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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"

18004 results found.

  1. GRB 250228A: Swift/BAT-GUANO localization skymap of a likely short burst
  2. GRB 250226B: Swift/BAT-GUANO localization skymap of a likely long GRB
  3. GRB 250226A: Swift/BAT-GUANO localization skymap of a long GRB
  4. GRB 250223B: Swift/BAT-GUANO localization skymap of a short burst
  5. GRB 250309B: PRIME near-infrared detection
  6. GRB 250225B: Swift-BAT refined analysis
  7. GRB 250311A/EP250311a: TRT optical upper limit
  8. IceCube-250309A: MITSuME Akeno and Seimei/TriCCS optical observations
  9. EP250311a/GRB 250311A: EP-WXT detection
  10. GRB 250309B / AT2025dws: further SAO RAS optical observations
  11. EP250308a: 1.6m Mephisto optical upper limits
  12. IPN triangulation of GRB 250308A (short)
  13. GRB 250309B/AT2025dws : COLIBRÍ Detection of the Optical Counterpart
  14. GRB 250309B / AT2025dws: SAO RAS optical observations
  15. AT 2025dws, likely optical counterpart of GRB 250309B: LCO confirmation of fast fading
  16. GRB250309B: One candidate counterpart from the Zwicky Transient Facility
  17. IceCube-250309A: No candidates from the Zwicky Transient Facility
  18. IceCube-250309A - IceCube observation of a high-energy neutrino candidate track-like event
  19. EP250308a: Einstein Probe detection of an X-ray transient
  20. EP250308a: NOT optical upper limit
  21. EP250304a: MeerKAT detection of a possible radio counterpart
  22. EP250302a:Xinglong optical observations
  23. LIGO/Virgo/KAGRA S250207bg: Update-5 NED Galaxies in the Localization Volume
  24. GRB250101A: Radio upper limits from VLA observations
  25. GRB 250305A: SVOM/GRM observation of a burst
  26. EP250302a: Optical Observations at CrAO and SAO RAS
  27. GRB 250219A: SVOM/C-GFT optical upper limit at early phase
  28. EP 250304A: Optical counterpart detection by LCO
  29. EP250302A: 1.3m DFOT optical afterglow detection
  30. IceCube-250302A: Upper limits from a search for additional neutrino events in IceCube
  31. EP250304a: refined analysis of the EP-WXT and EP-FXT observations
  32. EP250304a: REM NIR upper limits
  33. EP250304a: Swift/UVOT detection of an optical counterpart with a rising light curve
  34. EP250302a: Mondy Continued Optical Observations
  35. EP250304a: VLT/X-shooter redshift z = 0.200
  36. EP250304a: TRT optical counterpart detection
  37. LIGO/Virgo/KAGRA S250304cb: Identification of a GW compact binary merger candidate
  38. EP250304a: Einstein Probe detection of an X-ray transient
  39. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Swift/UVOT Upper Limits
  40. EP250302a: SAO RAS optical observations
  41. EP250302a : GIT optical follow-up
  42. EP250302a: Kinder optical follow-up observations
  43. EP250302a: Swift/UVOT detection
  44. EP250302a: NUTTelA-TAO Early Measurments
  45. EP250302a: optical observation from the INAF Asiago Observatory
  46. EP250302a: REM NIR upper limits
  47. EP250302a: Mondy Observations and Optical Light Curve
  48. EP250302a: VLT/MUSE optical redshift z = 1.131
  49. EP250302A: VLT near-infrared observations
  50. EP250302A: VLT/X-shooter tentative redshift
  51. EP250302a: OHP/T193 optical and spectroscopic observations
  52. EP250302a: Einstein Probe detection of an X-ray transient
  53. EP250302a: SVOM/C-GFT optical observations
  54. GRB 250226A: GRANDMA Optical Observations
  55. EP250302a: Montarrenti Observatory optical detection
  56. EP250302a: Nanshan/HMT optical counterpart detection
  57. LIGO/Virgo/KAGRA S250206dm: early X-ray upper limits from Einstein Probe WXT and preliminary results of FXT observations
  58. GRB 250225B: VLT near-infrared afterglow confirmation
  59. EP250228a: Optical observations with Kinder and Swift/UVOT
  60. GRB 250226A: KAO Optical Upper Limit
  61. GRB 250226A: AbAO AS-32 Optical Upper Limit
  62. EP250227a: TRT optical upper limit
  63. GRB 250225B: VLT/HAWKI near-infrared observations
  64. EP250227a: Optical upper limits with Kinder observations
  65. EP250227a: NOT optical observations
  66. EP250227a: Einstein Probe detected of a fast X-ray transient
  67. EP250228a: updates on the EP observations
  68. EP250223a: J band upper limit by SYSU 80cm telescope
  69. EP250228a: Einstein Probe detection of an X-ray transient
  70. GRB 250225B: VLT/Xshooter imaging
  71. GRB 250205A / EP250205A: further radio observations with the VLA
  72. EP250225a: NOT optical candidate counterpart
  73. EP250226a/GRB 250226A:Xinglong optical follow-up observations
  74. EP250226a/GRB 250226A: refined analysis of the EP-WXT and FXT observations
  75. EP250225a: TRT optical upper limits
  76. EP250226a/GRB 250226A: 1.6m Mephisto observations
  77. EP250226a/GRB 250226A: Kinder optical follow-up observations
  78. LIGO/Virgo/KAGRA S250223dk: Insight-HXMT/HE sub-threshold detection of a burst (HEB 250223501)
  79. LIGO/Virgo/KAGRA S250227e: Identification of a GW compact binary merger candidate
  80. LIGO/Virgo/KAGRA S250226dl: Identification of a GW compact binary merger candidate
  81. GRB 250221A: ATCA Detections and Upper Limits
  82. GRB 250225B: REM NIR upper limits
  83. LIGO/Virgo/KAGRA S250223dk: DECam optical detections of Swift X-ray sources
  84. EP250223a: CrAO ZTSH optical observation
  85. GRB 250225B: VLT optical and near-infrared candidate counterpart
  86. GRB 250225B: SVOM/GRM observation of a long burst
  87. EP250226a/GRB 250226A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  88. EP250226a / GRB 250226A: TRT optical counterpart observation
  89. LIGO/Virgo S250223dk: Swift XRT observations, 7 X-ray sources
  90. EP250226a/GRB 250226A: EP-WXT detection and FXT follow-up observation of an X-ray transient
  91. EP250223a: GMG Optical Observation
  92. EP250225a: Einstein Probe detected of a fast X-ray transient
  93. EP250223a: GROWTH-India Telescope optical observations
  94. EP250215A: J band upper limit by SYSU 80cm telescope
  95. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: DECam GW-MMADS candidates
  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. EP250223a: Kinder optical follow-up observations
  99. GRB 250222A: SVOM/GRM observation of a burst
  100. EP250223a: COLIBRÍ/DDRAGO Detection of the Optical Counterpart and Slow Fading

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