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GCN Circulars

GCN Circulars are rapid bulletins submitted by and distributed to the community. 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"

43110 results found.

  1. GRB 250309B / IceCube-250309A: GECAM-B observations
  2. GRB 250309B / AT2025dws: OSIRIS+/GTC spectroscopy z=1.898
  3. Liverpool Telecope observations of AT 2025dws / GRB 250309B
  4. GRB 250309B / AT2025dws: SAO RAS optical observations
  5. GRB 250309B / AT2025dws: Swift-UVOT detection
  6. AT 2025dws, likely optical counterpart of GRB 250309B: LCO confirmation of fast fading
  7. GRB 250309B: Fermi GBM Observation
  8. Fermi GRB 250309B: Global MASTER-Net observations report
  9. Fermi GRB 250309A: Global MASTER-Net observations report
  10. GRB250309B: One candidate counterpart from the Zwicky Transient Facility
  11. IceCube-250309A: No candidates from the Zwicky Transient Facility
  12. Fermi-LAT gamma-ray observations of IceCube-250309A
  13. GRB 250308A: SVOM/GRM detection of QPO in the tail emission
  14. GRB 250309B: Fermi GBM Final Localization
  15. Correction to GCN 39633 - Swift is observing GRB 250309B/IceCube-250309A!
  16. GRB 230509B: Tiled Swift observations
  17. GRB 250308A: SVOM/GRM observation of a bright short burst
  18. IceCube-250309A - IceCube observation of a high-energy neutrino candidate track-like event
  19. IceCube Alert 250309.32: Global MASTER-Net observations report
  20. GRB 250309B: BALROG localization (Fermi Trigger 763198715 / GRB 250309318)
  21. EP250308a: Global MASTER-Net observations report
  22. EP250308a: GSP optical upper limit
  23. EP250308a: FTW optical and NIR upper limits
  24. EP250308a: Einstein Probe detection of an X-ray transient
  25. EP250308a: NOT optical upper limit
  26. GRB 250309A: Fermi GBM Final Real-time Localization
  27. GRB 250306A: EIRSAT-1 GMOD detection
  28. The EP-WXT trigger 01709132387 is likely a flaring star
  29. Fermi GRB 250307A: Global MASTER-Net observations report
  30. Konus-Wind detection of GRB 250306A
  31. GRB 250307A: Fermi GBM Final Real-time Localization
  32. GRB 250306A: Swift-BAT refined analysis
  33. GRB 250306A: NuSTAR detection of the prompt emission
  34. EP250304a: MeerKAT detection of a possible radio counterpart
  35. IceCube-241016A: MASTER flaring blazar 5BZU J073038.29-320820.2 with Zhirkov effect
  36. GRB 250305A: AstroSat CZTI detection
  37. EP250302a:Xinglong optical observations
  38. GRB 250306A: AstroSat CZTI detection
  39. Fermi trigger No 762963055: Global MASTER-Net observations report
  40. Swift GRB 250306A: Global MASTER-Net observations report
  41. LIGO/Virgo/KAGRA S250207bg: Update-5 NED Galaxies in the Localization Volume
  42. GRB 250306A: Swift detection of a burst
  43. LIGO/Virgo/KAGRA S250207bg: Updated Sky localization
  44. GRB250101A: Radio upper limits from VLA observations
  45. LIGO/Virgo/KAGRA S250306ej: Retraction of GW compact binary merger candidate
  46. GRB 250305A: SVOM/GRM observation of a burst
  47. The EP-WXT trigger 01709132323 is likely a flaring star
  48. EP250304A: Upper limits from Fermi-GBM Observations
  49. Fermi GRB 250305A: Global MASTER-Net observations report
  50. Fermi-LAT Gamma-ray Observations of IceCube-250302A
  51. GRB 250305A: Fermi GBM Final Real-time Localization
  52. EP250302a: Optical Observations at CrAO and SAO RAS
  53. GRB 250219A: SVOM/C-GFT optical upper limit at early phase
  54. EP 250304A: Optical counterpart detection by LCO
  55. EP250302A: 1.3m DFOT optical afterglow detection
  56. IceCube-250302A: Upper limits from a search for additional neutrino events in IceCube
  57. EP250304a: refined analysis of the EP-WXT and EP-FXT observations
  58. Konus-Wind detection of GRB 250222A
  59. EP250304a: REM NIR upper limits
  60. IPN triangulation of GRB 250222A
  61. EP250304a: Swift/UVOT detection of an optical counterpart with a rising light curve
  62. EP250302a: Mondy Continued Optical Observations
  63. EP250304a: VLT/X-shooter redshift z = 0.200
  64. EP250304a: Swift-XRT detection of a fading X-ray source
  65. EP250304a: TRT optical counterpart detection
  66. LIGO/Virgo/KAGRA S250304cb: Identification of a GW compact binary merger candidate
  67. EP250304a: Global MASTER-Net observations report
  68. EP250304a: Einstein Probe detection of an X-ray transient
  69. EP250302a: SVOM/VT optical observation
  70. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Swift/UVOT Upper Limits
  71. EP250302a: SAO RAS optical observations
  72. EP250302a : GIT optical follow-up
  73. EP250302a: VLT/X-shooter redshift confirmation
  74. EP250225a: the candidate optical counterpart is an AGN
  75. EP250302a: Kinder optical follow-up observations
  76. LIGO/Virgo/KAGRA S250302av: 2 counterpart neutrino candidate events from an IceCube neutrino search
  77. EP250302a: Swift/UVOT detection
  78. EP250302a: NUTTelA-TAO Early Measurments
  79. EP250302a: optical observation from the INAF Asiago Observatory
  80. EP250302a: REM NIR upper limits
  81. IceCube-241113A: MASTER flaring blazar 5BZB J1311+0853 with Zhirkov effect
  82. EP250302a: Mondy Observations and Optical Light Curve
  83. EP250302a: VLT/MUSE optical redshift z = 1.131
  84. INTEGRAL: end of scientific operations
  85. EP250302A: VLT near-infrared observations
  86. EP250302A: VLT/X-shooter tentative redshift
  87. EP250302a: OHP/T193 optical and spectroscopic observations
  88. EP250302a: Global MASTER-Net observations report
  89. EP250302a: Xinglong F60B optical observation
  90. EP250302a: Swift-XRT observations of a fading X-ray source
  91. EP250302a: Einstein Probe detection of an X-ray transient
  92. EP250302a: SVOM/C-GFT optical observations
  93. GRB 250226A: GRANDMA Optical Observations
  94. EP250302a: Montarrenti Observatory optical detection
  95. Fermi GRB 250302A: Global MASTER-Net observations report
  96. EP250302a: FTW optical and NIR detection
  97. EP250302a: Nanshan/HMT optical counterpart detection
  98. IceCube-250302A - IceCube observation of a high-energy neutrino candidate track-like event
  99. GRB 250302A: Fermi GBM Final Real-time Localization
  100. GRB 250228A: Fermi GBM Final Localization

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