary merger candidate
  61. GRB 250903A: Swift-XRT observations
  62. EP250903a: Swift-XRT observations
  63. EP#01709201209: Swift-XRT observations
  64. EP250903a: retraction of the LCO candidate, and discovery of the likely counterpart
  65. EP-WXT trigger 01709201209: Liverpool Telescope upper limits
  66. GRB 250830C: VZLUSAT-2 detection
  67. EP250903a: refined analysis of the EP-WXT and EP-FXT observations
  68. LIGO/Virgo/KAGRA S250904br: Identification of a GW compact binary merger candidate
  69. GRB 250903A: VLT X-shooter spectroscopic redshift z = 1.590
  70. LIGO/Virgo/KAGRA S250904ae: Identification of a GW compact binary merger candidate
  71. GRB 250903A: EP-FXT counterpart detection
  72. GRB 250902A: GECAM-B detection
  73. GRB 250903A: LCO optical observation
  74. GRB 250903A: LCO optical afterglow detection
  75. GRB 250903A: SVOM/VT optical confirmation with VHF data
  76. EP250903a: SVOM/VT optical confirmation
  77. EP250901a: Mondy, Assy and SAO RAS optical limits
  78. Subject GRB 250903A: SVOM/MXT afterglow detection
  79. EP250903a: LCO candidate counterpart discovery
  80. GRB 250903A: TRT optical counterpart detection
  81. GRB 250902B: AstroSat CZTI detection
  82. EP250903a: Global MASTER-Net observations report
  83. EP250903a: TRT optical observations
  84. EP250903a: Einstein Probe detection of an X-ray transient
  85. EP 250827B: Detection of supernova counterpart by LCO.
  86. EP250827b / AT 2025wkm: TRT optical observations
  87. EP250827b: NOT spectroscopic observations and AT 2025wkm classification as a broad-lined type-Ic supernova
  88. EP250827b: continued Liverpool Telescope observations
  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. Fermi GRB 250902B: Global MASTER-Net observations report
  94. Fermi-LAT Gamma-ray Observations of IceCube-250831A
  95. GRB 250902A: Fermi GBM Detection
  96. GRB 250901A: Swift/UVOT Upper Limit
  97. IceCube-250831A: Upper limits from a search for additional neutrino events in IceCube
  98. LIGO/Virgo/KAGRA S250901cb: Updated Sky localization
  99. EP250827b: Liverpool Telescope observations
  100. GRB 250831A (SVOM trigger sb25083102): confirmation of a stellar flare by SVOM/VT

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