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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"

28726 results found.

  1. Liverpool Telecope observations of AT 2025dws / GRB 250309B
  2. GRB 250309B / AT2025dws: SAO RAS optical observations
  3. GRB 250309B / AT2025dws: Swift-UVOT detection
  4. AT 2025dws, likely optical counterpart of GRB 250309B: LCO confirmation of fast fading
  5. GRB 250309B: Fermi GBM Observation
  6. Fermi GRB 250309B: Global MASTER-Net observations report
  7. Fermi GRB 250309A: Global MASTER-Net observations report
  8. GRB250309B: One candidate counterpart from the Zwicky Transient Facility
  9. IceCube-250309A: No candidates from the Zwicky Transient Facility
  10. Fermi-LAT gamma-ray observations of IceCube-250309A
  11. GRB 250308A: SVOM/GRM detection of QPO in the tail emission
  12. Correction to GCN 39633 - Swift is observing GRB 250309B/IceCube-250309A!
  13. GRB 230509B: Tiled Swift observations
  14. IceCube-250309A - IceCube observation of a high-energy neutrino candidate track-like event
  15. EP250308a: Global MASTER-Net observations report
  16. EP250308a: GSP optical upper limit
  17. GRB 250306A: EIRSAT-1 GMOD detection
  18. Fermi GRB 250307A: Global MASTER-Net observations report
  19. Konus-Wind detection of GRB 250306A
  20. GRB 250306A: Swift-BAT refined analysis
  21. GRB 250306A: NuSTAR detection of the prompt emission
  22. EP250304a: MeerKAT detection of a possible radio counterpart
  23. IceCube-241016A: MASTER flaring blazar 5BZU J073038.29-320820.2 with Zhirkov effect
  24. GRB 250305A: AstroSat CZTI detection
  25. EP250302a:Xinglong optical observations
  26. GRB 250306A: AstroSat CZTI detection
  27. Swift GRB 250306A: Global MASTER-Net observations report
  28. LIGO/Virgo/KAGRA S250207bg: Updated Sky localization
  29. GRB250101A: Radio upper limits from VLA observations
  30. GRB 250305A: SVOM/GRM observation of a burst
  31. EP250304A: Upper limits from Fermi-GBM Observations
  32. Fermi GRB 250305A: Global MASTER-Net observations report
  33. Fermi-LAT Gamma-ray Observations of IceCube-250302A
  34. EP250302a: Optical Observations at CrAO and SAO RAS
  35. GRB 250219A: SVOM/C-GFT optical upper limit at early phase
  36. EP 250304A: Optical counterpart detection by LCO
  37. EP250302A: 1.3m DFOT optical afterglow detection
  38. IceCube-250302A: Upper limits from a search for additional neutrino events in IceCube
  39. EP250304a: refined analysis of the EP-WXT and EP-FXT observations
  40. Konus-Wind detection of GRB 250222A
  41. EP250304a: REM NIR upper limits
  42. IPN triangulation of GRB 250222A
  43. EP250304a: Swift/UVOT detection of an optical counterpart with a rising light curve
  44. EP250302a: Mondy Continued Optical Observations
  45. EP250304a: VLT/X-shooter redshift z = 0.200
  46. EP250304a: Swift-XRT detection of a fading X-ray source
  47. EP250304a: TRT optical counterpart detection
  48. LIGO/Virgo/KAGRA S250304cb: Identification of a GW compact binary merger candidate
  49. EP250304a: Global MASTER-Net observations report
  50. EP250302a: SVOM/VT optical observation
  51. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Swift/UVOT Upper Limits
  52. EP250302a: SAO RAS optical observations
  53. EP250302a : GIT optical follow-up
  54. EP250302a: VLT/X-shooter redshift confirmation
  55. EP250225a: the candidate optical counterpart is an AGN
  56. EP250302a: Kinder optical follow-up observations
  57. EP250302a: Swift/UVOT detection
  58. EP250302a: NUTTelA-TAO Early Measurments
  59. EP250302a: optical observation from the INAF Asiago Observatory
  60. EP250302a: REM NIR upper limits
  61. IceCube-241113A: MASTER flaring blazar 5BZB J1311+0853 with Zhirkov effect
  62. EP250302a: Mondy Observations and Optical Light Curve
  63. EP250302a: VLT/MUSE optical redshift z = 1.131
  64. INTEGRAL: end of scientific operations
  65. EP250302A: VLT near-infrared observations
  66. EP250302A: VLT/X-shooter tentative redshift
  67. EP250302a: OHP/T193 optical and spectroscopic observations
  68. EP250302a: Global MASTER-Net observations report
  69. EP250302a: Xinglong F60B optical observation
  70. EP250302a: Swift-XRT observations of a fading X-ray source
  71. EP250302a: Einstein Probe detection of an X-ray transient
  72. EP250302a: SVOM/C-GFT optical observations
  73. GRB 250226A: GRANDMA Optical Observations
  74. EP250302a: Montarrenti Observatory optical detection
  75. Fermi GRB 250302A: Global MASTER-Net observations report
  76. EP250302a: FTW optical and NIR detection
  77. LIGO/Virgo/KAGRA S250206dm: early X-ray upper limits from Einstein Probe WXT and preliminary results of FXT observations
  78. GRB 250225B: VLT near-infrared afterglow confirmation
  79. EP250228a: Optical observations with Kinder and Swift/UVOT
  80. Konus-Wind detection of GRB 250226A
  81. GRB 250225B: EIRSAT-1 GMOD Detection
  82. GRB 250226A: KAO Optical Upper Limit
  83. GRB 250226A: AbAO AS-32 Optical Upper Limit
  84. EP250227a: Global MASTER-Net observations report
  85. EP250223A: Upper limits from Fermi-GBM Observations
  86. EP250227a: TRT optical upper limit
  87. GRB 250225B: VLT/HAWKI near-infrared observations
  88. EP250227a: Optical upper limits with Kinder observations
  89. EP250227a: NOT optical observations
  90. EP250228a: updates on the EP observations
  91. GRB 250226A: Fermi GBM Observation
  92. EP250225a: EP-FXT follow-up observation
  93. EP250223a: J band upper limit by SYSU 80cm telescope
  94. EP250228a: Swift/XRT localisation
  95. EP250228a: Global MASTER-Net observations report
  96. GRB 250226A / EP250226a: LCO detection of the afterglow
  97. LIGO/Virgo/KAGRA S250227e: Updated Sky localization
  98. LIGO/Virgo/KAGRA S250226dl: Updated Sky localization
  99. GRB 250225B: VLT/Xshooter imaging
  100. GRB 250205A / EP250205A: further radio observations with the VLA

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