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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"

11778 results found.

  1. GRB 250314A: NOT near-infrared candidate counterpart
  2. GRB 250313A: Fermi GBM Detection
  3. GRB 250312B: Fermi GBM Observation
  4. GRB250314A: SVOM/VT lack of bright optical candidate from VHF data
  5. Konus-Wind detection of GRB 250313A
  6. Konus-Wind detection of GRB 250308A
  7. GRB 250314A: SVOM detection of a burst
  8. GRB 250313A: AstroSat CZTI detection of a bright long burst
  9. IceCube-250309A: MASTER detection of J140105.33-091631.6 blazar flare with Zhirkov effect
  10. GRB 250313A: Fermi-LAT detection
  11. GRB 250312B: Swift/BAT-GUANO localization skymap of a burst
  12. Fermi GRB 250313A: Global MASTER-Net observations report
  13. ATCA detection of the radio counterpart of GRB 250309B-AT2025dws
  14. EP250302a: Chandra X-ray Detection
  15. GRB 250312A: Swift-XRT refined Analysis
  16. Fermi trigger No 763509110: Global MASTER-Net observations report
  17. GRB 250312B: Fermi GBM Final Localization
  18. LIGO/Virgo/KAGRA S250304cb: Upper limits from Swift/BAT-GUANO
  19. GRB 250312A: Swift detection of a burst
  20. GRB 250309B: 1.3m DFOT Optical observations
  21. GRB 250308A: Swift/BAT-GUANO localization skymap of a short burst
  22. GRB 250302A: Swift/BAT-GUANO localization skymap of a burst
  23. GRB 250228A: Swift/BAT-GUANO localization skymap of a likely short burst
  24. GRB 250226B: Swift/BAT-GUANO localization skymap of a likely long GRB
  25. GRB 250226A: Swift/BAT-GUANO localization skymap of a long GRB
  26. GRB 250223B: Swift/BAT-GUANO localization skymap of a short burst
  27. GRB 250309B: PRIME near-infrared detection
  28. GRB 250311A/EP250311a: TRT optical upper limit
  29. EP250311a/GRB 250311A: EP-WXT detection
  30. GRB 250311A/MAXI J1457-026: MAXI/GSC detection
  31. Konus-Wind detection of GRB 250309B
  32. IPN triangulation of GRB 250308A (short)
  33. IceCube-241224A: MASTER detection of PKS 1217+02 blazar flare with Zhirkov effect
  34. GRB 250309B: Swift-XRT refined Analysis
  35. GRB 250309B / AT2025dws: Swift-UVOT detection
  36. Fermi GRB 250309A: Global MASTER-Net observations report
  37. Fermi-LAT gamma-ray observations of IceCube-250309A
  38. IceCube Alert 250309.32: Global MASTER-Net observations report
  39. EP250308a: Einstein Probe detection of an X-ray transient
  40. The EP-WXT trigger 01709132387 is likely a flaring star
  41. Fermi GRB 250307A: Global MASTER-Net observations report
  42. Konus-Wind detection of GRB 250306A
  43. IceCube-241016A: MASTER flaring blazar 5BZU J073038.29-320820.2 with Zhirkov effect
  44. GRB 250305A: AstroSat CZTI detection
  45. GRB 250306A: AstroSat CZTI detection
  46. Fermi trigger No 762963055: Global MASTER-Net observations report
  47. LIGO/Virgo/KAGRA S250207bg: Update-5 NED Galaxies in the Localization Volume
  48. Fermi-LAT Gamma-ray Observations of IceCube-250302A
  49. EP 250304A: Optical counterpart detection by LCO
  50. EP250302A: 1.3m DFOT optical afterglow detection
  51. IceCube-250302A: Upper limits from a search for additional neutrino events in IceCube
  52. EP250304a: refined analysis of the EP-WXT and EP-FXT observations
  53. Konus-Wind detection of GRB 250222A
  54. EP250304a: Einstein Probe detection of an X-ray transient
  55. EP250302a: SAO RAS optical observations
  56. EP250302a : GIT optical follow-up
  57. EP250302a: optical observation from the INAF Asiago Observatory
  58. IceCube-241113A: MASTER flaring blazar 5BZB J1311+0853 with Zhirkov effect
  59. EP250302A: VLT near-infrared observations
  60. EP250302a: OHP/T193 optical and spectroscopic observations
  61. EP250302a: Einstein Probe detection of an X-ray transient
  62. EP250302a: Montarrenti Observatory optical detection
  63. Fermi GRB 250302A: Global MASTER-Net observations report
  64. EP250302a: FTW optical and NIR detection
  65. IceCube-250302A - IceCube observation of a high-energy neutrino candidate track-like event
  66. EP250228a: Optical observations with Kinder and Swift/UVOT
  67. Konus-Wind detection of GRB 250226A
  68. GRB 250225B: VLT/HAWKI near-infrared observations
  69. EP250227a: Einstein Probe detected of a fast X-ray transient
  70. EP250223a: J band upper limit by SYSU 80cm telescope
  71. EP250228a: Einstein Probe detection of an X-ray transient
  72. GRB 250226B: INTEGRAL SPI-ACS and PICsIT detection
  73. EP250226a/GRB 250226A: refined analysis of the EP-WXT and FXT observations
  74. Konus-Wind detection of GRB 250225B
  75. GRB 250225B: VLT/FORS2 candidate optical afterglow
  76. EP250226a/GRB 250226A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  77. EP250226a / GRB 250226A: TRT optical counterpart observation
  78. LIGO/Virgo S250223dk: Swift XRT observations, 7 X-ray sources
  79. EP250226a/GRB 250226A: EP-WXT detection and FXT follow-up observation of an X-ray transient
  80. Fermi GRB 250226A: Global MASTER-Net observations report
  81. EP250225a: Einstein Probe detected of a fast X-ray transient
  82. Fermi GRB 250225A: Global MASTER-Net observations report
  83. EP250215A: J band upper limit by SYSU 80cm telescope
  84. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: AstroSat CZTI non-detection and upper limits
  85. GRB 250223C: Fermi GBM Final Real-time Localization
  86. GRB 250202B: VZLUSAT-2 detection
  87. GRB 250219A: EP-FXT afterglow detection
  88. EP250223a: 1.6m Mephisto and 50cm array observations
  89. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO trigger with ID 762004910: Identification of a GW compact binary merger candidate possibly associated with a sub-threshold Swift/BAT-GUANO trigger
  90. EP250223a: NOT optical afterglow candidate
  91. Fermi GRB 250223A: Global MASTER-Net observations report
  92. EP250223a: Einstein Probe detection of an X-ray transient
  93. LIGO/Virgo/KAGRA S250206dm: Upper limits from IceCube neutrino searches
  94. GRB 250221A: continued Assy optical observations, brightening afterglow confirmation
  95. Konus-Wind detection of GRB 250221A
  96. GRB 250221A: Assy optical observations
  97. EP250220a: FTW optical and NIR observations and upper limits
  98. EP250220a: EP-FXT follow-up observations
  99. GRB 250221A: Swift-XRT refined Analysis
  100. EP250220a: Liverpool Telescope upper limits

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