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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"

44399 results found.

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

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