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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. GRB 250309B: BALROG localization (Fermi Trigger 763198715 / GRB 250309318)
  2. EP250308a: Global MASTER-Net observations report
  3. EP250308a: GSP optical upper limit
  4. EP250308a: FTW optical and NIR upper limits
  5. EP250308a: Einstein Probe detection of an X-ray transient
  6. EP250308a: NOT optical upper limit
  7. GRB 250309A: Fermi GBM Final Real-time Localization
  8. GRB 250306A: EIRSAT-1 GMOD detection
  9. The EP-WXT trigger 01709132387 is likely a flaring star
  10. Fermi GRB 250307A: Global MASTER-Net observations report
  11. Konus-Wind detection of GRB 250306A
  12. GRB 250307A: Fermi GBM Final Real-time Localization
  13. GRB 250306A: Swift-BAT refined analysis
  14. GRB 250306A: NuSTAR detection of the prompt emission
  15. EP250304a: MeerKAT detection of a possible radio counterpart
  16. IceCube-241016A: MASTER flaring blazar 5BZU J073038.29-320820.2 with Zhirkov effect
  17. GRB 250305A: AstroSat CZTI detection
  18. EP250302a:Xinglong optical observations
  19. GRB 250306A: AstroSat CZTI detection
  20. Fermi trigger No 762963055: Global MASTER-Net observations report
  21. Fermi Gamma-ray Burst Monitor trigger 762963055/250306591 is not a GRB
  22. Swift GRB 250306A: Global MASTER-Net observations report
  23. LIGO/Virgo/KAGRA S250207bg: Update-5 NED Galaxies in the Localization Volume
  24. GRB 250306A: Swift detection of a burst
  25. LIGO/Virgo/KAGRA S250207bg: Updated Sky localization
  26. GRB250101A: Radio upper limits from VLA observations
  27. LIGO/Virgo/KAGRA S250306ej: Retraction of GW compact binary merger candidate
  28. GRB 250305A: SVOM/GRM observation of a burst
  29. The EP-WXT trigger 01709132323 is likely a flaring star
  30. EP250304A: Upper limits from Fermi-GBM Observations
  31. Fermi GRB 250305A: Global MASTER-Net observations report
  32. Fermi-LAT Gamma-ray Observations of IceCube-250302A
  33. GRB 250305A: Fermi GBM Final Real-time Localization
  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. EP250304a: Einstein Probe detection of an X-ray transient
  51. The EP-WXT trigger 01709132212 is not a real source
  52. EP250302a: SVOM/VT optical observation
  53. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Swift/UVOT Upper Limits
  54. EP250302a: SAO RAS optical observations
  55. EP250302a : GIT optical follow-up
  56. EP250302a: VLT/X-shooter redshift confirmation
  57. EP250225a: the candidate optical counterpart is an AGN
  58. EP250302a: Kinder optical follow-up observations
  59. LIGO/Virgo/KAGRA S250302av: 2 counterpart neutrino candidate events from an IceCube neutrino search
  60. EP250302a: Swift/UVOT detection
  61. EP250302a: NUTTelA-TAO Early Measurments
  62. EP250302a: optical observation from the INAF Asiago Observatory
  63. EP250302a: REM NIR upper limits
  64. IceCube-241113A: MASTER flaring blazar 5BZB J1311+0853 with Zhirkov effect
  65. EP250302a: Mondy Observations and Optical Light Curve
  66. EP250302a: VLT/MUSE optical redshift z = 1.131
  67. INTEGRAL: end of scientific operations
  68. EP250302A: VLT near-infrared observations
  69. EP250302A: VLT/X-shooter tentative redshift
  70. EP250302a: OHP/T193 optical and spectroscopic observations
  71. EP250302a: Global MASTER-Net observations report
  72. EP250302a: Xinglong F60B optical observation
  73. EP250302a: Swift-XRT observations of a fading X-ray source
  74. EP250302a: Einstein Probe detection of an X-ray transient
  75. EP250302a: SVOM/C-GFT optical observations
  76. GRB 250226A: GRANDMA Optical Observations
  77. EP250302a: Montarrenti Observatory optical detection
  78. Fermi GRB 250302A: Global MASTER-Net observations report
  79. EP250302a: FTW optical and NIR detection
  80. EP250302a: Nanshan/HMT optical counterpart detection
  81. IceCube-250302A - IceCube observation of a high-energy neutrino candidate track-like event
  82. GRB 250302A: Fermi GBM Final Real-time Localization
  83. GRB 250228A: Fermi GBM Final Localization
  84. The EP-WXT trigger 01709132140 is likely a flaring star
  85. LIGO/Virgo/KAGRA S250206dm: early X-ray upper limits from Einstein Probe WXT and preliminary results of FXT observations
  86. GRB 250225B: VLT near-infrared afterglow confirmation
  87. EP250228a: Optical observations with Kinder and Swift/UVOT
  88. Konus-Wind detection of GRB 250226A
  89. GRB 250225B: EIRSAT-1 GMOD Detection
  90. GRB 250226A: KAO Optical Upper Limit
  91. GRB 250226A: AbAO AS-32 Optical Upper Limit
  92. EP250227a: Global MASTER-Net observations report
  93. EP250223A: Upper limits from Fermi-GBM Observations
  94. EP250227a: TRT optical upper limit
  95. GRB 250225B: VLT/HAWKI near-infrared observations
  96. EP250227a: Optical upper limits with Kinder observations
  97. EP250227a: NOT optical observations
  98. EP250227a: Einstein Probe detected of a fast X-ray transient
  99. EP250228a: updates on the EP observations
  100. GRB 250226A: Fermi GBM Observation

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