We observed supernova 1987A ( SN 1987A ) with the Space Telescope Imaging Spectrograph ( STIS ) on the Hubble Space Telescope ( HST ) in 1999 September , and again with the Advanced Camera for Surveys ( ACS ) on the HST in 2003 November .
Our spectral observations cover ultraviolet ( UV ) and optical wavelengths from 1140–10266 Å , and our imaging observations cover UV and optical wavelengths from 2900–9650 Å .
No point source is observed in the remnant .
We obtain a limiting flux of F _ { opt } \leq 1.6 \times 10 ^ { -14 } ergs s ^ { -1 } cm ^ { -2 } in the wavelength range 2900–9650 Å for any continuum emitter at the center of the supernova remnant ( SNR ) .
This corresponds to an intrinsic luminosity of L _ { opt } \leq 5 \times 10 ^ { 33 } ergs s ^ { -1 } .
It is likely that the SNR contains opaque dust that absorbs UV and optical emission , resulting in an attenuation of \sim 35 % due to dust absorption in the SNR .
Correcting for this level of dust absorption would increase our upper limit on the luminosity of a continuum source by a factor of 1.54 .
Taking into account dust absorption in the remnant , we find a limit of L _ { opt } \leq 8 \times 10 ^ { 33 } ergs s ^ { -1 } .

We compare this upper bound with empirical evidence from point sources in other supernova remnants , and with theoretical models for possible compact sources .
We show that any survivor of a possible binary system must be no more luminous than an F6 main sequence star .
Bright young pulsars such as Kes 75 or the Crab pulsar are excluded by optical and X-ray limits on SN 1987A .
Other non-plerionic X-ray point sources have luminosities similar to the limits on a point source in SN 1987A ; RCW 103 and Cas A are slightly brighter than the limits on SN 1987A , while Pup A is slightly fainter .
Of the young pulsars known to be associated with SNRs , those with ages \leq 5000 years are all too bright in X-rays to be compatible with the limits on SN 1987A .
Examining theoretical models for accretion onto a compact object , we find that spherical accretion onto a neutron star is firmly ruled out , and that spherical accretion onto a black hole is possible only if there is a larger amount of dust absorption in the remnant than predicted .
In the case of thin-disk accretion , our flux limit requires a small disk , no larger than 10 ^ { 10 } cm , with an accretion rate no more than 0.3 times the Eddington accretion rate .
Possible ways to hide a surviving compact object include the removal of all surrounding material at early times by a photon-driven wind , a small accretion disk , or very high levels of dust absorption in the remnant .
It will not be easy to improve substantially on our optical-UV limit for a point souce in SN 1987A , though we can hope that better understanding of the thermal infrared emission will provide a more complete picture of the possible energy sources at the center of SN 1987A .