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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"

28057 results found.

  1. GRB 250226B: Swift/BAT-GUANO localization skymap of a likely long GRB
  2. GRB 250226A: Swift/BAT-GUANO localization skymap of a long GRB
  3. GRB 250223B: Swift/BAT-GUANO localization skymap of a short burst
  4. GRB 250309B: PRIME near-infrared detection
  5. GRB 250225B: Swift-BAT refined analysis
  6. GRB 250311A/EP250311a: TRT optical upper limit
  7. EP250311a/GRB 250311A: EP-WXT detection
  8. GRB 250311B: SVOM detection of a burst
  9. GRB 250311A/MAXI J1457-026: MAXI/GSC detection
  10. GRB 250309B / AT2025dws: further SAO RAS optical observations
  11. EP250308a: 1.6m Mephisto optical upper limits
  12. Konus-Wind detection of GRB 250309B
  13. IPN triangulation of GRB 250308A (short)
  14. IceCube-241224A: MASTER detection of PKS 1217+02 blazar flare with Zhirkov effect
  15. GRB 250309B/AT2025dws : COLIBRÍ Detection of the Optical Counterpart
  16. GRB 250309B: Swift-XRT refined Analysis
  17. GRB 250309B / IceCube-250309A: GECAM-B observations
  18. GRB 250309B / AT2025dws: SAO RAS optical observations
  19. AT 2025dws, likely optical counterpart of GRB 250309B: LCO confirmation of fast fading
  20. GRB 250309B: Fermi GBM Observation
  21. GRB250309B: One candidate counterpart from the Zwicky Transient Facility
  22. IceCube-250309A: No candidates from the Zwicky Transient Facility
  23. Fermi-LAT gamma-ray observations of IceCube-250309A
  24. IceCube-250309A - IceCube observation of a high-energy neutrino candidate track-like event
  25. GRB 250309B: BALROG localization (Fermi Trigger 763198715 / GRB 250309318)
  26. EP250308a: GSP optical upper limit
  27. EP250308a: Einstein Probe detection of an X-ray transient
  28. EP250308a: NOT optical upper limit
  29. GRB 250306A: EIRSAT-1 GMOD detection
  30. GRB 250306A: Swift-BAT refined analysis
  31. GRB 250306A: NuSTAR detection of the prompt emission
  32. EP250304a: MeerKAT detection of a possible radio counterpart
  33. IceCube-241016A: MASTER flaring blazar 5BZU J073038.29-320820.2 with Zhirkov effect
  34. GRB 250305A: AstroSat CZTI detection
  35. EP250302a:Xinglong optical observations
  36. LIGO/Virgo/KAGRA S250207bg: Update-5 NED Galaxies in the Localization Volume
  37. LIGO/Virgo/KAGRA S250207bg: Updated Sky localization
  38. GRB250101A: Radio upper limits from VLA observations
  39. GRB 250305A: SVOM/GRM observation of a burst
  40. The EP-WXT trigger 01709132323 is likely a flaring star
  41. EP250304A: Upper limits from Fermi-GBM Observations
  42. Fermi-LAT Gamma-ray Observations of IceCube-250302A
  43. EP250302a: Optical Observations at CrAO and SAO RAS
  44. GRB 250219A: SVOM/C-GFT optical upper limit at early phase
  45. EP 250304A: Optical counterpart detection by LCO
  46. EP250302A: 1.3m DFOT optical afterglow detection
  47. IceCube-250302A: Upper limits from a search for additional neutrino events in IceCube
  48. EP250304a: refined analysis of the EP-WXT and EP-FXT observations
  49. EP250304a: REM NIR upper limits
  50. EP250304a: Swift/UVOT detection of an optical counterpart with a rising light curve
  51. EP250302a: Mondy Continued Optical Observations
  52. EP250304a: Swift-XRT detection of a fading X-ray source
  53. EP250304a: TRT optical counterpart detection
  54. LIGO/Virgo/KAGRA S250304cb: Identification of a GW compact binary merger candidate
  55. EP250304a: Einstein Probe detection of an X-ray transient
  56. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Swift/UVOT Upper Limits
  57. EP250302a: SAO RAS optical observations
  58. EP250302a : GIT optical follow-up
  59. EP250225a: the candidate optical counterpart is an AGN
  60. EP250302a: Kinder optical follow-up observations
  61. LIGO/Virgo/KAGRA S250302av: 2 counterpart neutrino candidate events from an IceCube neutrino search
  62. EP250302a: Swift/UVOT detection
  63. EP250302a: optical observation from the INAF Asiago Observatory
  64. EP250302a: REM NIR upper limits
  65. IceCube-241113A: MASTER flaring blazar 5BZB J1311+0853 with Zhirkov effect
  66. EP250302a: Mondy Observations and Optical Light Curve
  67. EP250302a: VLT/MUSE optical redshift z = 1.131
  68. EP250302A: VLT near-infrared observations
  69. EP250302A: VLT/X-shooter tentative redshift
  70. EP250302a: OHP/T193 optical and spectroscopic observations
  71. EP250302a: Swift-XRT observations of a fading X-ray source
  72. EP250302a: Einstein Probe detection of an X-ray transient
  73. EP250302a: SVOM/C-GFT optical observations
  74. GRB 250226A: GRANDMA Optical Observations
  75. EP250302a: Montarrenti Observatory optical detection
  76. EP250302a: Nanshan/HMT optical counterpart detection
  77. LIGO/Virgo/KAGRA S250206dm: early X-ray upper limits from Einstein Probe WXT and preliminary results of FXT observations
  78. GRB 250225B: VLT near-infrared afterglow confirmation
  79. EP250228a: Optical observations with Kinder and Swift/UVOT
  80. Konus-Wind detection of GRB 250226A
  81. GRB 250225B: EIRSAT-1 GMOD Detection
  82. GRB 250226A: KAO Optical Upper Limit
  83. GRB 250226A: AbAO AS-32 Optical Upper Limit
  84. EP250227a: Global MASTER-Net observations report
  85. EP250223A: Upper limits from Fermi-GBM Observations
  86. EP250227a: TRT optical upper limit
  87. GRB 250225B: VLT/HAWKI near-infrared observations
  88. EP250227a: Optical upper limits with Kinder observations
  89. EP250227a: NOT optical observations
  90. EP250227a: Einstein Probe detected of a fast X-ray transient
  91. EP250228a: updates on the EP observations
  92. GRB 250226A: Fermi GBM Observation
  93. EP250223a: J band upper limit by SYSU 80cm telescope
  94. EP250228a: Swift/XRT localisation
  95. EP250228a: Einstein Probe detection of an X-ray transient
  96. GRB 250226A / EP250226a: LCO detection of the afterglow
  97. LIGO/Virgo/KAGRA S250227e: Updated Sky localization
  98. LIGO/Virgo/KAGRA S250226dl: Updated Sky localization
  99. GRB 250225B: VLT/Xshooter imaging
  100. GRB 250205A / EP250205A: further radio observations with the VLA

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