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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"

19547 results found.

  1. GRB 250314A: Swift/UVOT Upper Limits
  2. GRB 250314A: Swift XRT Detection
  3. EP250315a: optical counterpart candidate detected by Gemini North
  4. EP250315a: Einstein Probe detection of an X-ray transient
  5. GRB 250226A: Mondy AZT-33IK and Koshka Zeiss-1000 Optical Upper Limits
  6. SVOM/MXT upper limit on GRB 250314A
  7. GRB 250314A: SVOM/VT upper limit
  8. GRB 250314A: NOT near-infrared candidate counterpart
  9. GRB250314A: SVOM/VT lack of bright optical candidate from VHF data
  10. GRB 250314A: SVOM detection of a burst
  11. GRB 250313A: Swift ToO observations
  12. EP250304a: Pan-STARRS r and i-band imaging and photometry
  13. GRB 250312B: Swift/BAT-GUANO localization skymap of a burst
  14. GRB 250309B: PRIME near-infrared upper limits in 2nd epoch
  15. GRB 250312A: Enhanced Swift-XRT position
  16. LIGO/Virgo/KAGRA S250304cb: Upper limits from Swift/BAT-GUANO
  17. GRB 250309B/AT2025dws: Daochen/RC-10 optical counterpart observation
  18. GRB 250312A: Swift detection of a burst
  19. GRB 241213A: VIRT Optical Upper Limit
  20. GRB 241228A: VIRT Optical Upper Limit
  21. GRB 250311A/EP250311a: Optical upper limits with Kinder observations
  22. GRB 250309B: 1.3m DFOT Optical observations
  23. GRB 250308A: Swift/BAT-GUANO localization skymap of a short burst
  24. GRB 250302A: Swift/BAT-GUANO localization skymap of a burst
  25. GRB 250228A: Swift/BAT-GUANO localization skymap of a likely short burst
  26. GRB 250226B: Swift/BAT-GUANO localization skymap of a likely long GRB
  27. GRB 250226A: Swift/BAT-GUANO localization skymap of a long GRB
  28. GRB 250223B: Swift/BAT-GUANO localization skymap of a short burst
  29. GRB 250309B: PRIME near-infrared detection
  30. EP250304a: Chandra detection
  31. GRB 250225B: Swift-BAT refined analysis
  32. GRB 250311A/EP250311a: TRT optical upper limit
  33. GRB 250311A: Tiled Swift observations
  34. EP250311a/GRB 250311A: EP-WXT detection
  35. GRB 250308A: CALET Gamma-Ray Burst Monitor detection
  36. GRB 250311B: SVOM detection of a burst
  37. GRB 250309B / AT2025dws: further SAO RAS optical observations
  38. EP250308a: 1.6m Mephisto optical upper limits
  39. Konus-Wind detection of GRB 250309B
  40. IPN triangulation of GRB 250308A (short)
  41. GRB 250309B/AT2025dws : COLIBRÍ Detection of the Optical Counterpart
  42. GRB 250309B / AT2025dws: SAO RAS optical observations
  43. AT 2025dws, likely optical counterpart of GRB 250309B: LCO confirmation of fast fading
  44. GRB250309B: One candidate counterpart from the Zwicky Transient Facility
  45. IceCube-250309A: No candidates from the Zwicky Transient Facility
  46. Fermi-LAT gamma-ray observations of IceCube-250309A
  47. GRB 230509B: Tiled Swift observations
  48. EP250308a: Einstein Probe detection of an X-ray transient
  49. EP250308a: NOT optical upper limit
  50. EP250304a: MeerKAT detection of a possible radio counterpart
  51. GRB 250305A: AstroSat CZTI detection
  52. EP250302a:Xinglong optical observations
  53. GRB 250306A: AstroSat CZTI detection
  54. GRB250101A: Radio upper limits from VLA observations
  55. GRB 250305A: SVOM/GRM observation of a burst
  56. Fermi-LAT Gamma-ray Observations of IceCube-250302A
  57. EP250302a: Optical Observations at CrAO and SAO RAS
  58. GRB 250219A: SVOM/C-GFT optical upper limit at early phase
  59. EP 250304A: Optical counterpart detection by LCO
  60. EP250302A: 1.3m DFOT optical afterglow detection
  61. EP250304a: refined analysis of the EP-WXT and EP-FXT observations
  62. EP250304a: REM NIR upper limits
  63. EP250304a: Swift/UVOT detection of an optical counterpart with a rising light curve
  64. EP250302a: Mondy Continued Optical Observations
  65. EP250304a: TRT optical counterpart detection
  66. EP250304a: Einstein Probe detection of an X-ray transient
  67. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Swift/UVOT Upper Limits
  68. EP250302a: SAO RAS optical observations
  69. EP250302a : GIT optical follow-up
  70. EP250302a: Kinder optical follow-up observations
  71. EP250302a: Swift/UVOT detection
  72. EP250302a: optical observation from the INAF Asiago Observatory
  73. EP250302a: REM NIR upper limits
  74. EP250302a: Mondy Observations and Optical Light Curve
  75. EP250302a: VLT/MUSE optical redshift z = 1.131
  76. EP250302A: VLT near-infrared observations
  77. EP250302A: VLT/X-shooter tentative redshift
  78. EP250302a: OHP/T193 optical and spectroscopic observations
  79. EP250302a: Swift-XRT observations of a fading X-ray source
  80. EP250302a: Einstein Probe detection of an X-ray transient
  81. EP250302a: SVOM/C-GFT optical observations
  82. GRB 250226A: GRANDMA Optical Observations
  83. EP250302a: Montarrenti Observatory optical detection
  84. EP250302a: Nanshan/HMT optical counterpart detection
  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 250226A: KAO Optical Upper Limit
  90. GRB 250226A: AbAO AS-32 Optical Upper Limit
  91. EP250227a: TRT optical upper limit
  92. GRB 250225B: VLT/HAWKI near-infrared observations
  93. EP250227a: Optical upper limits with Kinder observations
  94. EP250227a: NOT optical observations
  95. EP250227a: Einstein Probe detected of a fast X-ray transient
  96. EP250228a: updates on the EP observations
  97. EP250223a: J band upper limit by SYSU 80cm telescope
  98. EP250228a: Einstein Probe detection of an X-ray transient
  99. GRB 250225B: VLT/Xshooter imaging
  100. GRB 250205A / EP250205A: further radio observations with the VLA

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