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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"

24881 results found.

  1. GRB 250314A: SVOM detection of a burst
  2. GRB 250313A: AstroSat CZTI detection of a bright long burst
  3. IceCube-250309A: MASTER detection of J140105.33-091631.6 blazar flare with Zhirkov effect
  4. GRB 250313A: Fermi-LAT detection
  5. EP250304a: Pan-STARRS r and i-band imaging and photometry
  6. GRB 250312B: Swift/BAT-GUANO localization skymap of a burst
  7. GRB 250309B: PRIME near-infrared upper limits in 2nd epoch
  8. GRB 250313A???: BALROG localization (Fermi Trigger / GRB 250313607)
  9. ATCA detection of the radio counterpart of GRB 250309B-AT2025dws
  10. GRB 250312A: Swift-XRT refined Analysis
  11. GRB 250312A: Enhanced Swift-XRT position
  12. LIGO/Virgo/KAGRA S250304cb: Upper limits from Swift/BAT-GUANO
  13. GRB 250226B: Fermi GBM Observation
  14. GRB 250302A: Fermi GBM Observation
  15. GRB 250309B/AT2025dws: Daochen/RC-10 optical counterpart observation
  16. GRB 250312A: Swift detection of a burst
  17. GRB 241213A: VIRT Optical Upper Limit
  18. GRB 241228A: VIRT Optical Upper Limit
  19. GRB 250311A/EP250311a: Optical upper limits with Kinder observations
  20. GRB 250311A: Swift-XRT observations
  21. GRB 230509B: 1.3m DFOT Optical observations
  22. IceCube-250309A: Upper limits from a search for additional neutrino events in IceCube
  23. GRB 250308A: Swift/BAT-GUANO localization skymap of a short burst
  24. GRB 250302A: Swift/BAT-GUANO localization skymap of a burst
  25. GRB 250228A: Swift/BAT-GUANO localization skymap of a likely short burst
  26. GRB 250226B: Swift/BAT-GUANO localization skymap of a likely long GRB
  27. GRB 250226A: Swift/BAT-GUANO localization skymap of a long GRB
  28. GRB 250223B: Swift/BAT-GUANO localization skymap of a short burst
  29. GRB 250309B: PRIME near-infrared detection
  30. GRB 250225B: Swift-BAT refined analysis
  31. GRB 250311A/EP250311a: TRT optical upper limit
  32. EP250311a/GRB 250311A: EP-WXT detection
  33. GRB 250311B: SVOM detection of a burst
  34. GRB 250311A/MAXI J1457-026: MAXI/GSC detection
  35. GRB 250309B / AT2025dws: further SAO RAS optical observations
  36. EP250308a: 1.6m Mephisto optical upper limits
  37. Konus-Wind detection of GRB 250309B
  38. IPN triangulation of GRB 250308A (short)
  39. IceCube-241224A: MASTER detection of PKS 1217+02 blazar flare with Zhirkov effect
  40. GRB 250309B/AT2025dws : COLIBRÍ Detection of the Optical Counterpart
  41. GRB 250309B: Swift-XRT refined Analysis
  42. GRB 250309B / IceCube-250309A: GECAM-B observations
  43. GRB 250309B / AT2025dws: SAO RAS optical observations
  44. AT 2025dws, likely optical counterpart of GRB 250309B: LCO confirmation of fast fading
  45. GRB 250309B: Fermi GBM Observation
  46. GRB250309B: One candidate counterpart from the Zwicky Transient Facility
  47. IceCube-250309A: No candidates from the Zwicky Transient Facility
  48. Fermi-LAT gamma-ray observations of IceCube-250309A
  49. IceCube-250309A - IceCube observation of a high-energy neutrino candidate track-like event
  50. GRB 250309B: BALROG localization (Fermi Trigger 763198715 / GRB 250309318)
  51. EP250308a: GSP optical upper limit
  52. EP250308a: Einstein Probe detection of an X-ray transient
  53. EP250308a: NOT optical upper limit
  54. GRB 250306A: EIRSAT-1 GMOD detection
  55. GRB 250306A: Swift-BAT refined analysis
  56. GRB 250306A: NuSTAR detection of the prompt emission
  57. EP250304a: MeerKAT detection of a possible radio counterpart
  58. IceCube-241016A: MASTER flaring blazar 5BZU J073038.29-320820.2 with Zhirkov effect
  59. GRB 250305A: AstroSat CZTI detection
  60. EP250302a:Xinglong optical observations
  61. LIGO/Virgo/KAGRA S250207bg: Update-5 NED Galaxies in the Localization Volume
  62. LIGO/Virgo/KAGRA S250207bg: Updated Sky localization
  63. GRB250101A: Radio upper limits from VLA observations
  64. GRB 250305A: SVOM/GRM observation of a burst
  65. The EP-WXT trigger 01709132323 is likely a flaring star
  66. EP250304A: Upper limits from Fermi-GBM Observations
  67. Fermi-LAT Gamma-ray Observations of IceCube-250302A
  68. EP250302a: Optical Observations at CrAO and SAO RAS
  69. GRB 250219A: SVOM/C-GFT optical upper limit at early phase
  70. EP 250304A: Optical counterpart detection by LCO
  71. EP250302A: 1.3m DFOT optical afterglow detection
  72. IceCube-250302A: Upper limits from a search for additional neutrino events in IceCube
  73. EP250304a: refined analysis of the EP-WXT and EP-FXT observations
  74. EP250304a: REM NIR upper limits
  75. EP250304a: Swift/UVOT detection of an optical counterpart with a rising light curve
  76. EP250302a: Mondy Continued Optical Observations
  77. EP250304a: Swift-XRT detection of a fading X-ray source
  78. EP250304a: TRT optical counterpart detection
  79. LIGO/Virgo/KAGRA S250304cb: Identification of a GW compact binary merger candidate
  80. EP250304a: Einstein Probe detection of an X-ray transient
  81. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Swift/UVOT Upper Limits
  82. EP250302a: SAO RAS optical observations
  83. EP250302a : GIT optical follow-up
  84. EP250225a: the candidate optical counterpart is an AGN
  85. EP250302a: Kinder optical follow-up observations
  86. LIGO/Virgo/KAGRA S250302av: 2 counterpart neutrino candidate events from an IceCube neutrino search
  87. EP250302a: Swift/UVOT detection
  88. EP250302a: optical observation from the INAF Asiago Observatory
  89. EP250302a: REM NIR upper limits
  90. IceCube-241113A: MASTER flaring blazar 5BZB J1311+0853 with Zhirkov effect
  91. EP250302a: Mondy Observations and Optical Light Curve
  92. EP250302a: VLT/MUSE optical redshift z = 1.131
  93. EP250302A: VLT near-infrared observations
  94. EP250302A: VLT/X-shooter tentative redshift
  95. EP250302a: OHP/T193 optical and spectroscopic observations
  96. EP250302a: Swift-XRT observations of a fading X-ray source
  97. EP250302a: Einstein Probe detection of an X-ray transient
  98. EP250302a: SVOM/C-GFT optical observations
  99. GRB 250226A: GRANDMA Optical Observations
  100. EP250302a: Montarrenti Observatory optical detection

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