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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"
  1. Fermi GRB 250309A: Global MASTER-Net observations report
  2. GRB250309B: One candidate counterpart from the Zwicky Transient Facility
  3. IceCube-250309A: No candidates from the Zwicky Transient Facility
  4. Fermi-LAT gamma-ray observations of IceCube-250309A
  5. GRB 250308A: SVOM/GRM detection of QPO in the tail emission
  6. GRB 250309B: Fermi GBM Final Localization
  7. Correction to GCN 39633 - Swift is observing GRB 250309B/IceCube-250309A!
  8. GRB 230509B: Tiled Swift observations
  9. GRB 250308A: SVOM/GRM observation of a bright short burst
  10. IceCube-250309A - IceCube observation of a high-energy neutrino candidate track-like event
  11. IceCube Alert 250309.32: Global MASTER-Net observations report
  12. GRB 250309B: BALROG localization (Fermi Trigger 763198715 / GRB 250309318)
  13. EP250308a: Global MASTER-Net observations report
  14. EP250308a: GSP optical upper limit
  15. EP250308a: FTW optical and NIR upper limits
  16. EP250308a: Einstein Probe detection of an X-ray transient
  17. EP250308a: NOT optical upper limit
  18. GRB 250309A: Fermi GBM Final Real-time Localization
  19. GRB 250306A: EIRSAT-1 GMOD detection
  20. The EP-WXT trigger 01709132387 is likely a flaring star
  21. Fermi GRB 250307A: Global MASTER-Net observations report
  22. Konus-Wind detection of GRB 250306A
  23. GRB 250307A: Fermi GBM Final Real-time Localization
  24. GRB 250306A: Swift-BAT refined analysis
  25. GRB 250306A: NuSTAR detection of the prompt emission
  26. EP250304a: MeerKAT detection of a possible radio counterpart
  27. IceCube-241016A: MASTER flaring blazar 5BZU J073038.29-320820.2 with Zhirkov effect
  28. GRB 250305A: AstroSat CZTI detection
  29. EP250302a:Xinglong optical observations
  30. GRB 250306A: AstroSat CZTI detection
  31. Fermi trigger No 762963055: Global MASTER-Net observations report
  32. Fermi Gamma-ray Burst Monitor trigger 762963055/250306591 is not a GRB
  33. Swift GRB 250306A: Global MASTER-Net observations report
  34. LIGO/Virgo/KAGRA S250207bg: Update-5 NED Galaxies in the Localization Volume
  35. GRB 250306A: Swift detection of a burst
  36. LIGO/Virgo/KAGRA S250207bg: Updated Sky localization
  37. GRB250101A: Radio upper limits from VLA observations
  38. LIGO/Virgo/KAGRA S250306ej: Retraction of GW compact binary merger candidate
  39. GRB 250305A: SVOM/GRM observation of a burst
  40. The EP-WXT trigger 01709132323 is likely a flaring star
  41. EP250304A: Upper limits from Fermi-GBM Observations
  42. Fermi GRB 250305A: Global MASTER-Net observations report
  43. Fermi-LAT Gamma-ray Observations of IceCube-250302A
  44. GRB 250305A: Fermi GBM Final Real-time Localization
  45. EP250302a: Optical Observations at CrAO and SAO RAS
  46. GRB 250219A: SVOM/C-GFT optical upper limit at early phase
  47. EP 250304A: Optical counterpart detection by LCO
  48. EP250302A: 1.3m DFOT optical afterglow detection
  49. IceCube-250302A: Upper limits from a search for additional neutrino events in IceCube
  50. EP250304a: refined analysis of the EP-WXT and EP-FXT observations
  51. Konus-Wind detection of GRB 250222A
  52. EP250304a: REM NIR upper limits
  53. IPN triangulation of GRB 250222A
  54. EP250304a: Swift/UVOT detection of an optical counterpart with a rising light curve
  55. EP250302a: Mondy Continued Optical Observations
  56. EP250304a: VLT/X-shooter redshift z = 0.200
  57. EP250304a: Swift-XRT detection of a fading X-ray source
  58. EP250304a: TRT optical counterpart detection
  59. LIGO/Virgo/KAGRA S250304cb: Identification of a GW compact binary merger candidate
  60. EP250304a: Global MASTER-Net observations report
  61. EP250304a: Einstein Probe detection of an X-ray transient
  62. The EP-WXT trigger 01709132212 is not a real source
  63. EP250302a: SVOM/VT optical observation
  64. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Swift/UVOT Upper Limits
  65. EP250302a: SAO RAS optical observations
  66. EP250302a : GIT optical follow-up
  67. EP250302a: VLT/X-shooter redshift confirmation
  68. EP250225a: the candidate optical counterpart is an AGN
  69. EP250302a: Kinder optical follow-up observations
  70. LIGO/Virgo/KAGRA S250302av: 2 counterpart neutrino candidate events from an IceCube neutrino search
  71. EP250302a: Swift/UVOT detection
  72. EP250302a: NUTTelA-TAO Early Measurments
  73. EP250302a: optical observation from the INAF Asiago Observatory
  74. EP250302a: REM NIR upper limits
  75. IceCube-241113A: MASTER flaring blazar 5BZB J1311+0853 with Zhirkov effect
  76. EP250302a: Mondy Observations and Optical Light Curve
  77. EP250302a: VLT/MUSE optical redshift z = 1.131
  78. INTEGRAL: end of scientific operations
  79. EP250302A: VLT near-infrared observations
  80. EP250302A: VLT/X-shooter tentative redshift
  81. EP250302a: OHP/T193 optical and spectroscopic observations
  82. EP250302a: Global MASTER-Net observations report
  83. EP250302a: Xinglong F60B optical observation
  84. EP250302a: Swift-XRT observations of a fading X-ray source
  85. EP250302a: Einstein Probe detection of an X-ray transient
  86. EP250302a: SVOM/C-GFT optical observations
  87. GRB 250226A: GRANDMA Optical Observations
  88. EP250302a: Montarrenti Observatory optical detection
  89. Fermi GRB 250302A: Global MASTER-Net observations report
  90. EP250302a: FTW optical and NIR detection
  91. EP250302a: Nanshan/HMT optical counterpart detection
  92. IceCube-250302A - IceCube observation of a high-energy neutrino candidate track-like event
  93. GRB 250302A: Fermi GBM Final Real-time Localization
  94. GRB 250228A: Fermi GBM Final Localization
  95. The EP-WXT trigger 01709132140 is likely a flaring star
  96. LIGO/Virgo/KAGRA S250206dm: early X-ray upper limits from Einstein Probe WXT and preliminary results of FXT observations
  97. GRB 250225B: VLT near-infrared afterglow confirmation
  98. EP250228a: Optical observations with Kinder and Swift/UVOT
  99. Konus-Wind detection of GRB 250226A
  100. GRB 250225B: EIRSAT-1 GMOD Detection

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