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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"

24849 results found.

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

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