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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"

32770 results found.

  1. EP250311a/GRB 250311A: EP-FXT follow-up observation
  2. ATCA detection of the radio counterpart of GRB 250309B-AT2025dws
  3. EP250302a: Chandra X-ray Detection
  4. Fermi GRB 250312B: Global MASTER-Net observations report
  5. GRB 250226B: Fermi GBM Observation
  6. Swift GRB 250312A: Global MASTER-Net observations report
  7. GRB 250302A: Fermi GBM Observation
  8. GRB 250309B/AT2025dws: Daochen/RC-10 optical counterpart observation
  9. GRB 241213A: VIRT Optical Upper Limit
  10. GRB 241228A: VIRT Optical Upper Limit
  11. GRB 250311A/EP250311a: Optical upper limits with Kinder observations
  12. GRB 250223B: Fermi GBM Observation
  13. GRB 250311A: Swift-XRT observations
  14. GRB 250228A: Fermi GBM Observation
  15. GRB 250309B: 1.3m DFOT Optical observations
  16. IceCube-250309A: Upper limits from a search for additional neutrino events in IceCube
  17. EP250311a: Global MASTER-Net observations report
  18. GRB 250308A: Swift/BAT-GUANO localization skymap of a short burst
  19. GRB 250302A: Swift/BAT-GUANO localization skymap of a burst
  20. GRB 250228A: Swift/BAT-GUANO localization skymap of a likely short burst
  21. GRB 250226B: Swift/BAT-GUANO localization skymap of a likely long GRB
  22. GRB 250226A: Swift/BAT-GUANO localization skymap of a long GRB
  23. GRB 250223B: Swift/BAT-GUANO localization skymap of a short burst
  24. GRB 250309B: PRIME near-infrared detection
  25. EP250304a: Chandra detection
  26. GRB 250225B: Swift-BAT refined analysis
  27. GRB 250311A/EP250311a: TRT optical upper limit
  28. IceCube-250309A: MITSuME Akeno and Seimei/TriCCS optical observations
  29. GRB 250311A: Tiled Swift observations
  30. EP250311a/GRB 250311A: EP-WXT detection
  31. GRB 250308A: CALET Gamma-Ray Burst Monitor detection
  32. GRB 250309B: SVOM/VT optical observation
  33. GRB 250309B / AT2025dws: further SAO RAS optical observations
  34. IceCube-250309A: Upper limits from Fermi-GBM Observations
  35. EP250308a: 1.6m Mephisto optical upper limits
  36. Konus-Wind detection of GRB 250309B
  37. GRB 250309B / AT2025dws: KMTNet-CTIO optical observations
  38. IPN triangulation of GRB 250308A (short)
  39. IPN triangulation of GRB 250309B
  40. IceCube-241224A: MASTER detection of PKS 1217+02 blazar flare with Zhirkov effect
  41. GRB 250309B/AT2025dws : COLIBRÍ Detection of the Optical Counterpart
  42. GRB 250309B: Swift-XRT refined Analysis
  43. GRB 250309B / IceCube-250309A: GECAM-B observations
  44. GRB 250309B / AT2025dws: OSIRIS+/GTC spectroscopy z=1.898
  45. Liverpool Telecope observations of AT 2025dws / GRB 250309B
  46. GRB 250309B / AT2025dws: SAO RAS optical observations
  47. GRB 250309B / AT2025dws: Swift-UVOT detection
  48. AT 2025dws, likely optical counterpart of GRB 250309B: LCO confirmation of fast fading
  49. GRB 250309B: Fermi GBM Observation
  50. Fermi GRB 250309B: Global MASTER-Net observations report
  51. Fermi GRB 250309A: Global MASTER-Net observations report
  52. GRB250309B: One candidate counterpart from the Zwicky Transient Facility
  53. IceCube-250309A: No candidates from the Zwicky Transient Facility
  54. Fermi-LAT gamma-ray observations of IceCube-250309A
  55. GRB 250308A: SVOM/GRM detection of QPO in the tail emission
  56. Correction to GCN 39633 - Swift is observing GRB 250309B/IceCube-250309A!
  57. GRB 230509B: Tiled Swift observations
  58. IceCube-250309A - IceCube observation of a high-energy neutrino candidate track-like event
  59. EP250308a: Global MASTER-Net observations report
  60. EP250308a: GSP optical upper limit
  61. GRB 250306A: EIRSAT-1 GMOD detection
  62. Fermi GRB 250307A: Global MASTER-Net observations report
  63. Konus-Wind detection of GRB 250306A
  64. GRB 250306A: Swift-BAT refined analysis
  65. GRB 250306A: NuSTAR detection of the prompt emission
  66. EP250304a: MeerKAT detection of a possible radio counterpart
  67. IceCube-241016A: MASTER flaring blazar 5BZU J073038.29-320820.2 with Zhirkov effect
  68. GRB 250305A: AstroSat CZTI detection
  69. EP250302a:Xinglong optical observations
  70. GRB 250306A: AstroSat CZTI detection
  71. Swift GRB 250306A: Global MASTER-Net observations report
  72. LIGO/Virgo/KAGRA S250207bg: Updated Sky localization
  73. GRB250101A: Radio upper limits from VLA observations
  74. GRB 250305A: SVOM/GRM observation of a burst
  75. EP250304A: Upper limits from Fermi-GBM Observations
  76. Fermi GRB 250305A: Global MASTER-Net observations report
  77. Fermi-LAT Gamma-ray Observations of IceCube-250302A
  78. EP250302a: Optical Observations at CrAO and SAO RAS
  79. GRB 250219A: SVOM/C-GFT optical upper limit at early phase
  80. EP 250304A: Optical counterpart detection by LCO
  81. EP250302A: 1.3m DFOT optical afterglow detection
  82. IceCube-250302A: Upper limits from a search for additional neutrino events in IceCube
  83. EP250304a: refined analysis of the EP-WXT and EP-FXT observations
  84. Konus-Wind detection of GRB 250222A
  85. EP250304a: REM NIR upper limits
  86. IPN triangulation of GRB 250222A
  87. EP250304a: Swift/UVOT detection of an optical counterpart with a rising light curve
  88. EP250302a: Mondy Continued Optical Observations
  89. EP250304a: VLT/X-shooter redshift z = 0.200
  90. EP250304a: Swift-XRT detection of a fading X-ray source
  91. EP250304a: TRT optical counterpart detection
  92. LIGO/Virgo/KAGRA S250304cb: Identification of a GW compact binary merger candidate
  93. EP250304a: Global MASTER-Net observations report
  94. EP250302a: SVOM/VT optical observation
  95. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Swift/UVOT Upper Limits
  96. EP250302a: SAO RAS optical observations
  97. EP250302a : GIT optical follow-up
  98. EP250302a: VLT/X-shooter redshift confirmation
  99. EP250225a: the candidate optical counterpart is an AGN
  100. EP250302a: Kinder optical follow-up observations

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