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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"

23578 results found.

  1. EP250315a: optical counterpart candidate detected by Gemini North
  2. EP250315a: Einstein Probe detection of an X-ray transient
  3. SVOM/MXT upper limit on GRB 250314A
  4. GRB 250313A: Fermi GBM Detection
  5. GRB 250313A: CALET Gamma-Ray Burst Monitor detection
  6. GRB 250313A: Swift-XRT observations
  7. GRB250314A: SVOM/VT lack of bright optical candidate from VHF data
  8. Konus-Wind detection of GRB 250313A
  9. Konus-Wind detection of GRB 250308A
  10. GRB 250314A: SVOM detection of a burst
  11. GRB 250313A: AstroSat CZTI detection of a bright long burst
  12. GRB 250313A: Fermi-LAT detection
  13. EP250304a: Pan-STARRS r and i-band imaging and photometry
  14. EP trigger ID 01709061302: Lick/Kast spectroscopy with the 3 m Shane telescope
  15. GRB 250312A: Swift-XRT refined Analysis
  16. GRB 250302A: Fermi GBM Observation
  17. GRB 250309B/AT2025dws: Daochen/RC-10 optical counterpart observation
  18. GRB 250312A: Swift detection of a burst
  19. GRB 250311A/EP250311a: Optical upper limits with Kinder observations
  20. GRB 250311A: Swift-XRT observations
  21. GRB 250228A: Fermi GBM Observation
  22. GRB 250226B: Swift/BAT-GUANO localization skymap of a likely long GRB
  23. GRB 250225B: Swift-BAT refined analysis
  24. GRB 250311A/EP250311a: TRT optical upper limit
  25. IceCube-250309A: MITSuME Akeno and Seimei/TriCCS optical observations
  26. GRB 250308A: CALET Gamma-Ray Burst Monitor detection
  27. GRB 250311B: SVOM detection of a burst
  28. GRB 250309B: SVOM/VT optical observation
  29. GRB 250311A/MAXI J1457-026: MAXI/GSC detection
  30. GRB 250309B / AT2025dws: further SAO RAS optical observations
  31. EP250308a: 1.6m Mephisto optical upper limits
  32. Konus-Wind detection of GRB 250309B
  33. IPN triangulation of GRB 250309B
  34. GRB 250309B/AT2025dws : COLIBRÍ Detection of the Optical Counterpart
  35. GRB 250309B / AT2025dws: OSIRIS+/GTC spectroscopy z=1.898
  36. GRB 250309B / AT2025dws: SAO RAS optical observations
  37. GRB 250309B / AT2025dws: Swift-UVOT detection
  38. AT 2025dws, likely optical counterpart of GRB 250309B: LCO confirmation of fast fading
  39. GRB250309B: One candidate counterpart from the Zwicky Transient Facility
  40. Fermi-LAT gamma-ray observations of IceCube-250309A
  41. EP250308a: GSP optical upper limit
  42. GRB 250306A: EIRSAT-1 GMOD detection
  43. Konus-Wind detection of GRB 250306A
  44. GRB 250306A: Swift-BAT refined analysis
  45. GRB 250305A: AstroSat CZTI detection
  46. EP250302a:Xinglong optical observations
  47. GRB 250306A: AstroSat CZTI detection
  48. Fermi trigger No 762963055: Global MASTER-Net observations report
  49. LIGO/Virgo/KAGRA S250207bg: Update-5 NED Galaxies in the Localization Volume
  50. GRB 250306A: Swift detection of a burst
  51. EP250304A: Upper limits from Fermi-GBM Observations
  52. Fermi-LAT Gamma-ray Observations of IceCube-250302A
  53. GRB 250219A: SVOM/C-GFT optical upper limit at early phase
  54. EP 250304A: Optical counterpart detection by LCO
  55. Konus-Wind detection of GRB 250222A
  56. EP250304a: REM NIR upper limits
  57. IPN triangulation of GRB 250222A
  58. EP250304a: TRT optical counterpart detection
  59. LIGO/Virgo/KAGRA S250304cb: Identification of a GW compact binary merger candidate
  60. The EP-WXT trigger 01709132212 is not a real source
  61. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Swift/UVOT Upper Limits
  62. EP250302a: SAO RAS optical observations
  63. EP250302a: Kinder optical follow-up observations
  64. LIGO/Virgo/KAGRA S250302av: 2 counterpart neutrino candidate events from an IceCube neutrino search
  65. EP250302a: NUTTelA-TAO Early Measurments
  66. EP250302a: REM NIR upper limits
  67. EP250302a: OHP/T193 optical and spectroscopic observations
  68. EP250302a: Xinglong F60B optical observation
  69. GRB 250226A: GRANDMA Optical Observations
  70. EP250302a: Montarrenti Observatory optical detection
  71. LIGO/Virgo/KAGRA S250206dm: early X-ray upper limits from Einstein Probe WXT and preliminary results of FXT observations
  72. EP250228a: Optical observations with Kinder and Swift/UVOT
  73. Konus-Wind detection of GRB 250226A
  74. GRB 250225B: EIRSAT-1 GMOD Detection
  75. GRB 250226A: KAO Optical Upper Limit
  76. EP250223A: Upper limits from Fermi-GBM Observations
  77. EP250227a: TRT optical upper limit
  78. GRB 250225B: VLT/HAWKI near-infrared observations
  79. EP250227a: Optical upper limits with Kinder observations
  80. EP250227a: NOT optical observations
  81. GRB 250226A / EP250226a: LCO detection of the afterglow
  82. GRB 250205A / EP250205A: further radio observations with the VLA
  83. EP250225a: NOT optical candidate counterpart
  84. EP250226a/GRB 250226A:Xinglong optical follow-up 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 S250226dl: Identification of a GW compact binary merger candidate
  89. GRB 250225B: Fermi GBM Observation
  90. GRB 250221A: ATCA Detections and Upper Limits
  91. GRB 250225B: REM NIR upper limits
  92. Konus-Wind detection of GRB 250225B
  93. GRB 250214A: SVOM/GRM observation
  94. EP250226a/GRB 250226A: GSP detects optical counterpart
  95. EP250226a/GRB 250226A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  96. EP250226a / GRB 250226A: TRT optical counterpart observation
  97. LIGO/Virgo S250223dk: Swift XRT observations, 7 X-ray sources
  98. Swift GRB 250225B: Global MASTER-Net observations report
  99. EP250225a: GSP optical upper limit
  100. EP250223a: GMG Optical Observation

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