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GCN Circulars

GCN Circulars are rapid bulletins submitted by and distributed to the community. 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"

20514 results found.

  1. GRB 250309B/AT2025dws: Daochen/RC-10 optical counterpart observation
  2. GRB 250312A: Swift detection of a burst
  3. GRB 241213A: VIRT Optical Upper Limit
  4. GRB 241228A: VIRT Optical Upper Limit
  5. GRB 250311A/EP250311a: Optical upper limits with Kinder observations
  6. GRB 250311A: Swift-XRT observations
  7. GRB 250309B: 1.3m DFOT Optical observations
  8. IceCube-250309A: Upper limits from a search for additional neutrino events in IceCube
  9. GRB 250308A: Swift/BAT-GUANO localization skymap of a short burst
  10. GRB 250302A: Swift/BAT-GUANO localization skymap of a burst
  11. GRB 250228A: Swift/BAT-GUANO localization skymap of a likely short burst
  12. GRB 250226B: Swift/BAT-GUANO localization skymap of a likely long GRB
  13. GRB 250226A: Swift/BAT-GUANO localization skymap of a long GRB
  14. GRB 250223B: Swift/BAT-GUANO localization skymap of a short burst
  15. GRB 250309B: PRIME near-infrared detection
  16. GRB 250225B: Swift-BAT refined analysis
  17. GRB 250311A/EP250311a: TRT optical upper limit
  18. IceCube-250309A: MITSuME Akeno and Seimei/TriCCS optical observations
  19. EP250311a/GRB 250311A: EP-WXT detection
  20. GRB 250309B / AT2025dws: further SAO RAS optical observations
  21. EP250308a: 1.6m Mephisto optical upper limits
  22. IPN triangulation of GRB 250308A (short)
  23. GRB 250309B/AT2025dws : COLIBRÍ Detection of the Optical Counterpart
  24. GRB 250309B / AT2025dws: SAO RAS optical observations
  25. AT 2025dws, likely optical counterpart of GRB 250309B: LCO confirmation of fast fading
  26. GRB250309B: One candidate counterpart from the Zwicky Transient Facility
  27. IceCube-250309A: No candidates from the Zwicky Transient Facility
  28. IceCube-250309A - IceCube observation of a high-energy neutrino candidate track-like event
  29. EP250308a: Einstein Probe detection of an X-ray transient
  30. EP250308a: NOT optical upper limit
  31. EP250304a: MeerKAT detection of a possible radio counterpart
  32. EP250302a:Xinglong optical observations
  33. LIGO/Virgo/KAGRA S250207bg: Update-5 NED Galaxies in the Localization Volume
  34. GRB250101A: Radio upper limits from VLA observations
  35. GRB 250305A: SVOM/GRM observation of a burst
  36. EP250302a: Optical Observations at CrAO and SAO RAS
  37. GRB 250219A: SVOM/C-GFT optical upper limit at early phase
  38. EP 250304A: Optical counterpart detection by LCO
  39. EP250302A: 1.3m DFOT optical afterglow detection
  40. IceCube-250302A: Upper limits from a search for additional neutrino events in IceCube
  41. EP250304a: refined analysis of the EP-WXT and EP-FXT observations
  42. EP250304a: REM NIR upper limits
  43. EP250304a: Swift/UVOT detection of an optical counterpart with a rising light curve
  44. EP250302a: Mondy Continued Optical Observations
  45. EP250304a: VLT/X-shooter redshift z = 0.200
  46. EP250304a: TRT optical counterpart detection
  47. LIGO/Virgo/KAGRA S250304cb: Identification of a GW compact binary merger candidate
  48. EP250304a: Einstein Probe detection of an X-ray transient
  49. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Swift/UVOT Upper Limits
  50. EP250302a: SAO RAS optical observations
  51. EP250302a : GIT optical follow-up
  52. EP250302a: Kinder optical follow-up observations
  53. EP250302a: Swift/UVOT detection
  54. EP250302a: NUTTelA-TAO Early Measurments
  55. EP250302a: optical observation from the INAF Asiago Observatory
  56. EP250302a: REM NIR upper limits
  57. EP250302a: Mondy Observations and Optical Light Curve
  58. EP250302a: VLT/MUSE optical redshift z = 1.131
  59. EP250302A: VLT near-infrared observations
  60. EP250302A: VLT/X-shooter tentative redshift
  61. EP250302a: OHP/T193 optical and spectroscopic observations
  62. EP250302a: Einstein Probe detection of an X-ray transient
  63. EP250302a: SVOM/C-GFT optical observations
  64. GRB 250226A: GRANDMA Optical Observations
  65. EP250302a: Montarrenti Observatory optical detection
  66. EP250302a: Nanshan/HMT optical counterpart detection
  67. LIGO/Virgo/KAGRA S250206dm: early X-ray upper limits from Einstein Probe WXT and preliminary results of FXT observations
  68. GRB 250225B: VLT near-infrared afterglow confirmation
  69. EP250228a: Optical observations with Kinder and Swift/UVOT
  70. GRB 250226A: KAO Optical Upper Limit
  71. GRB 250226A: AbAO AS-32 Optical Upper Limit
  72. EP250227a: TRT optical upper limit
  73. GRB 250225B: VLT/HAWKI near-infrared observations
  74. EP250227a: Optical upper limits with Kinder observations
  75. EP250227a: NOT optical observations
  76. EP250227a: Einstein Probe detected of a fast X-ray transient
  77. EP250228a: updates on the EP observations
  78. EP250223a: J band upper limit by SYSU 80cm telescope
  79. EP250228a: Einstein Probe detection of an X-ray transient
  80. GRB 250225B: VLT/Xshooter imaging
  81. GRB 250205A / EP250205A: further radio observations with the VLA
  82. EP250225a: NOT optical candidate counterpart
  83. EP250226a/GRB 250226A:Xinglong optical follow-up observations
  84. EP250226a/GRB 250226A: refined analysis of the EP-WXT and FXT observations
  85. EP250225a: TRT optical upper limits
  86. EP250226a/GRB 250226A: 1.6m Mephisto observations
  87. EP250226a/GRB 250226A: Kinder optical follow-up observations
  88. LIGO/Virgo/KAGRA S250223dk: Insight-HXMT/HE sub-threshold detection of a burst (HEB 250223501)
  89. LIGO/Virgo/KAGRA S250227e: Identification of a GW compact binary merger candidate
  90. LIGO/Virgo/KAGRA S250226dl: Identification of a GW compact binary merger candidate
  91. GRB 250221A: ATCA Detections and Upper Limits
  92. GRB 250225B: REM NIR upper limits
  93. LIGO/Virgo/KAGRA S250223dk: DECam optical detections of Swift X-ray sources
  94. EP250223a: CrAO ZTSH optical observation
  95. GRB 250225B: VLT optical and near-infrared candidate counterpart
  96. GRB 250225B: SVOM/GRM observation of a long burst
  97. EP250226a/GRB 250226A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  98. EP250226a / GRB 250226A: TRT optical counterpart observation
  99. LIGO/Virgo S250223dk: Swift XRT observations, 7 X-ray sources
  100. EP250226a/GRB 250226A: EP-WXT detection and FXT follow-up observation of an X-ray transient

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