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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"

28053 results found.

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

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