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High-time-resolution observations of supernovae with Aqueye+: ASASSN-15bd, MASTER OT J120451.50+265946.6, PSN J07285597+5611462

ATel #7351; L. Zampieri (INAF-Astronomical Observatory of Padova), E. Verroi (University of Padova), G. Naletto (University of Padova), C. Barbieri (University of Padova), M. Barbieri (Universidad de Atacama)
on 7 Apr 2015; 09:22 UT
Credential Certification: Luca Zampieri (luca.zampieri@oapd.inaf.it)

Subjects: Optical, Supernovae

As part of a pilot program for the search of optical timing signals in recent supernovae, we observed the following objects with the fast photon counter Aqueye+ mounted at the 182 cm Copernico telescope in Asiago Cima Ekar (for a short description of the instrument, see Naletto et al. 2013, Proc. SPIE 8875, Quantum Communications and Quantum Imaging XI, 88750D):

Object RA (J2000) DEC (J2000)
PSN J07285597+5611462 07:28:55.97 +56:11:46.2 (CBAT TOCP, ATel #6723, #6875; Type IIn)
MASTER OT J120451.50+265946.6 12:04:51.50 +26:59:46.6 (ATel #6634, #6639, #6640, #6641, #6755; Type Ib)
ASASSN-15bd 15:54:38.33 +16:36:38.06 (ATel #6945, #6956; Type IIb)

The selected targets are recent and bright (V<17) core collapse supernovae. Data were collected on 26 and 28 January 2015, as shown in the following table:

Object Date Start time Stop time Duration Mean count rate rms
(UTC) (UTC) (s) (1/s) (1/s)
PSN J07285597+5611462 2015 01 26 02:56:33 03:26:31 1798 3691 (334) [*] 254
MASTER OT J120451.50+265946.6 2015 01 26 04:07:32 04:37:31 1799 4659 (1965) [*] 207
ASASSN-15bd 2015 01 28 04:55:27 05:15:26 1199 1599 (662) [**] 116
[*] 3 on-source channels (white light)
[**] 1 on-source channel (white light)

Mean count rate and root mean square [rms] variation refer to the sum of the on-source channels. Numbers in parentheses are background (and dark count) subtracted. Values are not corrected for atmospheric extinction and seeing.

We binned the photon events of the (summed) on-source channels with different time bins from 0.5 ms to 1 s and computed for each time bin light curves and power density spectra. No optical pulsations were detected in the non-averaged power spectra. With a 0.5 ms time bin, the upper limit to the fractional rms variation of the signal power in the frequency range 0.5-1000 Hz is (90% confidence level):

Object Date Frequency resolution Fractional rms of signal power
(mHz)
PSN J07285597+5611462 2015 01 26 0.56 <0.0021
MASTER OT J120451.50+265946.6 2015 01 26 0.56 <0.0019
ASASSN-15bd 2015 01 28 0.83 <0.0043