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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.

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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"
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10922 results found.

  1. LIGO/Virgo/KAGRA S250818k: further MeerKAT monitoring
  2. GRB 250910A / EP250910a: VLT/X-shooter host galaxy redshift z = 0.592
  3. GRB 250926A: CALET Gamma-Ray Burst Monitor detection
  4. GRB 250925A: Mondy I-band optical observations
  5. GRB 250916A: SVOM/VT optical observation
  6. GRB 250925A: Swift/UVOT Upper Limits
  7. GRB 250925A: Mondy and AbAO optical observations
  8. GRB 250925A: COLIBRÍ photometric redshift
  9. GRB 250925A : MITSuME Akeno optical upper limits
  10. GRB 250925A: COLIBRÍ optical photometry of the afterglow
  11. GRB 250925A: Swift detection of a burst
  12. GRB 250924A: SAO RAS optical observations
  13. GRB 250924A: SVOM/VT optical observation
  14. GRB 250924A: Mondy optical observations, afterglow fading
  15. GRB 250920B: AbAO optical upper limits
  16. GRB 250920C: VLT redshift confirmation z = 1.399
  17. GRB 250920B: CrAO ZTSH optical observations
  18. GRB 250920B: SAO RAS optical observations
  19. GRB 250920C: PRIME near-infrared detection
  20. GRB 250916A: CrAO ZTSh R-band optical observations
  21. GRB 250916A: SAO RAS Zeiss-1000 optical observations
  22. GRB 250920B: Kitab-ISON optical upper limit
  23. GRB 250917B: Mondy and Zeiss-1000 SAO RAS optical observations, optical observations, afterglow candidate
  24. GRB 250920C: Swift/UVOT Detection
  25. GRB 250920C: Swift detection of a burst
  26. LIGO/Virgo/KAGRA S250920bq: Coverage and upper limits from MAXI/GSC observations
  27. GRB 250920B: Swift detection of a burst with a bright optical counterpart.
  28. GRB 250919A/EP250919a: SVOM/VT optical observation
  29. GRB 250916A: Mondy R-band optical observations
  30. GRB 250919A: Fermi-LAT detection
  31. EP250919a/GRB 250919A: Gemini/GMOS-S spectroscopic redshift z = 1.145
  32. GRB 250916A: further SAO RAS optical observations
  33. GRB 250916A: OSIRIS+/GTC redshift z = 2.015
  34. SVOM/sb25091517: Confirmation of a stellar flare by SVOM/VT
  35. GRB 250912A: SVOM/COLIBRÍ (FM-GFT) optical observations
  36. GRB 250912A: VLT observations
  37. GRB 250912A:SVOM/VT optical upper limit
  38. EP250908c: tentative VLT/FORS2 redshift z = 2.87
  39. GRB 250911A: Swift-BAT refined analysis
  40. EP250911a: SVOM/VT optical observation
  41. EP250911a: Optical detection with Kinder observations
  42. GRB 250911A: Swift/UVOT Detection
  43. GRB 250911A: Swift detection of a burst
  44. EP250910a/GRB 250910A: EP-WXT detection of a fast X-ray transient
  45. GRB 250910A: SVOM/VT optical upper limit
  46. GRB 250910A: LCO optical upper limit
  47. GRB 250702B: Late time Chandra observations
  48. GRB 250907A: CALET Gamma-Ray Burst Monitor detection
  49. EP250908c: SVOM/VT optical observation
  50. EP250908b: SVOM/VT optical candidate (Coordinate supplement for GCN 41758)
  51. EP250908b: SVOM/VT optical candidate
  52. SVOM/sb25090605: detection of an X-ray transient from the LMXB 4U 0513-40
  53. LIGO/Virgo/KAGRA S250830bp: DECam DESGW Epoch 2 Candidates
  54. EP250905a: Liverpool Telescope observations
  55. GRB 250902B: CALET Gamma-Ray Burst Monitor detection
  56. EP250827b: Gemini Spectroscopic Confirmation of AT2025wkm as a Ic-BL Supernova
  57. GRB 250904A: Swift detection of a burst
  58. GRB 250902A: CALET Gamma-Ray Burst Monitor detection
  59. GRB 250902A: VZLUSAT-2 detection
  60. EP250903a: retraction of the LCO candidate, and discovery of the likely counterpart
  61. EP-WXT trigger 01709201209: Liverpool Telescope upper limits
  62. GRB 250830C: VZLUSAT-2 detection
  63. GRB 250903A: VLT X-shooter spectroscopic redshift z = 1.590
  64. EP250903a: SVOM/VT optical confirmation
  65. EP250827b: SVOM/VT observation of AT 2025wkm
  66. GRB 250831A (SVOM trigger sb25083102): confirmation of a stellar flare by SVOM/VT
  67. GRB 250901A: EP-FXT follow-up observation
  68. EP250827b: Gemini Spectroscopy of AT 2025wkm
  69. EP250831a: NOT optical observations and tentative afterglow candidate
  70. LIGO/Virgo/KAGRA S250831cc: Coverage and upper limits from MAXI/GSC observations
  71. LIGO/Virgo/KAGRA S250830bp: Coverage and upper limits from MAXI/GSC observations
  72. EP-WXT trigger 01709200994: Liverpool Telescope upper limits
  73. GRB 250830B: MAXI/GSC detection
  74. GRB 250830A / MAXI J0853+337: MAXI/GSC detection
  75. EP250828a: Optical counterpart detection with Kinder observations
  76. EP250828a: SVOM/VT optical candidate
  77. EP250828a: Optical upper limit with Kinder observations
  78. EP250827A: VLT/X-shooter redshift confirmation
  79. GRB 250806A: HiPERCAM/GTC limits on a possible supernova
  80. LIGO/Virgo/KAGRA S250818k: SAO RAS BTA z-band observations of AT2025ulz
  81. LIGO/Virgo/KAGRA S250818k: MASTER predicovery limits of the AT2025ulz/ZTF25abjmnps KN candidate
  82. GRB 250823A: SVOM/VT optical observation
  83. GRB 250823A: Swift detection of a burst
  84. LIGO/Virgo/KAGRA S250818k: Rebrightening detected with Gemini/GMOS
  85. LIGO/Virgo/KAGRA S250818k: J-GEM follow-up observation for AT2025ulz
  86. LIGO/Virgo/KAGRA S250818k: PRIME nIR observations of AT2025ulz
  87. EP250821a: VLT X-shooter spectroscopic redshift z = 0.577
  88. LIGO/Virgo/KAGRA S250818k: GRAWITA TNG NIR observations of AT2025ulz
  89. EP250821a: SVOM/VT optical observation
  90. GRB 250814A: CMO SAI and SAO RAS izJ observations.
  91. LIGO/Virgo/KAGRA S250818k: WFST pre-discovery limits and follow-up observations of AT 2025ulz
  92. LIGO/Virgo/KAGRA S250818k: Multi-band Gemini GMOS Detections
  93. LIGO/Virgo/KAGRA S250818k: ATLAS pre-discovery limits for AT2025ulz
  94. GRB 250818B: optical afterglow detection with Lesedi (GOTO25fzq)
  95. GRB 250818B: Keck redshift of the optical afterglow
  96. LIGO/Virgo/KAGRA S250818k: Coverage and upper limits from MAXI/GSC observations
  97. GRB 250818B: SVOM/VT optical observation
  98. GRB 250813B: Liverpool Telescope optical upper limits
  99. GRB 250814A: detection of the afterglow candidate with Liverpool Telescope
  100. GRB 250812A: SVOM/VT optical continued observation

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