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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"

24386 results found.

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

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