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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"

24778 results found.

  1. IceCube-250309A: MASTER detection of J140105.33-091631.6 blazar flare with Zhirkov effect
  2. GRB 250313A: Fermi-LAT detection
  3. EP250304a: Pan-STARRS r and i-band imaging and photometry
  4. GRB 250312B: Swift/BAT-GUANO localization skymap of a burst
  5. GRB 250309B: PRIME near-infrared upper limits in 2nd epoch
  6. GRB 250313A???: BALROG localization (Fermi Trigger / GRB 250313607)
  7. ATCA detection of the radio counterpart of GRB 250309B-AT2025dws
  8. GRB 250312A: Swift-XRT refined Analysis
  9. GRB 250312A: Enhanced Swift-XRT position
  10. LIGO/Virgo/KAGRA S250304cb: Upper limits from Swift/BAT-GUANO
  11. GRB 250226B: Fermi GBM Observation
  12. GRB 250302A: Fermi GBM Observation
  13. GRB 250309B/AT2025dws: Daochen/RC-10 optical counterpart observation
  14. GRB 250312A: Swift detection of a burst
  15. GRB 241213A: VIRT Optical Upper Limit
  16. GRB 241228A: VIRT Optical Upper Limit
  17. GRB 250311A/EP250311a: Optical upper limits with Kinder observations
  18. GRB 250311A: Swift-XRT observations
  19. GRB 230509B: 1.3m DFOT Optical observations
  20. IceCube-250309A: Upper limits from a search for additional neutrino events in IceCube
  21. GRB 250308A: Swift/BAT-GUANO localization skymap of a short burst
  22. GRB 250302A: Swift/BAT-GUANO localization skymap of a burst
  23. GRB 250228A: Swift/BAT-GUANO localization skymap of a likely short burst
  24. GRB 250226B: Swift/BAT-GUANO localization skymap of a likely long GRB
  25. GRB 250226A: Swift/BAT-GUANO localization skymap of a long GRB
  26. GRB 250223B: Swift/BAT-GUANO localization skymap of a short burst
  27. GRB 250309B: PRIME near-infrared detection
  28. GRB 250225B: Swift-BAT refined analysis
  29. GRB 250311A/EP250311a: TRT optical upper limit
  30. EP250311a/GRB 250311A: EP-WXT detection
  31. GRB 250311B: SVOM detection of a burst
  32. GRB 250311A/MAXI J1457-026: MAXI/GSC detection
  33. GRB 250309B / AT2025dws: further SAO RAS optical observations
  34. EP250308a: 1.6m Mephisto optical upper limits
  35. Konus-Wind detection of GRB 250309B
  36. IPN triangulation of GRB 250308A (short)
  37. IceCube-241224A: MASTER detection of PKS 1217+02 blazar flare with Zhirkov effect
  38. GRB 250309B/AT2025dws : COLIBRÍ Detection of the Optical Counterpart
  39. GRB 250309B: Swift-XRT refined Analysis
  40. GRB 250309B / IceCube-250309A: GECAM-B observations
  41. GRB 250309B / AT2025dws: SAO RAS optical observations
  42. AT 2025dws, likely optical counterpart of GRB 250309B: LCO confirmation of fast fading
  43. GRB 250309B: Fermi GBM Observation
  44. GRB250309B: One candidate counterpart from the Zwicky Transient Facility
  45. IceCube-250309A: No candidates from the Zwicky Transient Facility
  46. Fermi-LAT gamma-ray observations of IceCube-250309A
  47. IceCube-250309A - IceCube observation of a high-energy neutrino candidate track-like event
  48. GRB 250309B: BALROG localization (Fermi Trigger 763198715 / GRB 250309318)
  49. EP250308a: GSP optical upper limit
  50. EP250308a: Einstein Probe detection of an X-ray transient
  51. EP250308a: NOT optical upper limit
  52. GRB 250306A: EIRSAT-1 GMOD detection
  53. GRB 250306A: Swift-BAT refined analysis
  54. GRB 250306A: NuSTAR detection of the prompt emission
  55. EP250304a: MeerKAT detection of a possible radio counterpart
  56. IceCube-241016A: MASTER flaring blazar 5BZU J073038.29-320820.2 with Zhirkov effect
  57. GRB 250305A: AstroSat CZTI detection
  58. EP250302a:Xinglong optical observations
  59. LIGO/Virgo/KAGRA S250207bg: Update-5 NED Galaxies in the Localization Volume
  60. LIGO/Virgo/KAGRA S250207bg: Updated Sky localization
  61. GRB250101A: Radio upper limits from VLA observations
  62. GRB 250305A: SVOM/GRM observation of a burst
  63. The EP-WXT trigger 01709132323 is likely a flaring star
  64. EP250304A: Upper limits from Fermi-GBM Observations
  65. Fermi-LAT Gamma-ray Observations of IceCube-250302A
  66. EP250302a: Optical Observations at CrAO and SAO RAS
  67. GRB 250219A: SVOM/C-GFT optical upper limit at early phase
  68. EP 250304A: Optical counterpart detection by LCO
  69. EP250302A: 1.3m DFOT optical afterglow detection
  70. IceCube-250302A: Upper limits from a search for additional neutrino events in IceCube
  71. EP250304a: refined analysis of the EP-WXT and EP-FXT observations
  72. EP250304a: REM NIR upper limits
  73. EP250304a: Swift/UVOT detection of an optical counterpart with a rising light curve
  74. EP250302a: Mondy Continued Optical Observations
  75. EP250304a: Swift-XRT detection of a fading X-ray source
  76. EP250304a: TRT optical counterpart detection
  77. LIGO/Virgo/KAGRA S250304cb: Identification of a GW compact binary merger candidate
  78. EP250304a: Einstein Probe detection of an X-ray transient
  79. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Swift/UVOT Upper Limits
  80. EP250302a: SAO RAS optical observations
  81. EP250302a : GIT optical follow-up
  82. EP250225a: the candidate optical counterpart is an AGN
  83. EP250302a: Kinder optical follow-up observations
  84. LIGO/Virgo/KAGRA S250302av: 2 counterpart neutrino candidate events from an IceCube neutrino search
  85. EP250302a: Swift/UVOT detection
  86. EP250302a: optical observation from the INAF Asiago Observatory
  87. EP250302a: REM NIR upper limits
  88. IceCube-241113A: MASTER flaring blazar 5BZB J1311+0853 with Zhirkov effect
  89. EP250302a: Mondy Observations and Optical Light Curve
  90. EP250302a: VLT/MUSE optical redshift z = 1.131
  91. EP250302A: VLT near-infrared observations
  92. EP250302A: VLT/X-shooter tentative redshift
  93. EP250302a: OHP/T193 optical and spectroscopic observations
  94. EP250302a: Swift-XRT observations of a fading X-ray source
  95. EP250302a: Einstein Probe detection of an X-ray transient
  96. EP250302a: SVOM/C-GFT optical observations
  97. GRB 250226A: GRANDMA Optical Observations
  98. EP250302a: Montarrenti Observatory optical detection
  99. EP250302a: Nanshan/HMT optical counterpart detection
  100. LIGO/Virgo/KAGRA S250206dm: early X-ray upper limits from Einstein Probe WXT and preliminary results of FXT observations

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