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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"

24385 results found.

  1. IceCube-250309A - IceCube observation of a high-energy neutrino candidate track-like event
  2. IceCube Alert 250309.32: Global MASTER-Net observations report
  3. GRB 250309B: BALROG localization (Fermi Trigger 763198715 / GRB 250309318)
  4. EP250308a: Global MASTER-Net observations report
  5. EP250308a: Einstein Probe detection of an X-ray transient
  6. GRB 250309A: Fermi GBM Final Real-time Localization
  7. GRB 250306A: EIRSAT-1 GMOD detection
  8. Fermi GRB 250307A: Global MASTER-Net observations report
  9. Konus-Wind detection of GRB 250306A
  10. GRB 250307A: Fermi GBM Final Real-time Localization
  11. GRB 250306A: Swift-BAT refined analysis
  12. GRB 250306A: NuSTAR detection of the prompt emission
  13. IceCube-241016A: MASTER flaring blazar 5BZU J073038.29-320820.2 with Zhirkov effect
  14. GRB 250305A: AstroSat CZTI detection
  15. EP250302a:Xinglong optical observations
  16. Fermi trigger No 762963055: Global MASTER-Net observations report
  17. Swift GRB 250306A: Global MASTER-Net observations report
  18. LIGO/Virgo/KAGRA S250207bg: Update-5 NED Galaxies in the Localization Volume
  19. GRB 250306A: Swift detection of a burst
  20. LIGO/Virgo/KAGRA S250207bg: Updated Sky localization
  21. LIGO/Virgo/KAGRA S250306ej: Retraction of GW compact binary merger candidate
  22. EP250304A: Upper limits from Fermi-GBM Observations
  23. Fermi GRB 250305A: Global MASTER-Net observations report
  24. Fermi-LAT Gamma-ray Observations of IceCube-250302A
  25. GRB 250305A: Fermi GBM Final Real-time Localization
  26. GRB 250219A: SVOM/C-GFT optical upper limit at early phase
  27. EP250302A: 1.3m DFOT optical afterglow detection
  28. IceCube-250302A: Upper limits from a search for additional neutrino events in IceCube
  29. EP250304a: refined analysis of the EP-WXT and EP-FXT observations
  30. Konus-Wind detection of GRB 250222A
  31. EP250304a: REM NIR upper limits
  32. IPN triangulation of GRB 250222A
  33. EP250304a: VLT/X-shooter redshift z = 0.200
  34. EP250304a: Swift-XRT detection of a fading X-ray source
  35. LIGO/Virgo/KAGRA S250304cb: Identification of a GW compact binary merger candidate
  36. EP250304a: Global MASTER-Net observations report
  37. The EP-WXT trigger 01709132212 is not a real source
  38. EP250302a: SVOM/VT optical observation
  39. EP250225a: the candidate optical counterpart is an AGN
  40. LIGO/Virgo/KAGRA S250302av: 2 counterpart neutrino candidate events from an IceCube neutrino search
  41. EP250302a: NUTTelA-TAO Early Measurments
  42. EP250302a: optical observation from the INAF Asiago Observatory
  43. EP250302a: REM NIR upper limits
  44. IceCube-241113A: MASTER flaring blazar 5BZB J1311+0853 with Zhirkov effect
  45. EP250302a: VLT/MUSE optical redshift z = 1.131
  46. EP250302a: Global MASTER-Net observations report
  47. EP250302a: Xinglong F60B optical observation
  48. EP250302a: Montarrenti Observatory optical detection
  49. Fermi GRB 250302A: Global MASTER-Net observations report
  50. EP250302a: Nanshan/HMT optical counterpart detection
  51. IceCube-250302A - IceCube observation of a high-energy neutrino candidate track-like event
  52. GRB 250302A: Fermi GBM Final Real-time Localization
  53. GRB 250228A: Fermi GBM Final Localization
  54. LIGO/Virgo/KAGRA S250206dm: early X-ray upper limits from Einstein Probe WXT and preliminary results of FXT observations
  55. EP250228a: Optical observations with Kinder and Swift/UVOT
  56. Konus-Wind detection of GRB 250226A
  57. GRB 250225B: EIRSAT-1 GMOD Detection
  58. EP250227a: Global MASTER-Net observations report
  59. EP250223A: Upper limits from Fermi-GBM Observations
  60. EP250227a: Optical upper limits with Kinder observations
  61. EP250227a: Einstein Probe detected of a fast X-ray transient
  62. GRB 250226A: Fermi GBM Observation
  63. EP250228a: Global MASTER-Net observations report
  64. LIGO/Virgo/KAGRA S250227e: Updated Sky localization
  65. LIGO/Virgo/KAGRA S250226dl: Updated Sky localization
  66. EP250226a/GRB 250226A:Xinglong optical follow-up observations
  67. EP250226a / GRB 250226A: SVOM/VT optical observations
  68. EP250226a/GRB 250226A: 1.6m Mephisto observations
  69. LIGO/Virgo/KAGRA S250206dm: Upper limits from SVOM/GRM Observations
  70. LIGO/Virgo/KAGRA S250223dk: Insight-HXMT/HE sub-threshold detection of a burst (HEB 250223501)
  71. LIGO/Virgo/KAGRA S250227y: Retraction of GW compact binary merger candidate
  72. LIGO/Virgo/KAGRA S250227e: Identification of a GW compact binary merger candidate
  73. Fermi GRB 250226B: Global MASTER-Net observations report
  74. LIGO/Virgo/KAGRA S250226dl: Identification of a GW compact binary merger candidate
  75. GRB 250226B: Fermi GBM Final Real-time Localization
  76. GRB 250225B: Fermi GBM Observation
  77. GRB 250225B: REM NIR upper limits
  78. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Updated Sky localization and Coincidence with External Event
  79. Konus-Wind detection of GRB 250225B
  80. GRB 250225B: VLT/FORS2 candidate optical afterglow
  81. GRB 250221A: EP-FXT detection of the X-ray afterglow
  82. EP250226a / GRB 250226A: VLT/X-shooter redshift of z = 3.315
  83. EP250226a: Global MASTER-Net observations report
  84. Swift GRB 250225B: Global MASTER-Net observations report
  85. EP250226a/GRB 250226A: EP-WXT detection and FXT follow-up observation of an X-ray transient
  86. Fermi GRB 250226A: Global MASTER-Net observations report
  87. Fermi trigger No 762205158: Global MASTER-Net observations report
  88. GRB 250226A: Fermi GBM Final Real-time Localization
  89. EP250225a: Global MASTER-Net observations report
  90. Fermi GRB 250225A: Global MASTER-Net observations report
  91. GRB 250225B: Swift detection of a burst
  92. GRB 250221A: Swift-BAT refined analysis
  93. GRB 250223C: SVOM/GRM observation of a long burst
  94. GRB 250225A: Fermi GBM Final Real-time Localization
  95. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: AstroSat CZTI non-detection and upper limits
  96. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Magellan upper limits.
  97. LIGO/Virgo/KAGRA S250223dk: DECam DESGW Candidates
  98. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Upper limits from Fermi-GBM Observations
  99. GRB 250119B: VZLUSAT-2 detection
  100. GRB 250223C: Fermi GBM Final Real-time Localization

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