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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"

32495 results found.

  1. GRB 250314A: VLT/X-shooter dropout, redshift z ~ 7.3
  2. GRB 250226A: Mondy AZT-33IK and Koshka Zeiss-1000 Optical Upper Limits
  3. SVOM/MXT upper limit on GRB 250314A
  4. GRB 250314A: SVOM/VT upper limit
  5. GRB 250314A: NOT near-infrared candidate counterpart
  6. GRB 250313A: Fermi GBM Detection
  7. GRB 250313A: CALET Gamma-Ray Burst Monitor detection
  8. GRB 250312B: Fermi GBM Observation
  9. GRB250314A: SVOM/VT lack of bright optical candidate from VHF data
  10. Konus-Wind detection of GRB 250313A
  11. Konus-Wind detection of GRB 250308A
  12. EP250311a/GRB 250311A: Correction to EP-WXT detection time
  13. GRB 250313A: SVOM/GRM observation of a bright long burst
  14. FRB 20250206A: Nondetection of Repeating Bursts from FRB 20250206A with FAST
  15. GRB 250313A: AstroSat CZTI detection of a bright long burst
  16. IceCube-250309A: MASTER detection of J140105.33-091631.6 blazar flare with Zhirkov effect
  17. GRB 250313A: Fermi-LAT detection
  18. GRB 250313A: Swift ToO observations
  19. EP250304a: Pan-STARRS r and i-band imaging and photometry
  20. GRB 250312B: Swift/BAT-GUANO localization skymap of a burst
  21. EP trigger ID 01709061302: Lick/Kast spectroscopy with the 3 m Shane telescope
  22. Fermi GRB 250313A: Global MASTER-Net observations report
  23. GRB 250309B: PRIME near-infrared upper limits in 2nd epoch
  24. EP250304a: SVOM/VT optical observation
  25. EP250311a/GRB 250311A: EP-FXT follow-up observation
  26. ATCA detection of the radio counterpart of GRB 250309B-AT2025dws
  27. EP250302a: Chandra X-ray Detection
  28. Fermi GRB 250312B: Global MASTER-Net observations report
  29. GRB 250226B: Fermi GBM Observation
  30. Swift GRB 250312A: Global MASTER-Net observations report
  31. GRB 250302A: Fermi GBM Observation
  32. GRB 250309B/AT2025dws: Daochen/RC-10 optical counterpart observation
  33. GRB 241213A: VIRT Optical Upper Limit
  34. GRB 241228A: VIRT Optical Upper Limit
  35. GRB 250311A/EP250311a: Optical upper limits with Kinder observations
  36. GRB 250223B: Fermi GBM Observation
  37. GRB 250311A: Swift-XRT observations
  38. GRB 250228A: Fermi GBM Observation
  39. GRB 250309B: 1.3m DFOT Optical observations
  40. IceCube-250309A: Upper limits from a search for additional neutrino events in IceCube
  41. EP250311a: Global MASTER-Net observations report
  42. GRB 250308A: Swift/BAT-GUANO localization skymap of a short burst
  43. GRB 250302A: Swift/BAT-GUANO localization skymap of a burst
  44. GRB 250228A: Swift/BAT-GUANO localization skymap of a likely short burst
  45. GRB 250226B: Swift/BAT-GUANO localization skymap of a likely long GRB
  46. GRB 250226A: Swift/BAT-GUANO localization skymap of a long GRB
  47. GRB 250223B: Swift/BAT-GUANO localization skymap of a short burst
  48. GRB 250309B: PRIME near-infrared detection
  49. EP250304a: Chandra detection
  50. GRB 250225B: Swift-BAT refined analysis
  51. GRB 250311A/EP250311a: TRT optical upper limit
  52. IceCube-250309A: MITSuME Akeno and Seimei/TriCCS optical observations
  53. GRB 250311A: Tiled Swift observations
  54. EP250311a/GRB 250311A: EP-WXT detection
  55. GRB 250308A: CALET Gamma-Ray Burst Monitor detection
  56. GRB 250309B: SVOM/VT optical observation
  57. GRB 250309B / AT2025dws: further SAO RAS optical observations
  58. IceCube-250309A: Upper limits from Fermi-GBM Observations
  59. EP250308a: 1.6m Mephisto optical upper limits
  60. Konus-Wind detection of GRB 250309B
  61. GRB 250309B / AT2025dws: KMTNet-CTIO optical observations
  62. IPN triangulation of GRB 250308A (short)
  63. IPN triangulation of GRB 250309B
  64. IceCube-241224A: MASTER detection of PKS 1217+02 blazar flare with Zhirkov effect
  65. GRB 250309B/AT2025dws : COLIBRÍ Detection of the Optical Counterpart
  66. GRB 250309B: Swift-XRT refined Analysis
  67. GRB 250309B / IceCube-250309A: GECAM-B observations
  68. GRB 250309B / AT2025dws: OSIRIS+/GTC spectroscopy z=1.898
  69. Liverpool Telecope observations of AT 2025dws / GRB 250309B
  70. GRB 250309B / AT2025dws: SAO RAS optical observations
  71. GRB 250309B / AT2025dws: Swift-UVOT detection
  72. AT 2025dws, likely optical counterpart of GRB 250309B: LCO confirmation of fast fading
  73. GRB 250309B: Fermi GBM Observation
  74. Fermi GRB 250309B: Global MASTER-Net observations report
  75. Fermi GRB 250309A: Global MASTER-Net observations report
  76. GRB250309B: One candidate counterpart from the Zwicky Transient Facility
  77. IceCube-250309A: No candidates from the Zwicky Transient Facility
  78. Fermi-LAT gamma-ray observations of IceCube-250309A
  79. GRB 250308A: SVOM/GRM detection of QPO in the tail emission
  80. Correction to GCN 39633 - Swift is observing GRB 250309B/IceCube-250309A!
  81. GRB 230509B: Tiled Swift observations
  82. IceCube-250309A - IceCube observation of a high-energy neutrino candidate track-like event
  83. EP250308a: Global MASTER-Net observations report
  84. EP250308a: GSP optical upper limit
  85. GRB 250306A: EIRSAT-1 GMOD detection
  86. Fermi GRB 250307A: Global MASTER-Net observations report
  87. Konus-Wind detection of GRB 250306A
  88. GRB 250306A: Swift-BAT refined analysis
  89. GRB 250306A: NuSTAR detection of the prompt emission
  90. EP250304a: MeerKAT detection of a possible radio counterpart
  91. IceCube-241016A: MASTER flaring blazar 5BZU J073038.29-320820.2 with Zhirkov effect
  92. GRB 250305A: AstroSat CZTI detection
  93. EP250302a:Xinglong optical observations
  94. GRB 250306A: AstroSat CZTI detection
  95. Swift GRB 250306A: Global MASTER-Net observations report
  96. LIGO/Virgo/KAGRA S250207bg: Updated Sky localization
  97. GRB250101A: Radio upper limits from VLA observations
  98. GRB 250305A: SVOM/GRM observation of a burst
  99. EP250304A: Upper limits from Fermi-GBM Observations
  100. Fermi GRB 250305A: Global MASTER-Net observations report

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