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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"

24763 results found.

  1. GRB 230509B: 1.3m DFOT Optical observations
  2. IceCube-250309A: Upper limits from a search for additional neutrino events in IceCube
  3. GRB 250308A: Swift/BAT-GUANO localization skymap of a short burst
  4. GRB 250302A: Swift/BAT-GUANO localization skymap of a burst
  5. GRB 250228A: Swift/BAT-GUANO localization skymap of a likely short burst
  6. GRB 250226B: Swift/BAT-GUANO localization skymap of a likely long GRB
  7. GRB 250226A: Swift/BAT-GUANO localization skymap of a long GRB
  8. GRB 250223B: Swift/BAT-GUANO localization skymap of a short burst
  9. GRB 250309B: PRIME near-infrared detection
  10. GRB 250225B: Swift-BAT refined analysis
  11. GRB 250311A/EP250311a: TRT optical upper limit
  12. EP250311a/GRB 250311A: EP-WXT detection
  13. GRB 250311B: SVOM detection of a burst
  14. GRB 250311A/MAXI J1457-026: MAXI/GSC detection
  15. GRB 250309B / AT2025dws: further SAO RAS optical observations
  16. EP250308a: 1.6m Mephisto optical upper limits
  17. Konus-Wind detection of GRB 250309B
  18. IPN triangulation of GRB 250308A (short)
  19. IceCube-241224A: MASTER detection of PKS 1217+02 blazar flare with Zhirkov effect
  20. GRB 250309B/AT2025dws : COLIBRÍ Detection of the Optical Counterpart
  21. GRB 250309B: Swift-XRT refined Analysis
  22. GRB 250309B / IceCube-250309A: GECAM-B observations
  23. GRB 250309B / AT2025dws: SAO RAS optical observations
  24. AT 2025dws, likely optical counterpart of GRB 250309B: LCO confirmation of fast fading
  25. GRB 250309B: Fermi GBM Observation
  26. GRB250309B: One candidate counterpart from the Zwicky Transient Facility
  27. IceCube-250309A: No candidates from the Zwicky Transient Facility
  28. Fermi-LAT gamma-ray observations of IceCube-250309A
  29. IceCube-250309A - IceCube observation of a high-energy neutrino candidate track-like event
  30. GRB 250309B: BALROG localization (Fermi Trigger 763198715 / GRB 250309318)
  31. EP250308a: GSP optical upper limit
  32. EP250308a: Einstein Probe detection of an X-ray transient
  33. EP250308a: NOT optical upper limit
  34. GRB 250306A: EIRSAT-1 GMOD detection
  35. GRB 250306A: Swift-BAT refined analysis
  36. GRB 250306A: NuSTAR detection of the prompt emission
  37. EP250304a: MeerKAT detection of a possible radio counterpart
  38. IceCube-241016A: MASTER flaring blazar 5BZU J073038.29-320820.2 with Zhirkov effect
  39. GRB 250305A: AstroSat CZTI detection
  40. EP250302a:Xinglong optical observations
  41. LIGO/Virgo/KAGRA S250207bg: Update-5 NED Galaxies in the Localization Volume
  42. LIGO/Virgo/KAGRA S250207bg: Updated Sky localization
  43. GRB250101A: Radio upper limits from VLA observations
  44. GRB 250305A: SVOM/GRM observation of a burst
  45. The EP-WXT trigger 01709132323 is likely a flaring star
  46. EP250304A: Upper limits from Fermi-GBM Observations
  47. Fermi-LAT Gamma-ray Observations of IceCube-250302A
  48. EP250302a: Optical Observations at CrAO and SAO RAS
  49. GRB 250219A: SVOM/C-GFT optical upper limit at early phase
  50. EP 250304A: Optical counterpart detection by LCO
  51. EP250302A: 1.3m DFOT optical afterglow detection
  52. IceCube-250302A: Upper limits from a search for additional neutrino events in IceCube
  53. EP250304a: refined analysis of the EP-WXT and EP-FXT observations
  54. EP250304a: REM NIR upper limits
  55. EP250304a: Swift/UVOT detection of an optical counterpart with a rising light curve
  56. EP250302a: Mondy Continued Optical Observations
  57. EP250304a: Swift-XRT detection of a fading X-ray source
  58. EP250304a: TRT optical counterpart detection
  59. LIGO/Virgo/KAGRA S250304cb: Identification of a GW compact binary merger candidate
  60. EP250304a: Einstein Probe detection of an X-ray transient
  61. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Swift/UVOT Upper Limits
  62. EP250302a: SAO RAS optical observations
  63. EP250302a : GIT optical follow-up
  64. EP250225a: the candidate optical counterpart is an AGN
  65. EP250302a: Kinder optical follow-up observations
  66. LIGO/Virgo/KAGRA S250302av: 2 counterpart neutrino candidate events from an IceCube neutrino search
  67. EP250302a: Swift/UVOT detection
  68. EP250302a: optical observation from the INAF Asiago Observatory
  69. EP250302a: REM NIR upper limits
  70. IceCube-241113A: MASTER flaring blazar 5BZB J1311+0853 with Zhirkov effect
  71. EP250302a: Mondy Observations and Optical Light Curve
  72. EP250302a: VLT/MUSE optical redshift z = 1.131
  73. EP250302A: VLT near-infrared observations
  74. EP250302A: VLT/X-shooter tentative redshift
  75. EP250302a: OHP/T193 optical and spectroscopic observations
  76. EP250302a: Swift-XRT observations of a fading X-ray source
  77. EP250302a: Einstein Probe detection of an X-ray transient
  78. EP250302a: SVOM/C-GFT optical observations
  79. GRB 250226A: GRANDMA Optical Observations
  80. EP250302a: Montarrenti Observatory optical detection
  81. EP250302a: Nanshan/HMT optical counterpart detection
  82. LIGO/Virgo/KAGRA S250206dm: early X-ray upper limits from Einstein Probe WXT and preliminary results of FXT observations
  83. GRB 250225B: VLT near-infrared afterglow confirmation
  84. EP250228a: Optical observations with Kinder and Swift/UVOT
  85. Konus-Wind detection of GRB 250226A
  86. GRB 250225B: EIRSAT-1 GMOD Detection
  87. GRB 250226A: KAO Optical Upper Limit
  88. GRB 250226A: AbAO AS-32 Optical Upper Limit
  89. EP250227a: Global MASTER-Net observations report
  90. EP250223A: Upper limits from Fermi-GBM Observations
  91. EP250227a: TRT optical upper limit
  92. GRB 250225B: VLT/HAWKI near-infrared observations
  93. EP250227a: Optical upper limits with Kinder observations
  94. EP250227a: NOT optical observations
  95. EP250227a: Einstein Probe detected of a fast X-ray transient
  96. EP250228a: updates on the EP observations
  97. GRB 250226A: Fermi GBM Observation
  98. EP250223a: J band upper limit by SYSU 80cm telescope
  99. EP250228a: Swift/XRT localisation
  100. EP250228a: Einstein Probe detection of an X-ray transient

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